Robert G. Keesee


Atmospheric Chemistry
Associate Professor
Office: Earth Science 214
Phone: (518) 442-4566

B.S.(Chemistry and Mathematics), 1975, University of Arizona
Ph.D. (Physical Chemistry), 1979, University of Colorado
National Research Council Postdoctoral Associate, 1979-81, NASA-Ames Research Center

Chemistry of planetary atmospheres, atmospheric aerosols and ions. Gas-to-particle conversion, nucleation phenomena, gas-surface interactions.

The interest in natural and anthropogenic atmospheric aerosols is driven by their significant influence on the physical properties of the atmosphere including cloud formation and precipitation, electrical phenomena, radiative transfer, visibility and temperature. Chemical properties are also affected since aerosols present pathways for reactions, transport, and deposition that would not occur in the gas phase alone. The heterogeneous or multiphase chemistry in which atmospheric aerosol particles and droplets participate is considerably less well understood than the homogeneous gas phase chemistry of the atmosphere. As a recent example, this lack of understanding contributed to a failure of atmospheric chemical models to anticipate the springtime Antarctic stratospheric ozone depletion.

Our current research is directed at exploring the chemistry of aerosols. The goals are two-fold. One is to identify and quantify processes of chemical aging for atmospheric aerosol particles and the other is to determine the roles of these processes in altering the ability of particles to serve as nuclei for formation of cloud droplets.

Our research approach involves experimental investigation in the laboratory of fundamental processes. We are developing methods to study heterogeneous nucleation and condensation on aerosol particles, the processes of chemical aging of aerosol particles, and the effects of aging on the properties of aerosol particles. The experimental system being developed to scrutinize these processes involves the combination of electric levitation of single particles with thermal gradient diffusion and optical detection techniques. The electric levitation technique is a variation of the well-known Millikan oil drop experiment and allows the experimenter to interrogate a single micron-sized particle for extended periods that can be comparable to the residence time of a particle in the atmosphere. The thermal gradient diffusion technique creates a steady supersaturated environment for study of vapor-to-liquid nucleation. Laser spectroscopic methods that include Mie scattering and Raman scattering are being instituted for additional diagnostics.