HO maser pumping: The effect of quasi-resonance energy transfer in collisions between H and HO molecules.

The effect of quasi-resonance energy transfer in collisions between H and HO molecules in HO maser sources is investigated. New data on the state-to-state rate coefficients for collisional transitions for HO and H molecules are used in the calculations. The results of ortho-HO level population inversion calculations for the 22.2-, 380-, 439-, and 621-GHz transitions are presented. The ortho-HO level population inversion is shown to depend significantly on the population distribution of the para-H J = 0 and 2 rotational levels. The possibility of quasi-resonance energy transfer in collisions between H molecules at highly excited rotational-vibrational levels and HO molecules is considered. The quasi-resonance energy transfer effect can play a significant role in pumping HO masers in the central regions of active galactic nuclei and in star-forming regions. [ABSTRACT FROM AUTHOR]