The electronic band system of nickel acetylide, NiCCH

This is the authors' abstract. We don't add key points for this paper.

Optical spectra of the supersonically cooled NiCCH radical have been recorded in the 530–650 nm region using the resonant two-photon ionisation method, and five of the observed bands have been rotationally resolved. The rotationally resolved studies demonstrate that the ground state of NiCCH is of symmetry, corresponding to a 3d9 configuration on the nickel atom, with the hole located in a 3dδ orbital. Most of the observed bands are assigned to the electronic transition, which shows a progression in the Ni–C stretching mode, ν3. In addition, single excitations of the modes ν2 (C≡C stretch), ν4 (C≡C–H bend), and ν5 (Ni–C≡C bend) are observed, allowing these vibrational intervals to be determined for the state. Hot bands also allow the determination of ν5 in the ground state. Quantum chemical computations have also been performed, confirming that the ground state is of 2Δ symmetry. The results are placed in context via comparison to other monovalent, monoligated Ni complexes, particularly NiCu, NiH, and NiCN.