Bulletin of the American Physical Society
82nd Annual Meeting of the APS Southeastern Section
Volume 60, Number 18
Wednesday–Saturday, November 18–21, 2015; Mobile, Alabama
Session F2: Atomic, Molecular and Optical Physics II |
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Chair: John Yukich, Davidson College Room: Riverview Plaza Hotel Mobile Bay Ballroom I |
Friday, November 20, 2015 8:30AM - 9:06AM |
F2.00001: Microwave Forces and Potentials with Atom Chips Invited Speaker: Seth Aubin We report on the successful observation of the AC Zeeman force produced by a microwave near-field on an atom chip. We have verified both its spin-dependence and bipolar nature using ultracold $^{87}$Rb atoms. In principle, AC Zeeman forces can confine any spin state at arbitrary magnetic fields and can simultaneously target qualitatively different potentials to individual states. Atom chips are ideal platforms for producing these traps since they can produce strong near-field potentials and gradients. Notably, the potential roughness associated with atom chip micro-magnetic traps is expected to be strongly suppressed in AC Zeeman chip traps. These microwave potentials are well suited for studies of one-dimensional quantum gases with tunable interactions and spin-dependent trapped atom interferometry. \\ \\ In collaboration with Charles Fancher and Andrew Pyle, College of William \& Mary. [Preview Abstract] |
Friday, November 20, 2015 9:06AM - 9:18AM |
F2.00002: Feedback-driven tracking and trapping in confocal fluorescence microscopy Invited Speaker: Lloyd M Davis In comparison to wide-field microscopy, confocal fluorescence microscopy offers superior signal-to-noise as well as sub-nanosecond time-resolved capabilities for studies of single molecules in solution. However, Brownian diffusion limits the observation time of a molecule within the confocal volume; immobilization of a molecule to a surface alters its local environment and may stereo-chemically restrict interactions; and optical trapping of a nanoscale object requires intensities that may give perturbations due to heating. This talk reviews feedback-driven tracking and trapping, which entail real-time adjustment of the position or motion of the fluorescent target with respect to the confocal volume in response to a measurement of its position, and which largely avoid the aforementioned limitations. Such methods enable prolonged observations of an individual molecule or nanoparticle and can also record the spatial domain that is explored and monitor changes in the diffusional and/or directed motion. The talk will also discuss our recent work on trapping and tracking of nanoparticles in three dimensions, using astigmatic imaging or spatially and temporally modulated laser excitation to estimate the position of the nanoparticle and 3D-piezo or microfluidic manipulation to re-center the target in the confocal volume. [Preview Abstract] |
Friday, November 20, 2015 9:18AM - 9:30AM |
F2.00003: Double Photoionization of Atomic Ions M. S. Pindzola, Y. Li, J. P. Colgan The semi-relativistic Schrodinger equation is solved using (l1 j1 l2 j2 J) coupled channels of spin-orbit eigenfunction products on a two dimensional (r1 r2) lattice. The two-active electron atom time-dependent close-coupling method is used to calculate double photoionization cross sections for a variety of atomic ions in support of free-electron laser experiments. [Preview Abstract] |
Friday, November 20, 2015 9:30AM - 9:42AM |
F2.00004: Classical Modeling of High-Order Harmonic Spectroscopy using an Elliptically Polarized Laser Field Paul Abanador, Francois Mauger, Kenneth Lopata, Mette Gaarde, Kenneth Schafer We model high harmonic generation (HHG) from atoms in elliptically polarized fields with purely classical electron trajectories initialized from a microcanonical ensemble. The trajectories are calculated in the presence of an atomic core potential and an elliptically polarized driving laser field. This numerical scheme allows the determination of the overall shape of the HHG spectrum from the statistics of electrons that return to the ionic core. We find that the threshold ellipticity, which is defined by the ellipticity where the relative intensity of a harmonic drops to 10{\%} with respect to linear polarization, decreases as the harmonic order increases for both ``short'' and ``long'' trajectories. Our results also show that the presence of an atomic core potential can give rise to two possible sets of trajectories that return to the core with the same energy and at same time but that ionized at different times, a feature that is absent in the strong field approximation description of HHG. [Preview Abstract] |
