Experimental evidence for the formation of H₃* by H ₅⁺/e^- dissociative recombination

The effects of temperature and hydrogen density on the efficiency of production of H₃* Rydberg levels in a hollow cathode discharge are determined by monitoring the 3s²A₁′→2p ²A₂″ transition of H₃*. Kinetic modeling of the ion-molecule reactions occurring in the discharge indicates that the observed H₃* spectral intensity dependence on discharge temperature and density can be accounted for if it is assumed that H ₅⁺/e^- dissociative recombination is the primary process leading to H₃* formation. The previously observed extensive Doppler-like broadening of the H₃* emission lines is explained in terms of the dissociative kinetic energy release of H ₅**.