9531790 Dalgarno Dr. Dalgarno will direct theoretical studies of X-ray dominated regions of space with the intent of identifying specific diagnostic probes that may distinguish between regions ionized by X-rays and by cosmic rays. The infrared response of molecular hydrogen as a function of density will be calculated. The chemistry of deuterated molecular species in the early Universe will be explored. The molecular composition of circumstellar shells will be examined using a refined treatment of radiative transfer. Particular attention will be given to the discrepancy between the present model abundance and the measured abundance of neutral carbon atoms in IRC+10216. Semiclassical calculations of rate coefficients of rovibrational transitions of molecular hydrogen in collision with H will be completed and quantal calculations required for low temperatures will be initiated. Charge transfer collisions of singly charged species interacting with neutral atoms will be studied. ***