Friday, November 20, 2015 9:42AM - 9:54AM |
F2.00005: Possible existence of van der Waals macrodimers Jianing Han Few-body interactions offer the opportunity to study the isolated atom to few-body coupled molecules, and to condensed matter transitions. Atoms in molecules and in condensed matters are coupled by different orders of multipole-multipole interactions, which all stem from different orders of approximations from coulomb interactions between multiple charges. The lowest order multipole-multipole interaction is the dipole-dipole interaction, which is proportional to the size of the dipole. In this article, we use Rydberg atoms, which have more than 1000 times greater electric dipoles than the ground state atoms, to study the van der Waals interaction between few bodies. In addition to the large dipoles, the kinetic energy of the atoms is significantly reduced by reducing the temperature, which makes these interactions stable and observable. Here we report on the 2D and 3D few-body interaction potentials and possible ways of creating semistable molecules in such an ultracold Rydberg gas with a temperature of $\approx$ 100 nK. Although we use Rydberg atoms in this article, this calculation can be applied to other states too. The results reported here are useful for studying repulsive van der Waals interactions and creating ultracold molecules. [Preview Abstract] |
Friday, November 20, 2015 9:54AM - 10:06AM |
F2.00006: Absorption and Dispersion for Classical Forced, Nonlinear Oscillators of Atomic Oscillators 'Kale Oyedeji, Ronald Mickens The classical explanation for absorption and dispersion is based on a physical model of forced, damped oscillations of atomic oscillators, i.e., electrons, driven by an electromagnetic wave [1]. From this theory one can derive the so-called " f " values which are related to the transition probabilities. A general mathematical formulation for these phenomena can be modeled by the expression \begin{equation} m\overset{\cdot \cdot }{x}+D(\overset{\cdot }{x})+g(x)=F_{0}\cos (\omega t), \tag{*} \end{equation}% where $D(-z)=-D(z),$ $\ \ \ D(0)=0,$ \ $D(z)$ \ monotonic increasing; and $% g(x)$ having exactly the same properties. Our main goal is to show that the relevant derived expressions for the effects of absorption and dispersion are insensitive to the exact functional forms used for $D(z)$ and $g(x).$ Our methodology is based on the application of the harmonic balance procedure to calculate an approximation to the periodic solution of Eq. (*). In addition to explaining physically why this result should be expected, we briefly discuss the "similar" case of Brownian motion. Our findings are consistent with the understanding that in the absence of a fundamental theory, macro-physical phenomena will not depend on the details of the micro-physics. [1] A. Thorne,Spectrophysics... [Preview Abstract] |
Friday, November 20, 2015 10:06AM - 10:18AM |
F2.00007: Experiment rejects all quantum interpretation models of light and does not reject the Newtonian model of diffraction John Hodge Young's double slit experiment conducted in 1801 of diffraction and interference remains unexplained. The Scalar Theory of Everything (STOE) model of single photon diffraction is a model with photons being directed by plenum forces along their trajectory as Newton speculated. A simulation using the STOE makes predictions of screen patterns. The experiment used an image resulting from a single slit projected onto a second mask. If the second mask slit is placed at the center of the image, a Fraunhofer diffraction pattern is projected onto the screen. One side of a slit in the minima examined the result of varying the intensity of the illumination across the slit and the result of only one of the double slits being illuminated. The resultant patterns on a screen were photographed and are on the opposite side of center from the illuminated side of the second mask. The STOE simulation reproduced the images. These observations reject all other models of diffraction. (http://intellectualarchive.com/?link$=$item$\backslash ${\&}id$=$1578) [Preview Abstract] |
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