NH分子特性和势能随外电场的变化规律

设置不同的外电场参量，采用B3P86/cc PV5Z方法优化计算，获得不同外电场中NH分子的键长、偶极矩、振动频率和红外光谱等物理性质参数. 在此基础上采用单双取代耦合团簇CCSD(T)方法和相同的基组，扫描计算单点能获得相关势能曲线. 结果分析表明物理性质参数和势能都随外电场的变化而变化，且外加反向电场时变化幅度更明显. 考虑到外电场与分子的相互作用，本文引入偶极近似构建外电场中的势能函数模型，编制程序拟合对应的势能函数，得出拟合参数，进而计算临界离解电场参量，结果与数值计算和理论分析较为一致，误差都在7%以内，说明构建的模型是合理和可靠的. 这为分析外电场中分子光谱、动力学特性和分子Stark效应冷却囚禁提供重要的理论和实验参考.

The change law of NH molecular characteristics and potential energy under external electric field

By setting different electric fields and adopting density functional B3P86/cc PV5Z method, the geometric structure of NH molecule is optimized, and the bond lengths, dipole moments, vibration frequencies and other physical properties parameters are obtained. On the basis of adopting the energy of high precision coupled cluster CCSD (T) method and the same basis set to scan single point energies, the potential energy curves of different external fields are given. The results show that the physical properties parameters and potential energy values will change with the changes of external electric fields, especially, of the reverse direction electric field. In order to get the critical dissociation electric parameter, the dipole approximation is adopted to construct potential model, then the model is put to fit the corresponding potential energy curve of external electric field. It is found that the fitted critical dissociation electric parameter is reasonably consistent with the numerical calculation; i.e., the relative errors are also less than 7%. So the model constructed is reliable and accurate. These will provide important theoretical and experimental reference for the studies of molecular spectroscopy, dynamics and molecular cooling with Stark effect.