Bulletin of the American Physical Society
80th Annual Meeting of the APS Southeastern Section
Volume 58, Number 17
Wednesday–Saturday, November 20–23, 2013; Bowling Green, Kentucky
Session DD: Atomic Molecular and Optical |
Hide Abstracts |
Chair: John Yukich, Davidson College Room: 3/4 |
Thursday, November 21, 2013 1:30PM - 1:42PM |
DD.00001: Hybrid optical dipole trap for ultracold rubidium and potassium with magnetometry applications Charles Fancher, Megan Ivory, Austin Ziltz, Andrew Pyle, Elana Urbach, Seth Aubin We present progress on the development of a hybrid magnetic-optical dipole trap for the rapid production of ultracold atomic samples of Rb and K. This optical trap adds single-chamber experimental capability to an existing dual-chamber atom chip apparatus. By using a magnetic trap to quickly load the dipole trap while simultaneously cooling the atoms via radio-frequency evaporative cooling we have produced samples of 10$^{\mathrm{7}}$ $^{\mathrm{87}}$Rb atoms at the $\mu $K level with a phase space density of 10$^{\mathrm{-3}}$ and are working to further cool the atomic cloud. We intend to load $^{\mathrm{39}}$K into the dipole trap by sympathetic cooling with rubidium using microwave evaporation. This optical dipole trap approach enables research on cold collisional physics, as well as atomic clocks and gradient magnetometry. A Larmor precession method that uses magnetically sensitive atomic states can be used to measure magnetic fields. Two spatially separated magnetometers, loaded into one or two dipole traps, can then be used to measure magnetic field gradients. [Preview Abstract] |
Thursday, November 21, 2013 1:42PM - 1:54PM |
DD.00002: Micro-plasma Parameter Inferences Utilizing Titanium Spectral Transitions Alexander Woods, Christian Parigger The availability of experimentally obtained data of TiO spectral transitions has enabled the computational modeling of molecular potentials to be used in a Rydberg-Klein-Rees method for the development of TiO line strengths for selected molecular transitions. These line strengths provide information necessary to generate computed spectra for diatomic molecules, given various input parameters. The value of such a parameter as temperature can be inferred for an experimentally obtained spectrum by fitting with computed spectra of varying parameters. In this effort, a Nelder-Mead algorithm is utilized as a fitting routine in the analysis of TiO spectra collected from laser-induced plasma. In measurements, a Nd:YAG laser is the excitation source, as a titanium sample is repeatedly exposed to nanosecond pulsed radiation. Gated detection provides time-resolved results used to infer temperature as a function of time following laser-induced breakdown. A local minimum can be seen in the temperature versus time profile when imaging certain areas of the plasma, as a slight increase in inferred temperature occurs at later collection times. Characteristic of combustion, this phenomenon is investigated by analyzing the effect of signal to noise ratios on temperature inferences. This is accomplished utilizing Monte Carlo type simulations providing random noise to the measured spectra and adjusting the baseline prior to fitting. Detectable at early as well as later delay times, atomic Ti structure is also addressed. [Preview Abstract] |
Thursday, November 21, 2013 1:54PM - 2:06PM |
DD.00003: C$_2$ Swan Bands Measurements Using Laser-Induced Breakdown Spectroscopy Michael Witte, Christian Parigger Laser Induced Breakdown Spectroscopy (LIBS) is used to analyze carbon-containing substances without significantly affecting the material being studied. In this study, we address C$_2$ diatomic molecular spectra that were recorded following optical breakdown generated with pulsed, nanosecond laser radiation. Our focus is on the $\Delta \nu =$ -1, 0, +1 transitions in the wavelength range of 450 nm to 565 nm, and for delay times on the order of 10-100 microseconds from optical breakdown. Measurements are conducted with the following, typical equipment for nanosecond LIBS: A Nd:YAG laser producing 190-mJ, 14-ns, pulsed 1064-nm radiation; a Jobin-Yvon HR 640 Czerny-Turner spectrometer; and an intensified linear diode-array and optical multichannel analyzer, or an ICCD camera. We compare recorded and computed, wavelength- and intensity- calibrated spectra. [Preview Abstract] |
Thursday, November 21, 2013 2:06PM - 2:18PM |
DD.00004: Plasma spectroscopy of hydrogen Balmer Series of in laboratory air Lauren Swafford, Christian Parigger Stark-broadened emission profiles for the hydrogen alpha and beta Balmer series lines in plasma are measured to characterize electron density and temperature. Plasma is generated using a typical LIBS arrangement that employs a focused a Q-switched ND:YAG laser, operating at a fundamental wavelength of 1064 nm. The temporal evolution of the hydrogen Balmer series lines are explored using LIBS. Plasma measurements are taken following laser-induced optical breakdown in laboratory air. Electron density is primarily inferred from Stark-broadened, emission experimental data collected at various time delays. Boltzmann plots are used to infer the electron temperature for well defined Balmer series lines. Due to the presence of nitrogen and oxygen in air, hydrogen alpha and beta lines become discernible from background radiation 0.4 $\mu $s and 1.4 $\mu$s, respectively. [Preview Abstract] |
Thursday, November 21, 2013 2:18PM - 2:30PM |
