Ab initio CI calculations on potential energy curves of low-lying states of BrF and its cation including spin–orbit coupling

Bromine monofluoride (BrF) and its cation (BrF+) have attracted much scientific attention because of their potential significance in the stratospheric ozone depletion and the development of chemical laser. Despite that the structure and spectroscopic properties of the 13Π0+ (B3Π0+) and 13Π1 states of BrF have been experimentally investigated in the literature, theoretical investigations of BrF and its cation are relatively sparse. In this paper, the low-lying electronic states for BrF/BrF+ were studied by means of relativistic multireference configuration interaction method (including Davidson correction). The spin–orbit coupling effect was considered by the state-interacting method with the full Breit-Pauli Hamiltonian. For BrF, the potential energy curves (PECs) of 12 Λ–S states and 23 Ω states generated from the Λ–S states were calculated. The avoided crossing mechanism of Ω = 0+ states were analyzed by the variations of dominant Λ–S composition for Ω states at several different internuclear distances. For BrF+, the PECs of the ground states (X2Π3/2 and X2Π1/2) were computed. The spectroscopic constants of the bound states of BrF/BrF+ were determined, which are in good agreement with previously available experimental results. Finally, the ionization energies from the neutral ground state (X1Σ+) to different ionic states (X2Π3/2, and X2Π1/2) were obtained.