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  • 1.
    Abel, Martin
    et al.
    Department of Physics, University of Texas, Austin, TX 78712, United States.
    Frommhold, Lothar
    Department of Physics, University of Texas, Austin, TX 78712, United States.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg, SE 412 96 Gothenburg, Sweden.
    Collision-induced absorption at wavelengths near 5 μm by dense hydrogen gas2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 18, article id 181102Article in journal (Refereed)
  • 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 kelvin2010In: 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, p. 251-257Conference paper (Refereed)
    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 association2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 430, no 2, p. 946-950Article in journal (Refereed)
    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, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Nyman, Gunnar
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Spin-orbit and rotational couplings in radiative association of C(3P) and N(4S) atoms2011In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, no 18, article id 184302Article in journal (Refereed)
  • 5.
    Antipov, Sergey V.
    et al.
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Sjölander, Tobias
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden; University of Oxford, Oxford, United Kingdom.
    Nyman, Gunnar
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Rate coefficient of CN formation through radiative association: A theoretical study of quantum effects2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 7, article id 74302Article in journal (Refereed)
  • 6.
    Buser, Michael
    et al.
    Physics Department, University of Texas, Austin, TX 78712, United States.
    Frommhold, Lothar
    Physics Department, University of Texas, Austin, TX 78712, United States.
    Gustafsson, Magnus
    Department of Chemistry, University of Colorado, Boulder, CO 80309-0215, United States.
    Moraldi, Massimo
    Dipartimento di Fisica, Universitá di Firenze, Unitá di Firenze, I-50019 Sesto Fiorentino, via G. Sansone 1, Italy.
    Champagne, Mark H.
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Far-infrared absorption by collisionally interacting nitrogen and methane molecules2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, no 6, p. 2616-2621Article in journal (Refereed)
  • 7.
    Ekman, Jonas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Törlind, Peter
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nilsson, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Öhrwall Rönnbäck, Anna
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Parida, Vinit
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Wolf, Veronika
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dordlofva, Christo
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Mendaza de Cal, Maria Teresa
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Jamali, Maryam
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Roos, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ottemark, Rikard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nieto, Chris
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Soria Salinas, Álvaro Tomás
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Vázquez Martín, Sandra
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nyberg, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Neikter, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindwall, Angelica
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Fakhardji, Wissam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Projekt: Rymdforskarskolan2015Other (Other (popular science, discussion, etc.))
    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 University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    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 −Xe2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 209, p. 232-242Article in journal (Refereed)
    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 University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, Patras GR-26500, Greece.
    Maroulis, George
    Department of Chemistry, University of Patras, Patras GR-26500, Greece.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Contribution from dimers to the collision-induced absorption spectra in an Ar–Kr gas mixture2019In: 24th International Conference on Spectral Lines Shapes 17-22 June 2018, Dublin, Ireland / [ed] John Costello, Patrick Hayden, Emma Sokell, Peter van der Bugt, Institute of Physics (IOP), 2019, article id 012021Conference paper (Refereed)
    Abstract [en]

    We have developed an empirical Barker, Fisher and Watts (BFW) interatomic potential for the Ar–Kr pair along with a dipole moment computed from first principles using Møller–Plesset perturbation theory to second order (MP2). Using these results, we performed molecular dynamics calculations to compute the Ar–Kr collision induced absorption (CIA) spectrum at different temperatures. By comparing them to other calculations using a two body interaction treated with quantum mechanics, we have shown that the difference is due to the dimer's contribution which grows in importance as the temperature is lowered.

  • 10.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Molecular dynamics simulations of collision-induced absorption: Implementation in LAMMPS2017In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 810, no 1, article id 012031Article in journal (Refereed)
    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

  • 11.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabo, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Physics and Materials Science, University of Luxembourg, Esch-sur-Alzette L-1511, Luxembourg.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Molecular dynamics calculations of collision-induced absorption in a gas mixture of neon and krypton2020In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 152, no 23, article id 234302Article in journal (Refereed)
    Abstract [en]

    We continue the development of the in-house molecular dynamics software package SpaCIAL and test it for the computation of the collision-induced absorption coefficients for a neon (Ne) and krypton (Kr) gas mixture. An apodization procedure for the dipole autocorrelation function is implemented and tested. We also carry out a statistical study of the convergence rate with respect to ensemble size. The resulting absorption coefficients show a good accordance with quantum mechanical results. Comparison with laboratory measurements shows agreement within 10%–20% at T = 295 K. At T = 480 K, a larger difference of 40%–80% is observed, which can presumably be explained by experimental uncertainties. For the study, an empirical (Barker, Fisher, and Watts) interaction-potential [Mol. Phys. 21, 657 (1971)] for Ne–Kr has been developed. Ab initio {coupled cluster with singles and doubles (triples) [CCSD(T)]} potentials for Ne–Ne, Kr–Kr, and Ne–Kr have been computed, as well as the CCSD(T) interaction-induced Ne–Kr dipole moment curve.

