Dean B. Atkinson - Research Notes

Assistant Professor of Chemistry

-Ph.D., 1995, University of Arizona

-National Research Council Postdoctoral Fellowship, National Institute of Standards and Technology, 1995-1997

Analytical/Physical Chemistry; Atmospheric Chemistry and Physics; Environmental Chemistry

Research Highlight:

The Royal Society of Chemistry journal The Analyst has recently published my review of environmental science applications of Cavity Ring-Down (CRD) spectroscopy. This Tutorial Review, intended to acquaint analytical chemists and others involved in environmental chemistry with the power of the CRD method, is entitled “Solving chemical problems of environmental importance using cavity ring-down spectroscopy” (Atkinson, D, Analyst, 128, 117, (2003).) The cover figure shows J.J. Scherer’s Ring-down Spectral Photography (RSP) image of a portion of the propane spectrum. RSP, a multi-wavelength variant of CRD is one of the emergent methods described in this paper which should be of great use in atmospheric monitoring applications.

Abstract: Cavity ring-down (CRD) is a sensitive variant of traditional absorption spectroscopy that has found increasing use in a number of chemical measurement applications. This review focuses on applications of cavity ring-down spectroscopy that will be of interest to environmental chemists and analytical chemists working on environmental problems. The applications are classified into direct monitoring approaches, indirect analysis methods and ancillary studies and a differentiation is made between field-tested instruments and proof of principle studies.

Please contact me for reprints if you are interested in this or any of our other work. DBA

Background

I received my Ph.D. in Physical Chemistry from the University of Arizona in Tucson, AZ in 1995. My doctoral work, done under the direction of Dr. Mark A. Smith, centered on the investigation of radical-molecule reaction dynamics at low temperatures (1 -250 K.) I was awarded an NRC postdoctoral fellowship at the National Institute of Standards and Technology in Gaithersburg, MD, where he worked with Dr. Jeffrey W. Hudgens from 1995-1997. In 1997, I accepted a faculty position in the chemistry department at Portland State University.

My research experience and training straddles the traditional areas of fluid mechanics, atmospheric, analytical and physical chemistry. A major concentration has been on the development of novel measurement methodologies for gas phase (free) radical chemical kinetics. We have measured the rate parameters for a number of radical plus radical and radical plus stable molecule chemical reactions under unprecedented conditions of temperature and density. These reactions are known to be important to the chemistry extant in the terrestrial atmosphere, as well as other planetary atmospheres and in combustion environments.

Current Research Statement

My group’s research focuses on the chemistry and physics of the terrestrial troposphere. A major theme is the use of innovative measurement methods for difficult analytical challenges. Our centerpiece project involves the use of near-infrared continuous-wave excitation cavity ring-down (CWCRD) absorption spectroscopic detection of radicals with pulsed laser photolysis in a kinetic reactor system. This system allows us to examine reaction kinetics of organic peroxy radicals which are key intermediates in the atmospheric oxidation of volatile organic compounds (VOCs). The novelty and power of this kinetic method derive from the specific and sensitive determination of the organic peroxy radicals using the CWCRD technique. This technique and recently obtained confirmatory results are detailed in Journal of Physical Chemistry A, 106, 8891, (2002). We are currently investigating the temperature and pressure dependence of the rate coefficient of the prototypical CH₃O₂ + CH₃CH₂O₂ reaction. We have also begun kinetic and spectroscopic investigations of the iso-propyl peroxy radical.

A relatively new project which we have initiated is the measurement of the stable products of the reactions within the CWCRD reactor. Samples of the effluent from the reactor are pressurized and concentrated and then analyzed by GC/MS and/or GC/FTIR. These measurements support the kinetics project by helping to establish the reaction mechanism which is being observed and modeled. An example is the CH₃CH₂O₂ + CH₃CH₂O₂ reaction system, where the ratio of acetaldehyde to ethanol produced in the reaction and the secondary chemistry following the reaction is a measure of the branching ratio into stable products vs. free radicals (which continue to react in our system and in the atmosphere.)

Another project combines the more traditional pulsed laser cavity ring-down approach with standard aerosol handling techniques to produce a new type of portable multi-wavelength transmissometer system for measurement of the optical extinction of the atmospheric aerosol, including particle size discrimination. Preliminary results and a description of the apparatus are published in The Analyst, 126, 1216 (2001). The co-author (Jared Smith) was an undergraduate student who went on to work with Dr. Craig Taatjes at the Sandia Combustion Research Facility and is currently in the graduate program in Chemistry at UC Berkley. This instrument recently participated in a laboratory-based group intercomparison experiment called the Reno Aerosol Optics Study, which was administered by NOAA’s CMDL aerosol group and supported by NOAA-ACIP (aerosol-climate interaction program) and DOE’s ARM (atmospheric radiation measurement) program. The results of the intercomparison will be presented in an upcoming publication.

