Simon W. North
Professor
Ph. D., University of California at Berkeley
Contact
Information:
Department of Chemistry
Texas A&M University
College Station, TX 77842
Phone:
(979) 845-4947
Fax: (979) 845-2971
north@chem.tamu.edu
Our research involves trying to understand chemical reactivity on a microscopic quantum-state resolved level. We focus on isolated molecules in the gas-phase to develop a detailed description of the factors which influence the rates, energy disposal, and final products in a reaction. In order to address these issues we use lasers to carefully control the preparation of excited molecules and to probe all the properties of the reaction products. Our specific interests include understanding stratospheric and upper tropospheric photochemistry and the tropospheric oxidation of biogenic hydrocarbons. Our photochemistry experiments combine molecular beam and state-resolved ionization techniques with position-sensitive ion imaging to determine the identity and energy content of photochemical products in the absence of secondary collisions. Studies focus on the ultraviolet photolysis of halocarbons, transient halogen oxides such as ClO, BrO, IO, and the important halogen reservoir species. Our studies seek to establish quantitative trends in the wavelength-dependent photochemistry of these molecules in order to assess their atmospheric significance.
Our group is also interested in understanding tropospheric chemistry. One effort involves the study of the oxidation of tropospheric biogenic hydrocarbons which has major implications for local and regional air quality. In recent years it has become increasing evident that refining our understanding of atmospheric chemistry of hydrocarbons requires detailed characterization of the elementary reaction mechanism that must involve combined experimental and theoretical studies. Our approach is based on this philosophy, combining state-of-the-art experimental techniques, chemical ionization mass spectrometry and laser photolysis/laser induced fluorescence, with modern ab initio and rates theory calculations to obtain a comprehensive and predictive description of hydrocarbon oxidation chemistry. Ultimately our goal is to predict ozone formation on the regional and global scales as well as the long-range transport of NOx. Recently we have extended our atmospheric studies to include the development and application of field instrumentation for measuring trace radical species.
Finally, our group is involved in collaborative efforts with Rodney Bowersox (Aerospace Engineering) and the National Aerothermochemistry Laboratory at Texas A&M University. We are currently developing novel laser diagnostics for velocity and basic state characterization in hypersonic flows. These diagnostics will be used to understand the phenomenon of Laminar-Turbulent transition in reacting flows over surfaces.
K. S. Dooley, J. N. Geidosch, and S. W. North "Ion Imaging Study of IO radical Photodissociation: Accurate Bond Dissociation Energy determination" Chem. Phys. Lett. 457, 303 (2008).
D. L. Osborn, P. Zou, H. Johnsen, C. C. Hayden, C. A. Taatjes, V. D. Knyazev, S. W. North, D. S. Peterka, M. Ahmed, and S. R. Leone "The multiplexed chemical kinetic photoionization mass spectrometer: A new approach to isomer-resolved chemical kinetics" Rev. Sci. Instrum. 79, 104103 (2008).
E. E. Greenwald and S. W. North,Y. Georgievskii and S. J. Klippenstein: "A Two Transition State Model for Radical-Molecule Reactions: Application to Isomeric Branching in the OH-Isoprene Reaction" J. Phys. Chem. A 111, 5582 (2007).
H. Kim, K. S. Dooley, S. W. North, G. E. Hall, and P. L. Houston: "Anisotropy of Photofragment Recoil as a Function of Dissociation Lifetime, Excitation Frequency, Rotational Level and Rotational Constant" J. Chem. Phys. 125 ,133316 (2006).
H. Kim, K. S. Dooley, E. R. Johnson, and S. W. North, "Photodissociation of the BrO Radical using Velocity Map Ion Imaging : Excited State Dynamics and Accurate D0(Br-O) Evaluation" J. Chem. Phys. 124, 134304 (2006).
H. Kim, K. S. Dooley, E. R. Johnson, and S. W. North, "Design and Characterization of a Late-Mixing Flash Pyrolytic Source for Expansion Cooled Radicals" Rev. Sci. Instrum. 76, 124101 (2005).
E. E. Greenwald, K. C. Anderson, J. Park, H. Kim, B. J. E. Reich, S. A. Miller, and S. W. North "The OH Initiated Oxidation of 1,3-Butadiene in the Presence of O2 and NO: A Photolytic Route to Study Isomeric Selective Reactivity" J. Phys. Chem. A 109, 7915 (2005).
E. E. Greenwald, S. W. North,Y. Georgievskii and S. J. Klippenstein, "A Two Transition State Model for Radical-Molecule Reactions: A Case Study of the Addition of OH to C2H4" J. Phys. Chem. A 109, 6031-6044 (2005).
