David Gidley, professor. Ph.D., Michigan, 1979. Experimental physics, atomic physics: leptons, positron physics, weak interactions.
Professor Gidley's research centers around precision measurements of the singlet and triplet decay rates of positronium as tests of quantum electrodynamics. His group's triplet decay rate measurements disagree with theory by six to nine standard deviations and represent the only discrepancy with QED at this time. Exotic positronium decay modes have been searched for as tests of fundamental conservation laws and discrete symmetries.
His studies on surface physics using low-energy positron beams include surface defects, positronium formation on adsorbed overlayers on Ni, and generation and polarimetry of spin polarized low energy positron beams. Re-emitted positron spectroscopy (RPS) has been developed as a probe of epitaxial thin films. Detailed studies of positron tunneling through, and re-emission from, pseudomorphically strained Ni films on Cu substrates have been performed. RPS studies of Ni and Co silicides are in progress.
Professor Gidley also studies fatigue initiation in glassy polymers using positron lifetime techniques, X-ray scattering and differential scanning calorimetry. The relative density and size of voids in polymers can be deduced from orthopositronium lifetimes spectra as a means of determining fatigue-induced microstructural changes that precede visible cracks/crazing (in collaboration with Professor Albert Yee of the Department of Material Science).
Professor Gidley is also developing applications of a new positron microscope/microprobe. The new design of a UHV positron microscope capable of yielding unique contrast images has been initiated for use in such research areas as thin film nucleation and growth (positron tunneling microscopy), bimetallic surface catalytic systems and semiconductor devides. His group is collaborating with the Phoenix Memorial Lab and the Idaho National Engineering Labs to generate the required intensity positron beams.
Assistant Research Scientists Ralph Conti and Mark Skalsey are directing experiments in the following areas: excited state positronium energy spectroscopy as a test of QED, discrete symmetry tests in positronium, T-tests in atomic systems, a neutral boson search in e^+-e^- scattering and feasibility studies of antihydrogen production and research.
Research Investigator: > William Frieze
Graduate Students: Gregory Demaggio, Terry Dull, Bita Ghaffari, Dan Kilper, Richard Vallery, Li Xie
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