Stepwise Excitation and Local Thermodynamic Equilibrium on Excited Hydrogen Levels in Helium-Hydrogen Plasma behind Shock Front

The calculation is carried out on the ionization relaxation as well as on the time developments of population densities of excited hydrogen levels for helium-atomic hydrogen mixtures (H: 0∼3 atomic %) behind the reflected shock front under the conditions of the experiment with an electromagnetic T-tube conducted by the present authors. The result gives the shortening of ionization relaxation time depending on mixing ratio of hydrogen and the characteristic initial hump in time development of population density, which is remarkable for low-lying excited levels of hydrogen in a mixture of low hydrogen mixing ratio. The temporal changes of the population and depopulation rates in the relaxation zone are presented for several excited hydrogen levels so that the existence of stepwise excitation between the coronal equilibrium and LTE is illustrated and the validity criterion is proposed for the establishment of LTE.