The isotropic spectrum of the CO2 Raman 2ν3 overtone: A line-mixing band shape analysis at pressures up to several tens of atmospheres

摘要

A line-mixing shape analysis of the isotropic remnant Raman spectrum of the 2ν3 overtone of CO2 is reported at room temperature and for densities, ρ, rising up to tens of amagats. The analysis, experimental and theoretical, employs tools of non-resonant light scattering spectroscopy and uses the extended strong collision model (ESCM) to simulate the strong line mixing effects and to evidence motional narrowing. Excellent agreement at any pressure is observed between the calculated spectra and our experiment, which, along with the easy numerical implementation of the ESCM, makes this model stand out clearly above other semiempirical models for band shape calculations. The hitherto undefined, explicit ρ-dependence of the vibrational relaxation rate is given. Our study intends to improve the understanding of pressure-induced phenomena in a gas that is still in the forefront of the news. © 2011 American Institute of Physics Article Outline INTRODUCTION EXPERIMENTAL THEORY Allowed Raman line positions Allowed Raman line intensities Band shape modeling The motional narrowing The extended strong collision model RESULTS AND DISCUSSION SYNOPSIS