Dynamic induction of satellite lines in rotational Raman spectra of liquid hydrogen

Abstract

A problem of satellite transitions induced in the vibration-rotation spectra of fastly rotating linear molecules by intermolecular interactions is explored. For this purpose, a dynamic, non-Markov perturbation theory is applied to the rotational Raman spectrum of liquid parahydrogen, where a weak satellite developing at the double frequency was detected and extensively studied by Zoppi et al. (Phys. Rev. A. 53, 1395 (1996); Phys. Rev. B. 55, 12223 (1997)) on the basis of a static perturbation theory. The static approach is presently revised by means of the dynamic line-mixing theory, which gives a more realistic picture of intermolecular interactions. Our approach allows us to calculate all satellite spectral characteristics and shows the satellite-integrated intensity to be two-fold overrated by the static theory. Upon due corrections and with an account for the collision-induced (CI) polarisability terms, the agreement between simulated and measured intensities is cardinally improved. Arguments are given that, on going from gas to liquid, the satellite shape is materially affected by the translational motional narrowing.