【作者】 高峰；

【导师】 杨传路；

【作者基本信息】 鲁东大学 ， 原子与分子物理， 2007， 硕士

【摘要】 第二副族金属二聚体HgZn,HgCd和ZnCd在激光方面有着重要的应用价值,可以作为高效的激光载体。本文利用高精度的从头计算(ab initio)方法-多参考组态相互作用方法,采用多种基函数组,计算了这三个体系基电子态(1Σ+)和三个低激发电子态(3Σ,1Π,3Π)的势能曲线。运用非线性曲线拟合方法和Murrel-Sorbie(MS)势函数对所得的势能曲线进行拟合,得到了三个体系各个电子态的解析势能函数(APEF)。通过计算解析势能函数的二阶、三阶和四阶力常数,确定了各个电子态的光谱常数,包括谐振频率ωe和非谐振频率ωeχe,转动常数Be ,αe和Dr ot。同时,利用我们的势能曲线,通过解分子中核运动的薛定谔方程,我们预测了三个体系各电子态的振动能级。对于HgZn体系,我们采用(Ahlrichs-VTZ)Zn/(ECP60MWB)Hg ,(ECP10MDF)Zn/(ECP60MWB)Hg, (Ahlrichs-pVDZ)Zn/(ECP60MWB)Hg以及(ECP10MDF)Zn/(ECP78MWB)Hg四组全电子和有效核势基函数组,计算了基态(1Σ+)的势能曲线。该电子态共计算了6条曲线,并从中选出四条结果合理的曲线拟合了解析势能函数。用有效核势基函数组(ECP28MWB)Zn/(ECP60MWB)Hg,计算了该体系两个低激发电子态(1Π,3Π)的势能曲线。根据所得势能曲线和解析势能函数,计算了各电子态的光谱常数,预测了振动能级,并和已有的实验和理论报道进行了比较。对于ZnCd体系,Zn原子和Cd原子采用统一的基函数LANL2DZ(该基组也是个有效核势),计算了基态(X1Σ)和三个低激发态(3Σ, 1Π,3Π)的势能曲线。为了便于比较分析,我们采用一定的技巧,对三个激发态(3Σ, 1Π,3Π)同时进行计算,以保证计算过程中最终用于CI计算的轨道波函数的一致性,这样的结果也更具有可比性。对于该体系,目前还没有相应的实验研究,我们的结果只和已有的理论结果进行了比较。对于HgCd体系,很难找到同时适合于计算其基态和激发态的统一的基函数组,我们精选出10组基函数组进行计算并比较分析,包括(ECP60MWB)Hg/(LANL2DZ)Cd, (ECP78MHF)Hg/(ECP28MWB)Cd,(ECP78MWB)Hg/(ECP28MHF)Cd,(ECP60MDF)Hg/ECP1), (ECP1)Hg/(LANL2DZ)Cd, (ECP78MWB)Hg/(ECP1)Cd, (ECP78MHF)Hg/(ECP1)Cd, (ECP78MWB)Hg/(LANL2DZ)Cd, (ECP1)Hg/(ECP1)Cd, (ECP60MDF)Hg/(LANL2DZ)Cd。四个态共计算16条势能曲线,并且每条曲线都拟合出了解析势能函数,计算了相应的光谱常数,并预测了体系的振动能级,所得的结果与现有理论和实验值进行了比较。更多还原

【Abstract】 The group IIB metal dimers such as HgZn, ZnCd and HgCd are of great importance in laser techniques, and have been suggested as high-efficiency laser systems. In the present paper, the potential energy curves (PECs) of the ground electronic state (1Σ+) and three low-lying excited electronic states (3Σ,1Π,3Π) of the three systems have been calculated using high-level ab initio method (the multireference configuration interaction method) by employing different basis sets. The obtained PECs of each states and systems have been fitted to the analytical potential energy functions (APEFs) using the Murrel-Sorbie (MS) potential function through nonlinear curve fit method. By calculating the quardratic, cubic and quartic force constants of the APEFs, we can determine the spectroscopic constants of each electronic state, including the harmonic vibrational frequencyωe, the inharmonic vibrational factorωeχe, the rigid-rotational factor Be, the nonrigid-rotational factor ae and the rotational constant Drot. Based on the ab initio PECs, the vibrational energy levels of each state have been predicted by solving the Schr?dinger equation of nuclear motion.For the HgZn system, we calculated the PECs of the ground state (1Σ+) using four groups of basis sets formed by full electronic basis sets and effective core potentials (ECPs). They are Ahlrichs-VTZ)Zn/(ECP60MWB)Hg , (ECP10MDF)Zn/(ECP60MWB)Hg, (Ahlrichs-pVDZ)Zn/(ECP60MWB)Hg and (ECP10MDF)Zn/(ECP78MWB)Hg. Totally, 6 curves of this state are calculated, of which 4 curves are obtained by CISD method, and the left two are obtained by MRCI treat. Based on the calculations of the ground state, we calculated the PECs of the excited electronic states (1Π,3Π) of the HgZn dimer using the effective core potential basis sets (ECP28MWB)Zn/(ECP60MWB)Hg. Based on the obtained PECs, we calculated the spectroscopic constants and predicted the vibrational levels, and the results are compared to theoretical as well as experimental reports available at present.The basis sets LANL2DZ have been used to calculate the PECs of the ground state (1Σ+) as well as the low-lying excited states (3Σ,1Π,3Π) of the ZnCd molecule. In order to compare the three excited states conveniently, we calculated them at the same time, which enables the fact that in the calculation process, the occupational orbital wave functions which is used in the CI calculation are the same. As there is no experimental works on the ZnCd system, we only compared our results with the present theoretical reports. As for the HgCd system, it is difficult for us to find the same basis sets for both the ground state and the excited states. As a result, we employed ten groups of basis sets to calculate the PECs of HgCd, they are ECP60MWB)Hg/(LANL2DZ)Cd ,(ECP78MHF)Hg/(ECP28MWB)Cd , (ECP78MWB)Hg/(ECP28MHF)Cd ,(ECP60MDF)Hg/ECP1 , (ECP1)Hg/(LANL2DZ)Cd , (ECP78MWB)Hg/(ECP1)Cd ,(ECP78MHF)Hg/(ECP1)Cd , (ECP78MWB)Hg/(LANL2DZ)Cd , (ECP1)Hg/(ECP1)Cd ,(ECP60MDF)Hg/(LANL2DZ)Cd. Totally, sixteen PECs have been obtained for the four states, and each PEC has been fitted to the APEF using the MS potential function. Furthermore, the corresponding spectroscopic constants and vibrational energy levels have also been calculated, which are compared to the present theoretical as well as experimental researches.更多还原