Bulletin of the American Physical Society
Joint Fall 2011 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 56, Number 7
Thursday–Saturday, October 6–8, 2011; Commerce, Texas
Session D2: Atomic, Molecular, and Optical Physics I |
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Chair: Donald Kobe, University of North Texas Room: Sam Rayburn Center Second Floor, Room Innovations B |
Friday, October 7, 2011 1:40PM - 1:52PM |
D2.00001: Microwave de-excitation schemes for Rydberg atoms Daniel Vrinceanu, Luca Perotti Control of Rydberg atom wavefunctions has evolved from static or periodic protocols to transport ones, exploiting either modulation or chirping of the controlling periodic field. Applications vary from quantum computing schemes using excitation blockades to the production of anti-hydrogen atoms in Penning traps. Theoretical studies have essentially been limited to 1-D models. Applications such as the production of anti-hydrogen atoms mentioned above, instead require the study of some 3D statistical ensemble of orbits. Our preliminary numerical 3D studies show that chirping of the microwave field is most effective in de-exciting atoms that are almost one dimensional, as transport terminates when the two parabolic quantum numbers are equal, thus seriously limiting its effciency for initial states which are not almost 1D. Alternative approaches are suggested. [Preview Abstract] |
Friday, October 7, 2011 1:52PM - 2:04PM |
D2.00002: Nonlinear Optical Spectroscopy of Silicon Nanocrystals Embedded in Silica Aaron Roberts, Junwei Wei, Michael Downer Light-emitting Silicon nanocrystals (Si NCs) embedded in silica are attracting much attention for their potential applications in silicon photonics. However, the relative contributions of the crystalline Si (c-Si) bulk and the nano-interfacial transition region to the photoluminescence remain controversial. Moreover, the micro-structure of the nano- interface separating the c-Si core from the amorphous silica matrix has proven difficult to characterize experimentally. Presented here are results from second harmonic generation spectroscopy and complementary spectroscopic-ellipsometric and micro-Raman measurements of Si NCs of different sizes. Spectroscopy results confirm the preservation of the basic electronic properties of bulk c-Si through the appearance of the E1 and E2 critical point resonances. However, they also demonstrate the existence of an intermediate resonance between E1 and E2 consistent with an amorphous Si nano-interfacial transition region that thins with increasing NC diameter. \\[4pt] [1] J. Wei et al., submitted to Phys. Rev. B (2011). [Preview Abstract] |
Friday, October 7, 2011 2:04PM - 2:16PM |
D2.00003: Accurate Current Integration for Ion Beam Techniques at University of North Texas Naresh Deoli, Duncan Weathers An experimental set ups have been designed to suppress secondary and tertiary electron currents generated during energetic ion irradiation to obtain accurate current integration for ion beam techniques at the University of North Texas. In one configuration, all secondary electrons were suppressed in the process of production of Bi thin films using sputtering technique by 10-50 keV noble gas atoms. In another configuration, a combination of an electron trap and a biased aluminum mesh was used to suppress any secondary and tertiary electrons in the heavy ion Rutherford backscattering technique for the analysis of thin films. Details of both experimental current integration set ups are presented. [Preview Abstract] |
Friday, October 7, 2011 2:16PM - 2:28PM |
D2.00004: Characterization of cluster/monomer ratio in pulse supersonic gas jets Richard Korzekwa, Xiaohui Gao, Xiaoming Wang, Bonggu Shim, Alexey Arefiev, Mike Downer We determine cluster mass fraction $f_c$({\boldmath $r,t$}) at position {\boldmath $r$} within, and time $t$ after firing, a pulsed supersonic gas jet by measuring femtosecond evolution of the jet's refractive index by single-shot frequency domain holography. A fs pump pulse singly ionizes monomers, while quasi-statically ionizing and heating clusters to a level at which recombination remains negligible as clusters expand. Under these conditions, index evolves in two simple steps corresponding to monomer and cluster contributions, allowing recovery of $f_c$ without detailed cluster dynamic modeling. Variations of $f_c$ with $t$ are measured. [Preview Abstract] |
Friday, October 7, 2011 2:28PM - 2:40PM |
D2.00005: Variation of phase of slow light in a uniformly moving dielectric medium Sankar Davuluri, Yuri Rostotsev It is very well known that moving objects can drag light. In this presentation, we report the variation of phase of a laser beam when it passes through a medium. We show that the sensitivity of phase of the laser beam to the velocity of moving medium can be greatly enhanced if the light travels with a slow group velocity in the moving medium. We have taken the moving medium consists of three level lambda atoms, and the medium is made transparent by employing a strong drive field to take advantage of electromagnetically induced transparency (EIT). EIT suppresses the absorption of probe beam around resonance and the steep dispersion of probe beam around the resonance results in slowing down the group velocity of probe beam. Finally, we present the dependence of phase as a function of probe beam and velocity of the medium. [Preview Abstract] |
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