Stanford Woods Institute for the Environment
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Marguerite Blake Wilbur Professor of Natural Science and Professor, by courtesy, of Physics
Current Research and Scholarly InterestsMy research group is exploring a variety of topics that range from the basic understanding of chemical reaction dynamics to the nature of the chemical contents of single cells.
Under thermal conditions nature seems to hide the details of how elementary reactions occur through a series of averages over reagent velocity, internal energy, impact parameter, and orientation. To discover the effects of these variables on reactivity, it is necessary to carry out studies of chemical reactions far from equilibrium in which the states of the reactants are more sharply restricted and can be varied in a controlled manner. My research group is attempting to meet this tough experimental challenge through a number of laser techniques that prepare reactants in specific quantum states and probe the quantum state distributions of the resulting products. It is our belief that such state-to-state information gives the deepest insight into the forces that operate in the breaking of old bonds and the making of new ones.
Space does not permit a full description of these projects, and I earnestly invite correspondence. The following examples are representative:
The simplest of all neutral bimolecular reactions is the exchange reaction H H2 -> H2 H. We are studying this system and various isotopic cousins using a tunable UV laser pulse to photodissociate HBr (DBr) and hence create fast H (D) atoms of known translational energy in the presence of H2 and/or D2 and using a laser multiphoton ionization time-of-flight mass spectrometer to detect the nascent molecular products in a quantum-state-specific manner by means of an imaging technique. It is expected that these product state distributions will provide a key test of the adequacy of various advanced theoretical schemes for modeling this reaction.
Analytical efforts involve the use of capillary zone electrophoresis, two-step laser desorption laser multiphoton ionization mass spectrometry, cavity ring-down spectroscopy, and Hadamard transform time-of-flight mass spectrometry. We believe these methods can revolutionize trace analysis, particularly of biomolecules in cells.
Professor of Electrical Engineering and of Geophysics
Current Research and Scholarly InterestsResearch
My students and I study the surfaces of Earth and planets using radar remote sensing methods. Our specialization is interferometric radar, or InSAR. InSAR is a technique to measure mm-scale surface deformation at fine resolution over wide areas, and much of our work follows from applying this technique to the study of earthquakes, volcanoes, and human-induced subsidence. We also address global environmental problems by tracking the movement of ice in the polar regions. whose ice mass balance affects sea level rise and global climate. We participate in NASA space missions such as Cassini, in which we now are examining the largest moon of Saturn, Titan, to try and deduce its composition and evolution. Our work includes experimental observation and modeling the measurements to best understand processes affecting the Earth and solar system. We use data acquired by spaceborne satellites and by large, ground-based radar telescopes to support our research.
I teach courses related to remote sensing methods and applications, and how these methods can be used to study the world around us. At the undergraduate level, these include introductory remote sensing uses of the full electromagnetic spectrum to characterize Earth and planetary surfaces and atmospheres, and methods of digital image processing. I also teach a freshman and sophomore seminar course on natural hazards. At the graduate level, the courses are more specialized, including the math and physics of two-dimensional imaging systems, plus detailed ourses on imaging radar systems for geophysical applications.
InSAR Review Board, NASA Jet Propulsion Laboratory (2006-present); editorial board, IEEE Proceedings (2005-present); NRC Earth Science and Applications from Space Panel on Solid Earth Hazards, Resources, and Dynamics (2005-present); Chair, Western North America InSAR (WInSAR) Consortium (2004-06); organizing committee, NASA/NSF/USGS InSAR working group; International Union of Radioscience (URSI) Board of Experts for Medal Evaluations (2004-05); National Astronomy and Ionospheric Center, Arecibo Observatory, Visiting Committee, (2002-04; chair, 2003-04); NASA Alaska SAR Facility users working group (2000-present); associate editor, IEEE Transactions on Geoscience and Remote Sensing (1998-present); fellow, IEEE (1998)