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  • 1.
    Abel, Martin
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Collision-induced absorption at wavelengths near 5 μm by dense hydrogen gas2009Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, nr 18, artikkel-id 181102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on a recent ab initiointeraction-induced dipole surface of collisionally interacting molecular hydrogen pairs H2–H2, we compute the binary absorption coefficients at wavelengths near 5 μm at temperatures of 77.5 and 297 K for comparison with existing laboratory measurements. We observe satisfactory agreement of the measurements with our calculations, thereby concluding an earlier study [Gustafsson et al., J. Chem. Phys.119, 12264 (2003)], which was based on an ab initiointeraction-induced dipole surface that was inadequate for the 5 μm band.

  • 2.
    Abel, Martin
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Wang, Fei
    Physics Department, Beijing Institute of Technology, China, University of Texas, Physics Department.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Li, Xiaoping
    Department of Chemistry, Michigan State University.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University, East Lansing, Department of Chemistry, Michigan State University.
    Collision-induced absorption by supermolecular complexes from a new potential energy and induced dipole surface, suited for calculations up to thousands of kelvin2010Inngår i: 20th International Conference on Spectral Line Shapes: St. John's, Newfoundland, Canada, 6 - 11 June 2010 ; [20th ICSLS] / [ed] John K.C. Lewis; Adriana Predoi-Cross, Melville, NY: American Institute of Physics (AIP), 2010, s. 251-257Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Absorption by pairs of H2 molecules is an important opacity source in the atmospheres of the outer planets, and thus of special astronomical interest. The emission spectra of cool white dwarf stars differ significantly from the expected blackbody spectra, amongst other reasons due to absorption by H2-H2, H2-He, and H2-H collisional complexes in the stellar atmospheres. To model the radiative processes in these atmospheres, which have temperatures of several thousand kelvin, one needs accurate knowledge of the induced dipole (ID) and potential energy surfaces (PES) of such collisional complexes. These come from quantum-chemical calculations with the H2 bonds stretched or compressed far from equilibrium. Laboratory measurements of collision-induced (CI) absorption exist only at much lower temperature. For H2 pairs at room temperature, the calculated spectra of the rototranslational band, the fundamental band, and the first overtone match the experimental data very well. In addition, with the newly obtained IDS it became possible to reproduce the measurements in the far blue wing of the rototranslational spectrum of H2 at 77.5 K, as well as at 300 K. Similarly good agreement between theory and measurement is seen in the fundamental band of molecular deuterium at room temperature. Furthermore, we also show the calculated absorption spectra of H2-He at 600 K and of H2-H2 at 2,000 K, for which there are no experimental data for comparison

  • 3.
    Antipov, Sergey V.
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Isotope effect in the formation of carbon monoxide by radiative association2013Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 430, nr 2, s. 946-950Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rate coefficients for the formation of 12CO and 13CO isotopologues of carbon monoxide by radiative association for T = 10–20 000 K are calculated using a quantum mechanical approach. It is shown that the presence of the potential barrier on the A1Π electronic state of CO leads to different formation channels for the isotopologues at low temperatures. The corresponding rate coefficients are fitted to an analytic formula.

  • 4.
    Antipov, Sergey V.
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Spin-orbit and rotational couplings in radiative association of C(3P) and N(4S) atoms2011Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, nr 18, artikkel-id 184302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The role of spin-orbit and rotational couplings in radiative association of C(3 P) and N(4 S) atoms is investigated. Couplings among doublet electronic states of the CN radical are considered, giving rise to a 6-state model of the process. The solution of the dynamical problem is based on the L2 method, where a complex absorbing potential is added to the Hamiltonian operator in order to treat continuum and bound levels in the same manner. Comparison of the energy-dependent rate coefficients calculated with and without spin-orbit and rotational couplings shows that the couplings have a strong effect on the resonance structure and low-energy baseline of the rate coefficient.

  • 5.
    Antipov, Sergey V.
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Sjölander, Tobias
    Department of Chemistry, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Rate coefficient of CN formation through radiative association: A theoretical study of quantum effects2009Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, nr 7, artikkel-id 74302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radiative association of CN is simulated using a quantum dynamical as well as a semiclassical approach. A comparison of the resulting energy-resolved cross sections reveals striking quantum effects that are due to shape resonances. These, in turn, arise because of states that are quasibound by the centrifugal barrier. The quantal rate coefficient for temperatures from 40 to 1900 K has been computed using the Breit–Wigner theory to account for the resonances. Comparison with the results obtained by Singh and Andreazza [Astrophys. J.537, 261 (2000)] shows that the semiclassical method, which completely omits the shape resonances, is accurate to within 25% above room temperature. At lower temperatures the contribution from the shape resonances to the radiative association rate is more significant.

  • 6.
    Buser, Michael
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Gustafsson, Magnus
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Moraldi, Massimo
    Dipartimento di Fisica, Universitá di Firenze and INFM, Unitá di Firenze.
    Champagne, Mark H.
    Department of Chemistry, Michigan State University.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University.
    Far-infrared absorption by collisionally interacting nitrogen and methane molecules2004Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, nr 6, s. 2616-2621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum line shape calculations of the rototranslational enhancement spectra of nitrogen-methane gaseous mixtures are reported. The calculations are based on a recent theoretical dipole function for interactingN2 and CH4 molecules, which accounts for the long-range induction mechanisms: multipolar inductions and dispersion force-induced dipoles. Multipolar induction alone was often found to approximate the actual dipole surfaces of pairs of interacting linear molecules reasonably well. However, in the case of the N2-CH4 pair, the absorption spectra calculated with such a dipole function still show a substantial intensity defect at the high frequencies (>250 cm−1) when compared to existing measurements at temperatures from 126 to 297 K, much as was previously reported.

  • 7.
    Ekman, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Törlind, Peter
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Kuhn, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Öhrwall Rönnbäck, Anna
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Zorzano Mier, Maria-Paz
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Parida, Vinit
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Wolf, Veronika
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Dordlofva, Christo
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Mendaza de Cal, Maria Teresa
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Jamali, Maryam
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Roos, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Ottemark, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nieto, Chris
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Soria Salinas, Álvaro Tomás
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vázquez Martín, Sandra
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nyberg, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Neikter, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lindwall, Angelica
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Fakhardji, Wissam
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Projekt: Rymdforskarskolan2015Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The Graduate School of Space Technology

  • 8.
    El-Kader, M.S.A.
    et al.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University.
    Godet, J-L
    Laboratoire de photonique d'Angers, Université d'Angers.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Maroulis, G.
    Department of Chemistry, University of Patras.
    Multi-property isotropic intermolecular potentials and predicted spectral lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) for H2Ne, −Kr and −Xe2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 209, s. 232-242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum mechanical lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) at room temperature (295 K) are computed for gaseous mixtures of molecular hydrogen with neon, krypton and xenon. The induced spectra are detected using theoretical values for induced dipole moment, pair-polarizability trace and anisotropy, hyper-polarizability and updated intermolecular potentials. Good agreement is observed for all spectra when the literature and the present potentials which are constructed from the transport and thermo-physical properties are used.

