Calculation of double photoionization of helium using the convergent close-coupling method

Abstract
We use the convergent close-coupling formalism to calculate the double-to-single-photoionization cross-section ratio in helium for photon energies from threshold up to 400 eV. Our results for the velocity and acceleration forms of the electromagnetic interaction operator are very close, and lie in between the measurements of Dörner et al. [Phys. Rev. Lett. 76, 2654 (1996)] and Levin et al. [Phys. Rev. Lett. 76, 1220 (1996)].