Double shake-off model for the triple photoionization of beryllium

We propose a model for the triple photoionization of Be in which a core 1s electron absorbs the photon gamma + 1s(2) 2s(2) Be --> is an element of(1)p+ 1s2s(2) Be+ and the valence 2s(2) electrons are shaken off into continuum due to the sudden change of the core potential. We decompose the double shake-off amplitude into a single shake-off 2s(2) --> nsis an element ofs and a subsequent electron impact ionization of the doubly charged Be2+ ion is an element ofs + 1sns Be2+ --> is an element of(2)l + is an element of(3)l + 1s Be3+. The latter process is described by the T-matrix of inelastic electron scattering on the 'semi-hollow' 1sns Be2+ ion in the monopole singlet channel. The convergent close-coupling method is used to evaluate the T-matrix.