INFRARED ABSORPTION SPECTROSCOPY OF JET-COOLED MOLECULAR IONS

$^{1}$T. Amano. J. Chem. Phys. 92, 6492 (1990)Author Institution: Advanced Technology Research Center, Mitsubishi Heavy Industries Ltd.; Department of Chemistry, University of North Carolina; Herzberg Institute of Astrophysics, National Research Council of Canada; Department of Physics, Ibaraki UniversityProtonated molecular ions $H^{+}_{3}, HN^{+}_{2}$, and $H_{3}O^{-}$ generated in a ``hollow-cathode” type discharge jet have recently been studied using infrared absorption spectroscopy. The rotational temperatures of these ions in the ground state were determined to be 120 $\pm 20K, 273 \pm 20 K and 150 \pm 20 K for H, HN^{+}_{2},$ and $H_{3}O^{+}$, respectively. This observation suggests different dynamics of ion formation under jet-expansion compared to usual hollow-cathode discharge cells, in which the rotational temperatures of the ions are determined by the temperature of the $coolant.^{1}$ The spectral linewidths and the concentrations of the ions at different positions of the jet stream will also discussed to shed light on the dynamic characteristics of the hollow-cathode discharge jet