A New Interpretation of the Photoelectron Spectra of CrC2-
Résumé
In this work, the computational quantum chemical DFT, CASPT2, and RCCSD(T) methods have been utilized to investigate the geometric and electronic structures of cyclic and linear CrC2-/0 clusters. The neutral ground state is firmly identified as the cyclic 5A1 state. For the anionic cluster, two nearly degenerate isomers were recognized, namely a cyclic 6A1 state and a linear 6Σ+ state. Therefore, assignments of the observed bands in the photoelectron spectra of CrC2- have been made based on both of these isomers. With the exception of the B band all other experimental observed bands could be ascribed to the cyclic isomer. The computed detachment energies show that the former band must be exclusively assigned to the ionization of 6Σ+ of the linear structure, which can possibly also contribute to some higher energy bands. Additional support for the proposed assignments is provided by multidimensional Franck-Condon factor simulations for the 6A1→5A1 and 6A1→5B1 transitions that show a nearly perfect match with the observed vibrational progressions of the X and A bands in the 532 nm spectra.