Atoms

8 pages, 1199 KiB

Open AccessArticle

CO Dissociation Induced by 1 keV/u Ar²⁺ Ion

by Chijun Zhang, Ruitian Zhang, Shaofeng Zhang and Xinwen Ma

Atoms 2024, 12(10), 53; https://doi.org/10.3390/atoms12100053 - 18 Oct 2024

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CO is one of the important molecules in dense molecular clouds, and its dissociation induced by cosmic ray heavy ions is a fundamental process for molecular breaking up and rearrangement in astronomical networks. Extensive laboratory simulations are required to understand molecular evolution in [...] Read more.

CO is one of the important molecules in dense molecular clouds, and its dissociation induced by cosmic ray heavy ions is a fundamental process for molecular breaking up and rearrangement in astronomical networks. Extensive laboratory simulations are required to understand molecular evolution in astrophysical contexts. Here, we investigate the CO dissociation induced by 1 keV/u

{Ar}^{2 +}

using cold target recoil ion momentum spectroscopy. Kinetic energy release for double electron capture

{Ar}^{2 +} + CO \to {Ar}^{0} + C^{+} + O^{+}

and transfer ionization

{Ar}^{2 +} + CO \to {Ar}^{+} + C^{+} + O^{+} + e^{-}

was obtained. The dissociation mechanisms are attributed to different KER distributions. The autoionization process is identified below the

{CO}^{2 +}

double ionization threshold. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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9 pages, 532 KiB

Open AccessArticle

An Extensive Analysis of Tsallis Statistics: π^±, K^± Mesons, and

p \bar{p}

Baryon in Inelastic pp Collisions

by Uzma Tabassam, Zain Ul Abidin, Khadija Gul and Irfan Siddique

Atoms 2024, 12(10), 52; https://doi.org/10.3390/atoms12100052 (registering DOI) - 15 Oct 2024

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Abstract

This study explores the inelastic doubly differential transverse momentum spectra of the primary charged particles,

(π^{+} + π^{-})

,

(K^{+} + K^{-})

and

(p \bar{p})

, as a function of observables associated [...] Read more.

This study explores the inelastic doubly differential transverse momentum spectra of the primary charged particles,

(π^{+} + π^{-})

,

(K^{+} + K^{-})

and

(p \bar{p})

, as a function of observables associated with underlying event (UE) at

\sqrt{s} = 13 T e V

. The particle production is measured on the basis of different angular regions like toward, transverse and away, elucidated with respect to the direction of leading particle of an event. To study the thermal freeze-out parameters, the non-extensive Tsallis distribution function is used to extract the temperature

T_{e f f}

and chemical potential

μ

, which provide a basis to explain the QCD matter. The Tsallis distribution function describes transverse momentum spectra in pseudorapidity region of

| η | < 0.8

. It is observed that effective temperature

T_{e f f}

changes from away to towards and forward region. Full article

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10 pages, 4757 KiB

Open AccessReview

High-Precision Experiments with Trapped Radioactive Ions Produced at Relativistic Energies

by Timo Dickel, Wolfgang R. Plaß, Emma Haettner, Christine Hornung, Sivaji Purushothaman, Christoph Scheidenberger and Helmut Weick

Atoms 2024, 12(10), 51; https://doi.org/10.3390/atoms12100051 - 8 Oct 2024

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Abstract

Research on radioactive ion beams produced with in-flight separation of relativistic beams has advanced significantly over the past decades, with contributions to nuclear physics, nuclear astrophysics, atomic physics, and other fields. Central to these advancements are improved production, separation, and identification methods.The FRS [...] Read more.

Research on radioactive ion beams produced with in-flight separation of relativistic beams has advanced significantly over the past decades, with contributions to nuclear physics, nuclear astrophysics, atomic physics, and other fields. Central to these advancements are improved production, separation, and identification methods.The FRS Ion Catcher at GSI/FAIRexemplifies these technological advancements. The system facilitates high-precision experiments by efficiently stopping and extracting exotic nuclei as ions and making these available at thermal energies. High-energy synchrotron beams enhance the system’s capabilities, enabling unique experimental techniques such as multi-step reactions, mean range bunching, and optimized stopping, as well as novel measurement methods for observables such as beta-delayed neutron emission probabilities. The FRS Ion Catcher has already contributed to various scientific fields, and the future with the Super-FRS at FAIR promises to extend research to even more exotic nuclei and new applications. Full article

(This article belongs to the Special Issue Advances in Ion Trapping of Radioactive Ions)

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19 pages, 2533 KiB

Open AccessArticle

Fisher Information-Based Optimization of Mapped Fourier Grid Methods

by Sotiris Danakas and Samuel Cohen

Atoms 2024, 12(10), 50; https://doi.org/10.3390/atoms12100050 - 8 Oct 2024

Viewed by 331

Abstract

The mapped Fourier grid method (mapped-FGM) is a simple and efficient discrete variable representation (DVR) numerical technique for solving atomic radial Schrödinger differential equations. It is set up on equidistant grid points, and the mapping, a suitable coordinate transformation to the radial variable, [...] Read more.

