Rotational distribution of para-H2 in He shock wave

Abstract

The rotational distribution and collision number Zr of para-H2 in the He shock wave are studied using the master equation and the quantum mechanical rate constant obtained by Rabitz and Zarur. For high Mach number, at the initial stage, the rotational distribution indicates a merging pattern of two Boltzmann distributions at the lower and higher rotational levels corresponding to the pre-shock temperature T1 and the reduced temperature T2Tc/(T2+Tc), where T2 and Tc are the post-shock and rate-constant temperatures, respectively. The rotational distribution at the final stage indicates a non-Boltzmann distribution with underpopulation at the higher levels, which is also observed for low Mach number. The rotational collision number Zr over the period of the rotational relaxation is found to show a step pattern with the plateaus corresponding to the rotational collision number Zjj′ of the two-level systems (jj′) = (02), (24), (46),....