ON GAS DYNAMICS WITH NONEQUILIBRIUM RADIATIVE AND COLLISIONAL IONIZATION,
BROWN UNIV PROVIDENCE R I
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The dynamics of a gas undergoing nonequilibrium ionization by both radiative bound-free and collisional transitions is formulated. It is shown that collisional ionization rates, if small, must never be completely neglected compared with the radiative rates, so a complementary limit for slow collisional rates does not exist. The ionization rates and emission and absorption coefficients are all evaluated explicitly from statistical results available for the monatomic gas considered. It is shown that spectral complexities can sometimes be removed by expansion in terms of a large thermal parameter, and there emerges rationally a gas which is approximately gray above the edge frequency. The general theory is applied to the strong normal shock wave structued by the nonequilibrium ionization processes. The nature of this problem is examined, the complete structure is computed, the photoionization in the precursor portion of the shock structure is also determined according to the black-body emitter model for comparison, and the spectral as well as a directional approximation are assessed.