Relative intensities of totally symmetrical vibrations in the Raman spectrum of completely deuterated neopentane in the gaseous state

The intensities of the Raman lines of the to tally symmetric vibrations of neopentane C(CH3)4 and deuterated neopentane C(CD3)4 in the gaseous state are determined photographically relative to the intensity of the v1 line of CF4, used as an internal standard. Assuming the simple Wolkenstein bond-polarizability theory, observed intensities are used to derive complete force-fields for the to tally symmetric class of vibrations, and it is found that no such field can account satisfactorily for all the intensities as well as all the frequencies. The simple Wolkenstein theory is thus shown to be inadequate. Knowledge of the intensities of C(CD3)4 perm its for the first time a test of the modification of the theory in which Wolkenstein’s assumption, that the polarizability of a bond is not affected by a change of bond orientation, is abandoned. Using an improved 4-parameter field, the modified theory is found to succeed where the simple theory fails.