中文摘要：

采用显关联多参考组态相互作用（explicitly correlated multi-reference configuration interaction method, MRCI-F12）方法和相关一致基组cc-pCVQZ-F12计算了双原子分子SO的基态X3Σ？和第一激发态a1△的势能曲线,研究中考虑了Davidson 修正,芯-价电子关联修正和标量相对论效应。通过对这两个束缚电子态势能曲线的拟合,给出了光谱常数并与其他理论和实验结果做了比较。进一步地,获得了这两个态的振-转能级信息。本文计算结果与实验的相对误差仅在千分之一量级,对将来的实验有重要的参考价值；同时也表明MRCI-F12方法可推广到小分子体系势能面的高效、精确计算研究中。

英文摘要：

Accurate spectroscopic constants and rovibrational level information are of great importance in molecular physics and astrophysical field. In this work, a new computational scheme is presented to further improve the accuracy of spectroscopic constants, and the two lowest electronic states of sulfur monoxide molecule are investigated as a typical case study. High-level ab initio calculations are carried out to compute the potential energy curves （PECs） of the lowest bound states, the ground triplet states X3Σg- , and the first excited singlet states a1△g of SO molecule. The explicitly correlated multi-reference configuration interaction method （MRCI-F12） and cc-pCVQZ-F12 basis set are adopted in the electronic structure computations. The Davidson correction is taken into account to eliminate the size-consistency error. The core-valence （CV） electron correlations of the n=2 shell of S atom and n=1 shell of O atom are estimated by the MRCI-F12 method, whereas only the 1 s orbital of S atom is excluded in the CV calculations. Moreover, we introduce the scalar relativistic effect into our study by utilizing the second-order Douglas-Kroll and Hess （DKH） one-electron integrals by the MRCI method through combining with the uncontracted cc-pCVQZ-F12 basis set. On the basis of the PECs of the SO dimer, the spectroscopic constants （Te, Re,ωe,ωeχe, Be,αe and De） of the two electronic states are determined by solving the one-dimensional nuclear rovibrational Schr？dinger equations. Our spectroscopic constants are found to be in excellent agreement with previous experimental and theoretical values. Furthermore, the detailed information about the vibrational energy levels and rotation spectroscopic constants （Bν, Dν） of the two states is also presented with a deviation of 0.1%order of magnitude from the available experimental results. Our present computational work is valuable for future experimental studies on the rovibrational energy levels for the SO molecule and also indicates that the MRCI