Assignment of Photoelectron Spectra of MC₂ (M= V, Cr, Fe, and Co)

Hybrid density functional theory (DFT) calculations are performed to study MC₂ (M= V, Cr, Fe and Co) clusters in the neutral and anionic charge states. We find that the equilibrium geometries of MC₂ and their anions are all cyclic structures with C_2v symmetry, which agrees well with the previous theoretical studies. The Mulliken charge and spin populations of MC₂ clusters and their anions are also calculated, and it is found that the electron charge transformations from anions to neutral molecules mainly take place on the M atoms. Time-dependent DFT is used to calculate the excited states, and a theoretical assignment for the features in the experimental photoelectron spectrum is given, which are in good agreement with the available experimental data.