Photoelectron imaging spectroscopy of MoC^- and NbN^- diatomic anions: A comparative study

The isoeletronic diatomic MoC^- and NbN^- anions have been prepared by laser ablation and studied by photoelectron imaging spectroscopy combined with quantum chemistry calculations. The photoelectron spectra of NbN^- can be very well assigned on the basis of literature reported optical spectroscopy of NbN. In contrast, the photoelectron spectra of MoC^- are rather complex and the assignments suffered from the presence of many electronically hot bands and limited information from the reported optical spectroscopy of MoC. The electron affinities of NbN and MoC have been determined to be 1.450 ± 0.003 eV and 1.360 ± 0.003 eV, respectively. The good resolution of the imaging spectroscopy provided a chance to resolve the Ω splittings of the X³Σ^- (Ω = 0 and 1) state of MoC and the X⁴Σ^- (Ω = 1/2 and 3/2) state of MoC^- for the first time. The spin-orbit splittings of the X²Δ state of NbN^- and the a²Δ state of MoC^- were also determined. The similarities and differences between the electronic structures of the NbN and MoC systems were discussed.