Rotationally resolved state-to-state photoelectron study of niobium carbide radical

By employing the two-color visible (VIS)-ultraviolet (UV) laser photoexcitation scheme and the pulsed field ionization-photoelectron (PFI-PE) detection, we have obtained rovibronically selected and resolved photoelectron spectra for niobium carbide cation (NbC+). The fully rotationally resolved state-to-state VIS-UV-PFI-PE spectra thus obtained allow the unambiguous assignments of rotational photoionization transitions, indicating that the electronic configuration and term symmetry of NbC+((X) over tilde) ground state are ... 10 sigma(2) 5 pi(4) 11 sigma(2) ((X) over tilde (1)Sigma(+)). Furthermore, the rotational analysis of these spectra yields the ionization energy of NbC [IE(NbC)] to be 56 369.2 +/- 0.8 cm(-1) (6.9889 +/- 0.0001 eV) and the rotation constant B-0(+) = 0.5681 +/- 0.0007 cm(-1). The latter value allows the determination of the bond distance r(0)(+) = 1.671 +/- 0.001 angstrom for NbC+((X) over tilde (1)Sigma(+)). Based on conservation of energy, the IE(NbC) determined in the present study along with the known IE(Nb) gives the difference of 0 K bond dissociation energies (D-0's) for NbC+ and NbC, D-0 (NbC+) - D-0(NbC) = -1855.4 +/- 0.9 cm(-1) (-0.2300 +/- 0.0001 eV). The energetic values and the B0+ constant determined in this work are valuable for benchmarking state-of-the-art ab initio quantum calculations of 4d transition metal containing molecules. (C) 2014 AIP Publishing LLC.