Atoms

4462 KiB

Open AccessArticle

Fundamental Features of Quantum Dynamics Studied in Matter-Wave Interferometry—Spin Weak Values and the Quantum Cheshire-Cat

by Stephan Sponar, Tobias Denkmayr, Hermann Geppert and Yuji Hasegawa

Atoms 2016, 4(1), 11; https://doi.org/10.3390/atoms4010011 - 11 Mar 2016

Cited by 14 | Viewed by 6069

Abstract

The validity of quantum-mechanical predictions has been confirmed with a high degree of accuracy in a wide range of experiments. Although the statistics of the outcomes of a measuring apparatus have been studied intensively, little has been explored and is known regarding the [...] Read more.

The validity of quantum-mechanical predictions has been confirmed with a high degree of accuracy in a wide range of experiments. Although the statistics of the outcomes of a measuring apparatus have been studied intensively, little has been explored and is known regarding the accessibility of quantum dynamics. For these sorts of fundamental studies of quantum mechanics, interferometry using neutron matter-waves in particular, provides almost ideal experimental circumstances. In this device quantum interference between spatially separated beams occurs on a macroscopic scale. Recently, the full determination of weak-values of neutrons 1 2 - spin adds a new aspect to the study of quantum dynamics. Moreover, a new counter-intuitive phenomenon, called quantum Cheshire Cat, is observed in an interference experiment. In this article, we present an overview of these experiments. Full article

(This article belongs to the Special Issue Atom Interferometry)

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4755 KiB

Open AccessArticle

Relativistic Ionization of Hydrogen Atoms by Positron Impact

by Amal Chahboune, Bouzid Manaut, Elmostafa Hrour and Souad Taj

Atoms 2016, 4(1), 10; https://doi.org/10.3390/atoms4010010 - 4 Mar 2016

Cited by 1 | Viewed by 4394

Abstract

Relativistic triple differential cross-sections (TDCS) for ionization of hydrogen atoms by positron impact have been calculated in the symmetric coplanar geometry. We have used Dirac wave functions to describe free electron’s and positron’s sates. The relativistic formalism is examined by taking the non [...] Read more.

Relativistic triple differential cross-sections (TDCS) for ionization of hydrogen atoms by positron impact have been calculated in the symmetric coplanar geometry. We have used Dirac wave functions to describe free electron’s and positron’s sates. The relativistic formalism is examined by taking the non relativistic limit. Present results are compared with those for the corresponding electron-impact case. In the first Born approximation, we found that the TDCS for positron impact ionization exceeds that for electron impact for all energies in accordance with the result obtained by several other theories. Full article

(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)

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1140 KiB

Open AccessArticle

Merkuriev Cut-off in e⁺ − H Multichannel Scattering Calculations

by Vitaly A. Gradusov, Vladimir A. Roudnev and Sergey L. Yakovlev

Atoms 2016, 4(1), 9; https://doi.org/10.3390/atoms4010009 - 1 Mar 2016

Cited by 5 | Viewed by 4294

Abstract

We present the results of positron-Hydrogen multichannel scattering calculations performed on the base of Faddeev-Merkuriev equations. We discuss an optimal choice of the Merkuriev’s Coulomb splitting parameters. Splitting the Coulomb potential in two-body configuration space is applicable for a limited energy range. Splitting [...] Read more.

We present the results of positron-Hydrogen multichannel scattering calculations performed on the base of Faddeev-Merkuriev equations. We discuss an optimal choice of the Merkuriev’s Coulomb splitting parameters. Splitting the Coulomb potential in two-body configuration space is applicable for a limited energy range. Splitting the potential in three-body configuration space makes it possible to perform calculations in a broader range of energies and to optimize the numerical convergence. Scattering cross sections for zero total angular momentum for all processes between the positronium formation threshold and the third excitation threshold of the Hydrogen atom are reported. Full article

(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)

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720 KiB

Open AccessArticle

Second Order Stark-Effect Induced Gailitis Resonances in e + Ps and p + ⁷Li

by Chi Yu Hu and Zoltan Papp

Atoms 2016, 4(1), 8; https://doi.org/10.3390/atoms4010008 - 26 Feb 2016

Cited by 2 | Viewed by 6124

Abstract

We present a detailed comparison between the first order Stark-effect induced Gailitis resonance in e⁺ + H (n = 2) and the second order Stark-effect induced resonance in e + Ps (n = 1). Common characteristics as well as differences [...] Read more.

