Atoms

312 KiB

Open AccessArticle

A Wigner Function Approach to Coherence in a Talbot-Lau Interferometer

by Eric Imhof, James Stickney and Matthew Squires

Atoms 2016, 4(2), 18; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020018 - 22 Jun 2016

Cited by 1 | Viewed by 4472

Using a thermal gas, we model the signal of a trapped interferometer. This interferometer uses two short laser pulses, separated by time T, which act as a phase grating for the matter waves. Near time

2 T

, there is an echo [...] Read more.

Using a thermal gas, we model the signal of a trapped interferometer. This interferometer uses two short laser pulses, separated by time T, which act as a phase grating for the matter waves. Near time

2 T

, there is an echo in the cloud’s density due to the Talbot-Lau effect. Our model uses the Wigner function approach and includes a weak residual harmonic trap. The analysis shows that the residual potential limits the interferometer’s visibility, shifts the echo time of the interferometer, and alters its time dependence. Loss of visibility can be mitigated by optimizing the initial trap frequency just before the interferometer cycle begins. Full article

(This article belongs to the Special Issue Atom Interferometry)

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1725 KiB

Open AccessArticle

Series of Broad Resonances in Atomic Three-Body Systems

by Daniel Diaz, Zoltan Papp and Chi-Yu Hu

Atoms 2016, 4(2), 17; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020017 - 20 Jun 2016

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Abstract

We re-examine the series of resonances found earlier in atomic three-body systems by solving the Faddeev-Merkuriev integral equations. These resonances are rather broad and line up at each threshold with gradually increasing gaps. This lining up takes place in the same way for [...] Read more.

We re-examine the series of resonances found earlier in atomic three-body systems by solving the Faddeev-Merkuriev integral equations. These resonances are rather broad and line up at each threshold with gradually increasing gaps. This lining up takes place in the same way for all thresholds and is irrespective of the spatial symmetry. We relate these resonances to the Gailitis mechanism, which is a consequence of the polarization potential. 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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2378 KiB

Open AccessArticle

Multi-Configuration Dirac–Hartree–Fock (MCDHF) Calculations for B-Like Ions

by Indu Khatri, Arun Goyal, Avnindra Kumar Singh and Man Mohan

Atoms 2016, 4(2), 13; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020013 - 06 May 2016

Cited by 2 | Viewed by 3972

Abstract

Relativistic configuration interaction results are presented for several B-like ions (Ge XXVIII, Rb XXXIII, Sr XXXIV, Ru XL, Sn XLVI, and Ba LII) using the multi-configuration Dirac–Hartree–Fock (MCDHF) method. The calculations are carried out in the active space approximation with the inclusion of [...] Read more.

Relativistic configuration interaction results are presented for several B-like ions (Ge XXVIII, Rb XXXIII, Sr XXXIV, Ru XL, Sn XLVI, and Ba LII) using the multi-configuration Dirac–Hartree–Fock (MCDHF) method. The calculations are carried out in the active space approximation with the inclusion of the Breit interaction, the finite nuclear size effect, and quantum electrodynamic corrections. Results for fine structure energy levels for 1s²2s²2p and 2s2p² configurations relative to the ground state are reported. The transition wavelengths, transition probabilities, line strengths, and absorption oscillator strengths for 2s²2p–2s2p² electric dipole (E1) transitions are calculated. Both valence and core-valence correlation effects were accounted for through single-double multireference (SD-MR) expansions to increasing sets of active orbitals. Comparisons are made with the available data and good agreement is achieved. The values calculated using core–valence correlation are found to be very close to other theoretical and experimental values. The behavior of oscillator strengths as a function of nuclear charge is studied. We believe that our results can guide experimentalists in identifying the fine-structure levels in their future work. Full article

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269 KiB

Open AccessCommunication

The Faddeev-Merkuriev Differential Equations (MFE) and Multichannel 3-Body Scattering Systems

by Chi Yu Hu

Atoms 2016, 4(2), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020016 - 03 May 2016

Cited by 1 | Viewed by 4161

Abstract

Numerical implementation of the modified Faddeev Equation (MFE) is presented in some detail. The Faddeev channel wave function displays unique properties of each and every open channel, respectively. In particular, near resonant energies, the structures of the resonances are beautifully displayed, from which, [...] Read more.