The mapped Fourier grid method (mapped-FGM) is a simple and efficient discrete variable representation (DVR) numerical technique for solving atomic radial Schrödinger differential equations. It is set up on equidistant grid points, and the mapping, a suitable coordinate transformation to the radial variable, deals with the potential energy peculiarities that are incompatible with constant step grids. For a given constrained number of grid points, classical phase space and semiclassical arguments help in selecting the mapping function and the maximum radial extension, while the energy does not generally exhibit a variational extremization trend. In this work, optimal computational parameters and mapping quality are alternatively assessed using the extremization of (coordinate and momentum) Fisher information. A benchmark system (hydrogen atom) is employed, where energy eigenvalues and Fisher information are traced in a standard convergence procedure. High-precision energy eigenvalues exhibit a correlation with the extrema of Fisher information measures. Highly efficient mapping schemes (sometimes classically counterintuitive) also stand out with these measures. Same trends are evidenced in the solution of Dalgarno–Lewis equations, i.e., inhomogeneous counterparts of the radial Schrödinger equation occurring in perturbation theory. A detailed analysis of the results, implications on more complex single valence electron Hamiltonians, and future extensions are also included. Full article

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15 pages, 279 KiB

Open AccessReview

Plasmas Containing Quasimonochromatic Electric Fields (QEFs): Review of the General Principles of Their Spectroscopy and Selected Applications

by Eugene Oks

Atoms 2024, 12(10), 49; https://doi.org/10.3390/atoms12100049 - 27 Sep 2024

Viewed by 314

Abstract

We review the general principles of the spectroscopy of plasmas containing quasimonochromatic electric fields (QEFs). We demonstrate that the underlying physics is very rich due to the complicated entanglement of four characteristic times: the typical time required for the formation of the quasienergy [...] Read more.

We review the general principles of the spectroscopy of plasmas containing quasimonochromatic electric fields (QEFs). We demonstrate that the underlying physics is very rich due to the complicated entanglement of four characteristic times: the typical time required for the formation of the quasienergy states, the lifetime of the excited state of the radiator, the typical time of the formation of the homogeneous Stark broadening by the electron microfield, and the typical time of the formation of the homogeneous Stark broadening by the dynamic part of the ion microfield. We exemplified how the shape and shift of spectral lines are affected by the mutual interactions of the three subsystems. Specifically, the interaction of the radiator with the plasma can be substantially influenced by the interaction of the radiator with the QEF, and vice versa, as well as by the interaction of the QEF and the plasma with each other. We also provide some applications of these various effects. Finally, we outline directions for future research. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Plasmas, Including Cases with External Electric and Magnetic Fields and Laser Plasma Interaction)

5 pages, 196 KiB

Open AccessArticle

Measurement and Flexible Atomic Code (FAC) Computation of Extreme Ultraviolet (EUV) Spectra of Eu

by Joel H. T. Clementson, Peter Beiersdorfer, Gregory V. Brown, Natalie Hell and Elmar Träbert

Atoms 2024, 12(10), 48; https://doi.org/10.3390/atoms12100048 - 27 Sep 2024

Viewed by 405

Abstract

A group of EUV lines of H- and He-like ions of C provides excellent wavelength calibrations for a position-sensitive multichannel detector at a high-resolution spectrograph. We have exploited this setting for a series of spectra of highly charged Eu ions recorded at the [...] Read more.

A group of EUV lines of H- and He-like ions of C provides excellent wavelength calibrations for a position-sensitive multichannel detector at a high-resolution spectrograph. We have exploited this setting for a series of spectra of highly charged Eu ions recorded at the Livermore SuperEBIT electron beam ion trap. A variation in the electron beam energy results in spectra with correspondingly staggered highest Eu ion charge states ranging from Na- through to Ni-like Eu ions. A number of spectral features can be identified from the literature, but the majority of line identifications need guidance from computations of simulated spectra on the basis of collisional-radiative models. For ions with more than two electrons in the valence shell, the typical computational results are of a markedly lower accuracy. We have applied the Flexible Atomic Code (FAC), which is capable of handling all our measured ions with reasonable accuracy. We look into the systematics of the deviation of the computed transition energies from the measured ones as a function of the electron number. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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19 pages, 3564 KiB

Open AccessArticle

Data-Based Kinematic Viscosity and Rayleigh–Taylor Mixing Attributes in High-Energy Density Plasmas

by Snezhana I. Abarzhi and Kurt C. Williams

Atoms 2024, 12(10), 47; https://doi.org/10.3390/atoms12100047 - 24 Sep 2024

Viewed by 335

Abstract

We explore properties of matter and characteristics of Rayleigh–Taylor mixing by analyzing data gathered in the state-of-the-art fine-resolution experiments in high-energy density plasmas. The eminent quality data represent fluctuations spectra of the X-ray imagery intensity versus spatial frequency. We find, by using the [...] Read more.

We explore properties of matter and characteristics of Rayleigh–Taylor mixing by analyzing data gathered in the state-of-the-art fine-resolution experiments in high-energy density plasmas. The eminent quality data represent fluctuations spectra of the X-ray imagery intensity versus spatial frequency. We find, by using the rigorous statistical method, that the fluctuations spectra are accurately captured by a compound function, being a product of a power law and an exponential and describing, respectively, self-similar and scale-dependent spectral parts. From the self-similar part, we find that Rayleigh–Taylor mixing has steep spectra and strong correlations. From the scale-dependent part, we derive the first data-based value of the kinematic viscosity in high-energy density plasmas. Our results explain the experiments, agree with the group theory and other experiments, and _carve the path for better understanding Rayleigh–Taylor mixing in nature and technology. Full article

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Atoms, Volume 12, Issue 10 (October 2024) – 7 articles

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