DIPOLE, QUADRUPOLE, OCTUPOLE, AND DIPOLE-DIPOLE QUADRUPOLE POLARIZABILITIES AND 2ND HYPERPOLARIZABILITIES AT REAL AND IMAGINARY FREQUENCIES FOR HELIUM IN THE 2(3)S STATE - DISPERSION ENERGY COEFFICIENTS FOR INTERACTIONS BETWEEN HE(2S-3) AND H(1S-2), HE(1S-1), HE(2S-3), OR H-2(X(1)SIGMA(G)+)

We have determined the dynamic dipole (alpha1), quadrupole (alpha2), octupole (alpha3), and dipole-dipole-quadrupole (B) polarizabilities and the second hyperpolarizability tensor (gamma) for the helium atom in its lowest triplet state (2(3)S). We have done so for both real and imaginary frequencies: in the former case, for a range of frequencies (omega) between zero and the first electronic-transition frequency, and in the latter case for a 32-point Gauss-Legendre grid running from zero to HomegaBAR = 20 E(h). We have also determined the dispersion-energy coefficients C6, C-8, and C-10 for the systems (H(1S))-S-2-(He(2S))-S-3, (He(1S))-S-1-(He(2S))-S-3, and (He(2)S))-S-3-(He(2S))-S-3 and C-6(0), C-6(2), C-8(0), C-8(2) and C-8(4) coefficients for the interaction (He(2S))-S-2-H-2(X1SIGMA(g)+). Our values of the higher-order multipolar polarizabilities and of gamma for the 2(3)S state of helium are, we believe, the first to be published.