Line strengths and transition dipole moment of the nu2 fundamental band of the methyl radical.
Line strengths and transition dipole moment of the nu2 fundamental band of the methyl radical.
复制标题
甲基自由基 nu2 基带的线强度和过渡偶极矩。
DOI：
10.1063/1.1812755
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
P. Davies
中科院分区：
文献类型：
--
作者：
G. Stancu;J. Röpcke;P. Davies
用半导体激光吸收光谱法测量了甲基自由基基态电子态nu（2）基能带中9条Q支线的强度。在氩气稀释的过氧化二叔丁基溶液中，用微波放电记录了甲基的振转光谱。当放电熄灭时，通过测量其动力学衰减来确定自由基的绝对浓度。的平移，旋转和振动的温度，也需要相关的线强度的跃迁偶极矩，确定从相对积分线强度和多普勒宽度的线后，允许仪器因素。利用9条Q分支线的线强度，导出了该带跃迁偶极矩的更精确值，μ（2）=0.215（25）D。通过在整个谱线轮廓上积分而不是测量峰值吸收并假设多普勒线宽来推断浓度，获得了比早期测量mu（2）（从单线的谱线强度导出）更高的精度。此外，一个更精确的值为甲基自由基重组的速率常数比以前可用。新的mu（2）值与高质量的从头计算非常一致。此外，气相中nu（2）和nu（3）基本带的跃迁偶极矩之比现在与凝聚相的比值非常令人满意地一致。
The line strengths of nine Q-branch lines in the nu(2) fundamental band of the methyl radical in its ground electronic state have been measured by diode laser absorption spectroscopy. The vibration-rotation spectrum of methyl was recorded in a microwave discharge in ditertiary butyl peroxide heavily diluted in argon. The absolute concentration of the radical was determined by measuring its kinetic decay when the discharge was extinguished. The translational, rotational, and vibrational temperatures, also required to relate the line strengths to the transition dipole moment, were determined from relative integrated line intensities and from the Doppler widths of the lines after allowing for instrumental factors. The line strengths of the nine Q-branch lines were used to derive a more accurate value of the transition dipole moment of this band, mu(2)=0.215(25) D. Improved accuracy over earlier measurements of mu(2) (derived from line strengths of single lines) was obtained by integrating over the complete line profile instead of measuring the peak absorption and assuming a Doppler linewidth to deduce the concentration. In addition, a more precise value for the rate constant for methyl radical recombination than available earlier was employed. The new value of mu(2) is in very good agreement with high-quality ab initio calculations. Furthermore, the ratio of the transition dipole moments of the nu(2) and nu(3) fundamental bands in the gas phase is now in highly satisfactory agreement with the ratio determined for the condensed phase.