Knowledge Bank

Protonated molecular ions $H3+,HN2+$, and $H3O-$ 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 $\pm 20K,273\pm 20Kand150\pm 20KforH,HN2+,$ and $H3O+$, 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.