Orientation parameters and dipole moments of He+ (n=2) states in He2++H collisions: comparison of CTMC and close-coupling results

Abstract

The orientation parameter and the dipole moment of the n=2 states of He+ resulting from electron capture in He2++H collisions are examined using the classical trajectory Monte Carlo (CTMC) method and the close-coupling expansion using two-centre atomic orbitals at 10, 25 and 50 keV amu-1. It is shown that the orientation parameters calculated from the two theories are in good agreement but large discrepancies exist for the dipole moments. Together with previous similar comparisons for p-H collisions, the authors conclude that the CTMC method is not reliable in predicting the coherence parameters of excited states formed in atomic collisions.