M. Pont et R. Shakeshaft, ASYMMETRY PARAMETER AND MOMENTUM DISTRIBUTION OF THE NUCLEUS IN DOUBLE PHOTOIONIZATION OF HELIUM, Physical review. A, 54(2), 1996, pp. 1448-1451
We have calculated the asymmetry parameter and the momentum distributi
on of the recoiling nucleus when a helium atom undergoes double ioniza
tion by one (linearly polarized) photon with energy 85, 99, or 159 eV.
An empirical fit, based on representing the dynamical part of the dou
bly differential cross section through a single-parameter Gaussian mod
el, is surprisingly accurate over this energy range.