次氟酸分子的势能函数及其振动光谱的同位素效应的理论研究

Theoretical Studies on Potential Energy Function and the Isotopic Effects of Vibrational Spectra for Hypofluorous Acid

用三原子振动激发态的变分计算程序（ＴＲＩＡＴＯＭ）精确计算次氟酸分子Ｈ１６ＯＦ的振动激发态的能级以及次氯酸分子中的Ｈ和Ｏ分别被Ｄ和１８Ｏ取代后的Ｈ^（１８）ＯＦ，Ｄ^（１６）ＯＦ和Ｄ^（１８）ＯＦ的同位素效应，理论计算值与已有的实验结果吻合较好。预测了一些尚未观测到的谱线频率及同位素效应，并确立了一个同位素位移的加和规则。

Various isotopic species of hypofluorous acid, HOF, have been a subject of many vibrational spectroscopic studies. The object of these detailed analyses is to obtain accurate spectroscopic data of the various isotopic species of this molecule and to provide information about the structures and the potential energy surface. In this paper, some force constants of hypofluorous acid have been optimized from the comparison between the experimental and the calculated vibrational energy levels,the others have been fixed to the values of the empirical force constants given by Halenon and Ha(J. Chem. Phys. , 1988, 89: 4885).A new potential energy function is obtained by using the transformation between the force constants and the potential energy parameters of the MORBID form suggested by Jensen(J.Mol.Spectrosc. , 1989, 133 : 4683. The spectra of the vibrational excited states of the molecules H16OF, H￣(18)OF, D￣(16)OF, and D￣(18)OF have been calculated by using the TRIATOM program,which uses the basis set expansion and is thus strictly variational.In molecules H￣(18)OF,D￣(16)OF, D￣(18)OF, the vibrational frequency shifts relative to HOF specie have been calculated.These calculated shifts are in agreement with the experimental values. In addition, for the vibrational excited states of the H16OF, H￣(18)OF, D￣(18)OF and D￣(18)OF, some unobserved vibrational energy levels and their isotopic effects have been predicted based on the new potential energy function of the hypofluorous acid(HOF). For molecules H￣(18)OF, D￣(16)OF, and D￣(18)OF,the vibrational frequency shifts relative to HOF species hold up appromately the combination rule:△v(H￣(18)OF)+△v(D￣(16)OF)≈△v(D￣(18)OF).In particular, for DOF molecule, it is shown that the stretching vibrational fundamental frequency blue shifts relative to HOF specie is 2. 13 cm￣(-1), which is close to the experimental values(- 2. 10 cm￣(-1)).For the stretching 3. vibrational excited states of the molecule DOF, the excited vibrational frequency blue shifts have been predicted, for example, the blue shift is -4.2 cm￣(-1) ,5. 6 cm￣(-1) ands.3 cm￣(-1)for the vibrational states(002) , (003) and (004) of the DOF, respectively.