atomic states
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Author(s):  
Christophe Blondel ◽  
Cyril Drag

Abstract Recent reviews of the hyperfine structure of xenon and krypton have highlighted the variety of the values taken by the hyperfine coefficients A and B of these atoms. These variations, as functions of the atomic angular momenta, were however not explained quantitatively. This article shows the simple picture and angular momentum algebra that make it possible to account for the observed trend. The only necessary approximations are to consider the interaction of the outer electron negligible with respect to the coupling of the p5 core with the nucleus, and to assume that the Racah ||(p5)j l[K]J F〉basis, conventionally used for the atomic states of noble gases, makes a fitting description of the hierarchy of their angular momentum couplings. The way the calculation corroborates the apparently erratic values of hyperfine coefficients A and B in Xe I and Kr I shows up as a confirmation of the validity of these approximations.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. E. Mossman ◽  
T. M. Bersano ◽  
Michael McNeil Forbes ◽  
P. Engels

AbstractTypically discussed in the context of optics, caustics are envelopes of classical trajectories (rays) where the density of states diverges, resulting in pronounced observable features such as bright points, curves, and extended networks of patterns. Here, we generate caustics in the matter waves of an atom laser, providing a striking experimental example of catastrophe theory applied to atom optics in an accelerated (gravitational) reference frame. We showcase caustics formed by individual attractive and repulsive potentials, and present an example of a network generated by multiple potentials. Exploiting internal atomic states, we demonstrate fluid-flow tracing as another tool of this flexible experimental platform. The effective gravity experienced by the atoms can be tuned with magnetic gradients, forming caustics analogous to those produced by gravitational lensing. From a more applied point of view, atom optics affords perspectives for metrology, atom interferometry, and nanofabrication. Caustics in this context may lead to quantum innovations as they are an inherently robust way of manipulating matter waves.


Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1339
Author(s):  
Jesús S. Dehesa

High dimensional atomic states play a relevant role in a broad range of quantum fields, ranging from atomic and molecular physics to quantum technologies. The D-dimensional hydrogenic system (i.e., a negatively-charged particle moving around a positively charged core under a Coulomb-like potential) is the main prototype of the physics of multidimensional quantum systems. In this work, we review the leading terms of the Heisenberg-like (radial expectation values) and entropy-like (Rényi, Shannon) uncertainty measures of this system at the limit of high D. They are given in a simple compact way in terms of the space dimensionality, the Coulomb strength and the state’s hyperquantum numbers. The associated multidimensional position–momentum uncertainty relations are also revised and compared with those of other relevant systems.


Atoms ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 71
Author(s):  
Łukasz Kłosowski ◽  
Mariusz Piwiński

A new geometry of a magnetic angle changer (MAC) device is proposed, which allows experiments to be run on electron impact excitation of long-lived states of target atoms. The details of the device’s design are presented and discussed together with a numerical analysis of its magnetic field.


2021 ◽  
Author(s):  
Sadek Ahmed Hanoura

Abstract The dynamics of the quantum entropies of a system of two cavities coupled by an optical fiber cable, each cavity contains a two-level atom interacting with a single electromagnetic field in addition to an external classical field, is investigated. Under canonical transformations, the considered Hamiltonian is diagonalized. Effective Hamiltonians in three different limiting regimes: namely large optical fiber cable coupling bstrength, large detunig, and comparable detuning and optical fiber cable coupling strength, are derived. The ith ¯ -tom are respectively prepared in the superposition coherent and the ground states while the fields are prepared in the vacuum states. An analytical expression for the solution of the Schr¨odinger equation for each dispersive is derived. The degree of entanglement (DEM) is studied by using von Neumann atomic entropies. The influences of both the optical fiber cable coupling strength and the detuning on the evolution of the DEM ”their values are closely chosen to be compatible with the imposed restrictions for the applications of the different regimes” are analyzed. General conclusions reached are illustrated by numerical results.


2021 ◽  
pp. 190-202
Author(s):  
Geoffrey Brooker
Keyword(s):  

“LS coupling; Hund's rules” describes LS coupling as it gives an account of our understanding of atomic states. Two “energy-level” diagrams commonly printed are shown to be wrong and highly misleading. Accompanying “explanations” are debunked. Correct diagrams, with explanations, are given, and compared with theoretical formulae. Hund's rules, when properly formulated, are shown to hold in all cases to which they can legitimately be applied. Hund's rules must be stated as given here (often they are not). This claim is validated because all possible variants are excluded by counterexamples.


2021 ◽  
pp. 228-240
Author(s):  
Geoffrey Brooker

The Einstein A and B coefficients for atom–photon reactions are defined: they describe absorption, stimulated emission, and spontaneous emission. We calculate B and consequently find A by the Einstein trick. The procedure is validated by application of detailed balance. Separating out frequencies permits introduction of the spectral lineshape function (normalized line profile). A reformulation describes transitions involving single atomic states and single field modes. This points to a link with quantum electrodynamics.


Akademos ◽  
2021 ◽  
Vol 60 (1) ◽  
pp. 29-33
Author(s):  
Marina Turcan ◽  

The equations of motion for the Raman and hyper-Raman conversion effect of atomic polarization are presented. At the same time, an experimental scheme previously used in the micromaser is proposed, which allows the determination of the number of atoms in the excited or in the ground state using the ionization method from the deaf cavity. Therefore, a method is proposed to link the number of atoms that have passed in the basic state of the induced-cooperative process of Stokes-type photon transformation in anti-Stokes (AS) photons in the case of Raman emission (RE) (following the micromaser model) or the transformation of photon pairs in the case of hyper-Raman emission (HRE)/


Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2660
Author(s):  
Stephan Fritzsche ◽  
Andrey Surzhykov

In atomic and many-particle physics, Green functions often occur as propagators to formally represent the (integration over the) complete spectrum of the underlying Hamiltonian. However, while these functions are very crucial to describing many second- and higher-order perturbation processes, they have hardly been considered and classified for complex atoms. Here, we show how relativistic (many-electron) Green functions can be approximated and systematically improved for few- and many-electron atoms and ions. The representation of these functions is based on classes of virtual excitations, or so-called excitation schemes, with regard to given bound-state reference configurations, and by applying a multi-configuration Dirac-Hartree-Fock expansion of all atomic states involved. A first implementation of these approximate Green functions has been realized in the framework of Jac, the Jena Atomic Calculator, and will facilitate the study of various multi-photon and/or multiple electron (emission) processes.


2021 ◽  
Vol 7 ◽  
Author(s):  
K. Wang ◽  
A. D. Lan ◽  
J. W. Qiao

The present work investigates the corrosion behavior of Al0.1CoCrFeNi high entropy alloy (HEA) in various concentrations of chloride-containing solutions. Electrochemical tests exhibit overall excellent corrosion resistance of this alloy against the attack of Cl−-containing solutions. The main type of corrosion topography presents an intergranular feature. In addition, electrochemical impedance spectroscopy (EIS) investigation of the HEA samples under immersion test suggests chloride anion–containing environment leads to the decline of passivation film quality. Further analysis of XPS results reveals that significant amounts of elements exist with atomic states in the passive films.


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