  • 9.
    Fakhardji, Wissam
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Molecular dynamics simulations of collision-induced absorption: Implementation in LAMMPS2017Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 810, nr 1, artikkel-id 012031Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We pursue simulations of collision-induced absorption in a mixture of argon and xenon gas at room temperature by means of classical molecular dynamics. The established theoretical approach (Hartmann et al. 2011 J. Chem. Phys. 134 094316) is implemented with the molecular dynamics package LAMMPS. The bound state features in the absorption spectrum are well reproduced with the molecular dynamics simulation in comparison with a laboratory measurement. The magnitude of the computed absorption, however, is underestimated in a large part of the spectrum. We suggest some aspects of the simulation that could be improved

  • 10.
    Fletcher, Leigh N.
    et al.
    Department of Physics and Astronomy, University of Leicester.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Orton, Glenn S.
    Jet Propulsion Laboratory, California Institute of Technology.
    Hydrogen Dimers in Giant-planet Infrared Spectra2018Inngår i: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 235, nr 1, artikkel-id 24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite being one of the weakest dimers in nature, low-spectral-resolution Voyager/IRIS observations revealed the presence of (H2)2 dimers on Jupiter and Saturn in the 1980s. However, the collision-induced H2-H2 opacity databases widely used in planetary science have thus far only included free-to-free transitions and have neglected the contributions of dimers. Dimer spectra have both fine-scale structure near the S(0) and S(1) quadrupole lines (354 and 587 cm-1, respectively), and broad continuum absorption contributions up to ±50 cm-1 from the line centers. We develop a new ab initio model for the free-to-bound, bound-to-free, and bound-to-bound transitions of the hydrogen dimer for a range of temperatures (40-400 K) and para-hydrogen fractions (0.25-1.0). The model is validated against low-temperature laboratory experiments, and used to simulate the spectra of the giant planets. The new collision-induced opacity database permits high-resolution (0.5-1.0 cm-1) spectral modeling of dimer spectra near S(0) and S(1) in both Cassini Composite Infrared Spectrometer observations of Jupiter and Saturn, and in Spitzer Infrared Spectrometer (IRS) observations of Uranus and Neptune for the first time. Furthermore, the model reproduces the dimer signatures observed in Voyager/IRIS data near S(0) on Jupiter and Saturn, and generally lowers the amount of para-H2 (and the extent of disequilibrium) required to reproduce IRIS observations.

  • 11.
    Franz, Jan
    et al.
    University of Gothenburg.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Formation of carbon-monoxide by radiative association: a quantum-dynamical study2011Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 414, nr 4, s. 3547-3550Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rate coefficients for the formation of carbon monoxide (CO) by radiative association of carbon and oxygen atoms are computed using quantum dynamical simulations. At temperatures above 10 K CO radiative association is dominated by C(3P) and O(3P) approaching on the A1Π potential energy curve. The rate coefficient is estimated as k=A(T/300 K)αexp−β/T with A= 1.39 × 10−18 cm3 s−1, α=−0.016 and β= 92.2 for temperatures between 6 and 127.2 K, and A= 1.36 × 10−17 cm3 s−1, α= 0.41 and β= 340 for temperatures between 127.2 and 15 000 K. Furthermore we computed the rate coefficients for approaching on the X1Σ+ curve. For temperatures below 200 K it is between 0.7 × 10−22 and 4 × 10−22 cm3 s−1.

  • 12.
    Frommhold, Lothar
    et al.
    University of Texas, Physics Department.
    Abel, Martin
    University of Texas, Physics Department.
    Wang, Fei
    Physics Department, Beijing Institute of Technology, China.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Li, Xiaoping
    Department of Chemistry, Michigan State University.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University.
    Infrared atmospheric emission and absorption by simple molecular complexes, from first principles2010Inngår i: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 108, nr 17, s. 2265-2272Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum chemical methods are used to obtain the interaction-induced dipole surfaces (IDS) of complexes of two interacting (i.e. colliding) molecules, for example H2–H2, H2–He, etc., collisional complexes, along with their potential energy surfaces (PES). Eight H2 bond distances, from 0.942 to 2.801 bohr, are chosen for each H2 molecule to account for rotovibrational excitations. Rotovibrational matrix elements of these ID and PE surfaces are computed as necessary for the study of supermolecular (‘collision-induced’) absorption spectra of dense hydrogen gas, and of gaseous mixtures of hydrogen and helium, at temperatures up to several thousand kelvin and for frequencies from 0 to those of several H2 overtone bands. Rotovibrational state to state scattering calculations couple the collisional complex perturbatively to single photons. The absorption process causes rotovibrational transitions in one molecule, or simultaneous transitions in both molecules (when H2–H2 collisional complexes are considered). The spectral profiles of tens of thousands of such transitions are computed from first principles. Individual ‘lines’ are very broad so that they overlap substantially, forming a supermolecular quasi-continuum. The comparison of the computed collision-induced absorption (CIA) spectra with existing laboratory measurements at low temperatures (≤ 300 K) shows close agreement so that our results for higher temperatures, where laboratory experiments do not exist, may be used with confidence. Similar calculations of CIA spectra at high temperatures and frequencies are underway for other collisional systems (e.g. H2–H) of interest in astrophysical applications (e.g. ‘cool’ stellar atmospheres). Collision-induced Raman spectra (CIRS) have been similarly obtained; computed Raman spectra also compare favourably with existing laboratory measurements.

