采用了从头算分子轨道理论(MP2，非限性的二级微扰理论)和密度泛涵理论(B3LYP)，分别在6－31G(d，p)，6－311G(d，p)，6－311+G(d，p)，6－311G(2d，p)，和6－311+G(2df，2p)基组上优化CH_3－nF_nO₂－Li⁺(n=0～3)的几何结构，计算出了相关的NBO电荷分布和锂离子相对于自由基CH_3－nF_nO₂的亲和能。并在同一水平上计算了自由基CH_3－nF_nO₂和络合物CH_3－nF_nO₂－Li⁺的相关伸缩振动频率。CH_3－nF_nO₂在UB3LYP／6－311G(d，p)得到的振动频率与实验值符合得很好。根据相关的文献报道，我们运用从头算分子轨道理论和密度泛涵理论计算出的锂离子相对于CH_3－nF_nO₂的亲和能都能够表明络合物CH_3－nF_nO₂－Li⁺在气态下能以一种稳定的物种形态被离子附着质谱检测。

The equilibrium geometries,harmonic vibrational frequencies,natural bond orbital(NBO)charge distributions,and the affinity energies of Li⁺ attachment to CH_3-nF_nO₂(n = 0～3)have been investigated using ab initio molecular orbital theory and density functional theory(DFT).The structures were determined using unrestricted second order M?ller-Plesset(UMP2)and unrestricted Beck's three-parameter Lee-Yang-Parr(UB3LYP)theories in conjunction with 6-31G(d,p),6-311G(d,p),6-311+G(d,p),6-311G(2d,p)and 6-311+G(2df,2p)basis sets,and the stretching vibrational frequencies were investigated for CH_3－nF_nO₂ and CH_3－nF_nO₂Li⁺,using optimized geometries at the same levels. The calculated vibrational frequencies of radicals at UB3LYP/6-311G(d,p)levels were consistent well with the experimental data. The affinity energies of Li⁺attachment to CH_3－nF_nO₂(n = 0～ 3),calculated by DFT and ab intio are all large which suggest that CH_3－nF_nO₂Li⁺ complexes could be possibly detected as stable species in gas phase by ion attachment mass spectrometry.