Philip Stevens received a B.A. in chemistry from Oberlin College, and a Ph.D. in physical chemistry from Harvard University (1990) working under the direction of Professor James G. Anderson. Before joining the faculty at Indiana University in 1995, Professor Stevens was a postdoctoral research associate in atmospheric chemistry at The Pennsylvania State University, working with Professor William H. Brune on the development of instrumentation for the measurement of atmospheric free radicals.
Professor Stevens’ research interests focus on characterizing the chemical mechanisms in the atmosphere that influence regional air quality and global climate change. Much of his group’s research is focused on improving our understanding of the influence of biogenic emissions and their oxidation products on the chemistry of the atmosphere. This research involves laboratory studies of the kinetics of important atmospheric reactions, theoretical studies of the reaction mechanisms, and field measurements of the atmosphere in both urban and forested environments.
Our research focuses on characterizing the chemical mechanisms in the atmosphere that influence regional air quality and global climate change. An accurate understanding of this chemistry is essential to assess, control, and predict the impact of anthropogenic perturbations on the chemical and radiative properties of the atmosphere. Research projects in our group include laboratory experiments that isolate important chemical reactions and in-situ measurements of free radicals in the atmosphere.
One specific area of research involves studies of the chemistry of biogenic emissions to the atmosphere that can contribute to the production of ozone, the primary component of photochemical smog. We are currently studying the chemical mechanism and efficiency of ozone production by these compounds in the laboratory using, resonance fluorescence, laser-induced fluorescence and mass spectrometric techniques for the detection of reactants, intermediates and products. These results are compared to predictions based on electronic structure calculations and reaction rate theories to help elucidate the factors controlling the reactivity of these systems.
Another area of research involves measurements of the hydroxyl radical (OH) in the atmosphere. The OH radical plays a central role in atmospheric chemistry, as reactions with OH are the primary removal process for most pollutants in the atmosphere. However because of its high reactivity, concentrations of OH in the atmosphere are extremely small (< 1 pptv) and its chemical lifetime very short (< 1 second). As a result, accurate measurements of OH, which provide a critical test of our understanding of atmospheric chemistry, are very difficult. We have constructed an instrument capable of detecting OH in the atmosphere with high sensitivity using laser-induced fluorescence techniques. This instrument is used for both ground-based measurements of ambient OH concentrations, as well as laboratory experiments of OH radical chemistry. These results are used to test and improve current models of atmospheric chemistry.
The OH laser-induced fluorescence detection axis on top of a 31-m tower in northern Michigan
Laser-induced fluorescence instrument for measuring OH radicals
"Measurements of OH and HO2 Concentrations during the Mexico City Metropolitan Area 2006 Field Campaign: Part 1 - Deployment of the Indiana University Laser-Induced Fluorescence Instrument". S. Dusanter, D. Vimal, P. S. Stevens, R. Volkamer and L. T. Molina. Atmospheric Chemistry and Physics Discussions, 8, 13689–13739, 2008
"Experimental and ab initio dynamical investigations of the kinetics and intra-molecular energy transfer mechanisms for the OH + 1,3-butadiene reaction between 263 and 423 K at low pressure". D. Vimal, A. B. Pacheco, S. S. Iyengar, and P. S. Stevens. Journal of Physical Chemistry A, 112, 7227-7237, 2008
"Measuring tropospheric OH and HO2 by laser-induced fluorescence at low pressure: A comparison of calibration techniques". S. Dusanter, D. Vimal, and P. S. Stevens. Atmospheric Chemistry and Physics, 8, 321–340, 2008
"Experimental and theoretical studies of the kinetics of the reactions of OH and OD with 2-methyl-3-buten-2-ol between 300 and 415 K at low pressure." M. Baasandorj and P. S. Stevens. Journal of Physical Chemistry A, 111, 640-649, 2007
"Experimental and theoretical study of the kinetics of the reactions of OH radicals with acetic acid, acetic acid–d3 and acetic acid–d4 at low pressure." D. Vimal and P. S. Stevens. Journal of Physical Chemistry A, 110, 11509-11516, 2006
"Experimental and theoretical studies of the kinetics of the reactions of OH and OD with acetone and acetone-d6 at low pressure." M. E. Davis, W. Drake, D. Vimal, and P. S. Stevens. The Journal of Photochemistry and Photobiology, A: Chemistry, 176, 162-171, 2005.
"Relative Rate and Product Studies of the OH-Acetone Reaction." J. D. Raff, P. S. Stevens, and R. A. Hites. Journal of Physical Chemistry A, 109, 4728-4735, 2005
"Monitoring the OH-Initiated Oxidation Kinetics of Isoprene and its Products using On-line Mass Spectrometry." W. Lee, M. Baasandorj, P. S. Stevens, and R. A. Hites. Environmental Science and Technology, 39, 1030-1036, 2005
"Measurements of the kinetics of the OH-initiated oxidation of ?-pinene: Radical propagation in the OH + α-pinene + O2 + NO reaction system." M. E. Davis and P. S. Stevens. Atmospheric Environment, 39, 1765-1774, 2005
Department of Chemistry | College of Arts and Sciences | Chemistry Library | OneStart | Personnel | CALM | Comments
800 E. Kirkwood Ave., Bloomington, IN 47405-7102 | Ph: (812) 855-9043 | Fx: (812) 855-8300
Copyright © 2008 | The Trustees of Indiana University | Copyright Complaints
Last Modified: Tuesday, August 26, 2008 XHTML / CSS
Designed and developed by Kevin Joseph Ruble in September 2008.