  • 13.
    Glaz, Waldemar
    et al.
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań.
    Bancewicz, Tadeusz
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University.
    Godet, Jean Luc
    Laboratoire de Photonique D'Angers, Université D'Angers.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras.
    Maroulis, George
    Department of Chemistry, University of Patras.
    Effects of anisotropic interaction-induced properties of hydrogen-rare gas compounds on rototranslational Raman scattering spectra: Comprehensive theoretical and numerical analysis2016Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, nr 3, artikkel-id 34303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A comprehensive study is presented of many aspects of the depolarized anisotropic collision induced (CI) component of light scattered by weakly bound compounds composed of a dihydrogen molecule and a rare gas (Rg) atom, H2-Rg. The work continues a series of earlier projects marking the revival of interest in linear light scattering following the development of new highly advanced tools of quantum chemistry and other theoretical, computational, and experimental means of spectral analyses. Sophisticated ab initio computing procedures are applied in order to obtain the anisotropic polarizability component's dependence on the H2-Rg geometry. These data are then used to evaluate the CI spectral lines for all types of Rg atoms ranging from He to Xe (Rn excluded). Evolution of the properties of CI spectra with growing polarizability/masses of the complexes studied is observed. Special attention is given to the heaviest, Kr and Xe based, scatterers. The influence of specific factors shaping the spectral lines (e.g., bound and metastable contribution, potential anisotropy) is discussed. Also the share of pressure broadened allowed rotational transitions in the overall spectral profile is taken into account and the extent to which it is separable from the pure CI contribution is discussed. We finish with a brief comparison between the obtained results and available experimental data

  • 14.
    Golubev, Nikolay V.
    et al.
    Department of Chemistry, M. V. Lomonosov Moscow State University.
    Bezrukov, Dmitry S.
    Department of Chemistry, M. V. Lomonosov Moscow State University.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Formation of the SiP radical through radiative association2013Inngår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, nr 34, s. 8184-8188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation of the SiP radical through radiative association of Si( 3P) and P(4S) atoms is studied using classical and quantum dynamics. Rate coefficients for formation in the two lowest doublet states and the two lowest quartet states are calculated for T = 10-20 000 K. Breit-Wigner theory is used to properly account for contribution from quantum mechanical resonances.

  • 15.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Career achivements of Professor Lothar Frommhold2010Inngår i: 20th International Conference on Spectral Line Shapes: St. John's, Newfoundland, Canada, 6 - 11 June 2010 ; [20th ICSLS] / [ed] John K.C. Lewis; Adriana Predoi-Cross, Melville, NY: American Institute of Physics (AIP), 2010, s. 294-300Konferansepaper (Annet vitenskapelig)
  • 16.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Classical calculations of radiative association in absence of electronic transitions2013Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, nr 7, artikkel-id 74308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A formula for the cross section of radiative association where no electronic transitions take place is derived and tested for diatomic molecules. The approach is based on classical mechanics and therefore it is valid for direct, i.e., non-resonant, radiative association. For the formation of carbon monoxide (CO) and the cyano radical (CN), in the X 1Σ+ and A 1Π states, respectively, the treatment reproduces the baselines of the cross sections obtained using quantum mechanical perturbation theory. The method overestimates the formation cross section of potassium sodide (NaK) by about 8%. For the lower mass diatoms hydrogen fluoride (HF) and deuterium hydride (HD), the formula overestimates the cross sections by 12% and 60%, respectively. The formula can be used alone for estimates of radiative association rate constants, or in combination with Breit-Wigner theory to include resonance contributions.

  • 17.
    Gustafsson, Magnus
    University of Texas, Physics Department.
    Collision-induced Absorption and Anisotropy of the Intermolecular Potential2002Doktoravhandling, med artikler (Annet vitenskapelig)
  • 18.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Diatom-diatom interactions with light: Applications and line shape theoretical aspects2008Inngår i: Spectral line shapes, volume 15: 19th International Conference on Spectral Line Shapes, Valladolid, Spain, 15 - 20 June 2008 ; ICSLS / [ed] Marco A. Gigosos; Manuel A. González, Melville, NY: American Institute of Physics (AIP), 2008, s. 297-301Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent advances in calculations of collision-induced absorption- and Raman-spectra in pure diatomic gases are presented. An extensive calculation of H2-H2 absorption from 40 K to 400 K has provided improved understanding of the atmosphere of Uranus. A highly advanced close-coupling calculation of H2-H2 light scattering has verified that the line shapes are affected by interference between the permanent H2 and the H2-H2 interaction-induced polarizabilities. A few directions that the research in astrophysical applications of collision-induced absorption is taking are also described. For instance, H2-H 2 dipole and potential surfaces for vibrations higher than v = 1 are currently being developed to enable simulations of collision-induced absorption at temperatures relevant for white dwarf atmospheres. For low temperature N 2-N2 absorption there is unresolved discrepancy between measurement and simulation. A possible solution to this puzzle is suggested

  • 19.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Far Wing Asymmetry of Rotational Raman Lines in Hydrogen2010Inngår i: International Journal of Spectroscopy, ISSN 1687-9449, E-ISSN 1687-9457, Vol. 2010, artikkel-id 705896Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Depolarized Raman spectra of compressed hydrogen gas have been computed rigorously previously for 36 K and 50 K (Gustafsson et al. (2009)). The far wings of the rotational lines show asymmetry that goes beyond that expected from the theory for intracollisional interference and Fano line shapes. Here we analyze the (0) line for pure hydrogen at 36 K in detail. The added asymmetry stems partly from a shape resonance which adds significant intensity to the higher frequency side of the line profile. The influence of the threshold energy for the rotational transition accounts for the remainder.

  • 20.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hydrogen dimer features in low temperature collision-induced spectra2017Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 810, nr 1, artikkel-id 012017Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The absorption of radiation in pure hydrogen (H2) gas around the S(0) and S(1) rotational transitions is computed at 20 K and compared with laboratory data. All transitions involving free state are included in the calculations of the absolute absorption. These calculations are done with an isotropic approximation for the H2–H2 pair potential. Agreement with the experiment is observed around the S(0) transition, while the computational approach appears to be slightly worse around the S(1) transition. The positions for bound-to-bound transitions are computed including the full anisotropic pair potential. The anisotropy seems to be crucial to achieve agreement with the measured bound-to-bound transition frequencies. However, those transitions contribute little to the total absorption. The present computed absolute absorptions will provide improved input for radiative transfer models of planetary atmospheres.

  • 21.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Calculation of interaction-induced spectra using complex absorbing potentials2010Inngår i: 20th International Conference on Spectral Line Shapes: St. John's, Newfoundland, Canada, 6 - 11 June 2010 ; [20th ICSLS] / [ed] John K.C. Lewis; Adriana Predoi-Cross, Melville, NY: American Institute of Physics (AIP), 2010, s. 240-244Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A complex absorbing potential method is implemented for calculation of collision-induced spectra. The scheme provides a way to avoid the integration of the Schrödinger equation to very large separations of the collisional pair. The method is tested by reproducing a previously computed absorption spectrum for H-He at two different temperatures.