  • 12.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabo, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, Patras, Greece.
    Maroulis, George
    Department of Chemistry, University of Patras, Patras, Greece.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Collision-induced absorption in Ar–Kr gas mixtures: A molecular dynamics study with new potential and dipole data2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 14, article id 144303Article in journal (Refereed)
    Abstract [en]

    We have implemented a scheme for classical molecular dynamics simulations of collision-induced absorption. The program has been applied to a gas mixture of argon (Ar) and krypton (Kr). The simulations are compared with accurate quantum dynamical calculations. The comparisons of the absorption coefficients show that classical molecular dynamics is correct within 10% for photon wave numbers up to 220 cm−1 at a temperature of 200 K for this system. At higher temperatures, the agreement is even better. Molecular dynamics accounts for many-body interactions, which, for example, give rise to continuous dimer formation and destruction in the gas. In this way, the method has an advantage compared with bimolecular classical (trajectory) treatments. The calculations are carried out with a new empirical Ar–Kr pair potential. This has been obtained through extensive analysis of experimental thermophysical and transport properties. We also present a new high level ab initio Ar–Kr potential curve for comparison, as well as ab initio interaction-induced dipole curves computed with different methods. In addition, the Ar–Kr polarizability and hyperpolarizability are reported. A comparison of the computed absorption spectra with an experiment taken at 300 K shows satisfactory agreement although a difference in absolute magnitude of 10%–15% persists. This discrepancy we attribute mainly to experimental uncertainty.

  • 13.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabó, Péter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Physics and Materials Science, University of Luxembourg, L-1511, Luxembourg.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Direct method for MD simulations of collision-induced absorption: application to an Ar–Xe gas mixture2021In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 276, article id 107926Article in journal (Refereed)
    Abstract [en]

    With the reformulation of the classical equations of collision-induced absorption, we present a method to perform the direct computation of the spectral density function. This way the absorption coefficient can be computed from classical molecular dynamics (MD) without the computationally demanding evaluation of the dipole autocorrelation function. In addition, we have developed an algorithm to extract the bound-to-bound dimer contribution to the MD simulated absorption. The method has been tested on the Ar–Xe rare gas system. Comparisons with quantum mechanical (QM) and conventional MD methods validate the approach. The obtained MD bound-to-bound spectra generally agree in shape and magnitude with QM results, including features stemming from rotations and vibrations of the Ar–Xe dimer.

  • 14.
    Fletcher, Leigh N.
    et al.
    Department of Physics and Astronomy, University of Leicester.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Orton, Glenn S.
    Jet Propulsion Laboratory, California Institute of Technology.
    Hydrogen Dimers in Giant-planet Infrared Spectra2018In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 235, no 1, article id 24Article in journal (Refereed)
    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.

  • 15.
    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 study2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 414, no 4, p. 3547-3550Article in journal (Refereed)
    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.

  • 16.
    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 principles2010In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 108, no 17, p. 2265-2272Article in journal (Refereed)
    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.

  • 17.
    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 University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    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 analysis2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 145, no 3, article id 34303Article in journal (Refereed)
    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

  • 18.
    Golubev, Nikolay V.
    et al.
    Department of Chemistry, M. V. Lomonosov Moscow State University, Moscow 119991, Russian Federation; Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Bezrukov, Dmitry S.
    Department of Chemistry, M. V. Lomonosov Moscow State University, Moscow 119991, Russian Federation.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Formation of the SiP radical through radiative association2013In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, no 34, p. 8184-8188Article in journal (Refereed)
  • 19.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Accurately computed H2–He collision-induced absorption coefficients for modeling of planetary atmospheres2023In: 25th International Conference on Spectral Line Shapes 19/06/2022 - 24/06/2022 Caserta, Italy / [ed] Castrillo, A.; De Rosa, M.; Gianfran, L., Institute of Physics (IOP), 2023, article id 012019Conference paper (Refereed)
    Abstract [en]

    Accurate collision-induced absorption profiles for H2–He pairs, in the rototranslational band of H2, are computed accounting for the full anisotropic interaction potential. The calculations are time consuming and complicated compared to those pursued in the isotropic potential approximation. A machine learning approach is implemented in order to produce highly accurate data on a dense frequency grid, by combining data computed in the full calculation with those from the isotropic approximation. Thus an extensive, highly accurate, data base can be obtained for a set of frequencies, temperatures, and ortho-H2/para-H2 fractions, appropriate for use in modeling of planetary atmospheres, in particular of the gas giants.

