Matthew Sprague

B.A., Physics, B.S., Chemistry, Ithaca College, 2005
Seventh-year graduate student

The focus of our research is measuring the spectroscopy and kinetics of atmospherically relevant radical reactions. In the laboratory, we use infrared cavity ringdown spectroscopy (IR-CRDS), a spectroscopic technique that uses an optical cavity (placing the sample between two highly reflective mirrors) to obtain an effective optical path length of kilometers. The main advantage to using IR-CRDS is sensitivity, as we can study reaction kinetics at very low concentrations, or of molecules that are typically weak IR absorbers.

In order to interpret laboratory measurements, we use quantum chemistry calculations to obtain geometries, energies, transition frequencies, and simulated spectra of the molecules that we are studying. (For those of you keeping track, my favorite methods are B3LYP and CCSD). These calculations can be crucial to obtaining quantitatively accurate chemical kinetics because fundamental molecular properties, such as hydrogen bonding, can cause the experimentally measured spectra to become more complicated than expected.

To date, I have studied three chemical systems:

Potential Energy Surface of Peroxynitrous Acid (HOONO) – HOONO is a weakly bound isomer of nitric acid, formed from the reaction OH+NO2. HOONO has a short lifetime, and therefore does not act as a sink of NO2. The lowest energy isomer of HOONO is a planar geometry containing an internal hydrogen bond. Torsional excitation in HOONO breaks this hydrogen bond, causing a shift in the OH stretch frequency. In collaboration with Professor Anne McCoy (Ohio State), we have computed potential energy surfaces to model the coupling between the torsional modes and OH stretch mode of HOONO. The simulated OH stretch spectrum will allow us to refine our interpretation of the previously acquired CRDS measurements.

Alkoxy Isomerization: Spectroscopy, Kinetics, and Quantum Chemistry of HOC4H8, HOC4H8OO, HOC5H10, HOC5H10OO – Alkoxy radicals are formed in the atmosphere by reaction of hydrocarbons with HOx and NOx, therefore playing a role in tropospheric ozone formation. Once formed, alkoxy radicals can isomerize or react with O2. We have measured the OH stretch and A-X electronic spectra of the primary isomerization products of n-butoxy and 2-pentoxy isomerization. Our current work, as well as prior work in the Okumura group, has shown that these spectroscopic bands can be used to derive the relative kinetics of isomerization vs. reaction with O2 with better precision than previously conducted end-product studies. Our quantum chemistry study reveals changes in the spectroscopic bands between HOR and HOROO, in excellent agreement with our laboratory measurements.

Reaction of Hydroperoxy (HO2) with Formaldehyde: Spectroscopy, Kinetics, and Quantum Chemistry of HOCH2OO – The reactions of HO2 with carbonyls are believed to be a sink for carbonyls in the upper troposphere / lower stratosphere (UT/LS). The reactants form a hydrogen bound complex before isomerizing into a hydroxyalkylperoxy. We have measured the OH stretch and A-X spectra of HOCH2OO, the product formed from reaction of HO2 and formaldehyde. Both bands have been used to obtain the kinetics of HOCH2OO formation and destruction. We have also used quantum chemistry calculations to obtain potential energy surfaces of HOCH2OO, model the spectroscopic bands of HOCH2OO, and to determine the most accurate methods for calculating relevant transition frequencies in substituted peroxy radicals.

Publications

  1. Sprague, M.K., E.R. Garland, A.K. Mollner, C. Bloss, B.D. Bean, M.L. Weichman, L.A. Mertens, M. Okumura, and S.P. Sander. "Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy," Submitted to J. Phys. Chem. A.

  2. Mollner, A.K., S. Valluvadasan, L. Feng, M.K. Sprague, M. Okumura, D.B. Milligan, W.J. Bloss, S.P. Sander, P.T. Martien, R.A. Harley, A.B. McCoy, and W.P.L. Carter, "Rate of Gas Phase Association of Hydroxyl Radical and Nitrogen Dioxide," Science 330 (2010): 646-649.

  3. McCoy, A.B., M.K. Sprague, and M. Okumura, "The role of torsion/torsion coupling in the vibrational spectrum of cis-cis HOONO," J. Phys. Chem. A 114 (2010): 1324-1333.

  4. Dentinger, P.M., B.A. Simmons, E. Cruz, and M. Sprague. “DNA-Mediated Delivery of Lipophilic Molecules via Hybridization to DNA-Based Vesicular Aggregates,” Langmuir 22 (2006): 2935-2937.

Funding

National Defense Science and Engineering Graduate Fellowship, 2006-2009

Extracurricular Interests

Music (trumpet, various flavors of saxophone, clarinet), computer repair, video games, board games, NFL Football (Buffalo Bills)