Various modern spectroscopies have been utilized with considerable success in recent years to probe the dynamics of vibrational and reorientational relaxation of molecules in condensed phases. We have studied the temperature dependence of the polarized and depolarized Raman spectra of various modes in the following dihalomethanes: dibromomethane, dichloromethane, dichloromethane-d2, and bromochloromethane. Among other observed trends, we have found the following: Vibrational dephasing times calculated from the bend) and (C-Br stretch) lineshapes are of the same magnitude in CI^B^. The vibrational dephasing time of [C-D(H) stretch] is twice as long in CD2Cl2 as in CH-^C^, and the relaxation time of (C-Cl …
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Various modern spectroscopies have been utilized with considerable success in recent years to probe the dynamics of vibrational and reorientational relaxation of molecules in condensed phases. We have studied the temperature dependence of the polarized and depolarized Raman spectra of various modes in the following dihalomethanes: dibromomethane, dichloromethane, dichloromethane-d2, and bromochloromethane. Among other observed trends, we have found the following: Vibrational dephasing times calculated from the bend) and (C-Br stretch) lineshapes are of the same magnitude in CI^B^. The vibrational dephasing time of [C-D(H) stretch] is twice as long in CD2Cl2 as in CH-^C^, and the relaxation time of (C-Cl stretch) is greater in CI^C^ than in CD2CI2. Isotropic relaxation times for all three stretching vibrations are significantly shorter in C^BrCl than in CI^C^ or CI^B^. Application of the Kubo model revealed that derived modulation times are close to equal for equivalent vibrations in the various dihalomethanes. Thus, the more efficient relaxation of the A^ modes in CE^BrCl can be attributed almost entirely to the broader mean squared frequency perturbation of the vibrations in this molecule.
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