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M.J. Kaufman (Dept. of Physics, San Jose State University \& NASA/Ames), M.G. Wolfire (Dept. of Astronomy, University of Maryland), D. J. Hollenbach (NASA Ames Research Center), M.L. Luhman (Naval Research Laboratory)
Photodissociation regions (PDRs) make up much of the Interstellar Media of galaxies. We have computed PDR models over a wide range of physical conditions, from those appropriate to giant molecular clouds and diffuse clouds (AV\gtrsim 1) illuminated by the interstellar radiation field to the conditions experienced by molecular clouds in close proximity to massive stars. These models use the most up-to-date values of atomic and molecular data,the latest chemical rate coefficients, and the newest grain photoelectric heating rates which include treatments of small grains and large molecules. In addition, we examine the effects of metallicity on the predicted line intensities. Results are presented for PDR models with densities over the range n=101\,-\,107\,\rm cm-3 and for incident far-ultraviolet radiation fields over the range G0=10-0.5\,-\,106.5 (where G0 is the FUV flux in units of the local interstellar value), for metallicities Z=1 and 0.1 times the local Galactic value,and for a range of PDR cloud sizes. We present line strength and/or line ratio plots for a variety of useful PDR diagnostics: [C~II] 158\mum, [O~I] 63\mum and 145\mum, [C~I] 370\mum and 609\mum, CO J=1-0, J=2-1, J=3-2, J=6-5 and J=15-14, as well as the strength of the far-infrared continuum. These plots will be useful for the interpretation of Galactic and extragalactic far infrared and submillimeter spectra observable with the Infrared Space Observatory, the Stratospheric Observatory for Infrared Astronomy, the Submillimeter Wave Astronomy Satellite, theFar Infrared and Submillimeter Telescope and other orbital and suborbital platforms. As examples, we apply our results to ISO and ground based observations of M82, the Large Magellenic Cloud, and several normal galaxies.