Atoms

6 pages, 713 KiB

Open AccessCommunication

Charge Exchange Spectroscopy of Multiply Charged Erbium Ions

by Yuki Nishimura, Saki Imaizumi, Hajime Tanuma, Nobuyuki Nakamura, Yuichiro Sekiguchi, Shinya Wanajo, Hiroyuki A. Sakaue, Daiji Kato, Izumi Murakami, Masaomi Tanaka and Gediminas Gaigalas

Atoms 2023, 11(2), 40; https://doi.org/10.3390/atoms11020040 - 15 Feb 2023

Viewed by 1554

Abstract

The origin of heavier elements than iron is still under discussion, and recent studies suggest that the contribution of the r-process in neutron star mergers is dominant. Future modeling of such processes will require a huge amount of spectroscopic data on multiply charged [...] Read more.

The origin of heavier elements than iron is still under discussion, and recent studies suggest that the contribution of the r-process in neutron star mergers is dominant. Future modeling of such processes will require a huge amount of spectroscopic data on multiply charged ions of heavy elements. However, these experimental data are extremely scarce for heavy elements. In this work, we have performed the measurements of charge exchange spectroscopy for multiply charged Er ions in the visible light range. We report observed emission lines from multiply charged Er ions and their identification based on theoretical estimates. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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6 pages, 3503 KiB

Open AccessCommunication

XUV Fluorescence Detection of Laser-Cooled Stored Relativistic Ions

by Ken Ueberholz, Lars Bozyk, Michael Bussmann, Noah Eizenhöfer, Volker Hannen, Max Horst, Daniel Kiefer, Nils Kiefer, Sebastian Klammes, Thomas Kühl, Benedikt Langfeld, Markus Loeser, Xinwen Ma, Wilfried Nörtershäuser, Rodolfo Sánchez, Ulrich Schramm, Mathias Siebold, Peter Spiller, Markus Steck, Thomas Stöhlker, Thomas Walther, Hanbing Wang, Christian Weinheimer, Weiqiang Wen and Danyal Winters Show full author list Hide full author list

Atoms 2023, 11(2), 39; https://doi.org/10.3390/atoms11020039 - 13 Feb 2023

Viewed by 1185

Abstract

An improved moveable in vacuo XUV fluorescence detection system was employed for the laser cooling of bunched relativistic (

β

= 0.47) carbon ions at the Experimental Storage Ring (ESR) of GSI Helmholtzzentrum Darmstadt, Germany. Strongly Doppler boosted XUV fluorescence (∼90 nm) was [...] Read more.

An improved moveable in vacuo XUV fluorescence detection system was employed for the laser cooling of bunched relativistic (

β

= 0.47) carbon ions at the Experimental Storage Ring (ESR) of GSI Helmholtzzentrum Darmstadt, Germany. Strongly Doppler boosted XUV fluorescence (∼90 nm) was emitted from the ions in a forward light cone after laser excitation of the 2s–2p transition (∼155 nm) by a new tunable pulsed UV laser system (257 nm). It was shown that the detected fluorescence strongly depends on the position of the detector around the bunched ion beam and on the delay (∼ns) between the ion bunches and the laser pulses. In addition, the fluorescence information could be directly combined with the revolution frequencies of the ions (and their longitudinal momentum spread), which were recorded using the Schottky resonator at the ESR. These fluorescence detection features are required for future laser cooling experiments at highly relativistic energies (up to

γ \sim

13) and high intensities (up to

10^{11}

particles) of ion beams in the new heavy ion synchrotron SIS100 at FAIR. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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10 pages, 7057 KiB

Open AccessCommunication

Differential Description of Multiple Ionization of Uracil by 3.5 MeV/u C⁶⁺ Impact

by N. D. Cariatore, N. Bachi and S. Otranto

Atoms 2023, 11(2), 38; https://doi.org/10.3390/atoms11020038 - 11 Feb 2023

Cited by 1 | Viewed by 947

Abstract

In this work, a theoretical analysis of the impact of the multiple ionization of uracil by 3.5 MeV/u C

^{6 +}

is developed in the framework of a classical trajectory Monte Carlo method, as recently introduced for multi-electronic targets. The electron emission contribution [...] Read more.

