Atomic Physics Latest Preprints | 2019-06-06
Atomic Physics
Multipolar and higher-order lattice shifts in the Sr and Mg clocks (1906.02024v1)
Fang-Fei Wu, Yong-Bo Tang, Ting-Yun Shi, Li-Yan Tang
2019-06-05
The progress in optical clock with uncertainty at a level of
requires unprecedented precision in estimating the contribution of multipolar and higher-order effects of atom-field interactions. Previous theoretical and experimental results of dynamic multipolar polarizabilities and hyperpolarizabilities at the 813 nm magic wavelength of the Sr clock differ substantially. We employ the sum-over-states method to calculate dynamic multipolar polarizabilities and hyperpolarizabilities for the Sr and Mg clocks. Our differential dynamic hyperpolarizability at the magic wavelength of 813.4280(5) nm for the Sr clock is
a.u., which agrees well with the recent theoretical and measurement results. Our differential multipolar polarizability of the Sr clock is
a.u., which is consistent with the theoretical work of Porsev {\em et al.} [Phys. Rev. Lett. 120, 063204 (2018)], but different from recent measurement of Ushijima {\em et al.} [Phys. Rev. Lett. 121, 263202 (2018)]. In addition, the lattice light shifts as the detuning and trap depth changed are studied in detail by using present multipolar polarizability and hyperpolarizability. It illustrates that for the Mg clock, there exists a distinctive operational lattice depth of
that allows the total light shift reduced to less than
over the trap depth variation of
.
Multimode collective scattering of light in free space by a cold atomic gas (1906.02000v1)
R. Ayllon, J. T. Mendonça, A. T. Gisbert, N. Piovella, G. R. M. Robb
2019-06-05
We have studied collective recoil lasing by a cold atomic gas, scattering photons from an incident laser into many radiation modes in free space. The model consists of a system of classical equations for the atomic motion of N atoms, where the radiation field has been adiabatically eliminated. We performed numerical simulations using a molecular dynamics code, Pretty Efficient Parallel Coulomb Solver or PEPC, to track the trajectories of the atoms. These simulations show the formation of an atomic density grating and collective enhancement of scattered light, both of which are sensitive to the shape and orientation of the atomic cloud. In the case of an initially circular cloud, the dynamical evolution of the cloud shape plays an important role in the development of the density grating and collective scattering. The ability to use efficient molecular dynamics codes will be a useful tool for the study of the multimode interaction between light and cold gases.
factor of the 
state of middle-
boronlike ions (1812.06431v2)
V. A. Agababaev, D. A. Glazov, A. V. Volotka, D. V. Zinenko, V. M. Shabaev, G. Plunien
2018-12-16
Theoretical \emph{g}-factor calculations for the first excited \exst state of boronlike ions in the range
Stochastic amplitude fluctuations of bosonic dark matter and revised constraints on linear couplings (1905.13650v2)
Gary P. Centers, John W. Blanchard, Jan Conrad, Nataniel L. Figueroa, Antoine Garcon, Alexander V. Gramolin, Derek F. Jackson Kimball, Matthew Lawson, Bart Pelssers, Joeseph A. Smiga, Yevgeny Stadnik, Alexander O. Sushkov, Arne Wickenbrock, Dmitry Budker, Andrei Derevianko
2019-05-31
If the dark matter is composed of virialized particles with mass
eV, it is well described as a classical bosonic field. This field is stochastic in nature, where the field oscillation amplitude fluctuates following a Rayleigh distribution. Most experimental searches have been in the regime
eV, where it is reasonable to assume a fixed field oscillation amplitude determined by the average local dark matter energy density. However, several direct-detection experiments are searching in the ultra-light mass regime where the dark matter field coherence time greatly exceeds the measurement time and the field oscillation amplitude is uncertain. We show that the corresponding laboratory constraints of bosonic dark matter field couplings to standard model particles are overestimated by as much as an order of magnitude.
Electric-field noise from thermally-activated fluctuators in a surface ion trap (1809.05624v2)
Crystal Noel, Maya Berlin-Udi, Clemens Matthiesen, Jessica Yu, Yi Zhou, Vincenzo Lordi, Hartmut Häffner
2018-09-15
We probe electric-field noise near the metal surface of an ion trap chip in a previously unexplored high-temperature regime. We observe a non-trivial temperature dependence with the noise amplitude at 1-MHz frequency saturating around 500~K. Measurements of the noise spectrum reveal a
-dependence and a small decrease in
between low and high temperatures. This behavior can be explained by considering noise from a distribution of thermally-activated two-level fluctuators with activation energies between 0.35~eV and 0.65~eV. Processes in this energy range may be relevant to understanding electric-field noise in ion traps; for example defect motion in the solid state and surface adsorbate binding energies. Studying these processes may aid in identifying the origin of excess electric-field noise in ion traps -- a major source of ion motional decoherence limiting the performance of surface traps as quantum devices.
Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten (1901.00745v3)
Suchandrima Das, Hongbing Yu, Edmund Tarleton, Felix Hofmann
2018-12-27
Tungsten is the main candidate material for plasma-facing armour components in future fusion reactors. In-service, fusion neutron irradiation creates lattice defects through collision cascades. Helium, injected from plasma, aggravates damage by increasing defect retention. Both can be mimicked using helium-ion-implantation. In a recent study on 3000 appm helium-implanted tungsten (W-3000He), we hypothesized helium-induced irradiation hardening, followed by softening during deformation. The hypothesis was founded on observations of large increase in hardness, substantial pile-up and slip-step formation around nano-indents and Laue diffraction measurements of localised deformation underlying indents. Here we test this hypothesis by implementing it in a crystal plasticity finite element (CPFE) formulation, simulating nano-indentation in W-3000He at 300 K. The model considers thermally-activated dislocation glide through helium-defect obstacles, whose barrier strength is derived as a function of defect concentration and morphology. Only one fitting parameter is used for the simulated helium-implanted tungsten; defect removal rate. The simulation captures the localised large pile-up remarkably well and predicts confined fields of lattice distortions and geometrically necessary dislocation underlying indents which agree quantitatively with previous Laue measurements. Strain localisation is further confirmed through high resolution electron backscatter diffraction and transmission electron microscopy measurements on cross-section lift-outs from centre of nano-indents in W-3000He.
Transition Probabilities in the Two-Level System with PT-Symmetric Non-Hermitian Hamiltonians (1906.01567v1)
Tommy Ohlsson, Shun Zhou
2019-06-04
In this work, we investigate how to define in a consistent way the probabilities of the transitions between the "flavor" states of the two-level quantum system, which is described by a non-Hermitian but parity and time-reversal (PT) symmetric Hamiltonian. Explicit calculations are carried out to demonstrate the conservation of probability if a proper definition of the final state is adopted. Finally, this formalism is applied to two-flavor neutrino oscillations
and
in vacuum, where the exact PT symmetry requires the vacuum mixing angle to be maximal, which is compatible with current neutrino oscillation experiments. A possible generalization to the three-flavor case is briefly discussed.
Transition rates for 
transitions in Al I (1905.11510v2)
Charlotte Froese Fischer, James F. Babb
2019-05-27
Fully relativistic calculations have been performed for two multiplets,
and
, in Al I. Wave functions were obtained for all levels of these multiplets using the GRASP programs. Reported are the E1 transitions rates for all transitions between levels of these multiplets. Transition energies and transition rates are compared with observed values and other theory. Our calculated transition rates are smaller by about 10% than observed rates, reducing a large discrepancy between earlier calculations and experiment.
Field ionization rate for PIC codes (1906.01358v1)
I. Yu. Kostyukov, A. A. Golovanov
2019-06-04
An improved formula is proposed for field ionization rate covering tunnel and barrier suppression regime. In contrast to the previous formula obtained recently in [I. Yu. Kostyukov and A. A. Golovanov, Phys. Rev. A 98, 043407 (2018)], it more accurately describes the transitional regime (between the tunnel regime and the barrier suppression regime). In the proposed approximation, the rate is mainly governed by two parameters: by the atom ionization potentials and by the external electric field, which makes it perfectly suitable for particle-in-cell (PIC) codes dedicated to modeling of intense laser-matter interactions.
New bounds from positronium decays on massless mirror dark photons (1905.09128v2)
M. Raaijmakers, L. Gerchow, B. Radics, A. Rubbia, C. Vigo, P. Crivelli
2019-05-22
We present the results of a search for a hidden mirror sector in positronium decays with a sensitivity comparable with the bounds set by the prediction of the primordial He
abundance from Big Bang Nucleosynthesis. No excess of events compatible with decays into the dark sector is observed resulting in an upper limit for the branching ratio of this process of
(
C.L.). This is an order of magnitude more stringent than the current existing laboratory bounds and it constraints the mixing strength of ordinary photons to dark mirror photons at a level of
.
