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<div><span id="docs-internal-guid-9f2a40ae-584d-f1f5-55e1-1a6b8e55fe71">
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<span style="font-size: 28pt; font-family: 'Times New Roman'; color: rgb(192, 0, 0); font-weight: 700; vertical-align: baseline;">Spring 2017 Colloquium</span></p>
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<span style="font-size: 16pt; font-family: 'Times New Roman'; font-weight: 700; vertical-align: baseline;">Department of Physics & Astronomy</span></p>
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<span style="font-size: 16pt; font-family: 'Times New Roman'; color: rgb(192, 0, 0); font-weight: 700; vertical-align: baseline;">April 27, Thursday, 4-5 PM in Science Building 127</span></p>
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<span style="font-size: 14pt; font-family: 'Times New Roman'; vertical-align: baseline;">(coffee and cookies will be served at 3:50 PM)</span></p>
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<span style="font-size: 18pt; font-family: 'Times New Roman'; color: rgb(0, 176, 80); font-weight: 700; vertical-align: baseline;">Atomic Molecular Optical (AMO) Physics
</span></p>
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<span style="font-size: 24pt; font-family: 'Times New Roman'; color: rgb(0, 0, 255); font-weight: 700; vertical-align: baseline;">Vortices in atomic collisions</span><span style="font-size: 24pt; font-family: 'Times New Roman'; color: rgb(0, 0, 255); font-weight: 700; vertical-align: baseline;"><br class="kix-line-break">
</span><span style="font-size: 14pt; font-family: 'Times New Roman'; font-weight: 700; vertical-align: baseline;">Dr. Sandra Quintanilla</span></p>
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<span style="font-size: 14pt; font-family: 'Times New Roman'; font-weight: 700; vertical-align: baseline;">University of North Texas
</span></p>
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<span style="font-size: 14pt; font-family: 'Times New Roman'; font-weight: 700; vertical-align: baseline;"><img src="https://lh4.googleusercontent.com/Y0IS9VBLxiqWR5Y9eh3Yb3n5UPnH9gb5GpVMKuYvJeBaZTMPP1-11vG9xaDaRtMH9bEU10FYmMnG5Fbnlq3RSyp4s84tE3-rfBVpvZllVxjnk5supjHU_hKC4Xp2xxjPNs_E4Z9X" width="170" height="183" originalwidth="170" originalheight="183" style="font-family: 'Times New Roman', serif; font-size: 16px; font-weight: normal; line-height: 22.08px; text-align: justify; border: none; transform: rotate(0rad);"></span></p>
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<span style="font-size: 12pt; font-family: 'Times New Roman'; vertical-align: baseline; background-color: rgb(255, 255, 255);"><br class="kix-line-break">
</span><span style="font-size: 10pt; font-family: Arial; vertical-align: baseline;">Dr. Sandra Ward Quintanilla earned B.Sc. with 1st class honours in 1983 in Physics at Royal Holloway College, University of London, UK. She earned her Ph.D. in 1986 in Atomic
Physics at the Royal Holloway & Bedford New College, University of London. The title of her Ph. D. thesis is “A Theoretical study of Elastic Electron Positronium Scattering and Photo-absorption by the Positronium Negative Ion". She worked as a post-doc at
York University, Toronto, Canada and at the University of Tennessee, Knoxville, before coming to the University of North Texas as an assistant professor in 1991. She was on Faculty Development Leave for the academic year where she divided her time between
the University of Tennesse, Knoxville, and the Institute of Theoretical Atomic and Molecular Physics at the Harvard-Smithsonian Center for Astrophysics. In 1997, Dr. Quintanilla was promoted to associate professor and in 2007 as full professor. Dr. Quintanilla’s
research is in theoretical atomic physics. </span><a href="http://physics.unt.edu/people/sandra-quintanilla-phd" style="text-decoration:none;"><span style="font-size: 11pt; font-family: Arial; color: rgb(17, 85, 204); text-decoration: underline; vertical-align: baseline;">http://physics.unt.edu/people/sandra-quintanilla-phd</span></a></p>
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<span style="font-size: 12pt; font-family: Arial; font-weight: 700; vertical-align: baseline;">Abstract:
</span><span style="font-size: 12pt; font-family: Arial; vertical-align: baseline;">Vortices are of interest in many areas of physics such as fluid dynamics, astrophysics, condensed matter, and nonlinear dynamics. Vortices have been studied for macroscopic
multiparticle systems, such as Bose-Einstein condensates. It is interesting that a zero in a complex function is related to the physical process of the transfer of angular momentum. Recently, a deep minimum in experimental measurements in the triply differential
cross section for electron-impact ionization of helium has been interpreted in terms of a vortex. We have theoretically obtained vortices in the atomic process of inner-shell ionization of carbon by electron impact, electron-impact ionization of atomic hydrogen
and positronium formation of positron-hydrogen collisions. This is exciting since it had been predicted that deep minima (exact zeros) in the triply differential cross section could not be obtained for ionization of hydrogen by electron impact.</span></p>
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