Difference frequency laser spectroscopy of the ngr;3fundamental band of NH+2

摘要

The ngr;3band of NH+2in theXtilde;thinsp;3B1ground electronic state was observed in direct absorption with a tunable difference frequency laser spectrometer in the 3 mgr; region, using velocity modulation detection. NH+2and NH+3ions were generated in an ac discharge of He and NH3, or of He, N2, and H2. Fiftyhyphen;three rovibrational transitions were measured and fit to a tripletAhyphen;reduced Hamiltonian to determine rotational, centrifugal distortion, and spinndash;rotation constants. The band origin was found to be ngr;0=3359.932 cmminus;1, in excellent agreement with a recent calculation of Jensen, Bunker, and McLean. Indirect evidence from the spectrum suggested that NH+2is quasilinear, but selection rules prevented a determination of theArotational constant.