  • 22.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Franz, Jan
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Refined theoretical study of radiative association: cross sections and rate constants for the formation of SiN2012Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, nr 10, artikkel-id 104301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radiative association of silicon mononitride (SiN) in its two lowest molecular electronic states is studied through quantum and classical dynamics. Special attention is paid to the behavior of the cross section at high collision energies. A modified expression for the semiclassical cross section is presented which excludes transitions to continuum states. This gives improved agreement with quantum mechanical perturbation theory at high energies. The high energy cross section is overestimated if conventional semiclassical theory is used. The modified semiclassical theory should be valid in general for radiative association transitions from an upper to a lower electronic state. We also implement a quantum dynamical optical potential method with the same type of modification. The rate coefficient is calculated using Breit–Wigner theory and the modified semiclassical formula for the resonance and direct contributions, respectively, for temperatures from 10 K to 20 000 K. A rapid decrease in the rate constant for formation of ground state SiN is observed above 2000 K which was not seen previously.

  • 23.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Effects of the anisotrophy of the intermulucular potential2002Inngår i: Spectral line shapes: volume 12 ; 16th International Conference on Spectral Line Shapes, ICSLS, Berkeley, California, 3-7 June 2002 / [ed] Christina A. Back, Melville, NY: American Institute of Physics (AIP), 2002, s. 216-227Konferansepaper (Fagfellevurdert)
  • 24.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Infrared absorption by H2-Ar collisional complexes and the anisotropy of the intermolecular interaction potential2006Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, artikkel-id 54703Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    H2-Ar scattering processes in the presence of a weak photon field are considered. Calculations are based on an accurate ab initio interaction-induced electric dipole surface and an anisotropic intermolecular potential energy surface. The close-coupled scheme of integrating the Schrödinger equation is employed to calculate the rototranslational absorption spectrum of H2-Ar pairs in the far-infrared region of the electromagnetic spectrum. The results are compared with previous work where the weak anisotropy of the intermolecular interaction potential was suppressed. Under the conditions considered, accounting for the anisotropy modifies the rototranslational absorption spectrum discernibly, but only at some frequency bands where the corrections are negative, typically below 10%.

  • 25.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Infrared Absorption Spectra of Collisionally Interacting He and H Atoms2001Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 546, nr 2, s. 1168-1170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    On the basis of recent state-of-the-art ab initio calculations of the interatomic potential and dipole surface of interacting helium (He) and hydrogen (H) atoms, we calculate the collision-induced absorption spectra in the infrared of the He-H pair, using a rigorous quantum mechanical formalism. Furthermore, we present a simple analytical model which is capable of reproducing these calculated spectra with precision, for frequencies from 50 to roughly 10,000 cm-1 and temperatures from 1500 to 10,000 K. For a given temperature and frequency, the ratio of the absorption coefficient and the product of the H and He densities may be evaluated in seconds, even on small computers (e.g., PCs), provided this ratio exceeds a certain (very small) lower numerical limit.

  • 26.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Intracollisional interference of R lines of HD in mixtures of deuterium hydride and helium gas2001Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 63, nr 5, artikkel-id 52514Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Line shapes of the R0(0) and R0(1) lines in the pure rotational band, and of the R1(0) and R1(1) lines in the fundamental band of HD are computed from first principles for HD molecules that interact collisionally with He atoms. Interference of the permanent dipole of the HD molecule and the interaction-induced dipole of HD–He supermolecular complex shapes these profiles. We use the close-coupling scheme for the scattering calculations which take into account the anisotropy of the HD–He interaction potential. Thus rotational level mixing is accounted for in a non-perturbative manner. The treatment is fully quantum mechanical and takes into account single binary collisions between HD and He. Spectral absorption profiles and line shape parameters of the R-lines are computed for comparison with existing measurements at 77 K. Agreement between theory and measurements is observed in the low-helium-density limit of the measured absorption as expected.

  • 27.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Spectra of 2- and 3-body van der Waals complexes2003Inngår i: Weakly interacting molecular pairs: unconventional absorbers of radiation in the atmosphere: [proceedings of the NATO Advanced Research Workshop on Weakly Interacting Molecular Pairs: Unconventional Absorbers of Radiation in the Atmosphere, Fontevraud, France, 29 April - 3 May, 2002] / [ed] Claude Camy-Peyret, Dordrecht: Kluwer Academic Publishers, 2003, s. 3-22Konferansepaper (Fagfellevurdert)
  • 28.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    The H_2-H infrared absorption bands at temperatures from 1000 K to 2500 K2003Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 400, nr 3, s. 1161-1162Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    H 2-H collision-induced absorption spectra are computed for temperatures from 1000 K to 2500 K and frequencies from 100 cm -1 to 10 000 cm -1. The calculations are quantum mechanical and the isotropic potential approximation has been applied. The computed absorption in the fundamental band agrees roughly with the one determined by Patch (1974). However, the absorption in the translational band, which has not been obtained before, is significantly stronger than in the fundamental band.

  • 29.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    The HD–He complex: Interaction-induced dipole surface and infrared absorption spectra2001Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, nr 12, s. 5427-5432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The collision-induced dipole surface of an HD molecule interacting with an He atom is derived from the ab initio dipole data of the H2–He complex [Gustafsson et al., J. Chem. Phys. 113, 3641, (2000)]. Collision-induced absorption spectra of gaseous mixtures of deuterium hydride and helium in the rotational and fundamental bands of HD are calculated, for comparison with an existing measurement taken at a temperature of 77 K. To that end, we integrate the close-coupled, radial Schrödinger equations, accounting for the anisotropy of the HD–He interaction potential. The computed absorption spectra generally agree reasonably well with the observed spectral profiles and intensities of the collision-induced spectra. We also consider the interference phenomena of the HD permanent dipole with the interaction-induced, supramolecular dipole by computing the wings of various R(j) lines and of the P1(1) line in single, binary collision limit. For comparison, the line broadening and shift for the P and R line shape parameters are also computed using the impact approximation. The close-coupled treatment of our calculation of the spectral profiles accounts for rotational level mixing in a nonperturbative manner. The treatment is fully quantum-mechanical and takes into account single binary collisions of HD and He.

