Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session Q08: Structure and Properties of Atoms, Ions, and Molecules |
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Chair: Loren Greenman, Kansas State University Room: Grand F |
Thursday, May 31, 2018 8:00AM - 8:12AM |
Q08.00001: Controlling electromagnetic waves in a class of invisible materials Yangjie Liu We propose a general methodology to manipulate the amplitude of an electromag- netic wave in a pre-defined way, without introducing any scattering. This leads to a whole class of isotropic spatially varying permittivity and permeability profiles that are invisible to incident waves. The theory is illustrated through various numerical examples, including the non-magnetic case. The implementation of the required material properties using metamaterials is discussed, as well as extensions of the method for controlling the phase of electromagnetic fields. Transformation optics is a powerful analytic tool to design impedance-matched material, which gives rise to scattering-free wave solutions up to designerâ€™s will. However, this method inevitably requires the material parameter to be anisotropic, which complicates its manufacturing process. Therefore, an isotropic material to achieve the required wave solution may solve this issue. Here in this conference contribution, we try to reveal one method to serve the purpose to cater for designerâ€™s requirements for electromagnetic waves. [Preview Abstract] |
Thursday, May 31, 2018 8:12AM - 8:24AM |
Q08.00002: Quantum optimal control of chiro-optical effects in the ultrafast multiphoton ionization regime Esteban Goetz, Loren Greenman The forward/backward asymmetry of the photoelectron emission of randomly oriented chiral molecules is a clear indication of chiral activity. Light-induced excitation is the first step towards the manipulation of the chiral activity for application purposes. However, a rigorous treatment of the laser-matter interaction becomes computationally prohibitive. Furthermore, it has been shown that a proper description of the continuum is critical for obtaining a quantitative agreement with experimental data. Here, we describe a simple model designed to manipulate chiro-optical effects with minimum computational effort. It relies on a second-order perturbative treatment of the electron dynamics, which allows us to keep track of the chiral signature imprinted in the photoelectron momentum distribution by interfering photoionization pathways arising from first and second order processes, a sufficient condition for the control of the electron dynamics. The description of the continuum is improved by employing the variational overset grid method, which enables us to efficiently extract the continuum spectrum of interest while simultaneously including the chiral description of the latter and the many-body character of the photoelectron-ion system. [Preview Abstract] |
Thursday, May 31, 2018 8:24AM - 8:36AM |
Q08.00003: Evaluation of Breit and QED effects on the $3d^9\ ^2D_{3/2}\rightarrow 3d^9\ ^2D_{5/2}$ transition energy using different approximations Ran Si, Charlotte Fischer, Tomas Brage, Chongyang Chen The multiconfiguration Dirac-Hartree-Fock (MCDHF) theory is used to calculate the $3d^9\ ^2D_{3/2}\rightarrow 3d^9\ ^2D_{5/2}$ transition energy for Co-like ions with $Z=27-100$. We investigate how electron correlation, frequency independent and dependent Breit interaction, and QED corrections vary along the sequence. Our study shows that the frequency independent Breit contribution Breit(0) has the largest contribution for all ions, correlation effect decreases rapidly with $Z$, the frequency dependent Breit contribution Breit($\omega$) is significant especially for high-$Z$ ions, self energy becomes the largest correction for $Z>50$. The self energy corrections are calculated using three different approximation methods, i.e., the approach implemented in the GRASP2K package [P.~J\"{o}nsson et al. \emph{Comput. Phys. Commun.} \textbf{184}, 2197 (2013)], the method based on Welton's concept [J.~A. Lowe et al. \emph{Radiat. Phys. Chem.} \textbf{85}, 118 (2013)], the QEDMOD approach [V.~M. Shabaev et al. \emph{Phys. Rev. A} \textbf{88}, 012513 (2013)]. Through the comparison with the experimental values, it seems that the QEDMOD results have the best agreement with the experimental values, the differences for high-$Z$ ions are about 0.03\%-0.04\%. [Preview Abstract] |
Thursday, May 31, 2018 8:36AM - 8:48AM |
