Decay of electronically excited singlet states of molecular hydrogen investigated by electron-photon coincidences

The decay of electronically excited H 2 and D 2 singlet states between 12.2 and 16 eV has been investigated by electron-photon coincidence measurements. Asymmetric structures representing a detectable exponential decay are not due to the lifetime of the initially excited states, but result from a threefold cascade decay. The lifetime of the considered n=3 gerade singlet states delivering light in the visible region is about 33 ns. The influence of predissociation is clearly observed.