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

奈特教授获得了实验物理化学项目的资助，利用电子自旋共振（ESR）光谱技术研究高能脉冲激光汽化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在几个领域可能是重要的，包括在微电子元件制造中涉及的硅沉积过程和在高层大气化学中涉及的反应中间体的鉴定。这项研究是与化学专业的本科生合作完成的，他们在激光、高真空技术、ESR光谱、质谱和光谱模拟方面积累了经验，所有这些都为科学和工程领域的职业生涯提供了良好的准备。通过脉冲激光汽化产生阳离子、阴离子和中性自由基，用飞行时间质谱法对这些自由基进行鉴定，并在4 K时被捕获在氖基体中。许多新的分子自由基离子在奈特教授的实验室中首次被生成和表征。所得的电子自旋共振谱线宽与气相相当，可以测定超精细结构和g值。超精细参数对电子波函数极其敏感，因此为从头算理论计算提供了严格的测试，这些计算正在与几个理论小组合作进行。

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.