中文摘要：

采用内收缩多参考组态相互作用（MRCI）方法,结合Dunning系列相关一致基,分别对75^As^32^S^＋和75^As^34^S^＋离子的X^3Σ-和A1Π电子态的势能曲线进行了计算,进一步拟合势能曲线,得到各电子态的光谱常数与分子常数.首先,采用MRCI方法结合相关一致基,aug-cc-p V5Z,对As S^＋离子的X^3Σ-和A^1Π电子态进行了计算,获得相应的势能曲线;然后,为进一步提高势能曲线的精度,对其进行了三种修正计算.采用Davidson（＋Q）方法修正MRCI方法计算过程中存在的基组大小不一致缺陷;利用二阶Douglas-Kroll哈密顿近似,在cc-p VQZ基组水平,修正了相对论效应对势能曲线的影响;利用两点能量外推法,在aug-cc-p VQZ和aug-cc-p V5Z基组水平对各能量点的势能值进行了外推,得到完全基组极限处的势能曲线.最后,利用修正（包括Davidson修正、相对论修正和基组外推）后的势能曲线,通过Vibrot程序,求解双原子分子核运动的径向Schr？dinger方程,并进行同位素质量识别,得到^75As32S^＋和^75As^34S^＋离子两个电子态的光谱常数（Te,Re,ωe,ωexe,αe和Be）和分子常数（G（υ）,Bυ,Dυ）.

英文摘要：

The ground state X^3Σ- and low-lying excited electronic state A^1Π of As S^＋ion are investigated employing the full valence complete active space self-consistent field method combined with the highly accurate valence internally contracted multireference configuration interaction（MRCI） approach. The basis set used in the calculations is Dunning correlation-consistent basis set, aug-cc-p V5 Z. To improve the quality of the potential energy curves（PECs）, three kinds of corrections are considered in the present work. First, the Davidson modification is adopted to deal with the sizeextensity errors from the MRCI calculations. Then, relativistic correction is calculated by the second-order Douglas-Kroll Hamiltonian approximation at the level of cc-p VQZ basis set. Finally, to eliminate the truncation errors of the basis set, the PECs of the two electronic states for each species are extrapolated to the complete basis set limit by the two-point energy extrapolation scheme. Two large basis sets, i.e., aug-cc-p VQZ and aug-cc-p V5 Z, are used to perform the extrapolation calculations. With the aid of VIBROT program, all the PECs of X^3Σ-and A^1Π obtained here are fitted to the analytical forms, which are used to derive the spectroscopic parameters（De, D0, ωeχe, αe and Be） of ^75As^32S^＋and75As^34S^＋. The effects of the Davidson modification, relativistic correction and basis set extrapolation are discussed respectively. The results indicate that the quality of almost all the spectroscopic parameters is improved by considering these corrections, which exhibit excellent agreement with the experimental data. Besides, the first 10 vibrational states for the two electronic states of 75As^32S^＋and75^As^34S^＋are determined when the rotational quantum number J equals zero. For the first 10 vibrational states, the vibrational level G（υ）, inertial rotation constant Bυ, and centrifugal distortion constant Dυ are evaluated when J = 0.