LOW TEMPERATURE, TEMPERATURE DEPENDENT PRESSURE BROADENING OF $HCO^{+}$ IN $H_{2}$.

Author Institution: Jet Propulsion Laboratory, Mail Stop 183-301, 4800 Oak Grove Dr., Pasadena, CA 91109.; The Ohio State University, 174 W. 18th Ave, Columbus, OH 43210.This work reports the first low temperature, temperature dependent pressure broadening study of a molecular ion, $HCO^{+}$ in $H_{2}$ gas. A novel new experimental apparatus combining and extending the experimental techniques used to produce large quantities of molecular ions and cool them below their gas phase freezing point was developed and characterized. The diagnostics used to analyze the performance of this cell and the applicability of this technique are discussed. This apparatus was used to determine the cross sections, the pressure broadening parameters and rate constants as a function of temperature. The use of capture theory as a theoretical method for calculating pressure broadening cross sections is proposed and the experimental results are compared to a capture theory model