We review recent advances in the study of atoms in electric and magnetic fields. We will especially examine the decay of unstable states. Calculations of the survival probability of typical classical systems have shown that the long time decay is algebraic rather than exponential. This is because points stick to regions of phase space that are close to stable regions. We study this decay by examining segments of a line of initial conditions that escape at various times. These segments exhibit what we call "epistrophic self-similarity": the segments organize themselves into self-similar geometric sequences, but the beginnings of these sequences are only partially predictable. Points that remain form a Cantor set which we call an "epistrophic fractal". We show predictions of results of experiments that might observe such fractal structure.

报告人简介：

John B. Delos
#@Professor of Physics
#@College of William and Mary, USA

#@
• Ph.D., Massachusetts Institute of Technology, 1970#@
• 1989 - Fellow of the American Physical Society, "For his many contributions to the field of atomic and molecular collisions, and for providing insight into the relationships between the classical and quantal behavior of atomic systems."#@
• 1990 - Outstanding Scientist of Virginia, (presented by Governor D. Wilder for the Science Museum of Virginia)#@
• Vice Chair, Gordon Conference on Atomic Physics, 1995-7; #@
• Chair, Gordon Conference on Atomic Physics, 1997-9. #@
• Chair Line, Division of Atomic, Molecular and Optical Physics, American Physical Society, 1999-2003. (Vice Chair 1999-2000, Incoming Chair 2000-1, Chair 2001-2, Past Chair 2002-3.) #@

To know more about him, please go to http://physics.wm.edu/People/Delos_cv.html.