Quadratic response functions for a multiconfigurational self-consistent field wave function

Abstract
We describe an efficient implementation of the quadratic response function for a multiconfiguration self‐consistent field reference wave function. The quadratic response function determines the hyperpolarizability and its residues determine the two‐photon transition matrix elements and the transition matrix elements between excited states. We report sample calculations for the hyperpolarizability of Ne and for the two‐photon transition matrix elements of Ne and H2.