  • 30.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Bailly, Denise
    Labaratoire de Photophysique Moléculaire, CNRS, Campus d’Orsay, France.
    Bouanich, Jean-Pierre
    Labaratoire de Photophysique Moléculaire, CNRS, Campus d’Orsay, France.
    Brodbeck, Claude
    Labaratoire de Photophysique Moléculaire, CNRS, Campus d’Orsay, France.
    Collision-induced absorption in the rototranslational band of dense hydrogen gas2003Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, nr 23, s. 12264-12270Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurements of the H2–H2 collision-induced absorption spectra at temperatures of 297.5 and 77.5 K are reported in the frequency range from 1900 to 2260 cm−1 at gas densities ranging from 51 to 610 amagat. Ab initio calculations of the absorption are carried out for comparison with the measurements. In these calculations, for the lower temperature close-coupled equations describe the H2–H2scattering in the presence of a weak electromagnetic radiation field; the anisotropy of the H2–H2interaction is accounted for. For the room temperature calculations, the isotropic potential approximation is employed. Agreement of measured and calculated spectral shapes is observed. However, in the far wing, at large frequencies (≳2000 cm−1), discrepancies of measured and calculated spectral intensities are observed which are somewhat larger than the combined, estimated uncertainties of theory and measurement. These differences remain unexplained at this stage.

  • 31.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Li, Xiaoping
    Department of Chemistry, Michigan State University.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University.
    Roto-translational Raman spectra of pairs of hydrogen molecules from first principles2009Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, nr 16, artikkel-id 164314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We calculate the collision-induced, roto-translational, polarized, and depolarized Raman spectra of pairs of H2 molecules. The Schrödinger equation of H2–H2scattering in the presence of a weak radiation field is integrated in the close-coupled scheme. This permits the accounting for the anisotropy of the intermolecular potential energy surface and thereby it includes mixing of polarizability components. The static polarizability invariants, trace and anisotropy, of two interactingH2 molecules were obtained elsewhere [Li et al., J. Chem. Phys.126, 214302 (2007)] from first principles. Here we report the associated spherical tensor components which, along with the potential surface, are input in the calculation of the supramolecular Raman spectra. Special attention is paid to the interferences in the wings of the rotational S0(0) and S0(1) lines of the H2 molecule. The calculated Raman pair spectra show reasonable consistency with existing measurements of the polarized and depolarized Raman spectra of pairs of H2 molecules.

  • 32.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Meyer, Wilfried
    Fachbereich Chemie, Universität Kaiserslautern, Germany.
    Infrared absorption spectra by H2–He collisional complexes: The effect of the anisotropy of the interaction potential2000Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, nr 9, s. 3641-3650Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As an extension of previous work which was based on the isotropic interaction approximation, absorption spectra in the rotational and fundamental bands of H2, induced by collisions with He, are calculated by numerical integration of the close-coupled Schrödinger equation to account for the anisotropy of the interaction potential. A refined quantum chemical dipole surface of interactingH2–He pairs is also obtained with an extended grid of molecular geometries. This dipole surface agrees generally well with previous results, but is smaller by about 5% in the isotropic overlap term which is significant only in the fundamental band. The effects of the anisotropy of the interaction are to reduce the peak intensities of the Q and S lines by roughly 10% and to increase absorption in the far wings by a similar amount. The accuracy of the dipole surface as well as that of the ab initiointeraction potential that enters the calculations of the spectra are believed to permit the prediction of absolute spectral intensities with an accuracy of about ±5%. Comparisons with the available measurements show very good agreement of the shapes of the spectral profiles, but the absolute intensities differ by up to 10% in some cases. These remaining differences between theory and measurements appear to be random and are generally smaller than the differences among comparable measurements. Our results should therefore provide a reliable basis for predicting absorption by H2–He pairs for temperatures and frequencies for which no laboratory measurements exist. This fact is of a special interest, for example, for the spectroscopic analyses of the atmospheres of the outer planets.

  • 33.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Meyer, Wilfried
    Fachbereich Chemie, Universität Kaiserslautern, Germany.
    Infrared Absorption Spectra of H2–He Collisional Complexes: The Effect of the Anisotropy of the Interaction Potential2001Inngår i: Spectral line shapes: volume 11 ; 15th ICSLS, Berlin, Germany, 10 - 14 July 2000 / [ed] Joachim Seidel, Melville, NY: American Institute of Physics (AIP), 2001, s. 425-427Konferansepaper (Fagfellevurdert)
  • 34.
    Gustafsson, Magnus
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Meyer, Wilfried
    Fachbereich Chemie, Universität Kaiserslautern, Germany.
    The H2–H complex: Interaction-induced dipole surface and infrared absorption spectra2003Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, nr 4, s. 1667-1472Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A quantum chemical dipole surface of interacting H2–H pairs is obtained and collision-induced absorption spectra are computed for temperatures from 200 to 1000 K and frequencies from 0 to 6000 cm−1. The effect of the anisotropy of the potential energy is investigated and turns out to be almost negligible at the temperature for which a close-coupled quantum calculation was done. The smallness of the effect stems from the short range character of the anisotropic potential components for H2–H. Accordingly the isotropic potential approximation could be applied in most of the present calculations. The accuracy of the dipole surface as well as that of the ab initiopotential energy surface that enters the calculations of the spectra are believed to permit prediction of absolute spectral intensities with an accuracy in the 5% range.

  • 35.
    Gustafsson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gļaz, Waldemar
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University.
    Bancewicz, Tadeusz
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University.
    Godet, Jean Luc
    Laboratoire de Photonique D'Angers, Université D'Angers.
    Maroulis, George
    Department of Chemistry, University of Patras.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras.
    Calculated isotropic Raman spectra from interacting H2-rare-gas pairs2014Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 548, artikkel-id 12027Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a theoretical study of the H2-He and H2-Ar pair trace-polarizability and the corresponding isotropic Raman spectra. The conventional quantum mechanical approach for calculations of interaction-induced spectra, which is based on an isotropic interaction potential, is employed. This is compared with a close-coupling approach, which allows for inclusion of the full, anisotropic potential. It is established that the anisotropy of the potential plays a minor role for these spectra. The computed isotropic collision-induced Raman intensity, which is due to dissimilar pairs in H2-He and H2-Ar gas mixtures, is comparable to the intensities due to similar pairs (H2-H2, He-He, and Ar-Ar), which have been studied previously.

