Motional narrowing of the rotational Raman band of compressed CO, N2, and CO2

Abstract

The depolarized rotational Raman, and depolarized Rayleigh spectra of compressed CO, N2, and CO2 were measured. The spectra, particularly that of CO2, show motional narrowing, collapsing to a single line at the laser frequency. The spectra are interpreted in terms of the J diffusion model and in terms of a simple two-line model spectrum. From the analyses, an empirical method is established for estimating the density at which motional narrowing will occur in rotational Raman bands. Two minor shortcomings in the J diffusion model are also identified.