2012ApJ...755..119C

Laboratory evidence suggests that recombination of adsorbed radicals may cause an abrupt temperature excursion of a dust grain to about 1000 K. One consequence of this is the rapid desorption of adsorbed H₂molecules with excitation temperatures of this magnitude. We compute the consequences of injection of hot H₂ into cold diffuse interstellar gas at a rate of 1% of the canonical H₂ formation rate. We find that the level populations of H₂ in J = 3, 4, and 5 are close to observed values, and that the abundances of CH⁺ and OH formed in reactions with hot hydrogen are close to the values obtained from observations of diffuse clouds.