R(V)-DEPENDENT INTERSTELLAR PHOTODESTRUCTION RATES

The photodestruction of molecules is an important process in interstellar chemistry. There are substantial differences in the ultraviolet extinction properties that correlate quite strongly to the value of R(V), the ratio of total to selective extinction. Since interstellar photodestruction rates depend on the level of extinction, we carried out R(V)-dependent rate calculations. Dust scattering parameters were environmentally characterized by deriving grain size distributions as a function of the level of the extinction. Since the interior of dark clouds can be much better illuminated at ultraviolet wavelengths than their nominal optical depth would suggest, photodestruction processes proceed at much faster rates than a direct use of the mean interstellar extinction curve might lead us to predict.