Dipole, quadrupole, octupole, and dipole–octupole polarizabilities at real and imaginary frequencies for H, HE, and H2 and the dispersion‐energy coefficients for interactions between them

Abstract

AbstractWe have calculated certain dynamic polarizabilities (for both real and imaginary frequencies) for H, He, and H2 and the dispersion‐energy coefficients for long‐range interactions between them. We have done so in a sum‐over‐states formalism with explicitly electron‐correlated wave functions to describe the states. To be precise, we have determined the dipole (α1), quadrupole (α2), and octupole (α3) polarizabilities of H and He for real frequencies (ω) in a range between zero and the first electronic‐transition frequency and for imaginary frequencies (iω) on a 32‐point Gauss‐Legendre grid running from zero to ħω = 20 Eh, and for H2, we have found the dipole (α), quadrupole (C), and dipole–octupole (E) polarizability tensors for the same real and imaginary frequencies. The dispersion‐energy coefficients, obtained by combining the sum‐over‐states for‐malism for the polarizabilities with analytic integration over ω, gave values of C6, C8, and C10 for the atom–atom systems; C, C, C, C, and C for the atom–diatom systems; and C6, C and C for the H2H2 system. Nearly all the results are considered to be more reliable than those hitherto published and some have been obtained for the first time, e.g., C(iω), E(ω), and E(iω) for H2 and C, C, and C for the HH2 system. © 1993 John Wiley & Sons, Inc.