CH_3自由基的v_2和v_3基带在高温下的谱线强度

Line intensities of v_2 and v_3 transition bands of CH_3 at high temperature

采用密度泛函理论(DFT)的B3P86方法,在6-311G^(**)基组水平上,优化出CH_3自由基的稳定构型为双重态D_(3h)构型,并得出基态的简正振动频率、转动常数.在此基础上,根据对称陀螺分子红外光谱跃迁定则,计算了谱线跃迁频率.使用以上数据,我们研究了不同温度下CH_3自由基v_2平行谱带谱线强度,并分析了谱线强度随温度的变化规律.结果表明直到1600K时,谱线强度计算值和实验结果符合很好.表明对CH_3自由基在高温下谱线强度的计算方法是成功的.进而计算了CH_3自由基在2000和3000 K时v_2谱带谱线强度及模拟光谱,并总结其光谱精细结构随温度变化的规律.同时本文也给出了CH_3自由基v_3垂直谱带在296和3000 K时的模拟光谱.

Using B3P86 density functional methods and 6-311G＊＊ basis set the molecular geometries, vibration frequency and rotation constants of the ground state of CH3 are calculated. The transition frequency were calculated using symmetric top model, and given the line intensities of v2 transition bands of CH3 at different temperature, and found the law of the line intensities changed with the temperature. Results showed that our line intensities data up to 1600 K are in excellent agreement with the experimental data, which provide a strong support for the calculation of line intensity at high temperature. Furthermore, the line intensities and spectral simulations of v2// band at the higher temperatures 2000 and 3000 K were presented and the change in fine structure of v2 band with the temperature was discussed. At the same time, the line intensity and spectral of v3 band of the CH3 radical at the temperature 296 and 3000 K were presented.