CALCULATION OF THE POLARIZABILITY AND HYPERPOLARIZABILITY TENSORS, AT IMAGINARY FREQUENCY, FOR H, HE, AND H2 AND THE DISPERSION POLARIZABILITY COEFFICIENTS FOR INTERACTIONS BETWEEN THEM

Accurate calculations of the polarizability and hyperpolarizability tensors at imaginary frequency, alpha(-i-omega;i-omega) and gamma(-i-omega;i-omega,0,0), for H, He, and H2 are reported for a range of frequencies (omega) useful for Gauss-Legendre quadrature. They have been used to evaluate the dispersion polarizability coefficients which govern the nonclassical contribution to the change in electronic polarizability due to long-range interactions between the aforementioned species. Previously, these coefficients have only been found by more approximate methods. The basis of the calculations of alpha(-i-omega;i-omega) and gamma(-i-omega;i-omega,0,0) was the sum-over-states method and, for He and H2, electron correlation was explicitly taken into account. With respect to gamma(-i-omega;i-omega,0,0), we believe these to be the first calculations of any kind.