In this work, a theoretical analysis of the impact of the multiple ionization of uracil by 3.5 MeV/u C

^{6 +}

is developed in the framework of a classical trajectory Monte Carlo method, as recently introduced for multi-electronic targets. The electron emission contribution arising from the multiple electron ionization is explicitly determined and the emission geometries and the reaction regions for double and triple ionization are explicitly identified. The present results suggest that double ionization is mainly characterized by the emission of slow electrons with a relative angle of 80

^{\circ}

–120

^{\circ}

. For triple ionization, on the other hand, the emission seems to occur with the three electrons holding similar interelectronic angles. Full article

(This article belongs to the Special Issue Interaction of Electrons with Atoms, Molecules and Surfaces)

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40 pages, 2540 KiB

Open AccessArticle

A Theoretical Study of Scattering of e^± by Tl Atom

by Sunzida Parvin, M. Masum Billah, Mahmudul H. Khandker, M. Ismail Hossain, M. M. Haque, Mehrdad Shahmohammadi Beni, Hiroshi Watabe, A. K. Fazlul Haque and M. Alfaz Uddin

Atoms 2023, 11(2), 37; https://doi.org/10.3390/atoms11020037 - 10 Feb 2023

Viewed by 1123

Abstract

This article incorporates details of our calculations of the observable quantities for the scattering of electrons and positrons from a post transition metal Thallium (Tl), in the energy range of 1 eV ≤

E_{i}

≤ 1 MeV, using the relativistic Dirac partial [...] Read more.

This article incorporates details of our calculations of the observable quantities for the scattering of electrons and positrons from a post transition metal Thallium (Tl), in the energy range of 1 eV ≤

E_{i}

≤ 1 MeV, using the relativistic Dirac partial wave (phase-shift) analysis employing a complex optical-potential. Absolute differential, integrated elastic and inelastic, transport, total ionization, and total cross sections and a thorough study of the critical minima in the elastic differential cross sections along with the associated angular positions of the maximum polarization points in the Sherman function are provided to study the collision dynamics. The optical potential model incorporates the interactions of the incident electron and/or positron with both the nucleus and the bound electrons of the target atom. In-depth analyses of the spin asymmetry, which are sensitive to phases related interference effect, brought on by the various ingredients of the lepton-atom interaction, are also presented. The performance of the current approach to explain the observations, with the exception of the extremely low energy domain, is shown by a comparison of the previous experimental and theoretical results on this target atom. Full article

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

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14 pages, 1363 KiB

Open AccessEditor’s ChoiceArticle

Robust Optimized Pulse Schemes for Atomic Fountain Interferometry

by Michael H. Goerz, Mark A. Kasevich and Vladimir S. Malinovsky

Atoms 2023, 11(2), 36; https://doi.org/10.3390/atoms11020036 - 10 Feb 2023

Cited by 6 | Viewed by 1558

Abstract

The robustness of an atomic fountain interferometer with respect to variations in the initial velocity of the atoms and deviations from the optimal pulse amplitude is examined. We numerically simulate the dynamics of an interferometer in momentum space with a maximum separation of [...] Read more.

The robustness of an atomic fountain interferometer with respect to variations in the initial velocity of the atoms and deviations from the optimal pulse amplitude is examined. We numerically simulate the dynamics of an interferometer in momentum space with a maximum separation of

20 ℏ k

and map out the expected signal contrast depending on the variance of the initial velocity distribution and the value of the laser field amplitude. We show that an excitation scheme based on rapid adiabatic passage significantly enhances the expected signal contrast, compared to the commonly used scheme consisting of a series of

π / 2

and

π

pulses. We demonstrate further substantial increase of the robustness by using optimal control theory to identify splitting and swapping pulses that perform well on an ensemble average of pulse amplitudes and velocities. Our results demonstrate the ability of optimal control to significantly enhance future implementations of atomic fountain interferometry. Full article

(This article belongs to the Special Issue Advances in and Prospects for Matter Wave Interferometry)

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7 pages, 911 KiB

Open AccessArticle

Methane Cluster Fragmentation by Fast Electron Impact

by Shuncheng Yan, Ruitian Zhang, Shaofeng Zhang and Xinwen Ma

Atoms 2023, 11(2), 35; https://doi.org/10.3390/atoms11020035 - 10 Feb 2023

Viewed by 1278

Abstract

We investigate the fragmentation of the CH₄ cluster by fast electron impact at stagnation pressures from 0.5 bar to 16 bar. By measuring the time of flight spectrum (TOF), two types of ions, including (CH₄)_n−1CH₅⁺ and [...] Read more.

