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Atoms, Volume 4, Issue 3 (September 2016)

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Research

Open AccessArticle Prospects for Precise Measurements with Echo Atom Interferometry
Atoms 2016, 4(3), 19; doi:10.3390/atoms4030019
Received: 30 March 2016 / Revised: 20 June 2016 / Accepted: 21 June 2016 / Published: 27 June 2016
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Abstract
Echo atom interferometers have emerged as interesting alternatives to Raman interferometers for the realization of precise measurements of the gravitational acceleration g and the determination of the atomic fine structure through measurements of the atomic recoil frequency ωq. Here we review
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Echo atom interferometers have emerged as interesting alternatives to Raman interferometers for the realization of precise measurements of the gravitational acceleration g and the determination of the atomic fine structure through measurements of the atomic recoil frequency ω q . Here we review the development of different configurations of echo interferometers that are best suited to achieve these goals. We describe experiments that utilize near-resonant excitation of laser-cooled rubidium atoms by a sequence of standing wave pulses to measure ω q with a statistical uncertainty of 37 parts per billion (ppb) on a time scale of ∼50 ms and g with a statistical precision of 75 ppb. Related coherent transient techniques that have achieved the most statistically precise measurements of atomic g-factor ratios are also outlined. We discuss the reduction of prominent systematic effects in these experiments using off-resonant excitation by low-cost, high-power lasers. Full article
(This article belongs to the Special Issue Atom Interferometry)
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Open AccessArticle Neutrons and Gamma-Ray Dose Calculations in Subcritical Reactor Facility Using MCNP
Atoms 2016, 4(3), 20; doi:10.3390/atoms4030020
Received: 10 April 2016 / Revised: 16 June 2016 / Accepted: 16 June 2016 / Published: 30 June 2016
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Abstract
In nuclear experimental, training and teaching laboratories such as a subcritical reactor facility, huge measures of external radiation doses could be caused by neutron and gamma radiation. It becomes imperative to place the health and safety of staff and students in the reactor
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In nuclear experimental, training and teaching laboratories such as a subcritical reactor facility, huge measures of external radiation doses could be caused by neutron and gamma radiation. It becomes imperative to place the health and safety of staff and students in the reactor facility under proper scrutiny. The protection of these individuals against ionization radiation is facilitated by expected dose mapping and shielding calculations. A three-dimensional (3D) Monte Carlo model was developed to calculate the dose rate from neutrons and gamma, using the ANSI/ANS-6.1.1 and the ICRP-74 flux-to-dose conversion factors. Estimation for the dose was conducted across 39 areas located throughout the reactor hall of the facility and its training platform. It was found that the range of the dose rate magnitude is between 7.50 E−01 μSv/h and 1.96 E−04 μSv/h in normal operation mode. During reactor start-up/shut-down mode, it was observed that a large area of the facility can experience exposure to a significant radiation field. This field ranges from 2.99 E+03 μSv/h to 3.12 E+01 μSv/h. There exists no noticeable disparity between results using the ICRP-74 or ANSI/ANS-6.1.1 flux-to-dose rate conversion factors. It was found that the dose rate due to gamma rays is higher than that of neutrons. Full article
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Open AccessArticle Analysis of Polarizability Measurements Made with Atom Interferometry
Atoms 2016, 4(3), 21; doi:10.3390/atoms4030021
Received: 1 June 2016 / Accepted: 4 July 2016 / Published: 6 July 2016
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Abstract
We present revised measurements of the static electric dipole polarizabilities of K, Rb, and Cs based on atom interferometer experiments presented in [Phys. Rev. A 2015, 92, 052513] but now re-analyzed with new calibrations for the magnitude and geometry of the applied electric
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We present revised measurements of the static electric dipole polarizabilities of K, Rb, and Cs based on atom interferometer experiments presented in [Phys. Rev. A 2015, 92, 052513] but now re-analyzed with new calibrations for the magnitude and geometry of the applied electric field gradient. The resulting polarizability values did not change, but the uncertainties were significantly reduced. Then, we interpret several measurements of alkali metal atomic polarizabilities in terms of atomic oscillator strengths fik, Einstein coefficients Aik, state lifetimes τk, transition dipole matrix elements Dik, line strengths Sik, and van der Waals C6 coefficients. Finally, we combine atom interferometer measurements of polarizabilities with independent measurements of lifetimes and C6 values in order to quantify the residual contribution to polarizability due to all atomic transitions other than the principal ns-npJ transitions for alkali metal atoms. Full article
(This article belongs to the Special Issue Atom Interferometry)
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Open AccessArticle Atomic Structure Calculations and Study of Plasma Parameters of Al-Like Ions
