Ab initio investigation of the sum-frequency hyperpolarizability of small chiral molecules

Using a sum-over-states procedure based on configuration interaction single s /6-311++G**, we have computed the sum-frequency hyperpolarizability beta (ijk)(-3 omega; 2 omega, omega) Of two small chiral molecules, R-monofluoro -oxirane and R-(+)-propylene oxide. Excitation energies were scaled to fit experimental UV-absorption data and checked with ab initio values from time -dependent density functional theory. The isotropic part of the computed hy perpolarizabilities, beta(-3 omega; 2 omega, omega), is much smaller than t hat reported previously from sum-frequency generation experiments on aqueou s solutions of arabinose. Comparison is made with a single-centre chiral mo del. (C) 2000 Elsevier Science B.V. All rights reserved.