We present a detailed comparison between the first order Stark-effect induced Gailitis resonance in e⁺ + H (n = 2) and the second order Stark-effect induced resonance in e + Ps (n = 1). Common characteristics as well as differences of these resonances will be identified. These results will be used to assess the presence of Gailitis resonances in the scattering of proton on the ground state of ⁷Li atom. During the lifetime of the Gailitis resonance, nuclear fusion is enhanced by the resonant entry of the proton into the nucleus of ⁷Li via a compound nuclear energy level of ⁸Be*. Full article

(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)

242 KiB

Open AccessEditorial

Guest Editor’s Notes on the “Atoms” Special Issue on “Perspectives of Atomic Physics with Trapped Highly Charged Ions”

by Elmar Träbert

Atoms 2016, 4(1), 7; https://doi.org/10.3390/atoms4010007 - 24 Feb 2016

Viewed by 4147

Abstract

The study of highly charged ions (HCI) was pursued first at Uppsala (Sweden), by Edlén and Tyrén in the 1930s. Their work led to the recognition that the solar corona is populated by such ions, an insight which forced massive paradigm changes in [...] Read more.

The study of highly charged ions (HCI) was pursued first at Uppsala (Sweden), by Edlén and Tyrén in the 1930s. Their work led to the recognition that the solar corona is populated by such ions, an insight which forced massive paradigm changes in solar physics. Plasmas aiming at controlled fusion in the laboratory, laser-produced plasmas, foil-excited swift ion beams, and electron beam ion traps have all pushed the envelope in the production of HCI. However, while there are competitive aspects in the race for higher ion charge states, the real interest lies in the very many physics topics that can be studied in these ions. Out of this rich field, the Special Issue concentrates on atomic physics studies that investigate highly charged ions produced, maintained, and/or manipulated in ion traps. There have been excellent achievements in the field in the past, and including fairly recent work, they have been described by their authors at conferences and in the appropriate journals. The present article attempts an overview over current lines of development, some of which are expanded upon in this Special Issue. Full article

(This article belongs to the Special Issue Perspectives of Atomic Physics with Trapped Highly Charged Ions)

520 KiB

Open AccessArticle

Two Photon Processes in an Atom Confined in Gaussian Potential

by Sonia Lumb, Shalini Lumb and Vinod Prasad

Atoms 2016, 4(1), 6; https://doi.org/10.3390/atoms4010006 - 17 Feb 2016

Cited by 5 | Viewed by 4326

Abstract

Transitions of an atom under the effect of a Gaussian potential and loose spherical confinement are studied. An accurate Bernstein-polynomial (B-polynomial) method has been applied for the calculation of the energy levels and radial matrix elements. The transition probability amplitudes, transparency frequencies, and [...] Read more.

Transitions of an atom under the effect of a Gaussian potential and loose spherical confinement are studied. An accurate Bernstein-polynomial (B-polynomial) method has been applied for the calculation of the energy levels and radial matrix elements. The transition probability amplitudes, transparency frequencies, and resonance enhancement frequencies for transitions to various excited states have been evaluated. The effect of the shape of confining potential on these spectral properties is studied. Full article

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176 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Atoms in 2015

by Atoms Editorial Office

Atoms 2016, 4(1), 5; https://doi.org/10.3390/atoms4010005 - 22 Jan 2016

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Abstract

The editors of Atoms would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article

2211 KiB

Open AccessArticle

Density Functional Theory (DFT) Study on the Ternary Interaction System of the Fluorinated Ethylene Carbonate, Li⁺ and Graphene Model

by Mami Mutoh, Shigeaki Abe, Teruo Kusaka, Mariko Nakamura, Yasuhiro Yoshida, Junichiro Iida and Hiroto Tachikawa

Atoms 2016, 4(1), 4; https://doi.org/10.3390/atoms4010004 - 29 Dec 2015

Cited by 7 | Viewed by 6821

Abstract

The ternary interaction system composed of fluorinated ethylene carbonate, denoted by EC(F), lithium ion (Li⁺) and a model of nano-structured graphene has been investigated by means of the density functional theory (DFT) method. For comparison, fluorinated vinylene carbonate, denoted by VC(F), [...] Read more.

The ternary interaction system composed of fluorinated ethylene carbonate, denoted by EC(F), lithium ion (Li⁺) and a model of nano-structured graphene has been investigated by means of the density functional theory (DFT) method. For comparison, fluorinated vinylene carbonate, denoted by VC(F), was also used. The model of graphene consisting of 14 benzene rings was examined as a nano-structured graphene. The effects of fluorine substitution on the electronic state and binding energy were investigated from a theoretical point of view. It was found that both EC(F) and VC(F) bind to a hexagonal site corresponding to the central benzene ring of the model of the graphene surface. The binding energies of Li⁺EC(F) and Li⁺VC(F) to the model of graphene decreased with increasing number of fluorine atoms (n). Full article

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5725 KiB

Open AccessArticle

Natural and Unnatural Parity Resonance States in the Positron-Hydrogen System with Screened Coulomb Interactions

by Ye Ning, Zong-Chao Yan and Yew Kam Ho

Atoms 2016, 4(1), 3; https://doi.org/10.3390/atoms4010003 - 26 Dec 2015

Cited by 13 | Viewed by 5614

Abstract

In the present work, we report calculations of resonances in the positron-hydrogen system interacting with screened Coulomb potentials using the method of complex scaling together with employing correlated Hylleraas wave functions. Resonances with natural and unnatural parities are investigated. For the natural parity [...] Read more.

