Detection and measurement of ro-vibrational populations in molecular hydrogen

Abstract
A technique has been developed for measuring ro-vibrational populations in H2 and its isotopes based on the observation of near-zero energy H- (D-) yields produced by the dissociative attachment process when a low energy electron beam interacts with the gas molecules. The method is sensitive in H2 to a number density of molecules of 1011 cm-3 for the v=0 level and rises to 5*105 cm-3 for high levels (v>5). In principle the maximum level that can be detected using this technique is v=9 for H2, v=10 for HD and v=13 for D2.