VIBRATIONAL HYPERPOLARIZABILITIES AND THE KERR-EFFECT IN CH4, CF4, AND SF6

The hyperpolarizabilities gamma of CH4, CF4, and SF6 were measured by the dc Kerr effect at wavelengths from 457.9 to 1092 nm. Vibrational h yperpolarizabilities gamma(nu) were obtained by combining these measur ements with electric-field-induced second harmonic generation (ESHG) m easurements. The vibrational contribution to the hyperpolarizability r anges from 6% to 35% of the total. At high optical frequency the diffe rence between gamma(nu) for Kerr and gamma(nu) for ESHG is approximate ly constant, and has values 18, 31, and 51 x 10(-63) C-4 m(4) J(-3) fo r CH4, CF4, and SF6, respectively. The experimental results are in goo d quantitative agreement with the results of recent ab initio calculat ions of the frequency dependence of gamma(nu) for CH4, except for a sm all but non-negligible discrepancy at high frequency. (C) 1996 America n Institute of Physics.