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Atoms, Volume 3, Issue 3 (September 2015), Pages 273-473

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Research

Open AccessArticle Spectra of W VIII and W IX in the EUV Region
Atoms 2015, 3(3), 273-298; doi:10.3390/atoms3030273
Received: 8 April 2015 / Revised: 21 May 2015 / Accepted: 15 June 2015 / Published: 30 June 2015
Cited by 2 | PDF Full-text (1981 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The results obtained on the W VIII spectrum as well as on the isoelectronic spectra Lu V, Hf VI, Ta VII, and Re IX in the VUV wavelength region are summarized with emphasis on the main trends along the isoelectronic sequence. A total
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The results obtained on the W VIII spectrum as well as on the isoelectronic spectra Lu V, Hf VI, Ta VII, and Re IX in the VUV wavelength region are summarized with emphasis on the main trends along the isoelectronic sequence. A total of 187 lines of W VIII in the region of 160–271 Å were accurately measured and identified, 98 levels were found, and transition probabilities calculated. The isoelectronic regularities support the data on W VIII. A list of spectral lines in the region of 170–199 Å, considered as belonging to W IX, is presented. Full article
(This article belongs to the Special Issue Atomic Data for Tungsten)
Open AccessArticle Detailed Analysis of Configuration Interaction and Calculation of Radiative Transition Rates in Seven Times Ionized Tungsten (W VIII)
Atoms 2015, 3(3), 299-319; doi:10.3390/atoms3030299
Received: 21 May 2015 / Revised: 15 June 2015 / Accepted: 23 June 2015 / Published: 30 June 2015
Cited by 1 | PDF Full-text (894 KB) | HTML Full-text | XML Full-text
Abstract
A new set of oscillator strengths and transition probabilities for EUV spectral lines of seven times ionized tungsten (W VIII) is reported in the present paper. These results have been obtained using the pseudo-relativistic Hartree-Fock (HFR) method combined with a semi-empirical optimization of
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A new set of oscillator strengths and transition probabilities for EUV spectral lines of seven times ionized tungsten (W VIII) is reported in the present paper. These results have been obtained using the pseudo-relativistic Hartree-Fock (HFR) method combined with a semi-empirical optimization of the radial parameters minimizing the discrepancies between computed energy levels and available experimental data. The final physical model considered in the calculations has been chosen further to a detailed investigation of the configuration interaction in this atomic system characterized by complex configurations of the type 4f145s25p5, 4f145s25p4nl, 4f145s5p6, 4f135s25p6, 4f135s25p5nl and 4f125s25p6nl (nl = 5d, 6s). Full article
(This article belongs to the Special Issue Atomic Data for Tungsten)
Open AccessArticle On the Classical Coupling between Gravity and Electromagnetism
Atoms 2015, 3(3), 320-338; doi:10.3390/atoms3030320
Received: 14 January 2015 / Revised: 30 May 2015 / Accepted: 17 June 2015 / Published: 30 June 2015
Cited by 1 | PDF Full-text (986 KB) | HTML Full-text | XML Full-text
Abstract
Coupling between electromagnetism and gravity, manifested as the distorted Coulomb field of a charge distribution in a gravitational field, has never been observed. A physical system consisting of an electron in a charged shell provides a coupling that is orders of magnitude stronger
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Coupling between electromagnetism and gravity, manifested as the distorted Coulomb field of a charge distribution in a gravitational field, has never been observed. A physical system consisting of an electron in a charged shell provides a coupling that is orders of magnitude stronger than for any previously-considered system. A shell voltage of one megavolt is required to establish a gravitationally-induced electromagnetic force equal in magnitude to the force of gravity on an electron. The experimental feasibility of detecting these forces on an electron is discussed. The effect establishes a relation between Einstein’s energy-mass equivalence and the coupling between electromagnetism and gravity. Full article
Open AccessArticle Influence of Virtual Photon Process on the Generation of Squeezed Light from Atoms in an Optical Cavity
Atoms 2015, 3(3), 339-347; doi:10.3390/atoms3030339
Received: 8 May 2015 / Accepted: 22 July 2015 / Published: 24 July 2015
Cited by 2 | PDF Full-text (321 KB) | HTML Full-text | XML Full-text
Abstract
We show that a collection of two-level atoms in an optical cavity beyond the rotating wave approximation and in the dispersive-adiabatic and non-dispersive adiabatic regime constitutes a nonlinear medium and is capable of generating squeezed state of light. It is found that squeezing
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We show that a collection of two-level atoms in an optical cavity beyond the rotating wave approximation and in the dispersive-adiabatic and non-dispersive adiabatic regime constitutes a nonlinear medium and is capable of generating squeezed state of light. It is found that squeezing produced in the non-dispersive adiabatic regime is significantly high compared to that produced in the dispersive-adiabatic limit. On the other hand, we also show that it could be possible to observe the Dicke superradiant quantum phase transition in the dispersive-adiabatic regime where the Ã2 term is negligible. Such a system can be an essential component of a larger quantum-communication system. Full article
