Intermolecular collisions and rotational recurrences

Abstract

The present work is aimed at analyzing the possibility of using rotational coherence spectroscopy (RCS) for obtaining knowledge about peculiarities of intermolecular collisions. By restricting ourselves to the consideration of linear molecules with atomic buffers, we derive simple analytical expressions for the time development of the rotational recurrences (RRs). It is demonstrated that collisions do not change the RR period, but the width, form and the rate of decay of the RRs is very collision specific. The RR time decay is proved to be governed by the rotationally invariant cross-sections σ^λ(j, j₁, j, j₁), describing broadening of individual lines in rotationally resolved spectra, and σ^λ(j, j, j′, j′), describing collisional relaxation of state multipoles. The RRs are severely damped by those collisions that substantially change the magnitude of the angular momentum. The RRs are less affected by the angular momentum reorienting collisions. Therefore, the implementation of RCS for determining the efficiency of the angular momentum change due to collisions appears to be quite promising.

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