中文摘要：

采用Davidson修正的内收缩多参考组态相互作用方法（icMRCI＋Q）结合Dunning等的相关一致基计算了PS自由基X 2Π态势能曲线.利用三阶Douglas-Kroll Hamilton近似结合cc-pV5Z相对论收缩基进行了相对论修正计算.利用aug-cc-pCV5Z基组对势能曲线进行了核价相关修正计算,并将总能量外推至完全基组极限.拟合得到了X2Π态的主要光谱常数Re,ωe,ωexe,ωeye, Be,αe和De,与实验结果符合较好.利用Breit-Pauli算符,研究了旋轨耦合效应对势能曲线的影响,得到了两条？态的势能曲线.详细分析了在旋轨耦合计算中,核电子相关与冻结核近似对电子结构和光谱性质的影响.在icMRCI＋Q/56＋DK＋CV＋SO理论水平上得到了两个？态的主要光谱常数Te, Re,ωe,ωexe,ωeye, Be和αe,结果与实验结果一致.在平衡位置处,本文的X2Π态旋轨耦合能量分裂值为323.73 cm？1,与实验结果321.93 cm？1较为一致.通过求解双原子分子核运动的径向Schr ¨odinger方程,找到了无转动PS自由基X2Π态及其两个？态的全部振动态,还分别计算了它们相应的振动能级和惯性转动常数等分子常数,这些结果与已有的实验值一致.

英文摘要：

The potential energy curve （PEC） of ground X 2Πstate of PS radical is studied using highly accurate internally contracted mul-tireference configuration interaction approach with the Davidson modification. The Dunning’s correlation-consistent basis sets are used for the present study.To improve the quality of PECs, scalar relativistic and core-valence correlation corrections are considered. Scalar relativistic correction calculations are performed using the third-order Douglas-Kroll Hamiltonian approximation at the level of a cc-pV5Z basis set. Core-valence correlation corrections are calculated with an aug-cc-pCV5Z basis set. All the PECs are extrap-olated to the complete basis set limit. Using the PEC, the spectroscopic parameters （Re,ωe,ωexe,ωeye, Be,αe and De） of the X2Πstate of PS are determined and compared with those reported in the literature. With the Breit-Pauli operator, the PECs of two？states of the groundΛ-S state are calculated. Based on these PECs, the spectroscopic parameters （Te, Re,ωe,ωexe,ωeye, Be andαe） of two？states of PS are obtained. Compared with those reported in the literature, the present results are accurate. The vibration manifolds are evaluated for each？andΛ-S state of non-rotation PS radical by numerically solving the radical Schr ¨odinger equation of nuclear motion. For each vibrational state, the vibrational level and inertial rotation constants are obtained, which are in excellent accordance with the experimental findings.