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    fulltext
  • 20.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Career achivements of Professor Lothar Frommhold2010In: 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, p. 294-300Conference paper (Other academic)
  • 21.
    Gustafsson, Magnus
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Classical calculations of radiative association in absence of electronic transitions2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 7, article id 74308Article in journal (Refereed)
  • 22.
    Gustafsson, Magnus
    University of Texas, Physics Department.
    Collision-induced Absorption and Anisotropy of the Intermolecular Potential2002Doctoral thesis, comprehensive summary (Other academic)
  • 23.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Diatom-diatom interactions with light: Applications and line shape theoretical aspects2008In: 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, p. 297-301Conference paper (Refereed)
    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

  • 24.
    Gustafsson, Magnus
    Department of Chemistry, University of Gothenburg.
    Far Wing Asymmetry of Rotational Raman Lines in Hydrogen2010In: International Journal of Spectroscopy, ISSN 1687-9449, E-ISSN 1687-9457, Vol. 2010, article id 705896Article in journal (Refereed)
    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.

  • 25.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Formation of NaCl through radiative association: Computations accounting for non-adiabatic dynamics2020In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 153, no 11, article id 114305Article in journal (Refereed)
    Abstract [en]

    The radiative association (RA) rate constant is computed for the formation of the diatomic sodium chloride (NaCl) molecule in the temperature interval 1 K–30 K. At these temperatures, RA of NaCl through non-adiabatic dynamics is important. A scattering program has been implemented to carry out calculations of RA cross sections, accounting for coupled dynamics on the lowest ionic and the lowest neutral diabatic 1Σ+ states. The study shows that the non-adiabatic treatment gives a cross section that exceeds that of conventional adiabatic dynamics by one to four orders of magnitude. The contribution to the RA rate constant from Na and Cl approaching each other in the A1Π state has also been computed using an established quantum mechanical method. Ab initio data from the literature have been used for the potential energy curves, the diabatic coupling, and the electric dipole moments of NaCl.

  • 26.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hydrogen dimer features in low temperature collision-induced spectra2017In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 810, no 1, article id 012017Article in journal (Refereed)
    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.

  • 27.
    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 potentials2010In: 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, p. 240-244Conference paper (Refereed)
    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.

  • 28.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Antipov, Sergey V.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Franz, Jan
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden; Mulliken Center for Theoretical Chemistry, University of Bonn, 53115 Bonn, Beringstr. 4-6, Germany.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Refined theoretical study of radiative association: Cross sections and rate constants for the formation of SiN2012In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 10, article id 104301Article in journal (Refereed)
  • 29.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211, Egypt.
    Collision-induced absorption in Ar-Xe: a comparative study of empirical and ab initio interaction potentials and electric dipole moments2022In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 292, article id 108362Article in journal (Refereed)
    Abstract [en]

    Empirical Barker-Fisher-Watts and modified Tang-Toennies potential energy curves are obtained through fit to experimental vibrational transition energies for argon–argon, xenon–xenon, and argon–xenon pairs. The potentials are tested against experimental thermophysical and transport properties, and agreement is observed. Also, an interaction-induced electric dipole moment curve for the argon–xenon pair is determined through a fit to experimental spectral moments for collision-induced absorption. The argon–xenon potentials and dipole are tested in a complete quantum dynamical calculation of the collision-induced absorption profiles, which can be compared with a laboratory measurement. This provides further analysis of the accuracy of the empirical argon–xenon data, as calculations of absorption profiles are highly sensitive to the input of molecular data.

  • 30.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Forrey, Robert C.
    Pennsylvania State University, Reading, USA.
    Semiclassical methods for calculating radiative association rate constants for different thermodynamic conditions: Application to formation of CO, CN, and SiN2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, ISSN 0021-9606, Vol. 150, no 22, article id 224301Article in journal (Refereed)
    Abstract [en]

    It is well-known that resonances can serve as a catalyst for molecule formation. Rate constants for resonance-induced molecule formation are phenomenological as they depend upon the mechanism used to populate the resonances. Standard treatments assume tunneling from the continuum is the only available population mechanism, which means long-lived quasibound states are essentially unpopulated. However, if a fast resonance population mechanism exists, the long-lived quasibound states may be populated and give rise to a substantial increase in the molecule formation rate constant. In the present work, we show that the semiclassical formula of Kramers and ter Haar [Bull. Astron. Inst. Neth. 10, 137 (1946)] may be used to compute rate constants for radiative association in the limit of local thermodynamic equilibrium. Comparisons are made with quantum mechanical and standard semiclassical treatments, and results are shown for two limits which provide upper and lower bounds for the six most important radiative association reactions leading to the formation of CO, CN, and SiN. These results may have implications for interstellar chemistry in molecular clouds, where the environmental and thermodynamic conditions often are uncertain.

