4-BODY CDW APPROXIMATION - DEPENDENCE OF PRIOR AND POST TOTAL CROSS-SECTIONS FOR DOUBLE CHARGE-EXCHANGE UPON BOUND-STATE WAVE-FUNCTIONS

Double electron capture by fast protons from helium (p + He --> H- + alpha) is examined by means of the strict four-body generalization of the continuum distorted wave (CDW) approximation, without any reference to the commonly employed independent particle model. We investigate the sensitivity of the ''prior'' Q(if)- and ''post'' Q(if)+ forms of the total cross sections to the choice of the ground state wave functions for He and H-. Three different orbitals due to Hylleraas, Green et al. and Lowdin yield results which are in mutual agreement to within 40% at impact energies greater than or equal to 100 keV. The so-called ''post-prior'' discrepancy is also dependent upon the choice of the bound state wave functions. At incident energies E greater-than-or-equal-to 100 keV, the values of the ratio of the ''post'' to the ''prior'' cross sections belong to the intervals [1.0, 1.3], [0.6, 0.9] and [0.8, 1.0] for the orbitals of Hylleraas, Green et al. and Lowdin, respectively.