Deviation from a Maxwellian velocity distribution in regions of interstellar molecular hydrogen

Abstract

view Abstract Citations (5) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Deviation from a Maxwellian velocity distribution in regions of interstellar molecular hydrogen. Gould, R. J. ; Levy, M. Abstract The deviation from a Maxwellian velocity distribution caused by excitation of the J = 2 rotational level of parahydrogen (followed by radiative decay) in a molecular hydrogen gas is investigated. It is noted that inelastic collisions deplete the high-velocity tail of the distribution, while elastic collisions tend to refill it; the resulting steady-state distribution has a small depletion in the tail which slightly reduces the cooling rate of the gas. The elastic-collision transport is approximated by a continuous process, a simplified expression is obtained for the inelastic-collision operator, and the Boltzmann equation is then solved analytically. A correction to the inelastic-collision rate is evaluated, and it is found that the relative magnitude of the effect of tail depletion on the inelastic-collision rate is strongly temperature-dependent. The critical molecular density above which the J = 2 level deexcites by superelastic collisions is shown to be a weak function of temperature. Publication: The Astrophysical Journal Pub Date: June 1976 DOI: 10.1086/154397 Bibcode: 1976ApJ...206..435G Keywords: Boltzmann Transport Equation; Hydrogen Clouds; Interstellar Gas; Maxwell-Boltzmann Density Function; Molecular Gases; Velocity Distribution; Collision Rates; Elastic Scattering; Inelastic Collisions; Molecular Collisions; Operators (Mathematics); Astrophysics full text sources ADS |