  • 31.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Effects of the anisotrophy of the intermulucular potential2002In: 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, p. 216-227Conference paper (Refereed)
  • 32.
    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 potential2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, article id 54703Article in journal (Refereed)
    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%.

  • 33.
    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 Atoms2001In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 546, no 2, p. 1168-1170Article in journal (Refereed)
    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.

  • 34.
    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 gas2001In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 63, no 5, article id 52514Article in journal (Refereed)
    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.

  • 35.
    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 complexes2003In: 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, p. 3-22Conference paper (Refereed)
  • 36.
    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 K2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 400, no 3, p. 1161-1162Article in journal (Refereed)
    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.

  • 37.
    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 spectra2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, no 12, p. 5427-5432Article in journal (Refereed)
    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.

  • 38.
    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 gas2003In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, no 23, p. 12264-12270Article in journal (Refereed)
    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.

  • 39.
    Gustafsson, Magnus
    et al.
    Department of Chemistry, University of Gothenburg, SE 412 96 Gothenburg, Sweden.
    Frommhold, Lothar
    Department of Physics, University of Texas, Austin, TX 78712-1081, United States.
    Li, Xiaoping
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
    Roto-translational Raman spectra of pairs of hydrogen molecules from first principles2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, no 16, article id 164314Article in journal (Refereed)
  • 40.
    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 potential2000In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, no 9, p. 3641-3650Article in journal (Refereed)
    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.

  • 41.
    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 Potential2001In: Spectral line shapes: volume 11 ; 15th ICSLS, Berlin, Germany, 10 - 14 July 2000 / [ed] Joachim Seidel, Melville, NY: American Institute of Physics (AIP), 2001, p. 425-427Conference paper (Refereed)
  • 42.
    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 spectra2003In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, no 4, p. 1667-1472Article in journal (Refereed)
    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.

  • 43.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    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 pairs2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 548, article id 12027Article in journal (Refereed)
    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.

  • 44.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Leigh, Fletcher
    Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK.
    Orton, Glenn
    Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
    A computational study of hydrogen dimers in giant-planet infrared spectra2019In: 24th International Conference on Spectral Lines Shapes 17-22 June 2018, Dublin, Ireland / [ed] John Costello, Patrick Hayden, Emma Sokell, Peter van der Bugt, Institute of Physics (IOP), 2019, article id 012010Conference paper (Refereed)
    Abstract [en]

    The absorption due to H2–H2 complexes is investigated theoretically. The potential and dipole surfaces for the complex are taken from the literature. Quantum dynamical calculations of the roto-translational absorption spectrum are performed. Special attention is paid to the fine features due to hydrogen dimers, (H2)2, at the centers of the collision-induced rotational S(0) and S(1) transitions. The computed absorption coefficients are used to analyze the spectra of the four giant planets of our solar system.

  • 45.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    Monge-Palacios, Manuel
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden; Departamento de Quimica Fisica, Universidad de Extremadura, 06071 Badajoz, Spain.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
    The rate constant for radiative association of HF: Comparing quantum and classical dynamics2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 18, article id 184301Article in journal (Refereed)
  • 46.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    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+ state2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 448, no 3, p. 2562-2565Article in journal (Refereed)
    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.

  • 47.
    Gustafsson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    The emission spectrum due to molecule formation through radiative association2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 548, article id 12003Article in journal (Refereed)
    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.

  • 48.
    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 filtering2007In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 434, no 1-3, p. 20-24Article in journal (Refereed)
    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.

  • 49.
    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 reactions2005In: Semiclassical and other methods for understanding molecular collisions and chemical reactions, Daresbury: Collaborative Computational Project on Molecular Quantum Dynamics (CCP6), Daresbury Laboratory , 2005, p. 34-42Chapter in book (Refereed)
  • 50.
    Gustafsson, Magnus
    et al.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, United States.
    Skodje, Rex T.
    Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan.
    The state-to-state-to-state model for direct chemical reactions: Application to D+H2 →hD+H2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, no 14, article id 144311Article in journal (Refereed)
12 1 - 50 of 78
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