A THEORETICAL DESCRIPTION OF ELECTRON-CAPTURE BY H+ FROM HE+ IONS USING SYMMETRIZED VARIATIONAL CONTINUUM DISTORTED WAVES

We present total cross sections in the laboratory energy range 17.5-50 0 keV amu(-1) for electron capture by protons in collision with He+(1s ). We describe this process theoretically by performing a close-coupli ng (CC) calculation using the symmetrized variational (SV) continuum d istorted-wave (CDW) collision ansatz. We discuss the SVCDW results in conjunction with another CC variational CDW calculation, with CDW pert urbation theory, and also with close-coupling calculations which invol ve a representation of the continuum by a set of pseudo-states which m ay include pseudo-states of the united atom. Moreover, we compare the SVCDW results with the available experimental data. The SVCDW results are found to be in very good agreement with the experiments of Peart e t al, Rinn et al and Watts et al at all energies, and consequently to be at variance with the experimental results of Angel et al. The SVCDW results are also found to be in good accord with a CC calculation inv olving Sturmian-type pseudo-states. We investigate this agreement furt her by comparing impact-parameter profiles at 50 and 17.5 keV amu(-1).