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Electron chemistry, detector physics.

Electron behavior lies at the heart of the research that merited this year's Nobel Prizes in Physics and in Chemistry.

French physicist Georges Charpak of the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland, won the physics prize for the invention and development of electronic particle detectors capable of tracking the ephemeral subatomic products of high-energy collisions between particles in accelerators.

Canadian-born physical chemist Rudolph A. Marcus of the California Institute of Technology in Pasadena won the chemistry prize for theoretical work elucidating the intricacy of chemical processes involving the transfer of electrons between molecules in solution.

In the late 1960s, Charpak invented the "multiwire proportional chamber" to cope with the demands of rapidly characterizing the large numbers of extremely short-lived, exotic particles created during high-energy interactions. His device consisted of a flat, closely spaced array of thin, parallel, positively charged wires placed between two negatively charged plates in a gas-filled chamber.

Any charged particle entering the chamber would tear electrons away from the gas atoms or molecules inside. The freed electrons would then stream toward the positively charged wires, producing electrical signals that could be amplified and sent directly to a computer for recording and analysis.

Such an arrangement, which ended reliance on photographed particle tracks in bubble chambers and inaugurated the age of electronic particle detection, allowed physicists to pinpoint individual particle trajectories with improved precision while handling hundreds of thousands of such events per second. Thus, researchers could sift through billions of interactions to focus on rare but particularly interesting examples of exotic particles.

Descendants of this type of detector played key roles in the discoveries of several new particles, including the W and Z particles. The Superconducting Super Collider, under construction near Waxahachie, Texas, will have similar detectors.

In the 1950s and '60s, Marcus, while at the Polytechnic Institute of Brooklyn and later at the University of Illinois at Urbana-Champaign, developed a theory describing how electrons can jump from one molecule to another without breaking chemical bonds. He found simple mathematical expressions for the way changes in the molecular structure of reacting molecules and their neighbors affect the energy of a molecular system. He could then calculate the rates of electron-transfer reactions and explain the surprisingly large differences in the rates at which various reactions occur in terms of these molecular rearrangements.

Initially controversial, Marcus' theory was vindicated by experimental work in the 1980s. His theory illuminates a variety of important chemical processes, from photosynthesis and chemiluminescence to corrosion and the behavior of electrically conducting polymers.
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Title Annotation:Nobel Prize in Physics and Chemistry awarded to Georges Charpak and Rudolph A. Marcus for innovative developments in particle analysis and electron reactions
Author:Peterson, Ivars
Publication:Science News
Article Type:Brief Article
Date:Oct 24, 1992
Words:421
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