title: Line interference effects using a refined Robert-Bonamy formalism: the test case of the isotropic Raman spectra of autoperturbed N2.
abstract: A symmetrized version of the recently developed refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] is proposed. This model takes into account line coupling effects and hence allows the calculation of the off-diagonal elements of the relaxation matrix, without neglecting the rotational structure of the perturbing molecule. The formalism is applied to the isotropic Raman spectra of autoperturbed N2 for which a benchmark quantum relaxation matrix has recently been proposed. The consequences of the classical path approximation are carefully analyzed. Methods correcting for effects of inelasticity are considered. While in the right direction, these corrections appear to be too crude to provide off diagonal elements which would yield, via the sum rule, diagonal elements in good agreement with the quantum results. In order to overcome this difficulty, a re-normalization procedure is applied, which ensures that the off-diagonal elements do lead to the exact quantum diagonal elements. The agreement between the (re-normalized) semi-classical and quantum relaxation matrices is excellent, at least for the Raman spectra of N2, opening the way to the analysis of more complex molecular systems.
authors.affiliation: Institut des Sciences Moléculaires d'Orsay (ISMO), CNRS (UMR8214) and Université Paris-Sud, Bât. 350, Campus d'Orsay F-91405, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Boulet
authors.affiliation: NASA/Goddard Institute for Space Studies and Department of Applied Physics and Applied Mathematics, Columbia University, 2880 Broadway, New York, New York 10025, USA.
authors.forename: Qiancheng
authors.initials: Q
authors.lastname: Ma
authors.affiliation: Institut de Physique de Rennes, UMR CNRS 6251, Université de Rennes 1, Campus de Beaulieu, Bât. 11B, F-35042 Rennes, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Thibault