  • 36.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Monge-Palacios, Manuel
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    The rate constant for radiative association of HF: Comparing quantum and classical dynamics2014Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, nr 18, artikkel-id 184301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radiative association for the formation of hydrogen fluoride through the A1Π → X1Σ+ and X 1Σ+ → X1Σ+ transitions is studied using quantum and classical dynamics. The total thermal rate constant is obtained for temperatures from 10 K to 20 000 K. Agreement between semiclassical and quantum approaches is observed for the A 1Π → X1Σ+ rate constant above 2000 K. The agreement is explained by the fact that the corresponding cross section is free of resonances for this system. At temperatures below 2000 K we improve the agreement by implementing a simplified semiclassical expression for the rate constant, which includes a quantum corrected pair distribution. The rate coefficient for the X1Σ+ → X 1Σ+ transition is calculated using Breit-Wigner theory and a classical formula for the resonance and direct contributions, respectively. In comparison with quantum calculations the classical formula appears to overestimate the direct contribution to the rate constant by about 12% for this transition. Below about 450 K the resonance contribution is larger than the direct, and above that temperature the opposite holds. The biggest contribution from resonances is at the lowest temperature in the study, 10 K, where it is more than four times larger than the direct. Below 1800 K the radiative association rate constant due to X1Σ+ → X1Σ+ transitions dominates over A 1Π→ X1Σ+, while above that temperature the situation is the opposite.

  • 37.
    Gustafsson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Radiative association rate constant for the formation of CO: the importance of the first excited 1Σ+ state2015Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 448, nr 3, s. 2562-2565Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal rate constant for production of carbon monoxide, in its electronic ground state, through radiative association of carbon (C) and oxygen (O) atoms is computed. A combination of quantum and classical dynamics methods are employed. In particular, we investigate the importance of the mechanism where C and O approach each other on the 21Σ+ potential energy curve. Accounting for this reaction turns out to add about 75 per cent to the rate constant at 10000 K. We expect the results to be important for studies of the chemistry in interstellar gas, particularly in metal-rich ejecta of supernovae. Since a significant isotope effect has been predicted previously both stable carbon isotopes 12C and 13C are considered in the present study.

  • 38.
    Gustafsson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    The emission spectrum due to molecule formation through radiative association2014Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 548, artikkel-id 12003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum mechanical and classical methods for theoretical analysis of the emission spectrum due to radiative association are presented. Quantum mechanical perturbation theory is employed to obtain the spectra when the diatomic molecule HF forms by transitions within the electronic ground state and when it forms by transitions between two electronic states. We contrast these spectra with each other. The former peaks in the infrared, while the latter peaks in the ultraviolet. The classical spectrum, which concerns transitions within the electronic ground state, is also calculated and found to favorably compare with that from quantum mechanical perturbation theory. The emission stemming from resonance mediated radiative association is also discussed.

  • 39.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Probing stereodynamics in reactive collisions using helicity filtering2007Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 434, nr 1-3, s. 20-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stereodynamic effects in the D + H2 reaction are studied using a new method that permits reagent-helicity dependent cross sections to be inferred from the scattering results obtained using randomly oriented reagent molecules. Employing fully converged quantum scattering calculations as a benchmark, it is demonstrated that the method yields useful results for all the helicity states corresponding to j = 1 and 2 of the H2 diatom.

  • 40.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    The state-to-state-to state model of direct chemical reactions2005Inngår i: Semiclassical and other methods for understanding molecular collisions and chemical reactions, Daresbury: Collaborative Computational Project on Molecular Quantum Dynamics (CCP6), Daresbury Laboratory , 2005, s. 34-42Kapittel i bok, del av antologi (Fagfellevurdert)
  • 41.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    The state-to-state-to-state model for direct chemical reactions: Application to D+H2 → HD+H2006Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, nr 14, artikkel-id 144311Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple theoretical model is developed to predict the state-to-state dynamics of direct chemical reactions. Motivated by traditional ideas from transition state theory, expressions are derived for the reactive S matrix that may be computed using the local transition state dynamics. The key approximation involves the use of quantum bottleneck states to represent the near separable dynamics taking place near the transition state. Explicit expressions for the S matrix are obtained using a Franck-Condon treatment for the inelastic coupling between internal states of the collision complex. It is demonstrated that the energetic thresholds for various initial reagent states of the D+H2reaction can be understood in terms of our theory. Specifically, the helicity of the reagent states are found to correlate directly to the symmetry of the quantum bottleneck states, which thus possess very different thresholds. Furthermore, the rotational product state distributions for D+H2 are found to be associated with interfering pathways through the quantum bottleneck states.

  • 42.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Zhang, Jianyang
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Dai, Dongxu
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Harich, Steven A.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Wang, Xiuyan
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Yang, Xueming
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Erratum: Observing the stereodynamics of chemical reactions using randomly oriented molecular beams ( Journal of Chemical Physics (2006) 124 (241105))2006Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, nr 22, artikkel-id 229901Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method is demonstrated to study the stereodynamics of simple chemical reactions that does not require the use of oriented (or aligned) molecular beams or measurements of the orientation state of product molecules. Instead, it is shown that by numerically combining accurate measurements of the state-to-state differential cross section for two or more rotational states of the reagent molecule, the separate contribution from the individual helicity states can be extracted. New molecular beam experiments are conducted for the D+H2→HD+Hreaction that confirm the validity of the method.

  • 43.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Zhang, Jianyang
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Dai, Dongxu
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Harich, Steven A.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Wang, Xiuyan
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Yang, Xueming
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Observing the stereodynamics of chemical reactions using randomly oriented molecular beams2006Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, artikkel-id 241105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method is demonstrated to study the stereodynamics of simple chemical reactions that does not require the use of oriented (or aligned) molecular beams or measurements of the orientation state of product molecules. Instead, it is shown that by numerically combining accurate measurements of the state-to-state differential cross section for two or more rotational states of the reagent molecule, the separate contribution from the individual helicity states can be extracted. New molecular beam experiments are conducted for the D+H2→HD+Hreaction that confirm the validity of the method.

  • 44.
    Głaz, Waldemar
    et al.
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University.
    Bancewicz, Tadeusz
    Nonlinear Optics Division, Faculty of Physics, Adam Mickiewicz University.
    Godet, Jean Luc
    Laboratoire de Photonique D'Angers, Université D'Angers.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Maroulis, George
    Department of Chemistry, University of Patras.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras.
    Intermolecular polarizabilities in H2-rare-gas mixtures (H2-He, Ne, Ar, Kr, Xe): Insight from collisional isotropic spectral properties2014Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, nr 7, artikkel-id 74315Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The report presents results of theoretical and numerical analysis of the electrical properties related to the isotropic part of the polarizability induced by interactions within compounds built up of a hydrogen H2 molecule and a set of noble gas atoms, Rg, ranging from the least massive helium up to the heaviest xenon perturber. The Cartesian components of the collisional polarizabilities of the H2-Rg systems are found by means of the quantum chemistry methods and their dependence on the intermolecular distance is determined. On the basis of these data, the spherical, symmetry adapted components of the trace polarizability are derived in order to provide data sets that are convenient for evaluating collisional spectral profiles of the isotropic polarized part of light scattered by the H2-Rg mixtures. Three independent methods of numerical computing of the spectral intensities are applied at room temperature (295 K). The properties of the roto-translational profiles obtained are discussed in order to determine the role played by contributions corresponding to each of the symmetry adapted parts of the trace polarizability. By spreading the analysis over the collection of the H 2-Rg systems, evolution of the spectral properties with the growing masses of the supermolecular compounds can be observed