We investigate the fragmentation of the CH₄ cluster by fast electron impact at stagnation pressures from 0.5 bar to 16 bar. By measuring the time of flight spectrum (TOF), two types of ions, including (CH₄)_n−1CH₅⁺ and (CH₄)_n−2(C₂H_m)⁺, are observed. In the 1D TOF spectrum, it is shown that for the stagnation pressure larger than 4 bar, the former ion is predominant for each n, similar to the previous experimental result. However, as the pressure decreases to 0.5 or 2 bar, the contribution of the C₂H_m⁺ ion is dominant over that of the CH₄CH₅⁺ ion. In the 2D coincident TOF spectrum, the above two patterns of ions are also distinguished, and the enhancement of C₂H_m⁺ is observed at 4 bar pressure. The phenomena appearing in 2D and 1D TOF spectra imply that the C₂H_m⁺ ion prefers to survive in a smaller cluster, while the stabilization of the protonated ion needs a more massive cluster environment. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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9 pages, 2107 KiB

Open AccessArticle

Probing the Fragmentation Pathways of an Argon Dimer in Slow Ion–Dimer Collisions

by Md Abul Kalam Azad Siddiki, Lokesh C. Tribedi and Deepankar Misra

Atoms 2023, 11(2), 34; https://doi.org/10.3390/atoms11020034 - 09 Feb 2023

Cited by 3 | Viewed by 1160

Abstract

We report the development of a supersonic jet assembly to study electron transfer collisions with atoms, molecules, and van der Waals clusters. A comparative study of Ar monomer and dimer cations is presented for different capture-associated channels with a 2.5 keV/u O²⁺ [...] Read more.

We report the development of a supersonic jet assembly to study electron transfer collisions with atoms, molecules, and van der Waals clusters. A comparative study of Ar monomer and dimer cations is presented for different capture-associated channels with a 2.5 keV/u O²⁺ projectile beam. For the Ar⁺ + Ar⁺ fragmentation channel, the interatomic relaxation channels are discussed. The vacancies of the dimer single site or double site show the dependence on capture mechanisms. In the Ar²⁺ + Ar⁺ fragmentation channel, double capture, in addition to the single ionization process, dominates. The orientation effect reflects the maximum yield at around 50 and 130 degrees, and angular distributions are nearly symmetric about the axis perpendicular to the dimer axis. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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7 pages, 251 KiB

Open AccessCommunication

Detailed Analysis of Spectra from Ga-like Ions of Heavy Elements Observed in High-Temperature Plasmas

by Chihiro Suzuki, Fumihiro Koike, Izumi Murakami, Daiji Kato, Naoki Tamura, Tetsutarou Oishi and Nobuyuki Nakamura

Atoms 2023, 11(2), 33; https://doi.org/10.3390/atoms11020033 - 07 Feb 2023

Viewed by 1106

Abstract

This study has systematically investigated the atomic number (Z) dependence of spectra from gallium-like (Ga-like) ions of heavy elements. We have mainly analyzed the experimental spectra recorded in high-temperature plasmas produced in the Large Helical Device (LHD) for various elements with [...] Read more.

This study has systematically investigated the atomic number (Z) dependence of spectra from gallium-like (Ga-like) ions of heavy elements. We have mainly analyzed the experimental spectra recorded in high-temperature plasmas produced in the Large Helical Device (LHD) for various elements with atomic numbers from 57 onward. The measured wavelengths are compared with theoretical values calculated with a multi-configuration Dirac Fock code. As a result, we have successfully obtained Z-dependent wavelengths of several prominent transitions of Ga-like ions, including a magnetic dipole (M1) transition. Many of them have been experimentally identified for the first time in this study. The present results manifest the significant effects of configuration interaction and spin–orbit interaction for highly charged heavy ions. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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9 pages, 243 KiB

Open AccessOpinion

The Atom at the Heart of Physics

by Jean-Patrick Connerade

Atoms 2023, 11(2), 32; https://doi.org/10.3390/atoms11020032 - 06 Feb 2023

Viewed by 1412

Abstract

A number of reasons are advanced for which atoms stand at the heart of research in the physical sciences. There are issues in physics which are both fundamental and only partly resolved or, at least, imperfectly understood. Rather than chase them towards higher [...] Read more.

