Is the Wannier threshold law for angular distribution in double photoionization of atoms true at practically attainable energies of ejected electrons?

摘要

We calculated ab initio the three-fold differential cross section of a doublesingle-photon Helium photoionization at equal energy sharing, and obtained fromone the Gaussian width parameter, describing the angular interelectroncorrelations, for the total electrons energies range E from 0.1 eV to 100 eV.The results are in excellent agreement with experimental data but indicate thatthe Wannier threshold law for angular distribition is not correct at energiesattainable in modern experiments. It is shown that the Gaussian width parameterdependence on energy is much better described by the modified threshold law,obtained by Kazansky and Ostrovsky [J. Phys. B 26, 2231 (1993)]. Also, weexplored the Gaussian width parameter for a double photoionization of thetargets with the strongly asymmetrical initial state configuration: the atomicHydrogen negative ion and the Helium in the 2s1S and 3s1S excited states. Wefound that the Gaussian width parameter dependence on the total ejectedelectrons energy for this targets has a maximum at low energies. We show alsothat the correlation parameter dependence on the interelectron angle for thesetargets is essentially non-Gaussian and has a number of peaks equal to a numberof initial state radial nodes, that reveals the new abilities for thequalitative analysis of electron structure.