Bulletin of the American Physical Society
2005 72nd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 10–12, 2005; Gainesville, FL
Session GC: Bose Einstein Condensates, Atomic, Molecular and Optical Physics |
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Chair: Cass Sackett, University of Virginia Room: Hilton Azalea |
Friday, November 11, 2005 10:45AM - 10:57AM |
GC.00001: Magnetism in Cobalt Clusters Louis Bloomfield, Forrest Payne, Wei Jiang We have measured the magnetic moments of cobalt clusters, ranging in size from $<$10 to 200 atoms. Improvements to our cluster source have allowed us to produce smaller and colder ($\sim $60K) clusters than we were able to study in previous work, and to study each cluster size individually. We will present measured values for the magnetic moments of these clusters as functions of size, temperature, and applied field. We have also investigated the superparamagnetic behaviors of cobalt clusters, looking for deviations from that behavior. Applications of this work in the area of magnetic data recording will be discussed. This presentation is based upon work supported by the National Science Foundation under Grant No. DMR-0405203. [Preview Abstract] |
Friday, November 11, 2005 10:57AM - 11:09AM |
GC.00002: The structured energy distribution of cluster assemble with isomers Songbai Ye, Louis Bloomfield The internal energy of cluster assemble without isomers will be a single-peak distribution in thermal equilibrium. However, if it has several isomers and each isomer has different state density distribution, the internal energy distribution will be structured in certain circumstance. By destroying the equilibrium of isomer populations and observing the building-up of the new equilibrium, we can gain information of the internal energy of the cluster assemble. We can also study the change of the internal energy of the cluster assemble by selectively burning some isomers before we proceed the deplete-probe method. [Preview Abstract] |
Friday, November 11, 2005 11:09AM - 11:21AM |
GC.00003: Microwave enhancement of dielectronic recombination from a continuum of finite bandwidth Edward Shuman, Jirakan Nunkaew, Tom Gallagher Dielectronic recombination (DR) is the recombination of an energetic electron and an ion via autoionizing Rydberg states lying below an excited state of the ion. We have examined the relative effects of microwave fields on DR from a continuum of finite bandwidth (CFB) with incoming electrons with different angular momenta. By studying DR from a CFB we can restrict the angular momentum of the intermediate state to a single value of $\ell$. Specifically, we have examined the relative effects of 18-26 GHz microwave fields on DR from two CFB's, the Ba $6p_{3/2}~11d$ and $6p_{3/2}~8g$ states. We have determined that lower microwave fields are required to enhance DR when the incoming electrons are $g$ rather than $d$ electrons. This observation is consistent with the fact that in Ba, the $ng$ energies are almost hydrogenic, with quantum defects of 0.05, whereas the $nd$ electrons have quantum defects of 0.25. We have also observed a shift in the binding energy at which the resonant enhancement occurs for the $ng$ states. For low microwave fields, the enhancement occurs at approximately the right binding energy to match the resonance requirement, $\omega=1/n^3$, but at higher fields the enhancement shifts quadratically with the microwave field to higher binding energy. [Preview Abstract] |
Friday, November 11, 2005 11:21AM - 11:33AM |
GC.00004: Non-intuitive Coherent Population Transfer H. Maeda, J.H. Gurian, D.V.L. Norum, T.F. Gallagher Coherent population transfer using a sequence of adiabatic rapid passages through single photon resonances is intuitive, i. e. the frequencies of the atomic transitions follow that of the chirped radiation field. Here we report efficient non-intuitive population transfer, which can occur even when the frequency is chirped in the wrong direction. The sequence of single photon transitions is replaced by a single multiphoton transition, enormously reducing the range of chirp required. [Preview Abstract] |
Friday, November 11, 2005 11:33AM - 11:45AM |
GC.00005: Dipole-Dipole Broadening in $^{85}$Rb Rydberg Samples Paul Tanner, B.J. Claessens, Wenhui Li, T.F. Gallagher A key interesting property of high-n Rydberg atoms is their large transition dipole moments. These dipole moments allow for observation and manipulation of electric dipole-dipole interactions between Rydberg atoms -- a key for quantum computing schemes. We measured the strength of the dipole-dipole interaction vs. Rydberg atom density in a magneto-optical trap -- specifically we measured the linewidths of microwave ns-np transitions and observed broadening of up 100 MHz. [Preview Abstract] |
Friday, November 11, 2005 11:45AM - 11:57AM |
GC.00006: Magnetic Field Mapping Results from the Compact Toroidal Hybrid Experiment J.T. Peterson, G.J. Hartwell, S.F. Knowlton, R.F. Kelly, C. Montgomery The Compact Toroidal Hybrid (CTH) is a recently completed device used for the study of the physics of magnetically confined fusion energy related plasmas. CTH is a five field-period, low aspect ratio ($R/a_{PLASMA} \quad \ge $ 3.5, $R$ = 0.75 m, $a_{VESSEL}$ = 0.29 m, $B \quad \le $ 0.6 T) torsatron with a highly flexible vacuum magnetic field configuration for stability studies. The main helical field is produced by a continuously-wound helical coil, and the vacuum rotational transform is varied with a set of toroidal field coils. Four independent poloidal field coil sets provide equilibrium control and shaping, and are also used for ohmic current drive. Results of electron beam field mapping will be presented. Electron beam field-mapping is a technique use to evaluate the vacuum field configuration using a movable electron gun and a phosphor-coated screen. These experiments compare the actual magnetic configuration with the design field, verify the planned flexibility and the range of accessible magnetic configurations, and identify and correct vacuum field errors. [Preview Abstract] |
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