A number of reasons are advanced for which atoms stand at the heart of research in the physical sciences. There are issues in physics which are both fundamental and only partly resolved or, at least, imperfectly understood. Rather than chase them towards higher and higher energies, which mainly results in greater complexity, it makes sense to restrict oneself to the simplest systems known, held together by the best understood force in nature, viz. those governed by the inverse square law. Our line of argument complements the adage of Richard Feynman, who asked: should Armageddon occur, is there a simple, most important idea to preserve as a testament to human knowledge? The answer he suggested is: the atomic hypothesis. Full article

(This article belongs to the Special Issue Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules, and Clusters)

5 pages, 204 KiB

Open AccessEditorial

“Atoms” Special Issue (Electron Scattering from Atoms, Ions and Molecules)

by Rajesh Srivastava and Dmitry V. Fursa

Atoms 2023, 11(2), 31; https://doi.org/10.3390/atoms11020031 - 06 Feb 2023

Cited by 1 | Viewed by 979

Abstract

Electron collision physics covers a broad range of processes in atoms and molecules [...] Full article

(This article belongs to the Special Issue Electron Scattering from Atoms, Ions and Molecules)

12 pages, 519 KiB

Open AccessArticle

Deep Laser Cooling of Thulium Atoms to Sub-µK Temperatures in Magneto-Optical Trap

by Daniil Provorchenko, Dmitry Tregubov, Denis Mishin, Mikhail Yaushev, Denis Kryuchkov, Vadim Sorokin, Ksenia Khabarova, Artem Golovizin and Nikolay Kolachevsky

Atoms 2023, 11(2), 30; https://doi.org/10.3390/atoms11020030 - 05 Feb 2023

Cited by 2 | Viewed by 1467

Abstract

Deep laser cooling of atoms, ions, and molecules facilitates the study of fundamental physics as well as applied research. In this work, we report on the narrow-line laser cooling of thulium atoms at the wavelength of

506.2 nm

with the natural linewidth of [...] Read more.

Deep laser cooling of atoms, ions, and molecules facilitates the study of fundamental physics as well as applied research. In this work, we report on the narrow-line laser cooling of thulium atoms at the wavelength of

506.2 nm

with the natural linewidth of

7.8 kHz

, which widens the limits of atomic cloud parameters control. Temperatures of about

400 nK

, phase-space density of up to

3.5 \times 10^{- 4}

and

2 \times 10^{6}

number of trapped atoms were achieved. We have also demonstrated formation of double cloud structure in an optical lattice by adjusting parameters of the

506.2 nm

magneto-optical trap. These results can be used to improve experiments with BEC, atomic interferometers, and optical clocks. Full article

(This article belongs to the Special Issue The Fundamental Role of Precision Atomic-Physics Measurements in Modern Science)

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39 pages, 9731 KiB

Open AccessArticle

Analysis of Plasma Emission Experiments and ‘Dips’

by Spiros Alexiou

Atoms 2023, 11(2), 29; https://doi.org/10.3390/atoms11020029 - 04 Feb 2023

Cited by 2 | Viewed by 837

Abstract

It has been claimed that recent experiments using high-powered lasers have identified dip structures in spectral line profiles in plasmas and that these were successfully used to reliably infer both plasma parameters and information on high and low-frequency turbulence. The analysis of those [...] Read more.

It has been claimed that recent experiments using high-powered lasers have identified dip structures in spectral line profiles in plasmas and that these were successfully used to reliably infer both plasma parameters and information on high and low-frequency turbulence. The analysis of those experiments relies on a flawed theory. In the present work, we computed the line spectra correctly using the parameters inferred in the original papers. The results bear little resemblance to the experimental profiles. The only way to reconcile the parameters deduced in these experiments is to invoke very broadband turbulence, with the relevant distribution functions that are neither known nor measured playing critical roles. Furthermore, the dip positions are shown to be sensitive to details such as field directionality and variations in the frequency and field amplitude. Hence, dips cannot be used to reliably diagnose such plasmas. 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)

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13 pages, 972 KiB

Open AccessArticle

Experimental and Theoretical Study of Photoionization of Cl III

by Sultana N. Nahar, Edgar M. Hernández, David Kilcoyne, Armando Antillón, Aaron M. Covington, Olmo González-Magaña, Lorenzo Hernández, Vernon Davis, Dominic Calabrese, Alejandro Morales-Mori, Dag Hanstorp, Antonio M. Juárez and Guillermo Hinojosa

Atoms 2023, 11(2), 28; https://doi.org/10.3390/atoms11020028 - 03 Feb 2023

Cited by 3 | Viewed by 1252

Abstract

Photoionization of Cl III ions into Cl IV was studied theoretically using the ab initio relativistic Breit–Pauli R-matrix (BPRM) method and experimentally at the Advanced Light Source (ALS) synchrotron at the Lawrence Berkeley National Laboratory. A relative-ion-yield spectrum of Cl IV was measured [...] Read more.

