H$_{2}$O Maser Pumping: The Effect of Quasi-Resonance Energy Transfer in Collisions between H$_2$ and H$_2$O Molecules

TL;DR

This study investigates how quasi-resonance energy transfer in H$_2$ and H$_2$O collisions influences maser pumping, using new rate data to analyze population inversion in various H$_2$O transitions relevant to astrophysical environments.

Contribution

It introduces new state-to-state rate coefficients and demonstrates the significant impact of quasi-resonance energy transfer on H$_2$O maser excitation in astrophysical regions.

Findings

Population inversion depends on para-H$_2$ rotational levels.

Quasi-resonance transfer significantly influences maser pumping.

Implications for maser activity in galactic nuclei and star-forming regions.

Abstract

The effect of quasi-resonance energy transfer in collisions between H$_2$ and H$_2$O molecules in H$_2$O maser sources is investigated. New data on the state-to-state rate coefficients for collisional transitions for H$_2$O and H$_2$ molecules are used in the calculations. The results of ortho-H$_2$O level population inversion calculations for the 22.2-, 380-, 439-, and 621-GHz transitions are presented. The ortho-H$_2$O level population inversion is shown to depend significantly on the population distribution of the para-H$_2$ $J = 0$ and $2$ rotational levels. The possibility of quasi-resonance energy transfer in collisions between H$_2$ molecules at highly excited rotational-vibrational levels and H$_2$O molecules is considered. The quasi-resonance energy transfer effect can play a significant role in pumping H$_2$O masers in the central regions of active galactic nuclei and in star-forming regions.