Theoretical investigation of the nonlinear optical properties ofH2andD2: Extended basis set

Calculations are reported of the dynamic second hyperpolarizabilities (γ) of ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ which are relevant to three different nonlinear optical processes. They have been carried out using an expanded basis set for the Δ states that occur in the sum-over-states formula. There is extremely good agreement with recent electric-field-induced second-harmonic-generation experiments; e.g., the experimentally derived static, averaged, γ${\mathrm{¯}}_{\mathrm{?}}$ (electronic) for ${\mathrm{H}}_2$ is 686±4 ${\mathit{e}}^4$ ${\mathit{a}}_0^4$ ${\mathit{E}}_{\mathit{h}}^{\mathrm{-}3}$, whereas our value is 683 ${\mathit{e}}^4$ ${\mathit{a}}_0^4$ ${\mathit{E}}_{\mathit{h}}^{\mathrm{-}3}$. Values of the dynamic B and C polarizabilities are also given.