X-RAY-INDUCED CHEMISTRY OF INTERSTELLAR CLOUDS

Calculations are reported of the molecular abundances in a cloud subje cted to varying ionizing fluxes and attention is drawn to the molecule s which survive as the intensity is increased. The calculations suppor t the suggestion of Phillips & Lazio (1995) that the absence of HCO+ n ear the hard X-ray source 1E1740.7-2942 may be due to a high X-ray flu x. The calculations also raise the possibility that the anomalous HCN/ CO ratio observed in the Seyfert Galaxy NGC 1068 may be a consequence of X-ray ionization. High abundances are predicted for CN and NO. Obse rvations of these may serve to distinguish between the different scena rios.