Photoionization of Cl III ions into Cl IV was studied theoretically using the ab initio relativistic Breit–Pauli R-matrix (BPRM) method and experimentally at the Advanced Light Source (ALS) synchrotron at the Lawrence Berkeley National Laboratory. A relative-ion-yield spectrum of Cl IV was measured with a photon energy resolution of 10 meV. The theoretical study was carried out using a large wave-function expansion of 45 levels of configurations

3 s^{2} 3 p^{2}

,

3 s 3 p^{3}

,

3 s^{2} 3 p 3 d

,

3 s^{2} 3 p 4 s

,

3 s 3 p^{2} 3 d

, and

3 p^{4}

. The resulting spectra are complex. We have compared the observed spectrum with photoionization cross sections (

σ_{P I}

) of the ground state

3 s^{2} 3 p^{3} (^{4} S_{3 / 2}^{o})

and the seven lowest excited levels

3 s^{2} 3 p^{3} (^{2} D_{5 / 2}^{o})

,

3 s^{2} 3 p^{3} (^{2} D_{3 / 2}^{o})

,

3 s^{2} 3 p^{3} (^{2} P_{3 / 2}^{o})

,

3 s^{2} 3 p^{3} (^{2} P_{1 / 2}^{o})

,

3 s 3 p^{4} (^{4} P_{5 / 2})

,

3 s 3 p^{4} (^{4} P_{3 / 2})

and

3 s 3 p^{4} (^{4} P_{1 / 2})

of Cl III, as these can generate resonances within the energy range of the experiment. We were able to identify most of the resonances as belonging to various specific initial levels within the primary Cl III ion beam. Compared to the first five levels, resonant structures in the

σ_{P I}

of excited levels of

3 s 3 p^{4}

appear to have a weaker presence. We have also produced combined theoretical spectra of the levels by convolving the cross sections with a Gaussian profile of experimental width and summing them using statistical weight factors. The theoretical and experimental features show good agreement with the first five levels of Cl III. These features are also expected to elucidate the recent observed spectra of Cl III by Sloan Digital Scan Survey project. Full article

(This article belongs to the Special Issue Photoionization of Atoms)

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27 pages, 1305 KiB

Open AccessEditor’s ChoiceArticle

Ideas and Tools for Error Detection in Opacity Databases

by Jean-Christophe Pain and Patricia Croset

Atoms 2023, 11(2), 27; https://doi.org/10.3390/atoms11020027 - 02 Feb 2023

Cited by 1 | Viewed by 1400

Abstract

In this article, we propose several ideas and tools in order to check the reliability of radiative opacity and atomic physics databases. We first emphasize that it can be useful to verify that mathematical inequalities, which impose lower and upper bounds on the [...] Read more.

In this article, we propose several ideas and tools in order to check the reliability of radiative opacity and atomic physics databases. We first emphasize that it can be useful to verify that mathematical inequalities, which impose lower and upper bounds on the Rosseland and/or Planck mean opacities, are satisfied, either for pure elements or mixtures. In the second part, we discuss the intriguing law of anomalous numbers, also named Benford’s law, which enables one to detect errors in line-strength collections, required in order to perform fine-structure calculations. Finally, we point out and illustrate the importance of quantifying the uncertainties due to interpolations in the density-temperature opacity (or more generally atomic-data) tables and performing convergence checks, which are crucial in the accuracy-completeness compromise inherent in opacity computations. Full article

(This article belongs to the Special Issue Development and Perspectives of Atomic and Molecular Databases)

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12 pages, 300 KiB

Open AccessArticle

High Lying Precise Resonance Energies from Photoionization Studies of Se³⁺ and Rb⁺ Ions Using the Screening Constant per Unit Nuclear Charge Formalism

by Ibrahima Sakho

Atoms 2023, 11(2), 26; https://doi.org/10.3390/atoms11020026 - 01 Feb 2023

Cited by 2 | Viewed by 935

Abstract

Resonance energies of the 4s4p (³P_0,1)np, 4s4p (³P₂)np (²P_3/2, ⁴D_7/2, ⁴D_5/2) and 4s4p (¹P₁)np ( [...] Read more.

