Spectroscopic Constants and Predissociation of the low-lying states in selenium dimer

Abstract

High-level ab initio calculations on the electronic structure and spectroscopic properties for the low-lying electronic states of selenium dimer (Se2) are performed by using internally contracted multireference-configuration interaction method (icMRCI) including Davidson correction (+Q) and scalar relativistic effect (SR). The spin-orbit coupling (SOC) effect is introduced in the computations via state-interacting technique with the full Breit-Pauli Hamiltonian. The potential energy curves (PECs) of 22 Λ-S states of Se2 are computed. After taking SOC effect into account, PECs of 28 Ω states generated from the Λ-S states with the energy under 36,000cm−1 are yielded. Moreover, from the calculated PECs, the spectroscopic constants of the bound Λ-S and Ω states are determined, and good agreement with available experimental and theoretical works is found. By virtue of the calculated SOC matrix elements and the PECs of the Λ-S states, the spin-orbit induced predissociation mechanism of the B3Σu− state is discussed. Our computations would provide helpful information on spectroscopic properties of the low-lying electronic states for the Se2, and deep understanding of the predissociation mechanism for the B3Σu− state.