Close-coupling calculations of electron capture cross sections from the n=2 states of H by protons and alpha particles

Cross sections for electron capture from the n=2 excited states of atomic hydrogen in collisions with protons and alpha particles are calculated using the semiclassical close-coupling method where the time-dependent wavefunction is expanded in terms of travelling atomic orbitals on each collision centre. The results are compared with existing close-coupling calculations in which molecular orbital expansions were used. The dependence of the total and partial electron capture cross sections on the alignment of the initial excited 2p states is examined.