On a possibility of detection of fine structure lines of atomic hydrogen in H2 regions

The emission of hydrogen lines due to transitions between fine structure levels with the small principal quantum number n is considered. The population of the fine structure levels with n=2 are calculated. The 22S1/2 level is more populated than the 22P1/2, and 22P3/2 in H2 regions, because of its metastability. The product bβ, that is the ratio of the actual optical depth of the line to the one in conditions of thermal equilibrium, gives a measure of the stimulated emission or enhanced absorption due to non-LTE effects and is very high: bβ ∼ - (109-1011) for the 22P1/2-22S1/2 transition and bβ ∼ 108-1010 for the 22S1/2-22P3/2 one. The line brightness temperature TL and the line-to-continuum ratio TL/TC are calculated for the Orion Nebulae: TL ∼ 1-30 mK, TL/TC ∼ (2-4)x10-6 for the 22P1/2-22S1/2 transition and TL ∼ -(1-30) mK, TL/TC ∼ -(0.8-1.5)x10-4 for the 22S1/2-22P3/2 in dependence on a telescope directional pattern