Bulletin of the American Physical Society
2005 TSAPS/AAPT/SPS Joint Fall Meeting
Thursday–Saturday, October 20–22, 2005; Houston, TX
Session A1: General Experimental I |
Hide Abstracts |
Room: Shamrock Main 261M |
Friday, October 21, 2005 10:30AM - 10:42AM |
A1.00001: Study of the Expansion of Ultracold Strontium Plasma Priya Gupta, Clayton Simien, Sampad Laha, Thomas Killian We probe the expansion of ultracold strontium plasma with spectroscopy of the $^{2}$S$_{1/2}-^{2}$P$_{1/2}$ transition of Sr+ at 422nm. The absorption spectrum is Doppler broadened, which gives a measure of the ion velocity. The expansion is driven by the electron pressure, and the ion acceleration gives a measure of the electron temperature. We will present the result of the study of the expansion of ultracold plasma including the effects of adiabatic expansion, recombination, and evaporation on the temperature of the electrons. [Preview Abstract] |
Friday, October 21, 2005 10:42AM - 10:54AM |
A1.00002: Ultracold Neutral Plasmas Thomas Killian Ultracold neutral plasmas [1], formed by photoionizing laser-cooled atoms near the ionization threshold, stretch the boundaries of traditional neutral plasma physics. The electron temperature in these plasmas is from 1-1000K and the ion temperature is around 1 K. The density can be as high as 10$^{10}$ cm$^{-3}$. Fundamental interest stems from the possibility of creating strongly-coupled plasmas, but recombination, collective modes, and thermalization in these systems have also been studied. Using optical absorption imaging [2], we study expansion dynamics of the plasma during the first few tens of microseconds after photoionization. Images record the spatial extent of the system, while the Doppler broadened absorption spectrum measures the ion velocity spectrally. The expansion is driven by the pressure of the electron gas, so the ion acceleration depends on the electron temperature. Understanding expansion dynamics is important for plans to laser cool and trap the plasma. This work is supported by the National Science Foundation and David and Lucille Packard Foundation. * In collaboration with Priya Gupta, Sampad Laha, and Clayton. E. Simien. [1] T. C. Killian, S. Kulin, S. D. Bergeson, L. A. Orozco, C. Orzel, and S. L. Rolston, Phys. Rev. Lett. \textbf{83}, 4776 (1999). [2] C. E. Simien, Y.C. Chen, P. Gupta, S. Laha, Y. N. Martinez, P. G. Mickelson, S. B. Nagel, T. C. Killian, Phys. Rev. Lett. \textbf{92}, 143001 (2004). [Preview Abstract] |
Friday, October 21, 2005 10:54AM - 11:06AM |
A1.00003: Effect of Hydrogen on nitrogen incorporation in RF nitrogen plasma assisted chemical beam epitaxy of III-V dilute nitrides Aristotelis Fotkatzikis, Alexandre Freundlich We investigate the impact of hydrogen on the growth mode and structural and optical properties of GaAsN epilayers grown on GaAs by RF nitrogen plasma assisted chemical beam epitaxy. Hydrogen interaction with the N-plasma was monitored real time using optical spectroscopy. Epilayer thickness was maintained below the critical thickness for lattice relaxation and the evolution of the growth mode was studied using RHEED. Small quantities of hydrogen were introduced independently in the growth chamber and the increase of background H pressure was directly correlated with an increase of the H$_{\alpha }$ line, the 1st term of the Balmer series of the hydrogen atom, in the nitrogen plasma spectrum. The growth mode (RHEED reconstruction) was affected be the presence of hydrogen in the CBE chamber. In addition, high resolution X-ray diffraction indicates a significant drop in nitrogen composition for GaAsN epilayers fabricated under excess hydrogen in the growth chamber. Finally the later samples exhibit a blue shift of their bandgap (beyond the one associated with the composition drop) and a significant degradation of their low temperature PL signal. [Preview Abstract] |
Friday, October 21, 2005 11:06AM - 11:18AM |
A1.00004: Spectroscopic Determination of Strontium Scattering Lengths Pascal Mickelson, S.B. Nagel, A.D. Saenz, Y.N. Martinez, Y.C. Chen, T.C. Killian, P. Pellegrini, R. Cote We perform photoassociative spectroscopy (PAS) of strontium in order to determine the scattering lengths of the most abundant bosonic isotopes, $^{88}$Sr and $^{86}$Sr. Unlike other PAS experiments, photoassociation occurs directly in a magneto-optical trap operating on the narrow intercombination line at 689 nm. A laser red-detuned from the principal atomic transition at 461 nm by as much as 1400 GHz induces the photoassociation of ground state atoms into excited molecular states. From variation in the strength of these transitions, we pinpoint the location of a node in the ground state wave function of $^{86}$Sr, the first such measurement for this isotope. In turn, we extract the ground state scattering lengths for both isotopes. The large positive scattering length of $^{86}$Sr and the small scattering length of $^{88}$Sr mean that achieving Bose-Einstein condensation of strontium, the main motivation for this work, should be more straight-forward for $^{86}$Sr than for $^{88}$Sr. [Preview Abstract] |
Friday, October 21, 2005 11:18AM - 11:30AM |
A1.00005: IR-VIS-UV Coherent Light Source utilizing the combined Stimulated Raman Scattering / Collinear Raman Generation effect Alexey Chugreev, Andrea Burzo, Alexei Sokolov Production of subfemtosecond optical pulses or light pulses with a pre-determined shape of the electric field demands a broadband coherent light source of few octaves of bandwidth. One alternative to the traditional mode-locked solid state laser technology is the discrete-spectrum coherent light source utilizing the collinear Raman generation effect [1]. We extend this approach by utilizing the Stimulated Raman Scattering effect to increase by one order of magnitude the number of sidebands and expand the capability of the pulse shaping. The design of the setup to increase the output power will be suggested. \newline \newline [1] S. E. Harris and A. V. Sokolov, Phys. Rev. Lett. 81, 2894 (1998) [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