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

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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.