TIME-DEPENDENT GAUGE-INVARIANT APPROACH TO THE CALCULATION OF DYNAMIC HYPERPOLARIZABILITIES - APPLICATION TO FH AND LIH

The variation-perturbation approach with a time-dependent electric field is used in order to obtain the third-order energy and to find the first hyperpolarizability with the first-order perturbed function. The function used is the same as the one described in a previous paper [M. Rerat, M. Merawa, and C. Pouchan, Phys. Rev. A 45, 6263 (1992)] relative to dynamic polarizability calculations from a time-dependent gauge-invariant method. Static-hyperpolarizability components are given for FH and LiH and discussed in comparison with previous calculations. Dynamic components are calculated for the electro-optic Pockels effect up to the first resonances.