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 115, 50, and $3.8\mathrm{eV}$ excess energies. With the energy of one of the electrons kept fixed, the double-energy-differential cross sections at $115\mathrm{eV}$ excess energy is found to be of “U-shape" (unequal energy sharing), and in very good agreement with ab initio results. At $50\mathrm{eV}$, it seems that a transition starts taking place to more equal energy sharing configurations. Close to threshold, at $3.8\mathrm{eV}$ excess energy, the equal energy sharing configurations are the dominant ones.