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

Abstract

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+(X̃) ground state are ...10σ2 5π4 11σ 2 (X̃1Σ+). 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 B0+ = 0.5681 ± 0.0007 cm-1. The latter value allows the determination of the bond distance r0+ = 1.671 ± 0.001 Å for NbC +(X̃1Σ+). 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 (D0's) for NbC+ and NbC, D0(NbC+) - D0(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. © 2014 AIP Publishing LLC.