In the present work, we report calculations of resonances in the positron-hydrogen system interacting with screened Coulomb potentials using the method of complex scaling together with employing correlated Hylleraas wave functions. Resonances with natural and unnatural parities are investigated. For the natural parity case, resonance parameters (energy and width) for D-wave resonance states with even parity lying below various positronium and hydrogen thresholds up to the H(N = 4) level are determined. For the unnatural parity case, results for P-even and D-odd resonance states with various screened Coulomb interaction strengths are located below different lower-lying Ps and H thresholds. Full article

(This article belongs to the Special Issue Positron Scattering and Annihilation with Atoms and Molecules including Emerging New Resonances and their Applications in other Systems)

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701 KiB

Open AccessArticle

An Optomechanical Elevator: Transport of a Bloch Oscillating Bose–Einstein Condensate up and down an Optical Lattice by Cavity Sideband Amplification and Cooling

by B. Prasanna Venkatesh, Duncan H.J. O’Dell and Jonathan Goldwin

Atoms 2016, 4(1), 2; https://doi.org/10.3390/atoms4010002 - 25 Dec 2015

Cited by 4 | Viewed by 6241

Abstract

In this paper we give a new description, in terms of optomechanics, of previous work on the problem of an atomic Bose–Einstein condensate interacting with the optical lattice inside a laser-pumped optical cavity and subject to a bias force, such as gravity. An [...] Read more.

In this paper we give a new description, in terms of optomechanics, of previous work on the problem of an atomic Bose–Einstein condensate interacting with the optical lattice inside a laser-pumped optical cavity and subject to a bias force, such as gravity. An atomic wave packet in a tilted lattice undergoes Bloch oscillations; in a high-finesse optical cavity the backaction of the atoms on the light leads to a time-dependent modulation of the intracavity lattice depth at the Bloch frequency which can in turn transport the atoms up or down the lattice. In the optomechanical picture, the transport dynamics can be interpreted as a manifestation of dynamical backaction-induced sideband damping/amplification of the Bloch oscillator. Depending on the sign of the pump-cavity detuning, atoms are transported either with or against the bias force accompanied by an up- or down-conversion of the frequency of the pump laser light. We also evaluate the prospects for using the optomechanical Bloch oscillator to make continuous measurements of forces by reading out the Bloch frequency. In this context, we establish the significant result that the optical spring effect is absent and the Bloch frequency is not modified by the backaction. Full article

(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)

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2585 KiB

Open AccessArticle

Cavity Optomechanics with Ultra Cold Atoms in Synthetic Abelian and Non-Abelian Gauge Field

by Bikash Padhi and Sankalpa Ghosh

Atoms 2016, 4(1), 1; https://doi.org/10.3390/atoms4010001 - 25 Dec 2015

Cited by 1 | Viewed by 7702

Abstract

In this article we present a pedagogical discussion of some of the optomechanical properties of a high finesse cavity loaded with ultracold atoms in laser induced synthetic gauge fields of different types. Essentially, the subject matter of this article is an amalgam of [...] Read more.

In this article we present a pedagogical discussion of some of the optomechanical properties of a high finesse cavity loaded with ultracold atoms in laser induced synthetic gauge fields of different types. Essentially, the subject matter of this article is an amalgam of two sub-fields of atomic molecular and optical (AMO) physics namely, the cavity optomechanics with ultracold atoms and ultracold atoms in synthetic gauge field. After providing a brief introduction to either of these fields we shall show how and what properties of these trapped ultracold atoms can be studied by looking at the cavity (optomechanical or transmission) spectrum. In presence of abelian synthetic gauge field we discuss the cold-atom analogue of Shubnikov de Haas oscillation and its detection through cavity spectrum. Then, in the presence of a non-abelian synthetic gauge field (spin-orbit coupling), we see when the electromagnetic field inside the cavity is quantized, it provides a quantum optical lattice for the atoms, leading to the formation of different quantum magnetic phases. We also discuss how these phases can be explored by studying the cavity transmission spectrum. Full article

(This article belongs to the Special Issue Cavity Quantum Electrodynamics with Ultracold Atoms)

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Atoms, Volume 4, Issue 1 (March 2016) – 11 articles

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