利用拉曼光谱技术测量了CH3CN和CD3CN在常温常压下的拉曼光谱,根据微扰理论建立了新的费米共振理论模型,结合同位素替换方法计算了CH3CN的ν2～ν3+ν4费米共振耦合系数,并且与利用传统Bertran公式计算结果进行了对比。新的费米共振理论模型利用振动能级的跃迁偶极矩实现了费米共振参数的计算,不仅能够计算未发生费米共振时两费米共振双线的初始光谱强度,而且还能够计算两费米共振双线的初始频率。最后,对利用Bertran公式计算获得的结果产生较大误差的原因进行了分析。

Raman spectra of CH3CN and CD3CN were measured at ambient pressure and room temperature.The new Fermi resonance theoretical model,which was built based on the perturbation theory,was used to calculate the parameters of ν2～ν3+ν4Fermi resonance of CH3CN with isotopic substitution method.In addition,we also compared the calculation results with the new theoretical model and the Bertran equations.The new theoretical model can be used not only to calculate the original intensity of the Fermi doublet,but also to calculate the frequencies of the Fermi doublet in absence of the Fermi resonance with the transition dipole moments of the two observed transitions.Besides,we also gave a detailed analysis on the difference between the calculated results based on the Bertran equations and the calculated results in the present work.