This paper utilizes multireference configuration interaction theory to calculate the lifetime of A2Пu state for nitrogen molecular ion N2＋. It obtains the transition moment function for A2Пu →X2∑g＋, Franck-Condon factors between vibrational levels of the two states. The calculated lifetimes are 16.81, 14.62, 13.10, 12.18, 11.40, and 11.64 its for v′ = 0, 1, 2, 3, 4, 5 vibrational levels of A2Пu state, respectively, which are in excellent agreement with available experimental values.
Theoretical investigation of low-lying electronic states and B3~u B3∑u^-X3∑g^-transition properties of selenium dimer using size-extensivity singly and doubly excitation multireference configuration interaction theory with nonrelativistic all-electron basis set and relativistic effective core potential plus its split valence basis set is presented in this paper. The spectroscopic constants of ten low-lying A-S bound states have been obtained and compared with experiments. Spin-orbit calculations for coupling between B3∑u^ sates and repulsive 1Лu, 5Лu states have been made to interpret the predissociation mechanisms of the B3∑u^- state. The lifetimes of B3∑u^-（v= 0 - 6） have been calculated with scalar relativistic effects included or excluded, respectively, and reasonably agree with experimental values.
