Resonant two-photon ionization spectroscopy of NiC

A spectroscopic investigation of jet-cooled diatomic NiC has revealed a complex pattern of vibronic levels in the wave number range from 21 700 to 27 000 cm-1. Of the more than 50 vibronic bands observed, 31 have been rotationally resolved and analyzed. All are ?'=0+??"=0+ transitions, consistent with the calculated 1S1 ground state of this molecule. Through the observation of vibrational hot bands in the spectra, these measurements have established that ?"e=875.155 cm-1, ?exe=5.38 cm-1, Be=0.640 38(14) cm-1, ?e=0.004 44(36) cm-1, and re =1.6273(2) ? for 58Ni12C. Several possible electronic band systems are observed, but the identification of these is hampered by extensive perturbations among the excited states. The observation of long-lived vibronic states as far to the blue as 26 951 cm21 indicates that D0(NiC) >3.34 eV, and the ionization energy of NiC has been determined to fall in the range IE(NiC) =8.73?0.39 eV. A discussion of these results, in the context of work on other 3d transition metal carbides is also presented.