On the dissociation of the H2 molecule following electron impact and leading to the obtention of atomic hydrogen in the n = 3 levels

The velocity distribution of H(n=3) atoms produced by electron impact on H2 has been obtained indirectly from the study of anti-crossing signals on the Halpha line of atomic hydrogen. Two distinct groups of velocities have been detected: slow atoms at 8 and 9 km s-1 appear above a threshold at 17.2 eV, fast atoms with a continuous range of velocities between 30 and 40 km s-1 above 27 eV.