Kerr constants, depolarization ratios, and hyperpolarizabilities of substituted methanes

The static Kerr constants of eight substituted methanes in the gas phase have been measured by a low-frequency null technique. Combining these results with gas phase depolarization ratio measurements we show that the hyperpolarizability contributions to the Kerr constant are small except for CH3F. The magnitudes of the hyperpolarizabilities obtained are in good agreement with the values obtained from second harmonic generation measurments. In the case of nitromethane the electric birefringence and depolarization ratio measurements are combined to obtain the three principal values of the polarizability tensor.