Theoretical Investigations on CaO Ions: Vibronic States and Photoelectron Spectroscopy

International audienceThe low-lying electronic states, X2Π and A2Σ+ of CaO+ and X2Σ+ and A2Π of CaO–, have been determined at the MRCI+Q level of theory with the aug-cc-pV5Z(O) and cc-pCV5Z(Ca) basis sets. The two states of CaO+ are close within <0.1 eV and coupled via spin–orbit effect. The X2Σ+ and A2Π states of CaO– are energetically separated by <1 eV such that the first excited state is close to the electronic ground state of neutral CaO and unstable with respect to electron detachment. Using the potential energy curves and the spin–orbit coupling terms, the vibronic energy levels of these ions have been determined. The ionization energy and the electron affinity of CaO are calculated at 6.79 and 0.79 eV, respectively. The photoelectron spectra of CaO– and CaO have also been simulated