TIME-DEPENDENT FLUORESCENT H-2 EMISSION

We present computations of the time-dependent infrared fluorescent emi ssion-line response of molecular hydrogen (H-2) gas in interstellar cl ouds exposed to far-ultraviolet radiation fields. In clouds exposed to intense fields the H-2 line intensities may be much larger at early t imes immediately following the onset of irradiation than under conditi ons of static equilibrium. Time-dependent effects in evolving photon-d ominated regions may be important in the fluorescent H-2 emitting regi ons in planetary and reflection nebulae and possibly in starburst gala xies and active galactic nuclei.