Application of the CCC method to the calculation of helium double-photoionization triply differential cross sections

The convergent close-coupling (CCC) formalism is employed to calculate the fully resolved triply differential cross section (TDCS) for helium double photoionization. This is the first ab initio calculation of the kind where all three gauges of the electromagnetic interaction produce TDCS within a few per cent of each other. Comparison is made with the experimental data in the range of photon energies 10-53 eV above the threshold, both for equal and unequal energy sharing. The present calculations agree very well, both in shape and where available in magnitude, with the experimental data obtained at the BESSY storage ring (Berlin, Germany) (Schmidt et al 1996 J. Electron Spectrosc. Relat. Phenom. 79 279 and references therein). In addition, excellent agreement is found with the calculations of Pont and Shakeshaft (1995 Phys. Rev. A 51 R2676).