Photodisintegration of Helium with Velocity-Dependent Potentials

The sum rules of Levinger and Bethe are applied to calculate the integrated (${\sigma }_{\mathrm{int}}$) and bremsstrahlung-weighted (${\sigma }_b$) cross sections of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ by using a two-body central velocity-dependent potential both in ${}_{}{}^1{}_{}{}^{}S$ and ${}_{}{}^3{}_{}{}^{}S$ states. For the wave function we use a modified Irving wave function whose parameters have been determined from a variational calculation of the binding energy of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$. There is reasonably good agreement of our values of ${\sigma }_{\mathrm{int}}$ and ${\sigma }_b$ with those of Goldhammer and Valk and with the experimental values of Gorbunov and Spiridonov. Moreover, our results confirm the conclusion of Dohnert and Rojo that the velocity-dependent correlations increase ${\sigma }_{\mathrm{int}}$ by 14% over the values obtained with purely central forces.