Polarizability of helium and the negative hydrogen ion

The authors have carried out precision calculations of the dipole and quadrupole polarizabilities of helium and the negative hydrogen ion and their non-adiabatic extensions. These quantities are obtained from second-order perturbation sums involving energy denominators raised to the power k=1, 2 or 3. The summation over intermediate states is carried out using Hylleraas two-particle wavefunctions of the appropriate symmetry and angular momentum. The measured mass of the nucleus is retained. The convergence is excellent for the helium case and somewhat poorer for H $ .