EXCITATION IN H(1S)-H(1S) COLLISIONS

Excitation cross sections have been calculated using a close-coupling approach involving two-centre single and double excited states for H-H collisions in the energy range 1-100 keV. The present results are in agreement with one of the two independent sets of measurements for the excitation H(2s) cross sections. For H(2p) cross sections the discrep ancies between previous calculations and the only set of existing meas urements remain unresolved. The present calculations indicate that the cross sections have a strong dependence on the total electronic spin: at low energies the cross section is dominated by triplet states, whe reas singlet states contribute mostly at intermediate energies.