ИСТИНА

Hydrogen and Helium discrete level occupation is not stationary behind a shock front in the atmospheres of ($G-M$) stars (shock velocity $20-50$ km/s). This is due to the relatively high excitation energy: all the excited states of the both chemical elements are located very close to the continuun, and far from the base level (in the energy scale). As a consequence, one can not neglect electron impact ionization as compared with discrete transition rates at the least for the levels with the main quantum number $n=2\div5$. This is why we should take into account the exchange between the discrete levels and the continuum, and the discrete level occupation is not stationary, as the continuum one. Chemical elements, such as Magnesium, Iron, and other metals, have discrete level structure different from H and He. Their excited levels lay close to the base level and rather far from the continuum. The ionization rate is small compared to the deexcitation rate, an one can solve separately two differen problems: nonstationary ionization and quasistationary discrete level occupation.