The role of symmetry in variational continuum distorted-wave models of electron capture by protons from hydrogen

By considering the asymptotic forms of continuum distorted-waves (CDWs) we present a new variational CDW ansatz which uniquely lifts the degeneracy between outgoing and incoming waves. When the target and projectile charges are equal, this ansatz has the important property that the wavefunctions form a time-symmetric basis set. We perform a two-state calculation employing this new time-symmetric ansatz for the specific case of charge transfer between protons and atomic hydrogen in the ground state. We calculate total cross sections in the energy range 10-1000 keV and show that the results at low and intermediate energies are significantly improved over previous two-state coupled channel continuum distorted-wave theories.