Vibrational relaxation of C-D stretching vibrations in CDCI_3,CDBr_3,and CDI_3

摘要

We present time-resolved transient grating measurements of the vibrational relaxation rates of the C-D stretching vibrations of deuterated haloforms in benzene and acetone.We compare our results with previous measurements of excited C-H stretches in the same solvents to obtain insight into the solvent effect on the vibrational relaxation.In deuterated molecules,there are more low-order-coupled states and the states are closer in energy to the C-D stretch than in the unlabeled isotopologs.Therefore,the relaxation is faster for the deuterated molecules.The relaxation also shows a significant solvent dependence.Bromoform and iodoform form charge-transfer complexes with both benzene and acetone which enhance the relaxation rate.For chloroform,hydrogen bonding to acetone is expected to be a more favorable interaction.Surprisingly,however,the vibrational relaxation of CDCl_3 is slower in acetone than in benzene.