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 …10σ(2) 5π(4) 11σ(2) (X̃(1)Σ(+)). 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(+)(X̃(1)Σ(+)). 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.