Theoretical study of the electronic nonadiabatic transitions in the photoelectron spectroscopy of F₂O

Abstract

The photoelectron spectrum of F₂O pertaining to ionizations to the ground (X̃²B₁) and low-lying excited electronic states (òB₂, B̃²A₁, and C̃²A₂) of F₂O⁺ is investigated theoretically. The near equilibrium potential energy surfaces of the ground electronic state (X̃²B₁) of F₂O and the mentioned ground and excited electronic states of F₂O⁺ reported by Wang et al. ( J. Chem. Phys.2001, 114, 10682) for the C_2v configuration are extended for the C_s geometry assuming a harmonic vibration along the asymmetric stretching mode. The vibronic interactions between the òB₂ and B̃²A₁ electronic states of F₂O⁺ are treated within a linear coupling approach, and the strength of the vibronic coupling parameter is calculated by an ab initio method. The nuclear dynamics is simulated by both time-independent quantum mechanical and time-dependent wave packet approaches. Although the first photoelectron band exhibits resolved vibrational progression along the symmetric stretching mode, the second one is highly overlapping. The latter is attributed to the nonadiabatic interactions among the energetically close òB₂, B̃²A₁, and C̃²A₂ electronic states of F₂O⁺. The theoretical findings are in good accord with the available experimental results.