The infrared vibrationhyphen;rotation spectrum of NHminus;has been obtained by autodetachment spectroscopy in a coaxial laserndash;ion beam spectrometer. Transitions from thev=0 tov=1 vibrational levels were excited with anFhyphen;center laser, and subsequent autodetachment from thev=1 levels was observed. The apparatus resolution was better than 20 MHz, allowing the resolution of the fine structure and Lgr;hyphen;doubling transitions. The linewidths of the autodetachment resonances revealed some of the dynamics of the autodetachment process. The autodetachment rates were, in general, much greater for the upper Lgr;hyphen;doublet levels of NHminus;(v=1) than for the lower levels. In addition, the increase of the autodetachment rate with rotational energy for the upper levels was much faster than would be predicted if vibrational autodetachment were the primary detachment mechanism. It therefore appears that rotationalhyphen;electronic coupling plays an important role in this system, and the differences in the Lgr;hyphen;doublet autodetachment rates are explained in terms of this mechanism.
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