Numerical implementation of the modified Faddeev Equation (MFE) is presented in some detail. The Faddeev channel wave function displays unique properties of each and every open channel, respectively. In particular, near resonant energies, the structures of the resonances are beautifully displayed, from which, the life-time of the resonances can be determined by simply using the uncertainty principle. The phase shift matrix, or the K-matrix, provides unique information for each and every resonance. This information enables the identification of the physical formation mechanism of the Gailitis resonances. A few of these resonances, previously known as the mysterious shape resonances, have occurred in a number of different collision systems. The Gailitis resonances are actually produced by a quantized Stark-effect within the various collision systems. Since the Stark-effect is a universal phenomenon, the Gailitis resonances are expected to occur in much broader classes of collision systems. We will present the results of a precision calculation using the MFE method in sufficient detail for interested students who wish to explore the mysteries of nature with a powerful theoretical tool. 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)

5254 KiB

Open AccessArticle

Novel Ion Trap Design for Strong Ion-Cavity Coupling

by Alejandro Márquez Seco, Hiroki Takahashi and Matthias Keller

Atoms 2016, 4(2), 15; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020015 - 26 Apr 2016

Cited by 2 | Viewed by 5584

Abstract

We present a novel ion trap design which facilitates the integration of an optical fiber cavity into the trap structure. The optical fibers are confined inside hollow electrodes in such a way that tight shielding and free movement of the fibers are simultaneously [...] Read more.

We present a novel ion trap design which facilitates the integration of an optical fiber cavity into the trap structure. The optical fibers are confined inside hollow electrodes in such a way that tight shielding and free movement of the fibers are simultaneously achievable. The latter enables in situ optimization of the overlap between the trapped ions and the cavity field. Through numerical simulations, we systematically analyze the effects of the electrode geometry on the trapping characteristics such as trap depths, secular frequencies and the optical access angle. Additionally, we simulate the effects of the presence of the fibers and confirm the robustness of the trapping potential. Based on these simulations and other technical considerations, we devise a practical trap configuration that isviable to achieve strong coupling of a single ion. Full article

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

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2135 KiB

Open AccessArticle

Atom Interferometry in the Presence of an External Test Mass

by Boris Dubetsky, Stephen B. Libby and Paul Berman

Atoms 2016, 4(2), 14; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020014 - 21 Apr 2016

Cited by 12 | Viewed by 4731

Abstract

The influence of an external test mass on the phase of the signal of an atom interferometer is studied theoretically. Using traditional techniques in atom optics based on the density matrix equations in the Wigner representation, we are able to extract the various [...] Read more.

The influence of an external test mass on the phase of the signal of an atom interferometer is studied theoretically. Using traditional techniques in atom optics based on the density matrix equations in the Wigner representation, we are able to extract the various contributions to the phase of the signal associated with the classical motion of the atoms, the quantum correction to this motion resulting from atomic recoil that is produced when the atoms interact with Raman field pulses and quantum corrections to the atomic motion that occur in the time between the Raman field pulses. By increasing the effective wave vector associated with the Raman field pulses using modified field parameters, we can increase the sensitivity of the signal to the point where such quantum corrections can be measured. The expressions that are derived can be evaluated numerically to isolate the contribution to the signal from an external test mass. The regions of validity of the exact and approximate expressions are determined. Full article

(This article belongs to the Special Issue Atom Interferometry)

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262 KiB

Open AccessArticle

Obtaining Atomic Matrix Elements from Vector Tune-Out Wavelengths Using Atom Interferometry

by Adam Fallon and Charles Sackett

Atoms 2016, 4(2), 12; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms4020012 - 30 Mar 2016

Cited by 10 | Viewed by 3687

Abstract

Accurate values for atomic dipole matrix elements are useful in many areas of physics, and in particular for interpreting experiments such as atomic parity violation. Obtaining accurate matrix element values is a challenge for both experiment and theory. A new technique that can [...] Read more.

Accurate values for atomic dipole matrix elements are useful in many areas of physics, and in particular for interpreting experiments such as atomic parity violation. Obtaining accurate matrix element values is a challenge for both experiment and theory. A new technique that can be applied to this problem is tune-out spectroscopy, which is the measurement of light wavelengths where the electric polarizability of an atom has a zero. Using atom interferometry methods, tune-out wavelengths can be measured very accurately. Their values depend on the ratios of various dipole matrix elements and are thus useful for constraining theory and broadening the application of experimental values. To date, tune-out wavelength measurements have focused on zeros of the scalar polarizability, but in general the vector polarizability also contributes. We show here that combined measurements of the vector and scalar polarizabilities can provide more detailed information about the matrix element ratios, and in particular can distinguish small contributions from the atomic core and the valence tail states. These small contributions are the leading error sources in current parity violation calculations for cesium. Full article

(This article belongs to the Special Issue Atom Interferometry)

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Atoms, Volume 4, Issue 2 (June 2016) – 7 articles

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