ON THE TRACE RAMAN-SCATTERING CROSS-SECTIONS OF BENZENE C6H6,C6D6, AND (C6H6)-C-13 IN THE GAS-PHASE

We have measured the absolute Raman trace scattering cross sections of benzene C6H6 and of its isotopic derivatives C6D6 and (C6H6)-C-13 in the gas phase in order to check for deviations from the double harmonic approximation. Because of the difficulties in working with condensable vapors, we discuss in some detail the effort taken to minimize sources of error in the experimental methods. The measured cross sections for the three isotopic species are consistent within the double harmonic approximation, as demonstrated by their transformation to a set of isotopically invariant intensity parameters. A comparison with previous measurements and ab initio calculations is also given.