All-electron MRCI+Q study on excited states of the SbBr molecule including spin-orbit coupling

Abstract

In this work, we performed spin-orbit coupling (SOC) included MRCI+Q calculation on electronic states of SbBr. The SOC effect is treated by using the state interaction method in combination with the Breit-Pauli operator. Molecular orbitals are constructed with all-electron aug-cc-pwCVQZ-DK basis sets. Without SOC, total 34 Λ-S states of SbBr are obtained. It is found that the lowest three Λ-S states X3Σ−, a1Δ, and b1Σ+ are characterized by a common electron configuration (π2). All of them possess an especially deep potential well. Predissociations of a1Δ and b1Σ+ are illuminated with the aid of SO matrix elements. Under the influence of SOC, total 74 Ω states arise from Λ-S states. The energy splitting of X3Σ− is calculated to be 868 cm−1, which well reproduces the measurement of 873 cm−1. Particularly, SOC effects significantly improve the excitation energy (Te) of b1Σ+. The deviation is decreased from 1378 cm−1 to 233 cm−1. In addition, the SOC effect has a great effect on transition properties of SbBr. This effect is responsible for the phosphorescence of transitions a1Δ-X3Σ− and b1Σ+-X3Σ−, and the corresponding transition mechanism is elucidated. Finally, radiative lifetimes of a1Δ and b1Σ+ are determined at a millisecond level.