Department of Physics

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Colloquia & Seminars, Fall 2006

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Dissociation of molecular ions studied by coincidence three-dimensional momentum imaging

Speaker: Prof. Pengqian Wang
Date: Thursday, November 30, 2006
Time: 4 p.m.
Room: 205 Currens Hall

Abstract
When a neutral molecule is ionized, the resultant molecular ion may dissociate through various pathways, each characterized by its own species of fragments and momentum distribution. Coincidence measurement and momentum imaging of the fragments are powerful techniques to disentangle the different breakup channels and explore the dynamics that governs each dissociation pathway. In this talk the details of multi-dimensional coincidence mass spectroscopy and three-dimensional momentum imaging will be presented. Experimental results from electron impact ionization of polyatomic molecules and intense laser interaction with molecular ion beams are shown as examples. Some interesting results, such as the abundance of different dissociation channels, sequential dissociation, and the identification of dissociation pathways in complex molecules are discussed.

About the speaker:
Dr. Pengqian Wang is an assistant professor at the Department of Physics of Western Illinois University. He received his Ph.D. degree from Peking University (China) in 1998. Before coming to Western Illinois University, Dr. Wang has held postdoctoral research positions at Riken (Japan), the Max-Planck Institute for Extraterrestrial Physics (Germany), and Kansas State University. His main interests are in molecular spectroscopy and laser-molecule interactions.

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Solid state physics in neutron stars: An introduction to color superconductivity

Speaker: Dr. Andreas Schmitt (Washington University, St. Louis)

Date: Thursday, November 16, 2006
Time: 4 p.m.
Room: 205 Currens Hall

Abstract:
Cold and dense quark matter is a color superconductor. A good candidate for such matter in nature is the interior of a neutron star. An introduction into the topic of color superconductivity and its applications to astrophysics is given, revealing parallels and differences to superconductors and superfluids in condensed matter systems. In particular, the current controversial discussion of the ground state at moderate (not asymptotically large) densities is reviewed, and possible candidates for this ground state are presented.

About the speaker:
Dr. Schmitt obtained his Ph.D. in 2004 from J. W. Goethe-University in Frankfurt am Main, Germany. From 2005 to 2006 he was a Postdoctoral Research Associate at Massachusetts Institute of Technology (MIT), and currently he is a Postdoctoral Research Associate at Washington University in St. Louis. His research deals with super-dense states of matter in neutron stars, as well as physics of cold gases of trapped atoms.

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Multidisciplinary Applications of State-Selected Atoms

Speaker: Prof. Ronald Walsworth
Date: Tuesday, October 24, 2006
Time: 4 p.m.
Room: 205 Currens Hall

Abstract:
State-selected atoms provide powerful tools to attack a wide range of problems in basic and applied science. Examples I will discuss include: atomic population inversion, which enables masers that can be used as high-stability clocks and for precision tests of relativity; spin polarization of noble gases, which enables high-sensitivity gas-phase NMR, with applications in biomedical imaging and materials science; and coherent superposition of atomic states, which can be crafted to enable "slow" and "stored" light, with applications in quantum information processing and photonics.

About the speaker:
Dr. Ronald Walsworth is a Senior Lecturer on Physics at Harvard University, and a Senior Scientist at the Smithsonian Institution. He leads a research group pursuing a wide range of investigations, including the development of atomic clocks; precise tests of fundamental physical laws and symmetries; 'stopped light' and applications to quantum information processing; studies of porous and granular media; and biomedical imaging with applications to pulmonary physiology and medicine. His research has been featured in the New York Times, boston Globe, National Public Radio, Scientific American, Science, Science News, MSNBC News, and Discover Magazine.