ROVIBRATIONALLY RESOLVED DIRECT PHOTODISSOCIATION THROUGH THE LYMAN AND WERNER TRANSITIONS OF H{sub 2} FOR FUV/X-RAY-IRRADIATED ENVIRONMENTS
- Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, GA 30602-2451 (United States)
- Math, Computers, Geology, and Physics Department, University of Cincinnati, Clermont Campus, Batavia, OH 45103 (United States)
- Department of Physics and Astronomy, University of Kentucky, Lexington, KY (United States)
- Centre for Excellence in Basic Sciences, UM-DAE, Vidhyanagari Campus, Mumbai-400098 (India)
- AWE plc, Aldermaston, Reading RG7 4PR (United Kingdom)
Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H{sub 2} through the B{sup 1}{Sigma}{sup +}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Lyman) and C{sup 1}{Pi}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 A to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and X-ray-dominated regions (XDRs). The models, which used the CLOUDY plasma/molecular spectra simulation code, demonstrate that direct photodissociation is comparable to fluorescent dissociation (or spontaneous radiative dissociation, the Solomon process) as an H{sub 2} destruction mechanism in intense far-ultraviolet or X-ray-irradiated gas. In particular, changes in H{sub 2} rotational column densities are found to be as large as 20% in the XDR model with the inclusion of direct photodissociation. The photodestruction rate from some high-lying rovibrational levels can be enhanced by pumping from H Ly{beta} due to a wavelength coincidence with cross-section resonances resulting from quasi-bound levels of the upper electronic states. Given the relatively large size of the photodissociation data set, a strategy is described to create truncated, but reliable, cross-section data consistent with the wavelength resolving power of typical observations.
- OSTI ID:
- 22011800
- Journal Information:
- Astrophysical Journal, Vol. 746, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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