The Effects of OH Collision Rates on the Production of OH MASERS

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Session 34 -- Atomic and Nuclear Astrophysics
Display presentation, Wednesday, June 14, 1995, 9:20am - 6:30pm

[34.01] The Effects of OH Collision Rates on the Production of OH MASERS

Eric Gauthier and Phil Lockett (Centre College//600 W. Walnut//Danville,KY 40422)

The modeling of astrophysical masers requires detailed calculations of the populations of molecular energy levels that are far from thermal equilibrium. These calculations require knowledge of all the physical processes that can transfer molecules from one level to another. The radiative rates are known fairly accurately, but the same cannot be said of the collision rates, for which one must usually rely on theoretically calculated collision cross sections of unknown accuracy. The early studies of the OH maser utilized simple hard sphere collision rates. In the 1980's, quantum mechanically calculated collision rates first became available for the lambda doublet transitions. (Dewangan et al. 1987) Collision rates for the hyperfine transitions have recently become available (Offer et al. 1994). There are significant differences in these rates and we have conducted a detailed study of their effects on the OH maser production. We will present a thorough comparison of the different cross sections and describe how maser production is affected. /newline Dewangan, D.P., Flower, D.R., & Alexander, 1987, MNRAS,226,505. /newline Offer, A., van Hemert, M., van Dishoeck, E. 1994, J.Chem.Phys.,100,362.

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