Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Y36: New Developments in Atomic, Molecular, and Optical Physics |
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Sponsoring Units: DAMOP Chair: Nathan Gemelke, Pennsylvnia State University Room: 211 |
Friday, March 6, 2015 8:00AM - 8:12AM |
Y36.00001: ABSTRACT WITHDRAWN |
Friday, March 6, 2015 8:12AM - 8:24AM |
Y36.00002: Emission spectrum of atoms in a harmonic trap Pooja Singh, Yuri Rostovtsev We consider an excited atom in a harmonic trap. The evolution of quantum atomic states is theoretically studied under adiabatic approximation. The emission spectra for trapped atoms are calculated. We have show interference effects as well as trapping effect in a trap that has a size larger than the wavelength of radiation. [Preview Abstract] |
(Author Not Attending)
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Y36.00003: When is the mode-summation method of calculating van der Waals force valid? Arvind Narayanaswamy Most calculations of van der Waals forces and Casimir forces can be categorized as variations of two ``proto methods'': (1) Lifshitz theory, and (2) mode summation method. In the Lifshitz theory, by which I include the subsequent generalization by Dzyaloshinskii, Lifshitz, and Pitaevskii [Adv. Phys. 10, 165 (1961); See also Zheng and Narayanaswamy, Phys. Rev. A 83, 042504 (2011)] the dispersion force is expressed in terms of the (dyadic) Green's function of the vector Helmholtz equation. In the mode summation method [see Casimir, Proc. Kon. Ned. Akad. Wetensch. 51, 793 (1948); Van Kampen, Nijboer, and Schram, Phys. Lett. A 26, 307 (1968)], the free energy of a configuration of objects is expressed in terms of the sum of the free energies of each of the possible electromagnetic modes. The derivative of this free energy with respect to variation of relative positions between the objects yields the force between two objects. However, we raised questions about the validity of the mode summation method when calculating van der Waals forces in dissipative media [see Narayanaswamy and Zheng, Phys. Rev. A 88, 012502 (2013) and Ninham, Parsegian, and Weiss, J. Stat. Phys. 2, 323 (1970)]. In this talk, I want to start a discussion about the validity of the mode summation method. [Preview Abstract] |
Friday, March 6, 2015 8:36AM - 8:48AM |
Y36.00004: Landau-Zener transitions mediated by an environment in the open-multistate model Savannah Garmon, Amro Dodin, Lena Simine, Dvira Segal We study Landau-Zener transitions between two linearly driven states with the addition of a shared discretized continuum. The continuum allows for population decay from the initial state as well as indirect transitions. The probability of nonadiabatic transition in this model preserves the standard Landau-Zener functional form apart from a shift in the usual exponential factor, reflecting population transfer into the continuum. We provide an intuitive explanation for this behavior assuming individual, independent transitions between pairs of states. In contrast, the ground state survival probability at long time shows a novel, non-monotonic, functional form with an oscillatory behavior in the sweep rate at low sweep rate values. We envision our system as a simplified model regarding memory preservation in a quantum dot as the dot interacts with the surrounding environment. \\[4pt] [1] A. Dodin, S. Garmon, L. Simine, and D. Segal, J. Chem. Phys. 140, 124709 (2014). [Preview Abstract] |
Friday, March 6, 2015 8:48AM - 9:00AM |
Y36.00005: ABSTRACT WITHDRAWN |
Friday, March 6, 2015 9:00AM - 9:12AM |
Y36.00006: Near field heat transfer in superlattices Raul Esquivel-Sirvent I present a theoretical calculation of the near field heat transfer between super lattices made of alternative layers of both metallic and semiconducting materials. The calculation of the near field transfer requires the knowledge of the reflectivities, that are obtained by calculating the surface impedance of the super lattice. Depending on the periodicity of the lattice and the dielectric function of the materials the near field heat transfer can be modulated or engineered. Additional control on the heat transfer is achieved by introducing defects in the superlattice. The results are extended to include photonic hypercrystals that effectively behave like a hyperbolic metamaterial even in the near field (1), where the tuning of the heat transfer is modified by (1) E. E. Narimanov, Phys. Rev. X 4, 041014 (2014). [Preview Abstract] |
Friday, March 6, 2015 9:12AM - 9:24AM |
Y36.00007: ABSTRACT WITHDRAWN |
Friday, March 6, 2015 9:24AM - 9:36AM |
