Frequency Dependence of the Hyperpolarizability Measured for Sf,

The second hyperpolarizability 7 of a molecule plays a role in non-linear optical processes [ 1,2] as well as in intermolecular interactions [3,4]. Usually y(--wo; WI, ~2, ~3) is measured by optical methods such as the dc Kerr effect, electric-field-induced second-harmonic generation (ESHG) of third-harmonic generation (THG), where these processes differ in the choice of the frequency arguments [2,5-7]_ In so far as the relevant y for intermolecular processes is the zero-frequency limit of the general 7, and because most calculations relate to the static limit, it would be useful to have information about the dispersion of 7_ Here we present measurements of the frequency dependence of y(--2~; w, w, 0) (i.e. the ESHG process) for the SF6 molecule, as well as a discussion of the relation between the various optical hyperpolarizabilities and the static hyperpolarizability.