Q08.00004: Accurate calculation of the 413 nm tune-out wavelength for 2$^{\mathrm{3}}$S$_{\mathrm{1}}$ state of helium Jun-Yi Zhang, Fang-Fei Wu, Pei-Pei Zhang, Li-Yan Tang, Yong-Hui Zhang, Ting-Yun Shi The tune-out wavelength is the wavelength at which the dynamic dipole polarizability vanishes. The 413 nm tune-out wavelength of the 2$^{\mathrm{3}}$S$_{\mathrm{1}}$ state of helium is proposed as a non-energy test quantum electrodynamic (QED)$^{\mathrm{[1]}}$, which sparks the great interest in high-precise measurement$^{\mathrm{[2]}}$ and high-accuracy calculations of the tune-out wavelength of helium$^{\mathrm{[3,4]}}$. So far, there exists 19 ppm discrepancy between the trapped atom dynamics measurement of 413.0938(9$_{\mathrm{stat}})$(20$_{\mathrm{syst}})$ nm$^{\mathrm{[2]}}$ and the relativistic configuration-interaction (RCI) calculation of 413.0859(4) nm$^{\mathrm{[3]}}$. In present work we performed larger-scale RCI calculation based on the Dirac-Coulomb-Breit (DCB) equation with the mass shift operators included directly in the Hamiltonian. The advantage of this developed RCI method is that the finite nuclear mass and relativistic nuclear recoil corrections on the tune-out wavelength are taken into account self-consistently in DCB framework. The QED correction on the tune-out wavelength is also estimated. Our result of tune-out wavelength is 413.090 14(5) nm with an uncertainty of 0.12 ppm, which is about 25 times more accurate than the experimental value from Ref. [2]. This work will motivate a future experimental campaign to seriously test QED at higher level of accuracy. Reference: [1] J. Mitroy and L.Y. Tang, Phys. Rev. A 88, 052515 (2013) [2] B. M. Henson, R. I. Khakimov, R. G. Dall, K. G. H. Baldwin, L.Y. Tang, and A. G. Truscott, Phys. Rev. Lett. 115, 043004 (2015) [3] Y. H. Zhang, L. Y. Tang, X. Z. Zhang, and T. Y. Shi, Phys. Rev. A 93, 052516 (2016) [4] G. W. F. Drake, private communication (2017). [Preview Abstract] |
Thursday, May 31, 2018 8:48AM - 9:00AM |
Q08.00005: Charge Hopping in an Optical Tweezer Array of Sr Atoms: An Application of Generalized Local Frame Transformation Theory T. J. Price, Chris H. Greene, J. P. Covey, Manuel Endres Tunneling of a Rydberg electron in highly excited states of Sr$_2^+$ is investigated. This work will complement an experiment to be performed by the Endres group involving an array of Sr atoms in optical tweezers. In the tweezer array, the distance between the Sr atoms is on the order of a micrometer. The large internuclear separation and high energies of the Sr$_2^+$ states lead to electronic wave functions that can't be treated with conventional quantum chemistry. Instead, we apply a generalized local frame transformation theory [Giannakeas {\it et al.}, Phys. Rev. A. {\textbf 94}, 013419 (2016)] to determine tunneling rates in Sr$_2^+$ in part from wave functions that we have calculated for H$_2^+$. This technique is based on the idea that near each nucleus the electronic wave function of H$_2^+$ is locally that of a hydrogen atom. We determine a local frame transformation matrix between H wave functions in spherical coordinates and H$_2^+$ wave functions in spheroidal coordinates. Then, we incorporate the effect of scattering from the Sr cores by using Green's functions and quantum defects of Sr. [Preview Abstract] |
Thursday, May 31, 2018 9:00AM - 9:12AM |
Q08.00006: Rydberg-atom electromagnetically induced transparency in strong magnetic fields Lu Ma, David Anderson, Rachel Sapiro, Georg Raithel We report on a rubidium vapor-cell Rydberg electromagnetically induced transparency (EIT) experiment in a 0.7~T magnetic field. We further discuss our progress towards manufacturing a miniaturized vapor-cell Penning trap. In the EIT scheme, all atomic levels involved are in the hyperfine Paschen-Back regime. The S-level Rydberg state further exhibits a strong diamagnetic interaction with the magnetic field. The isotope-mixed Rb cells allow us to explore both $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ EIT signals and to exploit differential features in magnetic-field measurement. A $0.2$\% relative uncertainty of the measured magnetic field is achieved by using the signals of both isotopes. The measured spectra are in excellent agreement with the results of a Monte Carlo calculation. Line shifts and broadenings due to small inhomogeneities of the magnetic field are included in the model. In order to further investigate the large Rydberg dephasing rates observed in this measurement, a room-temperature Penning-trap vapor cell is being manufactured using anodic-bonding methods. The compact design enables us to operate the Penning-trap cell in a strong magnetic field produced by permanent magnets, and to investigate Rydberg-atom interactions with trapped charges [Preview Abstract] |
Thursday, May 31, 2018 9:12AM - 9:24AM |
