电场作用下溴甲烷的光谱和解离特性（英文）

Spectrum and Dissociation Characteristics of Methyl Bromide in External Electric Field

采用了密度泛函理论（density functional theory,DFT）,在6-311＋＋G（d,p）基组水平上使用B3LYP方法研究外电场（0-0.05a.u.）对于溴甲烷分子的键长、能隙及解离势能面的影响.结果表明：外加电场的方向和大小对于分子结构和解离势能面均有显著的影响.随着负向外电场（Br-C键方向）从0增加到0.05a.u.,C-Br键的键长先减小后增大,C-H键的键长逐渐增加,分子能隙EG逐渐减小,C-Br键的str振动频率逐渐增加而IR振动频率逐渐减小.进一步计算发现：随着正向外电场（C-Br键方向）从0增加到0.03a.u.,溴甲烷分子的势能曲线有所降低,解离势垒逐渐减小.因此,可以通过外电场来控制CH_3Br分子的降解.

B3 LYP/6-311 ＋ ＋g（ d,p） method is adopted to optimize ground state structure of CH3 Br molecule. Bond length,energy gap and dissociation potential energy surface of CH3 Br molecule in external electric field（ 0-0. 05 a. u.）are studied. It shows that direction and magnitude of applied electric field is of great significance to molecular structure and potential energy surface. With negative electric field（ C-Br bond direction） increases from 0 to 0. 05 a. u.,bond length of C-Br bond decreases first and then increases. Bond length of C-H bond increases gradually. Molecular energy gap EG decreases gradually. Vibrational frequency of C-Br bond increases while IR vibration frequency decreases. It is found that potential energy of methyl bromide molecule decreases and dissociation barrier decreases,which indicating that CH3 Br molecule is easy to be excited and dissociated in external electric field.