Polarized Electron Physics

点击翻译按钮获取中文摘要

This project involves the study of collisions between polarized electrons (having an average spin that points preferentially in one direction) and chiral, or "handed" molecules as well as zinc atoms. The former experiments address physics questions about the dynamics of electron-molecule scattering, particularly with regard to the role played by electron spin in collisions with molecules that have a handed stereochemical structure. They will also provide important clues about the origins of biological homochirality -- the fact that all naturally-occurring DNA spirals in the same direction. The zinc experiments are being done to check the results of an experiment done recently by an Australian group in which states of zinc excited by polarized electrons exhibited linear polarization that was tilted relative to the incident beam direction in the collision. This result is forbidden by all known theories of atomic collisions; if the Australian result is reproduced, much of our basic theoretical knowledge of how electrons collide with atoms and molecules will be shown to be in error. Improved sources and analyzers of polarized electrons are being developed. We are testing increasingly compact designs of electron spin detectors. We also are studying multiphoton ionization of bulk materials such as the semiconductor GaAs to see if polarized electrons can be photoemitted from such material even when the surface has not been prepared to give it a negative electron affinity -- the normal method used to produce efficient photoemitters. This latter work holds the promise of providing new analytical tools for biological and materials research, and for industry. These experiments will have an impact beyond the immediate community of atomic, molecular, and optical science. In addition to its broader scientific implications, this work will have a significant educational component. Undergraduates working on these projects will have their first experience in scientific research. In an effort to expand the talent pool for atomic, molecular, and optical physics, women and underrepresented minorities will be especially recruited for these positions. The experiments with chiral molecules and their connection to astrobiological questions make an excellent topic for talks that will be given regularly to high school and civic groups, and that serve to illustrate the beauty of basic physics to a large lay audience.