(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)
Open AccessArticle Cavity-Assisted Generation of Sustainable Macroscopic Entanglement of Ultracold Gases
Atoms 2015, 3(3), 348-366; doi:10.3390/atoms3030348
Received: 29 June 2015 / Accepted: 29 July 2015 / Published: 4 August 2015
Cited by 3 | PDF Full-text (1926 KB) | HTML Full-text | XML Full-text
Abstract
Prospects for reaching persistent entanglement between two spatially-separated atomic Bose–Einstein condensates are outlined. The system setup comprises two condensates loaded in an optical lattice, which, in return, is confined within a high-Q optical resonator. The system is driven by an external laser that
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Prospects for reaching persistent entanglement between two spatially-separated atomic Bose–Einstein condensates are outlined. The system setup comprises two condensates loaded in an optical lattice, which, in return, is confined within a high-Q optical resonator. The system is driven by an external laser that illuminates the atoms, such that photons can scatter into the cavity. In the superradiant phase, a cavity field is established, and we show that the emerging cavity-mediated interactions between the two condensates is capable of entangling them despite photon losses. This macroscopic atomic entanglement is sustained throughout the time-evolution apart from occasions of sudden deaths/births. Using an auxiliary photon mode and coupling it to a collective quadrature of the two condensates, we demonstrate that the auxiliary mode’s squeezing is proportional to the atomic entanglement, and as such, it can serve as a probe field of the macroscopic entanglement. Full article
(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)
Open AccessArticle Experiments with Highly-Ionized Atoms in Unitary Penning Traps
Atoms 2015, 3(3), 367-391; doi:10.3390/atoms3030367
Received: 30 May 2015 / Revised: 5 August 2015 / Accepted: 5 August 2015 / Published: 14 August 2015
Cited by 2 | PDF Full-text (1721 KB) | HTML Full-text | XML Full-text
Abstract
Highly-ionized atoms with special properties have been proposed for interesting applications, including potential candidates for a new generation of optical atomic clocks at the one part in 1019 level of precision, quantum information processing and tests of fundamental theory. The proposed atomic
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Highly-ionized atoms with special properties have been proposed for interesting applications, including potential candidates for a new generation of optical atomic clocks at the one part in 1019 level of precision, quantum information processing and tests of fundamental theory. The proposed atomic systems are largely unexplored. Recent developments at NIST are described, including the isolation of highly-ionized atoms at low energy in unitary Penning traps and the use of these traps for the precise measurement of radiative decay lifetimes (demonstrated with a forbidden transition in Kr17+), as well as for studying electron capture processes. Full article
(This article belongs to the Special Issue Perspectives of Atomic Physics with Trapped Highly Charged Ions)
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Open AccessArticle Probing and Manipulating Fermionic and Bosonic Quantum Gases with Quantum Light
Atoms 2015, 3(3), 392-406; doi:10.3390/atoms3030392
Received: 25 June 2015 / Accepted: 27 August 2015 / Published: 2 September 2015
Cited by 13 | PDF Full-text (1111 KB) | HTML Full-text | XML Full-text
Abstract
We study the atom-light interaction in the fully quantum regime, with the focus on off-resonant light scattering into a cavity from ultracold atoms trapped in an optical lattice. The detection of photons allows the quantum nondemolition (QND) measurement of quantum correlations of the
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We study the atom-light interaction in the fully quantum regime, with the focus on off-resonant light scattering into a cavity from ultracold atoms trapped in an optical lattice. The detection of photons allows the quantum nondemolition (QND) measurement of quantum correlations of the atomic ensemble, distinguishing between different quantum states. We analyse the entanglement between light and matter and show how it can be exploited for realising multimode macroscopic quantum superpositions, such as Schrödinger cat states, for both bosons and fermions. We provide examples utilising different measurement schemes and study their robustness to decoherence. Finally, we address the regime where the optical lattice potential is a quantum dynamical variable and is modified by the atomic state, leading to novel quantum phases and significantly altering the phase diagram of the atomic system. Full article
(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)
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Open AccessArticle Extreme Ultraviolet Spectra of Few-Times Ionized Tungsten for Divertor Plasma Diagnostics
Atoms 2015, 3(3), 407-421; doi:10.3390/atoms3030407
Received: 11 April 2015 / Revised: 1 August 2015 / Accepted: 17 August 2015 / Published: 9 September 2015
Cited by 6 | PDF Full-text (939 KB) | HTML Full-text | XML Full-text
Abstract
The extreme ultraviolet (EUV) emission from few-times ionized tungsten atoms has been experimentally studied at the Livermore electron beam ion trap facility. The ions were produced and confined during low-energy operations of the EBIT-I electron beam ion trap. By varying the electron-beam energy