A fourth project seeks to extend the selectivity of membrane inlet mass spectrometry (MIMS) in measuring hydrocarbon concentrations in air samples. Because polluted air typically contains a complex mixture of hydrocarbons, and MIMS does not produce separation, the research focuses on ways of reducing the complexity of the mass spectrometric results. An approach based on an ozone reaction pretreatment step is described in Environmental Science & Tech., 36, 4152, (2002). Briefly, the ozone is used to convert alkenes into oxygenated species which are invisible to MIMS, while alkanes are unaffected and continue to be measured. Our current investigations are with various types of reagent ions which may be used (in Chemical Ionization mode) to simplify the mass spectra of permeated compounds.

A final project (conducted and funded jointly with Dr. O’Brien) uses mass spectrometry to follow reactions of atmospheric importance with essentially hands-off and complete detection of reactants and products. Hydrocarbons are oxidized by OH radicals and/or ozone and the complete reacting mixture is continuously drawn into an ion trap mass spectrometer where both products and reactants are analyzed. The complex chemistry involved in these reactions can be probed quickly and completely and rate parameters and/or details of the mechanism can be explored.

Publications

D. B. Atkinson, “Tutorial Review: Solving chemical problems of environmental importance using cavity ring-down spectroscopy”, Analyst, 128, 117, (2003).

F. Wedian and D. B. Atkinson, “Ozone Modulation of Volatile Hydrocarbons Using Membrane Introduction Mass Spectrometry”, Environmental Science & Tech., 36, 4152, (2002).

D. B. Atkinson and J. L. Spillman, “Alkyl Peroxy Radical Kinetics Measured Using CW-Cavity Ring-down Spectroscopy”, J. Phys. Chem. A, 106, 8891, (2002).

M. A. Ostrovsky, Y. V. Sergeev, D. B. Atkinson, L. V. Soustov, J. F. Hejtmancik, “Comparison of Ultraviolet Induced Photo-kinetics for Lens-derived and Recombinant b-crystallins”, Molecular Vision, 8, 72, (2002).

J. D. Smith and D. B. Atkinson, “A Portable Pulsed Cavity Ring-Down Transmissometer for Measurement of the Optical Extinction of the Atmospheric Aerosol”, Analyst, 126, 1216, (2001).

D. B. Atkinson and J. W. Hudgens, "Chlorination Chemistry 2. Rate Coefficients, Reaction

Mechanism, and Spectrum of the Chlorine Adduct of Allene", J. Phys. Chem. A., 104, 811, (2000).

D. B. Atkinson and J. W. Hudgens, "Chlorination Chemistry. 1. Rate Coefficients, Reaction Mechanisms, and Spectra of the Chlorine and Bromine Adducts of Propargyl Halides", J. Phys. Chem. A., 103, 7978, (1999).

D. B. Atkinson, J. W. Hudgens, and A. J. Orr‑Ewing, "Kinetic Studies of the Reactions of IO Radicals Determined by Cavity Ring‑Down Spectroscopy", J. Phys. Chem. A., 103, 6173 (1999).

D. B. Atkinson and J. W. Hudgens, "Rate Coefficients for the Propargyl Radical Self‑Reaction and Oxygen Addition Reaction Measured Using Ultraviolet Cavity Ring‑down Spectroscopy.", J. Phys. Chem. A., 103, 4242 (1999).

A. Fahr, P. Hassanzadeh, and D. B. Atkinson, “Ultraviolet Absorption Spectrum and Cross-sections of Vinyl (C₂H₃) Radical in the 225-238 nm Region.”, Chem. Phys., 236, 43 (1998).

D. B. Atkinson and J. W. Hudgens, "Chemical Kinetic Studies Using Ultraviolet Cavity Ring‑Down Spectroscopic Detection: Self‑Reaction of Ethyl and Ethylperoxy Radicals and the Reaction, O₂ + C₂H₅ ® C₂H₅O₂.", J. Phys. Chem. A., 101, 3901 (1997).

D. B. Atkinson, K. K. Irikura, and J. W. Hudgens, "Electronic Structure of the BF₂ Radical Determined by ab initio Calculations and Resonance Enhanced Multiphoton Ionization Spectroscopy.", J. Phys. Chem. A., 101, 2045 (1997).

D. B. Atkinson, V. I. Jaramillo, and M. A. Smith, "The Low Temperature Kinetic Behavior of the Bimolecular Reaction OH + HBr (76 ‑ 242 K).", J. Phys. Chem. A., 101, 3356 (1997).

D. B. Atkinson and M. A. Smith, "Design and Characterization of Pulsed Uniform Supersonic Expansions for Chemical Applications.", Rev. Sci. Inst., 66, 4434 (1995).

D. B. Atkinson and M. A. Smith, "Radical‑Molecule Kinetics in Pulsed Uniform Supersonic Flows: Termolecular Association of OH + NO Between 90 and 220K.", J. Phys. Chem., 98, 5797 (1994).