NH(X^3Σ^-)分子的振动能级及离心畸变常数

Investigation of Vibrational Levels and Centrifugal Distortion Constants of NH(X^3Σ^-)

采用耦合簇理论的CCSD和CCSD(T)方法,使用多个基组对NH分子基态(X3Σ-)的平衡核间距(Re)、离解能(De)和谐振频率(ωe)进行优化计算,发现在CCSD(T)/cc-PVQZ理论水平下得到的结果(Re=0.103 72nm,ωe=3 282.45cm-1,De=3.579)与实验值非常相符.在0.487 2~6.387 2的核间距内对NH分子的基态进行了单点能量扫描,采用最小二乘法拟合Murrell-Sorbie势能函数,利用拟合的势能函数计算了与该态相应的光谱常数(Be,αe和ωeχe),其结果与实验符合得较好.以得到的解析势能函数为基础,通过求解核运动的径向薛定谔方程找到了转动量子数J=0时NH分子基态的全部振动能级、转动惯量和离心畸变常数.

The coupled‐cluster singles‐doubles‐approximate‐triples theory [CCSD and CCSD (T )] presented in Gaussian03 program package is employed to calculate the equilibrium internuclear distance Re ,the harmonic fre‐quency ωe and the dissociation energy De of NH(X 3 Σ - ) under a number of basis sets .The results obtained at the CCSD(T )/cc‐PVQZ level of theory ,i? e? R3 (0?103 72 nm ) ,De (3?579) and ωe (3 282?45 cm - 1 ) , well agree with the values measured experimentally .The potential energy curve at this level is calculated o‐ver a wide internuclear separation range of 0?487 2 to 6?387 2 nm at a 0?05 nm step size and is fitted to the Murrell‐Sorbie function .With the potential obtained at the CCSD(T )/cc‐PVQZ level of theory ,the other spectroscopic constants (Be ,αe and ωe χe ) are calculated ,and values are in excellent agreement with the ex ‐perimental ones .By solving the radial Schrodinger equation of nuclear motion ,the vibration levels and in‐ertial rotation constant at rotational quantum number J = 0 are reported for the ground state .