Double energy differential cross sections for the Coulomb four-body problem in a quasiclassical framework

In a quasiclassical framework, we formulate the double energy differential cross sections for the Coulomb four-body problem. We present results for the triple photoionization from the Li ground state at 220.5, 115, 50 and 3.8 eV excess energies. With the energy of one of the electrons kept fixed, the double energy differential cross sections at 220.5 and 115 excess energies are found to be of "U-shape" (unequal energy sharing), with those at 115 eV being in very good agreement with ab-initio results. At 50 eV, it seems that a transition starts taking place to more equal energy sharing configurations. Close to threshold, at 3.8 eV excess energy, the equal energy sharing configurations are the dominant ones.