JILA, University of Colorado, National Institute of Standards and Technology, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
J Phys Chem A. 2013 Aug 15;117(32):7042-9. doi: 10.1021/jp312877k. Epub 2013 Mar 7.
High-resolution, fully rotationally resolved direct absorption spectra of hydroxymethyl radical, CH2OH, are presented in the infrared CH stretching region. As a result of low rotational temperatures and sub-Doppler linewidths obtained in the slit supersonic expansion, the Ka = 0 ← 0 band of the symmetric CH stretch for CH2OH has been unambiguously identified and analyzed. By way of chemical confirmation, hydroxymethyl radical is generated via two different slit jet discharge syntheses: (i) direct dissociation of CH3OH to form CH2OH and (ii) dissociation of Cl2 followed by the radical H atom extraction reaction Cl + CH3OH → HCl + CH2OH. The identified transitions are fit to a Watson A-reduced symmetric top Hamiltonian to yield first precision experimental values for the ground state rotational constants as well as improved values for the symmetric stretch rotational constants and vibrational band origin. The results both complement and substantially improve upon spectral efforts via previous double resonance ionization detected infrared methods by Feng et al. [J. Phys. Chem. A, 2004, 108, 7093], as well as offer high-resolution predictions for laboratory and astronomical detection of hydroxymethyl radical in the millimeter-wave region.
呈现了高分辨率、完全旋转分辨的羟甲基自由基（CH2OH）的直接吸收光谱，位于红外 CH 伸缩区域。由于在狭缝超声膨胀中获得的低旋转温度和亚多普勒线宽，CH2OH 的对称 CH 伸缩的 Ka = 0 ← 0 带已被明确识别和分析。通过化学确认，羟甲基自由基通过两种不同的狭缝射流放电合成生成：（i）甲醇直接解离形成 CH2OH 和（ii）Cl2 解离后自由基 H 原子提取反应 Cl + CH3OH → HCl + CH2OH。所识别的跃迁拟合到 Watson A-约化对称陀螺哈密顿量，得出基态转动常数的首次精密实验值，以及对称伸缩转动常数和振动带起源的改进值。这些结果不仅补充了 Feng 等人先前通过双共振电离检测红外方法进行的光谱研究[J. Phys. Chem. A, 2004, 108, 7093]，而且还为实验室和天文检测羟甲基自由基在毫米波区域提供了高分辨率的预测。
