Laser Vaporization Generation of Radical Ions and Reactive Intermediates for Matrix Isolation ESR Studies

奈特教授得到了实验物理化学计划的资助，利用电子自旋共振(ESR)光谱学研究在高能脉冲激光蒸发条件下产生的化学反应产物。从这些研究中获得的科学知识可在若干领域发挥重要作用，包括制造微电子部件所涉及的硅沉积过程以及鉴定大气上层化学中所涉及的活性中间体。这项研究是与化学专业的本科生合作完成的，他们获得了激光、高真空技术、ESR光谱、质谱学和光谱模拟的经验，所有这些都为在科学和工程领域的职业生涯做好了准备。阳离子、阴离子和中性自由基是由脉冲激光蒸发产生的，这些自由基通过飞行时间质谱仪进行鉴定，并在4K时被捕获在霓虹灯基质中。在奈特教授的实验室中，许多新的分子自由基离子正在产生并首次被表征。获得的电子自旋共振谱的线宽可与气相中的线宽相媲美，并允许测定超精细结构和g值。超精细参数对电子波函数非常敏感，因此提供了严格的从头计算测试，这些计算是与几个理论小组合作进行的。

Professor Knight is supported by a grant from the Experimental Physical Chemistry Program to study chemical reaction products generated under high energy pulsed laser vaporization conditions using electron spin resonance (ESR) spectroscopy. Scientific knowledge obtained from these studies could be important in several areas including silicon deposition processes involved in the fabrication of microelectronic components and identification of reactive intermediates involved in upper atmospheric chemistry. This research is done in collaboration with undergraduate students in chemistry who gain experience with lasers, high vacuum technology, ESR spectroscopy, mass spectrometry, and spectral simulations, all of which provide good preparation for careers in science and engineering. Cation, anion and neutral radicals are produced by pulsed laser vaporization, the radicals are identified by time-of-flight mass spectroscopy, and are trapped in a neon matrix at 4 K. Many new molecular radical ions are being generated and characterized for the first time in Prof. Knight's laboratory. The electron spin resonance spectra obtained have linewidths which are comparable to those in the gas phase and allow the determination of hyperfine structure as well as g values. Hyperfine parameters are extremely sensitive to the electronic wavefunction and hence provide stringent tests of ab initio theoretical calculations which are being carried out in collaboration with several theoretical groups.