采用从头算的多参考组态相互作用(MRCI)方法并结合基组aug-cc-pCVQZ计算了CO分子基态(X1Σ+)的势能曲线和偶极矩曲线,得到的势能曲线、偶极矩曲线分别与RKR势、文献的偶极矩曲线吻合较好.利用所得的势能,求解双原子分子核运动的Schr?dinger方程找到了CO分子 X1Σ+态转动量子数 J=0时的70个振动态,对于每一振动态,分别计算了其振动能级 G(v)、转动惯性常数 Bv和离心畸变常数Dv,并把计算结果与已知的42个实验值做了详细比较,结果表明,计算的振动能级G(v)、转动惯性常数 Bv、离心畸变常数 Dv与实验值符合较好.利用G(v),Bv导出的光谱常数[谐振频率 ωe(2160.1 cm -1)、非谐振频率 ωe χe(13.1 cm -1)、转动常数 Be(1.918 cm-1)、振转耦合常数αe(0.0173 cm -1)]也与实验值的光谱常数[ωe(2169.8 cm-1),ωe χe(13.3 cm -1),Be(1.931 cm-1),αe(0.0175 cm -1)]较为符合,这在一定程度上证明了方法MRCI/Aug-cc-pCVQZ对CO分子基态性质的计算是合适而可靠的.利用乘积近似方法计算了CO分子在常温、中温、高温时的配分函数,在此基础上,计算了CO分子在 T=296 K时的1-0跃迁带的谱线强度,通过比较发现,计算所得的线强度与HITRAN数据库符合较好.进一步计算的CO分子 X1Σ+态1-0,2-0,3-0,4-0,2-1,3-1和4-1跃迁带的带强度也与实验值较为吻合,同时首次计算了CO分子X1Σ+态3-2跃迁带、4-2跃迁带的线强度及带强度.
The potential energy curve(PEC)and dipole moment curve(DMC)for the ground state(X1Σ+)of CO molecule have been computed using the multi-reference configuration interaction(MRCI)method with aug-cc-pCVQZ basis sets.Results showed that the calculated PEC,DMC are in accord with RKR,reference,respectively.With the potential energy obtained at the MRCI/aug-cc-pCVQZ level of theory,70 vibrational states(J=0)of the ground state of CO molecule are obtained by nu-merically solving the radical Schr?dinger equation of nuclear motion.For each vibrational state,the vibrational energy levels G (v),the inertial rotation constants Bvand the centrifugal distortion constants Dvare reported,which accord well with the exper-imental values.The inertial rotation constants Bv,vibrational energy levels G(v)were fitted to determine spectroscopy con-stants,which the rotation coupling constant ωe(2 160.1 cm -1),the anharmonic constant ωe χe(13.3 cm -1),the equilibrium ro-tation constant Be(1.931 cm -1)and the vibration-rotation coupling constant αe(0.017 5 cm -1)are in good agreement with the experiment data[ωe(2 169.8 cm -1),ωe χe(13.3 cm -1),Be(1.931 cm -1),αe(0.017 5 cm-1)],it is evident that MRCI/Aug-cc-pCVQZ is reliable for the calculation for the ground state of CO molecule.The line intensity of 1 -0 transition band for the ground state of CO molecule is calculated by directly calculating the partition function at 296 K,the agreement between the cal-culated line intensity data and the data in HITRAN database is fairly good at 296 K.Band intensities of 1-0,2-0,3-0,4-0,2-1,3-1,4-1 bands are calculated for the ground state of CO molecule,which are in better agreement with the experi-mental values.Therefore,the line intensities and band intensities of 3-2 transition band,4-2 transition band are firstly calcu-lated.