Q08.00007: Thin film deposition using rarefied gas jet Dr. Sahadev Pradhan The rarefied gas jet of aluminium is studied at Mach number \textit{Ma }$=$\textit{ (U\textunderscore j / }$\backslash $\textit{sqrt\textbraceleft kb T\textunderscore j / m\textbraceright )}in the range \textit{.01 \textless Ma \textless 2}, and Knudsen number \textit{Kn }$=$\textit{ (1 / (}$\backslash $\textit{sqrt\textbraceleft 2\textbraceright }$\backslash $\textit{pi d\textasciicircum 2 n\textunderscore d H)} in the range \textit{.01 \textless Kn \textless 15}, using two-dimensional (2D) direct simulation Monte Carlo (DSMC) simulations, to understand the flow phenomena and deposition mechanisms in a physical vapor deposition (PVD) process for the development of the highly oriented pure metallic aluminum thin film with uniform thickness and strong adhesion on the surface of the substrate in the form of ionic plasma, so that the substrate can be protected from corrosion and oxidation and thereby enhance the lifetime and safety, and to introduce the desired surface properties for a given application. Here, $H$is the characteristic dimension, \textit{U\textunderscore j}and \textit{T\textunderscore j}are the jet velocity and temperature, \textit{n\textunderscore d}is the number density of the jet, $m$and $d$ are the molecular mass and diameter, and \textit{kb}is the Boltzmann constant. An important finding is that the capture width (cross-section of the gas jet deposited on the substrate) is symmetric around the centerline of the substrate, and decreases with increased Mach number due to an increase in the momentum of the gas molecules. DSMC simulation results reveals that at low Knudsen number \textit{((Kn }$=$\textit{ 0.01);}shorter mean free paths), the atoms experience more collisions, which direct them toward the substrate. However, the atoms also move with lower momentum at low Mach number$,$which allows scattering collisions to rapidly direct the atoms to the substrate. [Preview Abstract] |
Thursday, May 31, 2018 9:24AM - 9:36AM |
Q08.00008: Radiative ion-atom processes James Babb, Brendan McLaughlin Collisions between an ion and an atom in which a photon is emitted and either a molecular ion is formed or charge transfer occurs are of interest for astrophysical applications and for studies of trapped ions and atoms at low energies. We discuss recent calculations on collisions of C and a proton and of Ar with a helium ion. Results on other carbon-containing systems will be discussed. [Preview Abstract] |
Thursday, May 31, 2018 9:36AM - 9:48AM |
Q08.00009: Absolute total cross sections of methane molecules by fast antiproton and proton impact Pavel N. Terekhin, Michele A. Quinto, Juan M. Monti, Omar A. Fojon, Roberto D. Rivarola A detailed investigation of multiple electron processes (single and multiple ionization, single capture, transfer-ionization) of methane molecules is presented for antiproton and proton impact at intermediate and high collision energies. A prior-version of the three-body continuum distorted wave-eikonal initial state approximation within the independent electron approximation is used to calculate exclusive transition probabilities as a function of the impact parameter and pure and net absolute cross sections for the considered collisions. An exclusive statistical trinomial distribution is employed to describe multiple-electron processes. The results are compared with other theoretical calculations and available experimental data. The developed method for calculation of one-electron ionization and capture probabilities allows to study multiple electron processes for charged particles passing through the matter. It also can be used to investigate molecular fragmentation mechanisms. [Preview Abstract] |
Thursday, May 31, 2018 9:48AM - 10:00AM |
Q08.00010: X-ray imaging spectroscopic diagnostics on Nike. Y. Aglitskiy, M Karasik, V Serlin, J.L. Weaver, J. Oh, S.P. Obenschain, Yu. Ralchenko Replace this text with your ab Electron temperature and density diagnostics of the laser plasma produced within the focal spot of the NRL's Nike laser are being explored with the help of X-ray imaging spectroscopy. Spectra of He-like and H-like ions were taken by Nike focusing spectrometers in a range of lower (1.8 kev, Si XIV) and higher (6.7 kev, Fe XXV) x-ray energies. Data that were obtained with spatial resolution were translated into the temperature and density as functions of distance from the target. As an example electron density was determined from He-like satellites to Ly-alpha in Si XIV. The dielectronic satellites with intensity ratios that are sensitive to collisional transfer of population between different triplet groups of double-excited states 2l2l' in Si XIII were observed with high spatial and spectral resolution Lineouts taken at different axial distances from the planar Si target show changing spectral shapes due to the different electron densities as determined by supporting non-LTE simulations. These shapes are relatively insensitive to the plasma temperature which was measured using different spectral lines. stract body. [Preview Abstract] |
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