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Grains, or Molecules? Thermal, or non-Thermal?

Published online by Cambridge University Press:  23 September 2016

John R. Barker  and
Isabelle Cherchneff
John R. Barker
Affiliation:
Department of Atmospheric, Oceanic and Space Sciences Space Physics Research Laboratory The University of Michigan Ann Arbor, MI 48109-2143
Isabelle Cherchneff
Affiliation:
Department of Atmospheric, Oceanic and Space Sciences Space Physics Research Laboratory The University of Michigan Ann Arbor, MI 48109-2143

Abstract

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The effects of size and energy on infrared fluorescence (IRF) and on chemical reaction rates are investigated, using polycyclic aromatic hydrocarbons (PAHs) as examples. The range of validity of the Thermal Approximation (TA) is examined. It is found that for properties that have a near-linear dependence on the internal energy, the TA provides an adequate description of the non-thermal, time-dependent processes associated with ultraviolet photon absorption. Since IRF at high energy is nearly linear, the TA is adequate for IRF at high excitation energies, but care must be taken, because the TA fails at low energies. The TA is never adequate for chemical reactions under these conditions.

Type
Section II: The Overidentified Infrared Emission Features
Information
Symposium - International Astronomical Union , Volume 135: Interstellar Dust , 1989 , pp. 197 - 205
Copyright
Copyright © Kluwer 1989 

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