Y36.00008: Neutral Atom Nanolithography Using a Pulsed Magnetic Lens Erik Anciaux, Rodrigo Castillo-Garza, Jamie Gardner, Mark Raizen We present the status of a method of neutral atom lithography that achieves sub-10nm resolution. This method is based on the nanoscale imaging of a beam of metastable atoms with an aberration-corrected hexapole lens. The lens creates a magnetic field gradient that increases with the distance from the center of the lens so as to focus divergent low field seeking atoms toward a single focal spot past the lens. The scheme takes advantage of the narrow velocity distribution of a pulsed supersonic beam as well as an optical pumping and cooling scheme that selects the magnetic state of the atoms and further reduces its velocity dispersion. This method can be used not only to pattern but to spectroscopically probe surfaces with spatial resolution below 10nm. . [Preview Abstract] |
Friday, March 6, 2015 9:36AM - 9:48AM |
Y36.00009: Proposal of a new type of optical parametric amplifier for efficient X-ray generation Wayne Huang, Roger Bach, Herman Batelaan, Marlan Scully With an optical parametric amplifier (OPA), one can transfer energy from the pump light to the seeded light via sum parametric resonance (also called parametric down conversion). In this process, coherent light with frequency lower than the pump is generated. Using infrared as pump, one can obtain light in the mid/far-infrared regime. In contrast to OPA, the quantum amplification by super-radiant emission of radiation (QASER) suggests that energy transfer can occur when the pump frequency is equal to the difference of the seeded frequencies [1]. Thus, coherent light with frequency much higher than the pump can be generated. The physical mechanism behind QASER is called difference parametric resonance. We propose to build a new type of optical parametric amplifier based on this concept and transfer energy from infrared to X-ray. In this presentation, I would like to capture the main idea of QASER by discussing the difference parametric resonance in a coupled oscillating system. A perturbation analysis is given to provide insight into the mechanism as well as the conditions for experimental realization. We will also briefly discuss realizations of difference parametric resonance in electronic, mechanical, and acoustic systems. [1] M. O. Scully et al., Phys. Rev X 3, 041001 (2013). [Preview Abstract] |
Friday, March 6, 2015 9:48AM - 10:00AM |
Y36.00010: Measured Atomic Ground State Polarizabilities of 35 Metallic Elements John Indergaard, Lei Ma, Baiqian Zhang, Ilia Larkin, Ramiro Moro, Walter de Heer Advanced pulsed cryogenic molecular beam electric deflection methods utilizing a position-sensitive mass spectrometer and 7.87 eV ionizing radiation were used to measure the polarizabilities of more than half of the metallic elements in the periodic table for the first time. These measurements increase the total number of experimentally obtained atomic polarizabilities from 23 to 57. Concurrent Stern-Gerlach deflection measurements verified the ground state condition of the measured atoms. Generating higher temperature beams allowed for the comparison of relative populations of the ground and excited states in order to extract the true temperature of the atomic beam, which followed the nominal temperature closely over a wide temperature range. Comparison of newly measured polarizabilities with state-of-the-art calculations exposes significant systematic and isolated discrepancies throughout the periodic table. [Preview Abstract] |
Friday, March 6, 2015 10:00AM - 10:12AM |
Y36.00011: Complex time contours in tunnel ionization and low-energy structures Emilio Pisanty, Misha Ivanov In tunnel ionization, a strong low-frequency laser field removes an electron from an atom by setting up a slowly-varying potential energy barrier that the electron can tunnel through. During its subsequent oscillations in the laser field, the electron can revisit the neighbourhood of the remaining ion one or more times. Frequently, this is a soft recollision which affects the momentum distribution, although more substantial effects can happen. We use the Analytical R-Matrix theory to investigate the effect of these soft recollisions, focusing on low drift momenta, where the laser-induced trajectory has a turning point near the nucleus. Our framework provides a complex-valued trajectory perspective on the electron propagation, from first principles. We show that the presence of the Coulomb interaction, which is responsible for the soft recollisions, forbids certain common choices of contour within the complex time plane, and we describe an algorithm for safely circumventing the associated branch cuts. We find quantum analogues to the classical turning points near the ion, and we investigate their relation to the recently-discovered low-energy and very-low-energy structures in above-threshold ionization. [Preview Abstract] |
Friday, March 6, 2015 10:12AM - 10:24AM |
