Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session S19: Undergraduate Session II |
Hide Abstracts |
Sponsoring Units: SPS Chair: Monica Plisch, American Physical Society Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Director's Row 47 |
Monday, April 14, 2008 2:06PM - 2:18PM |
S19.00001: Optimization of CESR-c Optics for High Time-Integrated Luminosity Mackenzie Van Camp, James Crittenden The Cornell Electron Storage Ring (CESR) operates at world-record production rates for bound states of charm quarks, enabling unprecedented statistical precision in the study of their decays. Its success depends on maximizing the time-integrated collision rate between the counter-circulating e-/e+ beams in CESR, which is limited by a combination of stored beam current and beam lifetime. These are in turn constrained by the requirements of operating counter-circulating particle beams of opposite charge in a single beampipe, including managing the attraction between the beams as they collide and the repulsion between the beams as they pass each other in their orbits. Two strategies for regulating these interactions are adjusting the beam current, which can sacrifice luminosity, and adjusting the separation between the beams, which is limited by the size of the beampipe and the strength of the repulsion between the beams. We describe a modeling algorithm which optimizes operating currents and orbit separations. The algorithm successfully finds values for the beam current and orbit separation which are likely to increase the time-integrated collision rate, making it a useful new tool for optimizing CESR's optics. [Preview Abstract] |
Monday, April 14, 2008 2:18PM - 2:30PM |
S19.00002: ABSTRACT WITHDRAWN |
Monday, April 14, 2008 2:30PM - 2:42PM |
S19.00003: Bio-Photons of Various Cellular Cultures and Tissues Patrick Hann, Ernst Knoesel, Maria Garzon, Samuel Lofland, Erik Pfieffer Since it is non-invasive, there has been increased research in the field of bio-optics. Many biological systems display an unusual phenomenon, delayed luminescence, produced by what is known as bio-photons. We present an apparatus and procedure for the detection of these ultra-weak photonic emissions using a single photon detection device. The results of bread yeast, saccramyces, and algae will be presented and compared to other reports in the literature. [Preview Abstract] |
Monday, April 14, 2008 2:42PM - 2:54PM |
S19.00004: Whispering-Gallery-Mode Resonances in FLourescent Microspheres Mary Williams, D. Brian Thompson We are collecting emission spectra from fluorescent microspheres, aligned to form coupled cavities. A single fluorescent microsphere can act as a Fabry-Perot resonance cavity, so that it will exhibit morphology-dependent resonances (MDRs), also known as whispering gallery mode (WGM) resonances, as intense narrow peaks superimposed upon the free-space fluorescence emission background. Two or more microspheres in close proximity may form a coupled cavity, where the coupling arises from evanescent fields between the microspheres. The coupling strength then should be a strong function of separation distance between spheres. We use an optical tweezers to position the microspheres, to guide the excitation light, and to collect the emission from the microspheres for spectral analysis. The goal of these measurements is to examine the behavior of MDRs in the emission spectra of two coupled microspheres as separation distances are varied. However, at this stage in our work, we are examining how various dye-staining methods impact the spectra we collect. [Preview Abstract] |
Monday, April 14, 2008 2:54PM - 3:06PM |
S19.00005: Probing the Unusual Thresholds of AlH+/AlD+ formation by Molecular Dynamic Simulations on MRCI Potential Energy Surfaces Nathan Brewer In an experiment performed by P. Armentrout (Int. Rev. Phys. Chem. \textbf{1990}, $9$, 115), the Al$^{+}$ cation was accelerated into the various isotopic combinations of H$_{2}$ to form AlH$^{+}$ and AlD$^{+}$. It was found that the product-forming reactions proceed very inefficiently. The experiments also showed a reduction of $\sim $29{\%} in the threshold for the formation of AlD$^{+}$ from the HD reactant whereas all other AlH$^{+}$ and AlD$^{+}$ products formed at the same energetic threshold. Four previous theoretical attempts at capturing this unusual phenomenon have not been successful. The lowest energy singlet surfaces for the reaction of Al$^{+}$ with H$_{2}$ have been calculated at the multi-reference configuration interaction (MRCI) level of theory. The real/imaginary boundary of the symmetry-breaking b$_{2}$ vibrational mode was examined in three dimensions using Hessian matrices computed at a multi-configurational self-consistent field (MCSCF) level of theory. Molecular dynamic simulations numbering on the order of 10$^{7}$ were performed, sampling initial conditions reflective of the experiments. The simulations were run until they reached the location where the b$_{2}$ vibrational mode became unbound. A dissociation model was applied at these greatly compressed geometries to model the dissociation into AlH$^{+}$ and AlD$^{+}$ products. [Preview Abstract] |
Monday, April 14, 2008 3:06PM - 3:18PM |
S19.00006: The late--time tails in the Reissner--Nordstr\"{o}m space-time revisited Carl J. Blaksley, Lior M. Burko We propose that the late-time tail problem in the Reissner-Nordstr\"{o}m (RN) spacetime is dual to a tail problem in the Schwarzschild spacetime with a different initial data set: at a fixed observation point the asymptotic decay rate of the fields are equal. This duality is used to find the decay rate for tails in RN. This decay rate is exactly as in Schwarzschild, including the case of the extremely-charged RN spacetime (ERN). The only case where any deviation from the Schwarzschild decay rate is found is the case of the tails along the event horizon of an ERN spacetime, where the decay rate is the same as at future null infinity. As observed at a fixed location, the decay rate in ERN is the same as in Schwarzschild. We verify these expectations with numerical simulations. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700