Production of excited hydrogen atoms by photodissociation of the H2 molecule near threshold

Abstract
The photodissociation of the hydrogen molecule near the dissociation threshold into H(1s)+H(2s,2p) states is considered. The experimentally observed formation of H(2p) can only be explained by the interaction of the covalent and ionic electronic states of the H2 molecule at large internuclear distances in the vicinity of the avoided crossing of the potential curves. The theory is based on the Landau-Zener model with a quantum description of nuclear motion. The calculated relative yields of H(2s) and H(2p) atoms are 59.8% and 40.2% compared with 57% and 43% obtained in a recent experiment (Mental and Guyon (1977)).