Improved dynamic hyperpolarizabilities and field-gradient polarizabilities for helium

Abstract

Accurate and explicitly electron-correlated wave functions have been used to determine the dynamic hyperpolarizability tensor (γ) and the dynamic field-gradient polarizabilities (B and C) for helium. The γ-tensor is related to nonlinear optical processes such as the Kerr effect, second- and third-harmonic generation and degenerate-four-wave mixing. In the static limit our results agree completely with a previous highly accurate variational-perturbation treatment. For second-harmonic generation at λ=4880 Å the ratio γzzzz/γxxzz is 2.950, which may be compared with the experimental value of 2.949.