Hydrogen radiative relaxation time

The most drastic effect on the losses of the thermal energy is due to dissociation of molecular hydrogen. According to Fox and Wood (1985) as much as a half of the thermal energy behind the shock front is absorbed due to dissociation of Hg molecules. At the same time photodissociation of Hg molecules in the precursor causes retardation of the collisional ionization in the relaxation zone, whereas the precursor structure is very sensitive to the radiation flowing from the wake (Gillet and Lafon 1983 1984). So, the self-consistent model of the radiative shock is urgently needed. 

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