中文摘要：

采用Davidson修正的内收缩多参考组态相互作用方法（MRCI＋Q）及Dunning等的相关一致基aug-cc-pV6Z计算了BCl分子X1Σ＋, a3Π和A1Π态的势能曲线。利用总能量外推公式,将这3个态的总能量分别外推至完全基组极限。对势能曲线进行核价相关修正及相对论修正计算,得到了同时考虑这两种修正的外推势能曲线。拟合势能曲线得到了3个态的主要光谱常数Te, Re,ωe,ωexe, Be,αe 和De 等,它们与已有的实验结果较为一致。利用获得的势能曲线,通过求解双原子分子核运动的径向Schr？dinger方程,找到了BCl分子X1Σ＋, a3Π和A1Π态的全部振动态,并得到了相应的振动能级和惯性转动常数等分子常数。还计算了a3Π-X1Σ＋和A1Π-X1Σ＋的跃迁偶极矩、Franck-Condon因子,预测了若干跃迁的辐射寿命。

英文摘要：

The X1Σ＋, a3Πand A1Πstates of BCl molecule are studied using the highly accurate valence internally contracted multireference configuration interaction approach including the Davidson modification. The Dunning’s correlation-consistent basis sets, aug-cc-pV6Z and aug-cc-pV5Z, are used in the study. To obtain more reliable results, the potential energy curves （PECs） of three electronic states are extrapolated to the complete basis set limit by the two-point total-energy extrapolation scheme. The effects of the core-valence correlation and relativistic corrections on the PECs are taken into account. By fitting these PECs, the spectroscopic parameters （Te , Re , ωe , ωe x e , B e , αe and D e ） of the X1Σ＋, a3Π and A1Π states of BCl are determined. These parameter values coincide with the experimental results. In addition, the whole vibrational states for X1Σ＋, a3Πand A1Πstates at J =0 （J is the rotational quantum number） are determined by numerically solving the radical Schr？dinger equation of the nuclear motion of diatomic molecules. For each vibrational state, the vibrational level and inertial rotation constants are obtained, which are in excellent accordance with the experimental results. With the potential energy curves obtained at MRCI＋Q/56＋CV＋DK level and the MRCI wave functions, the Franck-Condon factors, radiative lifetime of transition from a3Π and A1Π to the ground state are computed.