DD.00005: Above-threshold ionization as temporal multi-slit interference W. Blake Laing, B.D. Esry When atoms are subjected to a laser pulse of sufficiently high intensity, electrons are ionized by absorbing multiple photons in excess of the ionization potential. The resulting sequence of peaks in the photoelectron spectrum separated by the energy of one photon is called ``above-threshold ionization'' (ATI). This time-independent description of ATI invokes the language of photons, even though calculations are performed using the time-dependent Schr\"odinger equation with a classical electric field. We demonstrate that the energy-periodic structure of ATI can be understood from the interference of ionized electron wavepackets produced periodically each half-cycle of the laser field. Using this simple picture, rather analytic expressions for the ATI spectrum can be derived. [Preview Abstract] |
Thursday, November 21, 2013 2:30PM - 2:42PM |
DD.00006: Specificity of exchange and correlation in elastic electron scattering off semifilled shell atoms Valeriy Dolmatov, Miron Amusia, Larissa Chernysheva Atoms with multielectron semifilled shells in their ground states possess the highest spin multiplicity among other atoms. The current understanding of electron scattering off such atoms is rudimentary. Choosing e$^{-}+$Mn($3d^{5}$$4s^{2}$, $^{6}S$) elastic scattering as a case study, we scrutinize scattering phase shifts, partial, and total scattering cross sections versus the energy and spin polarization of a scattered electron. A drastic dependence of a correlation impact on electron scattering versus the spin-orientation of a scattered electron is unraveled. This, in turn, is found to be due to a specific impact of exchange interaction on correlation in the e$^{-}+$ atom system. The findings are argued to be inherent features of electron scattering off any multielectron semifilled shell atom. They result in significant differences between scattering of oppositely spin-polarized electrons off the atom. In particular, the existence of a narrow resonant maximum in the total scattering cross section of spin-down electrons near $\epsilon \approx 8$ eV but the absence of such in the cross section of spin-up electrons elastically scattered off the Mn atom is predicted. A ``spin-polarized'' Hartree-Fock approximation in combination with the Dyson equation for the self-energy part of the Green function of a scattered electron are employed in the study. [Preview Abstract] |
Thursday, November 21, 2013 2:42PM - 2:54PM |
DD.00007: Break
|
Thursday, November 21, 2013 2:54PM - 3:06PM |
DD.00008: Maxwell's Equations may have to change for Superconducting Phenomena Richard Kriske A completely original theory was proposed by this author several years ago that a Quantum Mechanical Capillary Action theory based on an extended view of semi-conductor Physics was possible. With recent advances in Room Temperature Superconductors, this theory is on the verge of being proven. Apparently Electrons are able to travel along 'cracks' in crystals, which appears to be a sort of Capillary Action (which seems to be Superconducting at room temperature). It has long been thought that Capillary Action was Classical in nature, but then there was the strange behavior Superfluid Helium, that appeared to be Capillary Action, but occured in an environment that would be conducive to Superconduction. This author would like to propose that these things are not contradictory, but rather Capillary Action is an Extension of the Maxwell Equations and is a type of Superconduction at room temperature. Apparently when Quantum Mechanics is seen directly in Classical Physics, one sees things like the rise of liquids with no work being done. This theory is far more exciting than that in that Laminar flow, which is regarded as Classical Physics, can be also seen to be a type of Capillary Action, so it can now be viewed as being a direct result of Quantum Mechanics. [Preview Abstract] |
Thursday, November 21, 2013 3:06PM - 3:18PM |
DD.00009: Elastic electron scattering off $A$@C$_{60}$ versus off C$_{60}$ versus off a free atom Maisey Hunter, Matthew Cooper, Valeriy Dolmatov The recent decade or so has seen much of research on the structure and spectra of endohedral fullerenes $A$@C$_{60}$. However, to the best of our knowledge, electron elastic scattering off $A$@C$_{60}$ has so far escaped its study, despite of its obvious basic significance. Can one detect the presence of an encapsulated atom $A$ inside the hollow cage of C$_{60}$ by performing a e$+A$@C$_{60}$ elastic scattering experiment? If a ``yes'', how much does the atom $A$ in $A$@C$_{60}$ contribute to electron scattering off $A$@C$_{60}$ compared to scattering off empty C$_{60}$? If the encapsulated atom has a non-zero spin, could this lead to appreciable differences between scattering of oppositely spin-polarized electrons off e$+A$@C$_{60}$? The present work unravels positive answers to the above questions within, so to speak, a zero-order approximation, as the very first step in understanding of e$+A$@C$_{60}$ scattering. There, the C$_{60}$ cage itself is modeled by a spherical potential shell [as in numerous $A$@C$_{60}$ photoionization studies, see, e.g., V. K. Dolmatov, Adv. Quant. Chem. \textbf{58}, 13 (2009)], the atom $A$ is placed at the center of the shell, and, as a strong simplification of the problem, both the encapsulated atom $A$ and C$_{60}$ cage are regarded as rigid, i.e., non-polarizable targets. This study itself, as well as differences between its results and (future) more sophisticated calculations, should be viewed as a first step in identifying measurements to perform. [Preview Abstract] |
