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JENNIFER L. GOTTFRIED, CHRISTOPHER P. MORONG AND TAKESHI OKA, Department of Chemistry, Department of Astronomy & Astrophysics, and the Enrico Fermi Institute, University of Chicago, Chicago, IL 60637.
Like its isoelectronic cousins BH2- and CH2, the amidogen cation NH2+ has a quasilinear ground state X3B1 with a low barrier to linearity (155~cm-1) and metastable excited electronic states a1A1 and b1B1 that become degenerate (1
) at linearity. In addition to its theoretical interest (due to the quasilinearity and the Renner effect), NH2+ is one of the most fundamental molecular ions that exist abundantly in laboratory plasmas containing hydrogen and nitrogen. Despite this, only two high-resolution experimental detections of NH2+ have been reported (the observation of the antisymmetric N-H stretch at 3360~cm-1, and four hot bands from 2900-3500~cm-1).
In an attempt to observe the predicted near-infrared electronic absorption spectrum of NH2+, we have recently obtained new spectra of positive ions in a liquid-nitrogen-cooled positive column He/N2/H2 plasma. The spectra were recorded using a high-resolution, high-sensitivity spectrometer based on a Ti:sapphire laser (11,000-13,000~cm-1) and incorporating velocity modulation, phase modulation with heterodyne detection, noise subtraction, and optical multi-passing. The observation and assignment of the spectra is complicated by the presence of thousands of lines from the A2
u - X2
g+ system of N2+. We will report the results of our analysis of the new spectra.