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The extreme ultraviolet (EUV) emission from few-times ionized tungsten atoms has been experimentally studied at the Livermore electron beam ion trap facility. The ions were produced and confined during low-energy operations of the EBIT-I electron beam ion trap. By varying the electron-beam energy from around 30–300 eV, tungsten ions in charge states expected to be abundant in tokamak divertor plasmas were excited, and the resulting EUV emission was studied using a survey spectrometer covering 120–320 Å. It is found that the emission strongly depends on the excitation energy; below 150 eV, it is relatively simple, consisting of strong isolated lines from a few charge states, whereas at higher energies, it becomes very complex. For divertor plasmas with tungsten impurity ions, this emission should prove useful for diagnostics of tungsten flux rates and charge balance, as well as for radiative cooling of the divertor volume. Several lines in the 194–223 Å interval belonging to the spectra of five- and seven-times ionized tungsten (Tm-like W VI and Ho-like W VIII) were also measured using a high-resolution spectrometer. Full article
(This article belongs to the Special Issue Perspectives of Atomic Physics with Trapped Highly Charged Ions)
Open AccessArticle Quantum Entanglement and Shannon Information Entropy for the Doubly Excited Resonance State in Positronium Negative Ion
Atoms 2015, 3(3), 422-432; doi:10.3390/atoms3030422
Received: 15 July 2015 / Revised: 7 September 2015 / Accepted: 10 September 2015 / Published: 21 September 2015
Cited by 3 | PDF Full-text (389 KB) | HTML Full-text | XML Full-text
Abstract
In the present work, we report an investigation on quantum entanglement in the doubly excited 2s21Se resonance state of the positronium negative ion by using highly correlated Hylleraas type wave functions, determined by calculation of the density of resonance
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In the present work, we report an investigation on quantum entanglement in the doubly excited 2s2 1Se resonance state of the positronium negative ion by using highly correlated Hylleraas type wave functions, determined by calculation of the density of resonance states with the stabilization method. Once the resonance wave function is obtained, the spatial (electron-electron orbital) entanglement entropies (von Neumann and linear) can be quantified using the Schmidt decomposition method. Furthermore, Shannon entropy in position space, a measure for localization (or delocalization) for such a doubly excited state, is also calculated. Full article
Open AccessArticle A Realization of a Quasi-Random Walk for Atoms in Time-Dependent Optical Potentials
Atoms 2015, 3(3), 433-449; doi:10.3390/atoms3030433
Received: 30 June 2015 / Accepted: 15 September 2015 / Published: 23 September 2015
PDF Full-text (1022 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We consider the time dependent dynamics of an atom in a two-color pumped cavity, longitudinally through a side mirror and transversally via direct driving of the atomic dipole. The beating of the two driving frequencies leads to a time dependent effective optical potential
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We consider the time dependent dynamics of an atom in a two-color pumped cavity, longitudinally through a side mirror and transversally via direct driving of the atomic dipole. The beating of the two driving frequencies leads to a time dependent effective optical potential that forces the atom into a non-trivial motion, strongly resembling a discrete random walk behavior between lattice sites. We provide both numerical and analytical analysis of such a quasi-random walk behavior. Full article
(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)
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Open AccessArticle Cavity Quantum Electrodynamics of Continuously Monitored Bose-Condensed Atoms
Atoms 2015, 3(3), 450-473; doi:10.3390/atoms3030450
Received: 10 July 2015 / Revised: 2 September 2015 / Accepted: 11 September 2015 / Published: 23 September 2015
Cited by 2 | PDF Full-text (1060 KB) | HTML Full-text | XML Full-text
Abstract
We study cavity quantum electrodynamics of Bose-condensed atoms that are subjected to continuous monitoring of the light leaking out of the cavity. Due to a given detection record of each stochastic realization, individual runs spontaneously break the symmetry of the spatial profile of
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We study cavity quantum electrodynamics of Bose-condensed atoms that are subjected to continuous monitoring of the light leaking out of the cavity. Due to a given detection record of each stochastic realization, individual runs spontaneously break the symmetry of the spatial profile of the atom cloud and this symmetry can be restored by considering ensemble averages over many realizations. We show that the cavity optomechanical excitations of the condensate can be engineered to target specific collective modes. This is achieved by exploiting the spatial structure and symmetries of the collective modes and light fields. The cavity fields can be utilized both for strong driving of the collective modes and for their measurement. In the weak excitation limit the condensate–cavity system may be employed as a sensitive phonon detector which operates by counting photons outside the cavity that have been selectively scattered by desired phonons. Full article
(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)
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