Thursday, November 21, 2013 3:18PM - 3:30PM |
DD.00010: Programming Berendsen Thermostat Subroutines for Molecular Dynamics Simulations Ward Howard, Michael Salazar, Brittany Hagler Molecular dynamics (MD) provides a powerful tool for computing the behavior of atoms and molecules using force calculations over all particles in a system. MD simulations are broken up into many time steps. At each step, the quantum mechanical (QM) and molecular mechanical (MM) energy and forces, positions, velocities, and accelerations are recalculated from the values found at the previous time step. These MD basics are nearly always supplemented by other considerations, such as temperature control. We investigated several thermostat variations that provide such functionality to an adaptive, multilevel QM/MM interpolation-based code. The Accelerated Molecular Dynamics with Chemistry (AMolDC) is designed for simulations of large molecular systems that can undergo very complex reactions. Unlike some Berendsen thermostats that act on simple particles in Brownian motion, we created thermostats that control temperature for molecules in several different ways, such as molecular center-of-mass velocity frame transformations, Gaussian thermostat control via system-level velocity scaling of all atoms, and intramolecular- level velocity scaling. This is primarily application-based research that integrates well-known methods into a specific and groundbreaking code. Results are extremely preliminary, but these tests show promise for future enhancements to the capability of AMolDC. [Preview Abstract] |
Thursday, November 21, 2013 3:30PM - 3:42PM |
DD.00011: Analysis of Aluminum Monoxide Emission Spectra in a Simulated Solid Rocket Propellant Flame David Surmick, Christian Parigger, Aren Haug, A. Burl Donaldson, Walt Gill Characterization of temperatures from an uncontrolled aluminized solid rocket propellant flame is an important aspect in developing a complete model of the propellant combustion. Emission spectra recorded from a simulated aluminized propellant flame are analyzed for the purpose of developing an experimental model of the propellant temperature in an uncontrolled burn. Due to the costs and safety issues associated with using solid rocket propellants for testing, laboratory scale simulations of the propellant flame are studied. The flame is simulated by feeding micron sized aluminum powder into an oxyacetylene torch burning vertically downward while spectral measurements are recorded along the height of the plume. Spectra are analyzed using various methods to determine the temperatures within the flame. Diatomic aluminum monoxide emissions are fit to accurate line strength files using a Nelder-Mead algorithm, while broadband spectral emissions are analyzed using Planck's radiation law for varying emissivity. [Preview Abstract] |
Thursday, November 21, 2013 3:42PM - 3:54PM |
DD.00012: Photodetachment Spectroscopy of the $S_{2}^{-}$ Anion John Yukich, Jessica Barrick Numerous experiments have investigated the properties and dynamics of single-atom negative ions. Similar experiments may also be conducted with molecular anions. Laser photodetachment spectroscopy of such ions is more complex due to rotational and vibrational structure, but often yields spectroscopic benchmarks such as rotational constants and vibrational energies. We have conducted low-resolution photodetachment spectroscopy of the $S_{2}^{-}$ anion over a range of roughly 2000 $cm^{-1}$. The ions are created in a Penning ion trap by a two-step dissociative attachment process. The photodetachment is achieved with a tunable titanium:sapphire laser. Our results are consistent with a model adapted from previous studies of single-atom photodetachment, and also show evidence of successful evaporative cooling of the ion cloud. Future experiments will focus on high-resolution detachment spectroscopy of these and other ions with an eye toward measurement of their molecular constants. [Preview Abstract] |
Thursday, November 21, 2013 3:54PM - 4:06PM |
DD.00013: Atom chip-based ultracold potassium for testing microwave and RF potentials Austin Ziltz, Megan Ivory, Charles Fancher, Andrew Pyle, Seth Aubin We present progress on an experiment to manipulate and trap ultracold atoms with microwave and RF ($\mu $/RF) AC Zeeman potentials produced with an atom chip. These $\mu $/RF potentials are well suited for atom interferometry and 1D many-body physics studies due to their inherent spin-dependent nature and ability to operate in conjunction with magnetic Feshbach resonances to tune interactions. We have completed a dual species, dual chamber apparatus for producing ultracold rubidium and potassium gases on an rf-capable atom chip. The system produces Bose-Einstein condensates of 10$^{\mathrm{4}}$ $^{\mathrm{87}}$Rb atoms. Recently, we have successfully trapped $^{\mathrm{39}}$K on the atom chip, and are working towards cooling it sympathetically via microwave evaporation of rubidium. We intend to exploit the $\mu $/RF potentials for atom interferometry as a spin-dependent beam splitter acting on optically trapped $^{\mathrm{39}}$K in the vicinity of the atom chip. [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. |
© 2025 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