Ab initio potential energy surface and pressure broadening coefficients for the He-CH3F complex |
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Authors: | Béatrice Bussery-Honvault Robert Moszynski Joël Boissoles |
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Institution: | a Laboratoire PALMS, UMR 6627 du CNRS, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France b Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland |
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Abstract: | Symmetry-adapted perturbation theory has been applied to compute the He-CH3F potential with the CH3F molecule assumed rigid. The potential has a global minimum of −48.9 cm−1 at the center of mass separation of 7.2 bohr with the helium atom lying along the C-F bond on the hydrogen’s side. The computed points were fitted to an analytic energy surface with a correct asymptotic behaviour. This potential has been used to compute the pressure broadening (PB) coefficients for the (j, k) = (0, 0) → (1, 0) and (1, 0) → (2, 0) rotational transitions of CH3F perturbed by helium for a wide range of temperatures. Close-coupling results are compared with the experimental data of Willey et al. J. Chem. Phys. 97 (1992) 4723], Beaky et al. J. Mol. Struct. 352/353 (1995) 245] and infinite order sudden results are compared with those of Grigoriev et al. J. Mol. Struct. 186 (1997) 48] for the ν6 band of CH3F perturbed by helium at room temperature. To our knowledge, present work is the first attempt of making fully ab initio calculations of collisional cross-sections and pressure broadening coefficients for this simple symmetric top system at low and room temperature. |
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