Highhyphen;resolution measurement of the infrared rotationndash;vibration spectrum of the negative molecular ion15NHminus;: Isotopic shifts and equilibrium constants

摘要

A coaxial ion beam/laser beam spectrometer has been used to measure 52 transitions in the fundamental rotationndash;vibration band of the Xthinsp;2Pgr; electronic state of the molecular anion15NHminus;. InfraredP,Q, andRhyphen;branch transitions (2950ndash;3320 cmminus;1) are excited by a color center laser beam to autodetaching states, and the fast neutral NH is detected. The uncertainty (1 SD) is 0.01 cmminus;1. The spectroscopic constants returned by a leasthyphen;squares fit to an effective Hamiltonian have been combined with our previous results on14NHminus;to yield equilibrium vibrational constants ohgr;eand ohgr;exefor both isotopes (cmminus;1): ohgr;e(14NHminus;)=3191.5plusmn;2.1, ohgr;exe(14NHminus;)=85.6plusmn;1.9, ohgr;e(15NHminus;)=3184.4plusmn;2.1, and ohgr;exe(15NHminus;)=85.2plusmn;1.9. There is good agreement with the theoretical calculation for14NHminus;by Manz, Zilch, Rosmus, and Werner: ohgr;e=3179, ohgr;exe=89. The electron affinity has been measured: EA(15NH)=0.3761plusmn;0.0025 eV.