Non-Equilibrium Populations of Hydrogen in High-Redshift Galaxies
  We investigate the possibility of maser amplification in hydrogen
recombination lines from the galaxies of first generation, at z<~30. Combining
analytical and computational approaches, we show that the transitions between
the hydrogen Rydberg energy levels induced by the radiation from the ionizing
star and by the (warmer than currently) Cosmic Microwave Background can produce
noticeable differences in the population distribution, as compared with
previous computations for the contemporary H+ regions, most of which ignored
the processes induced by the star radiation. In particular, the low (n<~30)
alpha-transitions show an increased tendency toward population inversion, when
ionization of the H+ region is caused by a very hot star at high redshift. The
resulting maser/laser amplification can increase the brightness of the emitted
lines and make them detectable. However, the limiting effects of maser
saturation will probably not allow maser gains to exceed one or two orders of
magnitude.
