HIGH-ORDER MULTIPOLAR HYPERPOLARIZABILITIES WITH IMAGINARY FREQUENCY FOR H AND HE

Calculations are reported of X(zz,zz,z,z)(3)(-i omega; i omega, 0, 0), X(zz,zz,x,x)(3)(-i omega, i omega, 0, 0), X(zzz,z,z,z)(3)(-i omega; i omega, 0, 0), X(zz,z,z,z,z)(4)(-i omega; i omega, 0, 0, 0), and X(zz, x,x,z,z)(4)(-i omega; i omega, 0, 0, 0) for H and He. These are the in dependent components of the atomic (quadrupole)(2)-(dipole)(2), (octup ole)-(dipole)3, and (quadrupole)-(dipole)(4) hyperpolarizability tenso rs for an imaginary frequency i omega. The first three quantities have been used for the determination of the R(-8) dispersion contribution to the H-H, H-He, and He-He collision-induced pair polarizability func tions. The last two quantities will be needed in future calculations o f the leading order (R(-7)) dispersion contributions to the collision- induced first hyperpolarizability (beta) for the H-He pair. The calcul ations were based on sum-overstates formulations with near-exact wave functions for H and highly accurate explicitly electron-correlated wav e functions for He. For this reason we believe them to be of benchmark quality. (C) 1996 John Wiley & Sons, Inc.