TIME-DEPENDENT FLUORESCENT H-2 EMISSION

We present computations of the time-dependent infrared fluorescent emission-line response of molecular hydrogen (H-2) gas in interstellar clouds exposed to far-ultraviolet radiation fields. In clouds exposed to intense fields the H-2 line intensities may be much larger at early times immediately following the onset of irradiation than under conditions of static equilibrium. Time-dependent effects in evolving photon-dominated regions may be important in the fluorescent H-2 emitting regions in planetary and reflection nebulae and possibly in starburst galaxies and active galactic nuclei.