  • 45.
    Hartmann, Jean-Michel
    et al.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University.
    Tran, Ha
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique.
    Armante, Raymond
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University.
    Boulet, Christian
    Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay.
    Campargue, Alain
    Univ. Grenoble Alpes, CNRS.
    Forget, François
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique.
    Gianfrani, Livio
    Dipartimento di Matematica e Fisica, Università degli Studi della Campania "Luigi Vanvitelli".
    Gordon, Iouli
    Harvard-Smithsonian Center for Astrophysics, Atomic and Molecular Physics Division, Cambridge, MA .
    Guerlet, Sandrine
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hodges, Joseph T.
    National Institute of Standards and Technology.
    Kassi, Samir
    Univ. Grenoble Alpes, CNRS.
    Lisak, Daniel
    Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University.
    Thibault, Franck
    Institut de Physique de Rennes, UMR CNRS 6251, Université de Rennes .
    Toon, Geoffrey C.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.
    Recent advances in collisional effects on spectra of molecular gases and their practical consequences2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 213, s. 178-227Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We review progress, since publication of the book "Collisional effects on molecular spectra: Laboratory experiments and models, consequences for applications" (Elsevier, Amsterdam, 2008), on measuring, modeling and predicting the influence of pressure (ie of intermolecular collisions) on the spectra of gas molecules. We first introduce recently developed experimental techniques of high accuracy and sensitivity. We then complement the above mentioned book by presenting the theoretical approaches, results and data proposed (mostly) in the last decade on the topics of isolated line shapes, line-broadening and -shifting, line-mixing, the far wings and associated continua, and collision-induced absorption. Examples of recently demonstrated consequences of the progress in the description of spectral shapes for some practical applications (metrology, probing of gas media, climate predictions) are then given. Remaining issues and directions for future research are finally discussed.

  • 46.
    Hayes, Michael
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Gustafsson, Magnus
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Mebel, Alexander M.
    Department of Chemistry and Biochemistry, Florida International University, Miami.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    An improved potential energy surface for the F+H2 reaction2005Inngår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 308, nr 3 Special Issue, s. 259-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new ground state potential energy surface has been developed for the F+H2 reaction. Using the UCCSD(T) method, ab initio calculations were performed for 786 geometries located mainly in the exit channel of the reaction. The new data was used to correct exit channel errors that have become apparent in the potential energy surface of Stark and Werner [J. Chem. Phys. 104 (1996) 6515]. While the entrance channel and saddlepoint properties of the Stark–Werner surface are unchanged on the new potential, the exit channel behavior is more satisfactory. The exothermicity on the new surface is much closer to the experimental value. The new surface also greatly diminishes the exit channel van der Waals well that was too pronounced on the Stark–Werner surface. Several preliminary dynamical scattering calculations were carried out using the new surface for total angular momentum equal to zero for F+H2 and F+HD. It is found that gross features of the reaction dynamics are quite similar to those predicted by the Stark–Werner surface, in particular the reactive resonance for F+HD and F+H2 survive. However, the most of the exit channel van der Waals resonances disappear on the new surface. It is predicted that the differential cross-sections at low collision energy for the F+H2 reaction may be drastically modified from the predictions based on the Stark–Werner surface.

  • 47.
    Kanagarajan, Kathir
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The rate constant for formation of HCl through radiative association2017Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 470, nr 3, s. 3068-3070Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation of HCl in its electronic ground state through radiative association is studied. We ignore spin-orbit couplings and then the formation can happen through two dipole-allowed reactions, one involving an electronic transition and one where the H and Cl atoms approach and remain in the ground electronic molecular state. The radiative association rate constant is computed, through a combination of classical and quantum methods, for use in modelling of interstellar chemistry

  • 48.
    Li, Xiaoping
    et al.
    Department of Chemistry, Michigan State University.
    Harrisson, James F.
    Department of Chemistry, Michigan State University.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University.
    The anisotropic polarizability of pairs of hydrogen molecules and the depolarized collision-induced roto-translational Raman light scattering spectra2010Inngår i: Journal of Computational Methods in Sciences and Engineering, ISSN 1472-7978, E-ISSN 1875-8983, Vol. 10, nr 3-6, s. 367-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In earlier work, Li, Ahuja, Harrison, and Hunt have calculated the collision-induced polarizability Δα of a pair of hydrogen molecules at CCSD(T) level with an aug-cc-pV5Z basis, for 178 relative orientations of the pair, with the bond length in each molecule fixed at r=1.449 a.u. Here we present new results from an expansion of the second-rank tensor components of Δα as series in the spherical harmonics of the molecular orientation angles and the orientation angles of the intermolecular vector. The coefficients in this expansion depend on the separation R between the molecules. We compare the ab initio coefficients with predictions from long-range perturbation theory, including the dipole-induced-dipole interactions at first and second order, higher-multipole induction, effects of nonuniform local fields, hyperpolarization, and van der Waals dispersion. Li and Hunt have derived equations for the long-range coefficients complete to order R^{-6}, using spherical-tensor methods developed by Bancewicz, Głaz, and Kielich for collision-induced light scattering by centrosymmetric linear molecules. We also give new results here for the van der Waals dispersion terms in both isotropic and anisotropic polarizability coefficients. We have calculated these coefficients by 64-point Gauss-Legendre quadrature, using the H_{2} polarizabilities and hyperpolarizabilities at imaginary frequencies computed by Bishop and Pipin, with explicitly correlated wave functions for isolated H_{2} molecules. We show that the ab initio values for the larger anisotropic polarizability coefficients converge to the predictions of the long-range theory, as the separation R between the molecules increases. The coefficients computed ab initio have been used by Gustafsson, Frommhold, Li, and Hunt to calculate the depolarized collision-induced roto-translational Raman spectra of hydrogen gas at 36 K and 50 K out to 800~cm^{-1}, and at 296 K out to 300 cm^{-1}. The general features of the experimental spectra are well reproduced, although the calculated intensities are ∼30% too large over much of the frequency range.

