Bulletin of the American Physical Society
Joint Fall 2010 Meeting of the Texas Sections of the APS, AAPT, Zone 13 of SPS and the National Society of Hispanic Physicists
Volume 55, Number 11
Thursday–Saturday, October 21–23, 2010; San Antonio, Texas
Session FM1: Atomic, Molecular, and Optical Physics I |
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Chair: Harry Downing, Stephen F. Austin State University Room: University Center III Travis Room, 2nd floor |
Friday, October 22, 2010 10:00AM - 10:12AM |
FM1.00001: Effect of Pulse Shaping on Electromagnetic Induced Transparency and its Applications Dong Sun, Sumanta Das, Zoe-Elizabeth Sariyanni, Yuri Rostovtsev We have theoretically studied the effect of pulse shapes on Electromagnetic Induced Transparency (EIT) and the propagation of pulses inside EIT medium. Our numerical simulations are based on an isotropic homogeneous medium composed of 3-level $\Lambda $ type atoms coupled to two co-propagating laser fields. It has been found that even with the two-photon resonance, if these two fields have unmatched pulse shapes, there is still no EIT. The mechanism is explained in the dressed state, in which a pulse shape dependent interaction is found. We also observed the nonlinear effect of EIT on pulse propagation inside medium by using Fourier Analysis. Some possible applications are proposed. [Preview Abstract] |
Friday, October 22, 2010 10:12AM - 10:24AM |
FM1.00002: Evaluating Entanglement in Stern-Gerlach Dynamics Jean-Francois S. Van Huele, Bailey C. Hsu The Stern-Gerlach experiment that revealed the reality of space quantization in 1922 is also an exemplary model for entanglement between space and spin. Based on the result of analytical and numerical dynamical Stern-Gerlach calculations, we search for a representative measure of space-spin entanglement. We compare different entanglement measures that have been proposed and apply some of them to the dynamics of spin separation in a beam of neutral particles traversing inhomogeneous magnetic fields. [Preview Abstract] |
Friday, October 22, 2010 10:24AM - 10:36AM |
FM1.00003: Testing Ionizers for Nitrogen Discharge of Interferometer Optics Timothy Amen, Dennis Ugolini Interferometric gravitational-wave observatories consist of suspended optics in a vacuum chamber. Charge can build up on and then discontinuously jump across an optic, creating a changing electric field, causing the optic to sway, creating a false signal. We studied possible ways to discharge an optic without damaging their reflective coatings. We tried two types of electron guns. The first was built at the University of Washington and uses an ultraviolet LED to free electrons from a magnesium target. We found the current to be three orders of magnitude less than necessary for discharge in a reasonable time. The second gun used was a Bayard-Alpert gauge. To eliminate sputtering caused by the gauge above 10$^{-4}$ torr, we employed a differential pumping system. We were able to flow nitrogen gas through the main chamber at pressures between 10$^{-2}$ and 10$^{-3}$ torr while the gauge chamber was kept two orders of magnitude lower. We successfully discharged the optic. The discharge rate varied exponentially with charge level and operating current and nearly linearly with acceleration voltage, and peaked when the pressure was 8 x 10$^{-3}$ torr in the main chamber. [Preview Abstract] |
Friday, October 22, 2010 10:36AM - 10:48AM |
FM1.00004: FTIR Argon Matrix and DFT Study of the Vibrational Spectrum of SiC$_{5}$ T.H. Le, W.R.M. Graham This is the first Fourier transform infrared (FTIR) study on SiC$_{5}$, which is a part of ongoing FTIR and density functional theory (DFT) research, investigating the structures and vibrations of silicon-carbon molecules. Vibrational spectra of SiC$_{5}$ were obtained by Nd:YAG laser ablation of a sintered rod, made of $^{13}$C-enriched graphite and silicon, and trapping the resulting vapor in solid Ar at $\sim $15 K. The \textit{$\nu $}$_{4}$(\textit{$\sigma $}$_{u})$ asymmetric stretching fundamental of SiC$_{5}$ has been observed at 936.9 $\pm $ 0.2 cm $^{-1}$. The measured isotopic shifts are in good agreement with the predictions of DFT calculations. This information will help in identifying SiC$_{5}$ in circumstellar and interstellar environments. Also, it has potential applications for optoelectronic and semi-conductor devices. [Preview Abstract] |
Friday, October 22, 2010 10:48AM - 11:00AM |
