Dr. Geoffrey A Blake

The Blake group utlizes state-of-the-art spectroscopic tools to examine a number of problems related to climate and global change. The focus at present is primarily on laboratory studies, though we are building new instruments that we hope to use in a variety of field measurements. Two major areas of investigation are the role of stable isotopic studies as tracers of biobeochemical cycles, particularly that of nitrogen; and the development of novel ultraviolet through mid-IR coherent spectrometers. In the first area we are studying the isotopic systematics in the UV photolysis of nitrous oxide. This species falls under the Kyoto 1997 Protocal, but estimates of its global budget have large uncertainties. We have recently verified a novel wavelength-dependent fractionation mechanism in the UV photolysis of N2O that obviates the need for exotic chemistry in the middle atmosphere, and that will provide a new tracer of atmospheric transport in general and troposphere-stratosphere exchange in particular. Field studies of this effect will require the development of miniaturized isotope ratio spectrometers, and we are now constructing such an instrument based on IR-laser induced fluorescence. UV analogs of this technology are also being developed. These spectrometers are being used with Prof. Paul Wennberg's group at Caltech to investigate the photochemistry of species such as peroxyntric acid and to construct a new Br and BrO instrument with sub-ppt sensitivity and Hz response rates.