  • 49.
    Li, Xiaoping
    et al.
    Department of Chemistry, Michigan State University, Department of Chemistry, Michigan State University, East Lansing.
    Harrisson, James F.
    Department of Chemistry, Michigan State University.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Wang, Fei
    University of Texas, Physics Department.
    Abel, Martin
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University, East Lansing.
    Collision-induced dipoles and polarizabilities of pairs of hydrogen molecules: Ab initio calculations and results from spherical tensor analysis2012Inngår i: International Conference of Computational Methods in Sciences and Engineering 2009: (ICCMSE 2009); Rhodes, Greece, 29 September - 04 October 2009, Melville, NY: American Institute of Physics (AIP), 2012, s. 100-135Konferansepaper (Fagfellevurdert)
    Abstract [en]

    New ab initio results are reported for the interaction-induced changes in the dipole moments and polarizabilities of pairs of hydrogen molecules, computed using finite-field coupled-cluster methods in MOLPRO 2000 and GAMESS, with an aug-cc-pV5Z (spdf) basis set. Earlier work by X. Li, C. Ahuja, J. F. Harrison, and K. L. C. Hunt, J. Chem. Phys. 126, 214302 (2007), on collision-induced polarizabilities Δα has been extended with 170 additional geometrical configurations of the H2 pairs. In calculations of Δα, we have used a "random field" technique, with up to 120 different field strengths, having components that range from 0.001 to 0.01 a.u. Numerical tests show that the pair dipoles Δμ can be obtained accurately from calculations limited to 6 values of the field in each direction, so this approach has been used to compute Δμ by X. Li, K. L. C. Hunt, F. Wang, M. Abel, and L. Frommhold, Int. J. Spectroscopy 2010, 371201 (2010). We have evaluated the collision-induced dipoles of H2 pairs for 28 combinations of bond lengths (ranging from 0.942 a.u. to 2.801 a.u.), 7 intermolecular separations R, and 17 different relative orientations. In our work on Δα, the bond lengths are fixed at 1.449 a.u. Our results agree well with the previous ab initio work of W. Meyer, A. Borysow, and L. Frommhold, Phys. Rev. A 40, 6931 (1989), and of Y. Fu, C. G. Zheng and A. Borysow, J. Quant. Spectroscopy and Rad. Transfer, 67, 303 (2000)-where those data exist-for Δμ of H2 pairs. For Δα, our results agree well with the CCSD(T) results obtained by G. Maroulis, J. Phys. Chem. A 104, 4772 (2000) for two pair orientations and fixed R. The pair polarizability anisotropies also agree well with the small-basis self-consistent field results of D. G. Bounds, Mol. Phys. 38, 2099 (1979), although the trace of the polarizability differs by factors of 2 or more from Bounds' results. We have determined the expansion coefficients for Δμ and Δα, expressed as series in the spherical harmonics of the orientation angles of the intermolecular vector and of unit vectors along the molecular axes. The leading coefficients converge at long range to the predictions from perturbation theory, derived by J. E. Bohr and K. L. C. Hunt, J. Chem. Phys. 87, 3821 (1987); T. Bancewicz, W. G.az, and S. Kielich, Chem. Phys. 128, 321 (1988); and X. Li and K. L. C. Hunt, J. Chem. Phys. 100, 7875 (1994); ibid, 9276 (1994). Based on our results for Δμ, we find excellent agreement for the binary rototranslational absorption spectrum of H2 at 297.5 K as calculated by X. Li, K. L. C. Hunt, F. Wang, M. Abel, and L. Frommhold, Int. J. Spectroscopy 2010, 371201 (2010) and as determined experimentally by G. Bachet, E. R. Cohen, P. Dore, and G. Birnbaum, Can. J. Phys. 61, 591 (1983), out to ∼1500 cm-1. We have also calculated the vibrational spectra out to 20,000 cm-1, at T = 600 K, 1000 K, and 2000 K, for which there are no experimental data. We are currently working to extend the temperature range in the calculations to 7000 K, for application in modeling the spectra of cool white dwarf stars. We have used the results for Δα to calculate collision-induced rototranslational Raman spectra for H2 pairs [M. Gustafsson, L. Frommhold, X. Li, and K. L. C. Hunt, J. Chem. Phys. 130, 164314 (2009)]. Experimental results for the Raman spectra have been reported by U. Bafile, M. Zoppi, F. Barocchi, M. S. Brown, and L. Frommhold, Phys. Rev. A 40, 1654 (1989); U. Bafile, L. Ulivi, M. Zoppi, F. Barocchi, M. Moraldi, and A. Borysow, Phys. Rev. A 42, 6916 (1990); and M. S. Brown, S.-K. Wang, and L. Frommhold, Phys. Rev. A 40, 2276 (1989). Agreement between our calculations and experiment is good for both the polarized and depolarized spectra, with the remaining discrepancies probably attributable to the difference between the static (calculated) and frequency-dependent (experimental) values of Δα.

  • 50.
    Nyman, Gunnar
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Computational methods to study the formation of small molecules by radiative association2015Inngår i: International reviews in physical chemistry (Print), ISSN 0144-235X, E-ISSN 1366-591X, Vol. 34, nr 3, s. 385-428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To form a stable molecule by association of two colliding fragments, energy must be removed or else the fragments will eventually dissociate again. Energy can be removed by a third body and by emission of a photon, where the latter process is termed radiative association. Radiative association is a ubiquitous process for forming molecules, albeit not so well known as on Earth it is normally outcompeted by three body collisions. In interstellar space however, particularly in regions with little dust (few grains), it can be important. There are only few experimental studies of radiative association as the process is improbable and therefore hard to measure. We will briefly mention the experimental work but our main focus is on theoretical approaches to calculate radiative association cross sections and thermal rate constants. We limit the descriptions to the formation of diatomic molecules. We begin with an introduction to and overview of radiative association. This is followed by a brief section on how cross sections are related to the thermal rate constant. Thereafter we describe methods for obtaining radiative association cross sections, with a bias towards methods that are our own favorites. This will include quantum mechanically based perturbation theory and an optical potential approach that is also quantum mechanically based. From the optical potential method the derivation of a semi-classical method is given. We also describe a recent classical approach that is applicable to transitions within the same electronic state, which the semi-classical approach is not. The semi-classical and classical methods do not treat resonances, which are of quantal origin. We therefore describe Breit–Wigner theory for treating the resonance contribution to the cross sections. Thereafter we review the techniques that are used in the quantum dynamics calculations themselves. The methods discussed are then illustrated in three applications to the formation of diatomic molecules, viz. HF, CO and CN. We end with concluding remarks and summary. In this review we do not discuss electronic structure calculations for obtaining the potential energy and dipole curves that are used in the dynamics calculations.

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