Spectroscopy and Chemistry of Jet-Cooled Free Radicals

有机和高分子化学项目的这项拨款支持科罗拉多大学的G.Barney Ellison博士研究喷射冷却有机自由基的红外吸收光谱。还将在快速流动反应器中研究自由基与离子的反应。自由基是不稳定的反应中间体，在许多燃烧过程和高温等离子体中起着至关重要的作用；需要光谱探测器来监测这些亚稳物种的去向。该企业将开发一种实验，该实验将能够通过自由喷射膨胀来制备强自由基光束。甲基、烯丙基和氰甲基等自由基将通过各种光化学和热源来制备。信号源将由光电离质谱计监测。将制备密度约为1mTorr的自由基，这些反应物种将被喷注冷却到约20K的旋转温度。这些自由基将用红外吸收光谱和傅里叶变换红外光谱进行研究。选择研究的是甲基自由基家族：甲基、氟甲基、二氟甲基、三氟甲基和氰甲基。在所有情况下，都计划建立分子几何结构和振动频率。由于烯丙基是最简单的共轭碳氢化合物，所以人们对它也很感兴趣。清洁、特化的自由基束将用于研究负离子(如氢氧离子或甲氧离子)与碳氢自由基(如烯丙基或苄基)之间的反应。埃里森博士希望确定烯丙基的气相酸度，以与丙烯或甲苯进行对比。单独的实验将使用这些自由基源来研究甲基自由基在清洁的金或石墨表面上的散射。这将确定这些自由基的附着系数以及分子沉积的速率。

This grant in the Organic and Macromolecular Chemistry Program supports research of Dr. G. Barney Ellison, University of Colorado, to study the infrared absorption spectroscopy of jet-cooled organic radicals. The reactions of radicals with ions will also be studied in a fast flow reactor. Radicals are unstable reactive intermediates which are of paramount importance in many combustion processes and high temperature plasmas; spectroscopic probes are needed to monitor the fate of these metastable species. The enterprise is to develop an experiment which will enable preparation of intense radical beams via a free jet expansion. Radicals such as methyl, allyl, and cyanomethyl will be prepared by a variety of photochemical and thermal sources. Sources will be monitored by a photoionization mass spectrometer. Radical densities on the order of 1 mTorr will be prepared and these reactive species will be cooled by the jet to rotational temperatures of about 20 K. These radicals will be investigated by infrared absorption spectroscopy with an FTIR. Selected for study are the family of methyl radicals: methyl, fluoromethyl, difluoromethyl, trifluoromethyl, and cyanomethyl. In all cases, it is planned to establish the molecular geometries and vibrational frequencies. The allyl radical is of similar interest since it is the simplest conjugated hydrocarbon. Clean, characterized radical beams will be used to study the reactions between negative ions, such as hydroxide ion or methoxide ion, and hydrocarbon radicals such as allyl or benzyl. Dr. Ellison hopes to establish the gas phase acidity of allyl to contrast with propene or toluene. Separate experiments will use these radical sources to study the scattering of methyl radicals off clean gold or graphite surfaces. This will establish the sticking coefficients of these radicals as well as the rate of molecular deposition.