Y36.00012: Fast spectrophotometry with compressive sensing David Starling, Ian Storer Spectrophotometers and spectrometers have numerous applications in the physical sciences and engineering, resulting in a plethora of designs and requirements. A good spectrophotometer balances the need for high photometric precision, high spectral resolution, high durability and low cost. One way to address these design objectives is to take advantage of modern scanning and detection techniques. A common imaging method that has improved signal acquisition speed and sensitivity in limited signal scenarios is the single pixel camera. Such cameras utilize the sparsity of a signal to sample below the Nyquist rate via a process known as compressive sensing. Here, we show that a single pixel camera using compressive sensing algorithms and a digital micromirror device can replace the common scanning mechanisms found in virtually all spectrophotometers, providing a very low cost solution and improving data acquisition time. We evaluate this single pixel spectrophotometer by studying a variety of samples tested against commercial products. We conclude with an analysis of flame spectra and possible improvements for future designs. [Preview Abstract] |
Friday, March 6, 2015 10:24AM - 10:36AM |
Y36.00013: Red Shifted Absorbance of A-site Substituted Bismuth Titanate Pyrochlore: Characterization and Stability Analysis from First Principles Cedric Mayfield, Muhammad Huda Transition metal inclusion has enhanced photocatalytic activity of bismuth titanate (Bi2Ti2O7) up to an impurity threshold concentration. Beyond the threshold, spectral absorbance is continually red shifted but increased photocurrent is not reciprocated. We investigated, from first principles, the origin of decreased photocurrent in modified Bi2Ti2O7 (BTO) by calculating the electronic structures of a representative set of doping configurations and by performing a phase stability analysis of the doping. We report our theoretical/computational strategy of analyzing free energy space and show an explicit dependence of pure phase synthesis on changes in free energy. Also, we present a probability distribution of the doping configurations based on formation enthalpy to better understand the nature of doping in BTO. We found that transition metal substitutions are favorable at the A-sites due to unchanging coordination with O ions. [Preview Abstract] |
Friday, March 6, 2015 10:36AM - 10:48AM |
Y36.00014: Dopant concentration dependent optical and X-Ray induced photoluminescence in Eu$^{3+}$ doped La$_{2}$Zr$_{2}$O$_{7}$ Madhab Pokhrel, Mikhail Brik, Yuanbing Mao Herein, we will be presenting the dopant (Eu) concentration dependent high density La$_{2}$Zr$_{2}$O$_{7}$ nanoparticles for optical and X-ray scintillation applications by use of X - ray diffraction, Raman, FTIR, scanning electron microscope (SEM), transmission electron microscopy (TEM), optically and X-ray excited photoluminescence (PL). Several theoretical methods have been used in order to investigate the structural, electronic, optical, elastic, dynamic properties of Eu doped La$_{2}$Zr$_{2}$O$_{7}$. It is observed that Eu: La$_{2}$Zr$_{2}$O$_{7}$ shows an intense red luminescence under 258, 322, 394 and 465 nm excitation. The optical intensity of Eu: La$_{2}$Zr$_{2}$O$_{7}$ depends on the dopant concentration of Eu$^{3+}$. Following high energy excitation with X-rays, Eu: La$_{2}$Zr$_{2}$O$_{7}$ shows an atypical Eu PL response (scintillation) with a red emission. The intense color emission of Eu obtained under 258 nm excitation, the X-ray induced luminescence property along with reportedly high density of La$_{2}$Zr$_{2}$O$_{7}$, makes these nanomaterials attractive for optical and X-ray applications. [Preview Abstract] |
Friday, March 6, 2015 10:48AM - 11:00AM |
Y36.00015: Semi-Classical and Quantum-Field Descriptions for the Non-Linear Electromagnetic Response of Many-Electron Systems Verne Jacobs Semi-classical and quantum-field descriptions for the non-linear electromagnetic response relevant to resonant pump-probe optical phenomena in quantized many-electron systems are formulated within a general reduced-density-matrix framework. Time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are developed in a unified and self-consistent manner. A preliminary semi-classical perturbation treatment of the electromagnetic interaction is adopted, in which the electromagnetic field is described as a classical field satisfying the Maxwell equations. It is emphasized that the development of a quantized-field approach will be essential for a fully self-consistent quantum-mechanical formulation. Compact Liouville-space operator expressions are obtained for the general (n'th order) non-linear electromagnetic-response tensors describing moving many-electron atomic systems. The tetradic matrix elements of the Liouville-space self-energy operators are evaluated for environmental collisional and radiative interactions. [Preview Abstract] |
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