Anharmonic-potential-effective-charge approach for computing Raman cross sections of a gas.

Abstract

An anharmonic-potential--effective-charge approach for computing relative Raman intensities of a gas is developed. The equations of motion are set up and solved for the driven anharmonic molecular vibrations. An explicit expression for the differential polarizability tensor is derived and its properties discussed. This expression is then used within the context of Placzek's theory [Handbuch der Radiologie (Akademische Verlagsgesellschaft, Leipzig, 1934), Vol. VI] to compute the Raman cross section and depolarization ratio of a gas. The computation is carried out for the small molecules ${\mathrm{CO}}_{2}$, ${\mathrm{CS}}_{2}$, ${\mathrm{SO}}_{2}$, and ${\mathrm{CCl}}_{4}$; results are compared with experimental measurements and discussed.