FM1.00005: Collision-Induced Infrared Absorption by Hydrogen-Helium gas mixtures at Thousands of Kelvin Martin Abel, Lothar Frommhold, Xiaoping Li, Katharine L.C. Hunt The interaction-induced absorption by collisional pairs of H$_{2}$ molecules is an important opacity source in the atmospheres of the outer planets and cool stars $^{[1]}$. The emission spectra of cool white dwarf stars differ significantly in the infrared from the expected blackbody spectra of their cores, which is largely due to absorption by collisional H$_{2}$--H$_{2}$, H$_{2}$--He, and H$_{2}$--H complexes in the stellar atmospheres. Using quantum-chemical methods we compute the atmospheric absorption from hundreds to thousands of kelvin $^{[2]}$. Laboratory measurements of interaction-induced absorption spectra by H$_{2}$ pairs exist only at room temperature and below. We show that our results reproduce these measurements closely $^{[2]}$, so that our computational data permit reliable modeling of stellar atmosphere opacities even for the higher temperatures $^{[2]}$. [1] L. Frommhold, Collision-Induced Absorption in Gases, Cambridge University Press, Cambridge, New York, 1993 and 2006 [2] Xiaoping Li, Katharine L. C. Hunt, Fei Wang, Martin Abel, and Lothar Frommhold, ``Collision-Induced Infrared Absorption by Molecular Hydrogen Pairs at Thousands of Kelvin'', International Journal of Spectroscopy, vol. 2010, Article ID 371201, 11 pages, 2010. doi: 10.1155/2010/371201 [Preview Abstract] |
Friday, October 22, 2010 11:00AM - 11:12AM |
FM1.00006: Characterization of Resonant Cavities in Terahertz Parallel Plate Waveguides Blake McCracken, Victoria Astley, Rajind Mendis, Dan Mittleman Parallel-plate waveguides are among the most common low-loss broadband waveguides in the terahertz frequency regime with a large variety of applications. One application is microfluidic detection. Adding a groove into one of the waveguide plates leads to a resonant feature of relatively high quality factor, which will shift to different frequencies when the groove is filled with different liquids. We experimentally investigate the resonant frequencies and transmission characteristics of different-sized grooves in aluminum plates in order to determine which groove will be most suitable for microfluidic sensing. This apparatus is formed by machining grooves of varying geometries into aluminum plates which are then used to form parallel-plate waveguides. Sub-picosecond terahertz pulses are used to excite the lowest-order transverse-electric (TE1) mode in the waveguides and the output spectrum is analyzed to determine the resonant frequency and Q-factor of each groove geometry. We can use the information gathered in order to determine which groove gives the highest quality factor (Q-factor), increasing the sensitivity of a groove-based microfluidic sensor. [Preview Abstract] |
Friday, October 22, 2010 11:12AM - 11:24AM |
FM1.00007: Quantum lithography beyond the diffraction limit via Rabi oscillations Zeyang Liao, Muhammad Al-Amri, Muhammad Suhail Zubairy We propose a quantum optical method to do the sub-wavelength lithography. Our method is similar to the traditional lithography but adding a critical step before dissociating the chemical bound of the photoresist. The subwavelength pattern is achieved by inducing the multi-Rabi-oscillation between the two atomic levels. The proposed method does not require multiphoton absorption and the entanglement of photons. It is expected to be realizable using current technology. [Preview Abstract] |
Friday, October 22, 2010 11:24AM - 11:36AM |
FM1.00008: Structures and Vibrational Spectra of Potential Astrophysical Molecules: MnC$_{3}$ Micheline Bejjani, Magnus Rittby, William Graham This study on MnC$_{3}$ is part of an ongoing project investigation of the structures and vibrations of small metal-carbon clusters using Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT). These species are of interest as potential species in circumstellar shells or other astronomical environments and for understanding the structure and bonding of larger metal-carbide molecules such as metallocarbohedrenes. MnC$_{3}$was produced by trapping the products from the dual laser Nd-YAG lased ablation of carbon and manganese rods in solid Ar at $\sim $12 K. Fourier transform infrared measurements of frequencies and $^{13}$C isotopic shifts were compared with the predictions of density functional theory calculations performed for three possible structures: two cyclic isomers with transannular C-C or C-Mn bonds and an asymmetric linear form. Based on this analysis the asymmetric stretching fundamental \textit{$\nu $}$_{1}$(\textit{$\sigma $}) has been identified at 1846.9 cm$^{-1}$. This is the first optical detection of any isomer of MnC$_{3}$. A previous study by photoelectron spectroscopy [1] reported evidence for the cyclic isomer with transannular Mn-C stretch based on preliminary DFT calculations. The results of calculations performed in conjunction with the present work will also be reported. \\[4pt] [1] L. S. Wang and X. Li, J. Chem. Phys. \textbf{112}, 3602 (2000). [Preview Abstract] |
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