Stancil, P. C. ; Gay, C. D. ; Cieszewski, R. M. ; el-Qadi, W. ; Kuri, A. ; Miyake, S. ; Abel, N. ; Porter, R. L. ; Shaw, G. ; Ferland, G. J. ; van Hoof, P. A. M.

published in Bulletin of the American Astronomical Society, 43, pp. 134.03 (2011)

Abstract: Molecules are primarily destroyed in diffuse and translucent regions, in protoplanetary disks, in cool stellar atmospheres, in photodissociation regions, and in x-ray dominated regions via photodissociation (PD) due to the incident radiation field. The majority of astrochemical/spectral modeling codes available today use pre-computed exponentially-attenuated photorates based on dust scattering/absorption for an ``average" interstellar cloud. Since there is clearly a large scatter in the dust properties and local radiation field for various environments in the Galaxy and beyond, the adoption of such pre-computed photorates can lead to considerable errors in predicted abundances. To improve current modeling capabilities, we are computing new rovibrationally-resolved PD cross sections for H_2, HD, HeH+, NH, C_2, CN, and CS and implementing the cross sections in the spectral simulation code Cloudy for explicit computation of local photorates. We present model results using the new photodissociation cross sections for a variety of environments emphasizing differences in total and state-specific molecular column densities. This work was partially supported by NASA grants NNG06GJ11G and HST-AR-11776.01-A, NSF grant AST-0607733, and the PRODEX Programme of ESA.

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