Atoms 2016, 4(3), 22; doi:10.3390/atoms4030022
Received: 7 November 2015 / Revised: 27 June 2016 / Accepted: 30 June 2016 / Published: 11 July 2016
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Abstract
In the present paper, the spectroscopic properties and plasma characteristics of Al-like ions are investigated in an extensive and detailed manner by adopting the GRASP2K package based on fully relativistic Multi-Configuration Dirac–Hartree–Fock (MCDHF) wave-functions in the active space approximation. We have presented energy
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In the present paper, the spectroscopic properties and plasma characteristics of Al-like ions are investigated in an extensive and detailed manner by adopting the GRASP2K package based on fully relativistic Multi-Configuration Dirac–Hartree–Fock (MCDHF) wave-functions in the active space approximation. We have presented energy levels for Al-like ions for Valence-Valence (VV) and Core-Valence (CV) correlations under the scheme of active space. We have also provided radiative data for E1 transitions for Al-like ions and studied the variation of the transition wavelength and transition probability for electric dipole (E1) Extreme Ultraviolet (EUV) transitions with nuclear charge. Our calculated energy levels and transition wavelengths match well with available theoretical and experimental results. The discrepancies of the GRASP2K code results with CIV3 and RMPBT (Relativistic Many Body Perturbation Theory) results are also discussed. The variations of the line intensity ratio, electron density, plasma frequency and plasma skin depth with plasma temperature and nuclear charge are discussed graphically in detail for optically thin plasma in Local Thermodynamic Equilibrium (LTE). We believe that our obtained results may be beneficial for comparisons and in fusion and astrophysical plasma research. Full article
(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)
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Open AccessArticle Scalar Aharonov–Bohm Phase in Ramsey Atom Interferometry under Time-Varying Potential
Atoms 2016, 4(3), 23; doi:10.3390/atoms4030023
Received: 23 February 2016 / Revised: 26 July 2016 / Accepted: 28 July 2016 / Published: 2 August 2016
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Abstract
In a Ramsey atom interferometer excited by two electromagnetic fields, if atoms are under a time-varying scalar potential during the interrogation time, the phase of the Ramsey fringes shifts owing to the scalar Aharonov–Bohm effect. The phase shift was precisely examined using a
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In a Ramsey atom interferometer excited by two electromagnetic fields, if atoms are under a time-varying scalar potential during the interrogation time, the phase of the Ramsey fringes shifts owing to the scalar Aharonov–Bohm effect. The phase shift was precisely examined using a Ramsey atom interferometer with a two-photon Raman transition under the second-order Zeeman potential, and a formula for the phase shift was derived. Using the derived formula, the frequency shift due to the scalar Aharonov–Bohm effect in the frequency standards utilizing the Ramsey atom interferometer was discussed. Full article
(This article belongs to the Special Issue Atom Interferometry)
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Open AccessArticle Electron Impact Excitation of F-Like W LXVI
Atoms 2016, 4(3), 24; doi:10.3390/atoms4030024
Received: 13 May 2016 / Revised: 19 July 2016 / Accepted: 20 July 2016 / Published: 26 July 2016
Cited by 2 | PDF Full-text (2180 KB) | HTML Full-text | XML Full-text
Abstract
Electron impact excitation collision strengths are calculated for all transitions among 113 levels of the 2s22p5, 2s2p6, 2s22p43, 2s2p53, and 2p63 configurations of F-like
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Electron impact excitation collision strengths are calculated for all transitions among 113 levels of the 2s 2 2p 5 , 2s2p 6 , 2s 2 2p 4 3, 2s2p 5 3, and 2p 6 3 configurations of F-like W LXVI. For this purpose, Dirac Atomic R-matrix Code (DARC) has been adopted and results are listed over a wide energy range of 1000 to 6000 Ryd. For comparison purposes, analogous calculations have also been performed with the Flexible Atomic Code (FAC), and the results obtained are comparable with those from DARC. Full article
(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)
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Open AccessArticle Decoherence Spectroscopy for Atom Interferometry
Atoms 2016, 4(3), 25; doi:10.3390/atoms4030025
Received: 31 March 2016 / Revised: 2 August 2016 / Accepted: 4 August 2016 / Published: 17 August 2016
Cited by 1 | PDF Full-text (690 KB) | HTML Full-text | XML Full-text
Abstract
Decoherence due to photon scattering in an atom interferometer was studied as a function of laser frequency near an atomic resonance. The resulting decoherence (contrast-loss) spectra will be used to calibrate measurements of tune-out wavelengths that are made with the same apparatus. To
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Decoherence due to photon scattering in an atom interferometer was studied as a function of laser frequency near an atomic resonance. The resulting decoherence (contrast-loss) spectra will be used to calibrate measurements of tune-out wavelengths that are made with the same apparatus. To support this goal, a theoretical model of decoherence spectroscopy is presented here along with experimental tests of this model. Full article
(This article belongs to the Special Issue Atom Interferometry)
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