OBSERVATION OF l-TYPE DOUBLING TRANSITIONS IN $HN_{2}^{+}$ USING INFRARED-MICROWAVE DOUBLE RESONANCE SPECTROSCOPY

The l-type doubling in the $\\nu_{2}$ and $\\nu_{1} + \\nu_{2}$ states of the $HN_{2}^{+}$ molecular ion has been studied using infrared microwave double resonance spectroscopy. The molecular constants q and $q_{1}$ were determined for both states from our observed transition frequencies. This work is a continuation of our application of this sensitive technique to molecular ions and represents the first observation of centimeter wave transitions of a molecular ion. The $HN_{2}^{+}$ ion was produced in a hollow cathode discharge at a pressure of 50 mTorr. Microwave transitions for $J=6, 7$, and 8 in the $\\nu_{2}$ state and $J=6$ and 7 in the $\\nu_{1} + \\nu_{2}$ state were pumped with 6 Watts of radiation produced by a centimeter wave synthesizer and amplified by a traveling wave tube amplifier. This radiaiton was introduced into the hollow cathode cell via an X-band waveguide soldered to the hollow cathode. A color center laser served both to saturate the infrared transition and as a probe of the microwave transition. Similar l-type doubling transition were first observed for the isoelectronic neutral HCN. In addition, many collision-induced transitions were observed for HCN.