Positron Impact Excitation of the nS States of Atomic Hydrogen

The excitation cross sections of the nS states, n = 2 to 6, of atomic hydrogen at various incident positron energies (10.23 to 300 eV) were calculated using the variational polarized-orbital method. Nine partial waves were used to obtain converged cross sections. The present results should be useful for comparison with results obtained from other theories and approximations. The positron-impact cross section was found to be higher than the electron-impact cross sections. Experimental and other theoretical results are discussed. The threshold law of excitation is discussed and the cross sections in this region were seen to obey the threshold law proportional to ${(\ln k_f)}^{-2}$ . Cross sections were calculated in the Born approximation also and compared to those obtained using the variational polarized orbital method.