US-France Cooperative Research: Kinetics and Dynamics of Refractory Radical Reactions

该奖项将支持Rensselaer理工学院的Arthur Fontijn博士和法国波尔多大学光物理和光化学实验室的G. Dorth博士之间的合作研究。这项研究的目的是进行交叉分子束实验，这将使研究人员能够研究孤立的化学反应，并精确地确定反应进行所需的阈值能级。了解难熔元素自由基的气相反应是一项重要的基础知识，也是对包括燃烧、化学气相沉积和高层大气化学等许多方面的实际问题进行建模所必需的。然而，由于难以获得这些物质的足够浓度，很少有研究者测量它们的反应，大多数研究都是在室温下进行的。在建议的程序中，选择的“难熔自由基”的反应将通过两种互补的方法进行研究。它们的动力学将在300 - 1800 K范围内通过伦斯勒独特的HTFFR（高温快流反应器）和/或HTP（高温光化学）技术进行测量。它们的动力学将通过波尔多同样独特的脉冲交叉超音速分子束（用激光蒸发难熔物质）技术进行研究。来自动力学测量的激发函数将使用动力学功的绝对值转换为速率系数与温度的关系图，从而允许对单通道，将动力学结果外推到更宽的温度范围。动力学工作涉及处于热平衡激发态的反应物，而动力学研究产生状态到状态的信息。结果的差异可以揭示重要的第二通道，例如可归因于振动激励。波尔多反应能量的准确测定将为解释反应的伦斯勒结果提供宝贵的帮助，例如那些不充分了解这些数据的碱土原子的反应。

The award will support collaborative research between Dr. Arthur Fontijn, Rensselaer Polytechnic Institute, and Dr. G. Dorth, Laboratory of Photophysics and Photochemistry, University of Bordeaux, France. The objective of the research is to carry out crossed molecular beam experiments, which will allow the investi- gators to study isolated chemical reactions and to determine precisely the threshold energy level necessary for the reactions to proceed. Knowledge of gas-phase reactions of radicals of refractory elements is of fundamental interest, and is required for the modeling of practical problems including many aspects of combustion, chemical vapor deposition and upper atmospheric chemistry. Yet, because of the difficulties inherent in obtaining adequate concentrations of such species, their reactions have been measured by few investigators and most studies made concern near room- temperature kinetics. In the proposed program, selected reactions of "refractory radicals" will be studied by two complementary approaches. Their kinetics will be measured in the 300 - 1800 K range by the unique HTFFR ( high-temperature fast-flow reactor) and/or HTP (high-temperature photochemistry) techniques at Rensselaer. Their dynamics will be investigated by the equally unique pulsed crossed supersonic molecular beams (with laser evaporation of the refractory species) technique in Bordeaux. The excitation functions from the dynamics measurements will be converted to rate coefficient versus temperature plots using absolute values from the kinetics work and thus allow, for single channels, extrapolation of the kinetic results to wider temperature ranges. The kinetic work involves reactants in thermal equilibrium excitation states, while the dynamics studies yield state-to-state information. Differences in results can reveal important second channels, such as are attributable to vibrational excitation. The accurate determination of the reaction energetics in Bordeaux will provide an invaluable aid to the interpretation of the Rensselaer results for reactions, such as those of the alkaline earth atoms, where these data are not adequately known.