The magnetic hyperpolarizability anisotropy of some two-electron systems

Abstract

The magnetic hyperpolarizability η is calculated at the near-Hartree-Fock level for Li⁺, He and H₂. Connections between η and B hyperpolarizabilities are derived. For H₂ values of Δη = 9·76 and 10·31 a.u. (0·26 and 0·28 × 10^-42 (4πϵ₀) cm³ G^-2, respectively) are found in different basis sets. Zero-point averaging adds an estimated 1·7 a.u. to the equilibrium value for the H₂ isotopomer, and field-induced changes in vibration a further 0·2 a.u., to give a total ab initio result that is 78 per cent of the value deduced from the most recent experimental measurement of the Cotton-Mouton constant.