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This Week at Physics

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Events on Thursday, September 20th, 2012

R. G. Herb Condensed Matter Seminar
Surprises! and Puzzles? from Probing Neutral Atoms Trapped in Noble Gas Ice
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Jaideep Singh, Argonne National Lab
Abstract: Our goal is to demonstrate that a guest species trapped in a solid noble gas matrix is a quiet environment for the manipulation of nuclear spins. Applications include studies of rare isotopes and tests of fundamental symmetries. We have studied the optical spectrum of Ytterbium atoms embedded in a solid Neon matrix with the goal of spin polarizing the Yb-171 nuclei via optical pumping. The optical spectrum of the embedded atoms resembles that of free atoms with significantly matrix-shifted line-centers. We have observed spectral line-widths that vary by at least two orders of magnitude depending on the exact nature of the transition. Although some of the transitions are nanometers wide, we have evidence that they are homogenous, making optical pumping feasible. In this talk, we'll present our most recent results and discuss our progress towards the optical pumping of Yb-171.
Host: McDermott & Yavuz
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Albrecht Karle
Evidence of Electron Neutrino Appearance at T2K
Time: 2:30 pm
Place: 4274 Chamberlin
Speaker: Melanie Day, University of Rochester
Host: Albrecht Karle
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Astronomy Colloquium
"Turbulence and Cosmic-Rays in Galaxy Clusters"
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Peng Oh, UC Santa Barbara
Abstract: Although the non-thermal component of the ICM has a relatively low energy density, it can still exert a profound influence. Turbulence provides pressure support, affects magnetic field topology and thus thermal conduction, and is a source of dissipation, heat and metal diffusion. Cosmic-rays likewise provide pressure support and heating, and contain archaeological information about cosmological shocks and AGN activity, which can be mined in radio and gamma-ray data. We discuss several aspects. Turbulence: we develop a novel spectral analysis technique for Astro-H which exploits not just the line width but the entire line shape, and show how the excellent spectral resolution of Astro-H can overcome its relatively poor spatial resolution in making detailed inferences about the ICM velocity field. Cosmic rays: we show how super-Alfvenic streaming of cosmic rays can turn off radio halos, potentially explaining the observed bimodality in radio halo luminosity. We also show how diffusive shock acceleration in previous structure formation shocks can leave behind a fossil a^1/4 MeV electron population in the cluster outskirts, in the face of loss processes. Relic reacceleration can dominate over fresh injection at low Mach numbers, allowing weak shocks which would would be otherwise invisible to glow in radio emission, potentially visible with LOFAR.
Host: Ellen Zweibel
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Graduate Introductory Seminar
Condensed Matter Experimental
Time: 5:45 pm
Place: 2223 Chamberlin Hall
Speaker: Eriksson, Himpsel, Lagally, McDermott, Onellion, Rzchowski, Winokur, UW Madison
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