Professor of Chemistry & Chemical Engineering and Director, Center for Atmospheric Particle Studies
Atmospheric Chemistry, Organic Aerosol, Kinetics, Reaction Dynamics, Radical-Molecule Reactivity, Ozonolysis, Mass Spectrometry
His principal interest is in the oxidation chemistry of Earth's atmosphere — specifically the oxidation of organic compounds and the associate radical processes in the atmosphere. Two closely connected areas are ozonolysis chemistry and the chemistry controlling organic-aerosol levels and properties in the atmosphere. Aerosols — fine particulate matter, or PM — are of interest for two major reasons: particles play a central role in climate, and they kill people. The leading uncertainty on the forcing side of climate science is the degree to which cloud properties have changed between 1850 and now due to changes in the number concentrations of fine, water-soluble particles that act as cloud-condensation nuclei (CCN). Also, approximately 50,000 people die prematurely each year in the U.S. alone from inhalation of elevated levels of fine PM. More than half of the fine PM mass is composed of a very complex mixture of highly oxidized organic compounds. They are water soluble and have unknown health effects but appear to correlate positively with observed health endpoints.
Recent research largely directed by Prof. Donahue within the Center for Atmospheric Particle Studies (CAPS) has established that organic aerosol exists in a dynamic balance connecting phase partitioning and oxidation chemistry. Oxidation of large, reduced organics typical of fresh emissions tends to functionalize the carbon backbone, leading to lower vapor pressure products that spend more time in the particulate (condensed) phase, but continued oxidation tends to fragment the carbon backbone as it drives the products towards the oxidative endpoint — CO2. Understanding this multiphase chemistry in the extremely rich and complex mixture that is organic aerosol is a major current research focus.
In parallel, the Donahue group is pursuing the short-lived intermediates involved in gas-phase ozonolysis chemistry, including the carbonyl-oxide (Criegee Intermediate). Reactions in the gas phase show a strong dependence on both pressure and the carbon number because energy transfer from highly-excited reaction products via collisions with the bath gas is inefficient. The group uses both experimental (spectroscopic) and theoretical (quantum chemistry coupled to statistical reaction dynamics) tools to probe the nature and fate of these intermediates.
|2008–present||Professor of Chemistry, Chemical Engineering, and Engineering and Public Policy, Carnegie Mellon University|
|2005–2008||Associate Professor of Chemistry and Chemical Engineering, Carnegie Mellon University|
|2000–2005||Assistant Professor of Chemistry and Chemical Engineering, Carnegie Mellon University|
|1991–2000||Postdoctoral Associate and Research Scientist, Harvard University|
|1991||Ph.D. Meteorology, MIT|
|2011||Fellow, American Geophysical Union|
|2010||Carnegie Institute of Technology Outstanding Research Award|
|1991–1993||DOE Distinguished Postdoctoral Fellow|
|1985–1988||NASA Graduate Student Researcher|
|1985||MIT Jule Charney Award|
Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions. Proc. Nat. Acad. Sci. 109, 13503–13508 (N. M. Donahue, K. M. Henry, T. F. Mentel, A. K. Scharr, C. Spindler, B. Bohn, T. Brauers, H. P. Dorn, H. Fuchs, R. Tillmann, A. Wahner, H. Saathoff, K. H. Naumann, O. Möhler, T. Leisner, L. Müller, M.-C. Reinnig, T. Hoffmann, K. Salow, M. Hallquist, M. Frosch, M. Bilde, T. Tritscher, P. Barmet, A. P. Praplan, P. F. DeCarlo, J. Dommen, A. S. H. Prévôt, and U. Baltensperger) 2012 (5).
MRCISD studies of the dissociation of vinylhydroperoxide, CH2CHOOH: there is a saddle point. J. Phys. Chem. A 116, 6823–6830 (T. Kurtén and N. M. Donahue) 2012 (1).
Adventures in ozoneland: Down the rabbit-hole. Phys. Chem. Chem. Phys. 13, 10848–10857 (N. M. Donahue, G. T. Drozd, S. A. Epstein, A. A. Presto, and J. H. Kroll) 2011 (10).
2,3-dimethyl-2-butene (TME) ozonolysis: Pressure dependence of stabilized Criegee intermediates and evidence of stabilized vinyl hydroperoxides. J. Phys. Chem. A 115, 161–166 (G. T. Drozd, J. H. Kroll, and N. M. Donahue) 2011.
Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol. Nature Chemistry 3, 133–139 (J. H. Kroll, N. M. Donahue, J. L. Jimenez, S. Kessler, M. R. Canagaratna, K. Wilson, K. E. Alteri, L. R. Mazzoleni, A. S. Wozniak, H. Bluhm, E. R. Mysak, J. D. Smith, C. E. Kolb, and D. R. Worsnop) 2011.
Functionalization vs fragmentation: n-aldehyde oxidation mechanisms and secondary organic aerosol formation. Phys. Chem. Chem. Phys. 12, 13975–13982 (H. J. Chacon-Madrid, A. A. Presto, and N. M. Donahue) 2010.
The HOOH UV spectrum: Importance of the transition dipole moment and torsional motion from semi-classical caluclations on an ab-initio PES. J. Chem. Phys. 132, 084304 (G. T. Drozd, A. Mel- nichuk, and N. M. Donahue) 2010.
Evolution of organic aerosols in the atmosphere: A new framework connecting measurements to models. Science 326, 1525–1529 (J. L. Jimenez, M. R. Canagaratna, N. M. Donahue et al) 2009.
Reactivity of oleic acid in organic particles: changes in oxidant uptake and reaction stoichiometry with particle oxidation. Phys. Chem. Chem. Phys. 11, 7951–7962 (A. M. Sage, A. L. Robinson, and N. M. Donahue) 2009.
Secondary organic aerosol formation from multiphase oxidation of limonene by ozone: Mechanistic constraints via two-dimensional heteronuclear NMR spectroscopy. Phys. Chem. Chem. Phys. 11, 7810–7818 (C. S. Maksymiuk, C. Gayathri, R. R. Gil, and N. M. Donahue) 2009.
Rethinking organic aerosols: Semivolatile emissions and photochemical aging. Science 315, 1259–1263 (A. L. Robinson, N. M. Donahue, M. K. Shrivastava, A. M. Sage, E. A. Weitkamp, A. P. Grieshop, T. E. Lane, J. R. Pierce, and S. N. Pandis) 2007.
Coupled partitioning, dilution, and chemical aging of semivolatile organics. Environ. Sci. Technol. 40, 2635 – 2643 (N. M. Donahue, A. L. Robinson, C. O. Stanier, and S. N. Pandis) 2006.
Reaction barriers: Origin and evolution. Chem. Rev. 103, 4593?4604 (N. M. Donahue) 2003.