Resonance energies of the 4s4p (³P_0,1)np, 4s4p (³P₂)np (²P_3/2, ⁴D_7/2, ⁴D_5/2) and 4s4p (¹P₁)np (²D_3/2, ²D_5/2) Rydberg series of Se³⁺ ions along with resonance energies of the 4s²4p⁵ (²P°_1/2) nd¹P°₁ and 4s4p⁶ (²S_1/2) np ¹P°₁ series of Rb⁺ ions are reported. Calculations are done in the framework of the screening constant per unit nuclear charge (SCUNC) formalism. The fine structure splitting of the 4s4p (³P₂)np (²P_3/2, ⁴D_7/2, ⁴D_5/2) series from n = 10 to n = 27 and for the 4s4p (¹P₁)np (²D_3/2, ²D_5/2) series from n = 8 to 11 are resolved in this paper. Very good agreements are obtained between the present calculations and the available experimental and theoretical literature data. The present predicted data up to n = 40 may be of great importance for the atomic physics community in connection with the understanding of the chemical evolution of the Se and Rb elements in the Universe. Full article

10 pages, 746 KiB

Open AccessCommunication

Three Particle Muon-Electron Bound Systems in Quantum Electrodynamics

by Alexey V. Eskin, Vladimir I. Korobov, Alexei P. Martynenko and Fedor A. Martynenko

Atoms 2023, 11(2), 25; https://doi.org/10.3390/atoms11020025 - 31 Jan 2023

Cited by 1 | Viewed by 1765

Abstract

The muonic 2P-2S Lamb shift in muon-electron atoms and ions of helium, lithium, beryllium, and boron with the electron in the ground state was calculated by the perturbation theory using the fine structure constant and the electron-muon mass ratio. The corrections of first- [...] Read more.

The muonic 2P-2S Lamb shift in muon-electron atoms and ions of helium, lithium, beryllium, and boron with the electron in the ground state was calculated by the perturbation theory using the fine structure constant and the electron-muon mass ratio. The corrections of first- and second-orders of perturbation theory on the Coulomb interaction and nucleus recoil were taken into account. The obtained analytical results were validated numerically using calculations within the variational method. Full article

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

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15 pages, 5037 KiB

Open AccessArticle

Analytical and Statistical Modelling of a Fast Ion Source Formed by Injection of a Neutral Beam into Magnetically Confined Plasma

by Pavel Goncharov

Atoms 2023, 11(2), 24; https://doi.org/10.3390/atoms11020024 - 30 Jan 2023

Cited by 1 | Viewed by 1415

Abstract

Mathematical modelling of heating and current drive as well as yields and distributions of fusion products in a magnetically confined plasma subject to neutral beam injection requires, in turn, modelling of distributions of fast ions, which is a complex task including calculations of [...] Read more.

Mathematical modelling of heating and current drive as well as yields and distributions of fusion products in a magnetically confined plasma subject to neutral beam injection requires, in turn, modelling of distributions of fast ions, which is a complex task including calculations of the source of suprathermal particles, i.e., the number of fast ions occurring in unit volume during unit time owing to the injection of fast atoms. The knowledge of the magnetohydrodynamic equilibrium, beam injection geometry and spatial distribution of the magnetic field are the necessary prerequisites. Explicit general analytical formulae for the source of fast ions have been obtained by two different methods. In addition, a method of statistical modelling is presented. Calculations of spatial and angular distributions of the fast ion source for a tokamak and verifications of the obtained results have been performed by a number of methods. Full article

(This article belongs to the Special Issue Neutral Atoms in Controlled Fusion and Space Plasmas)

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26 pages, 723 KiB

Open AccessArticle

Variational Study of Atomic Properties of Ions and Atoms from He to Ne

by Néstor R. Arista

Atoms 2023, 11(2), 23; https://doi.org/10.3390/atoms11020023 - 28 Jan 2023

Viewed by 889

Abstract

An extension of the variational approach for the study of atomic properties of ions and atoms containing up to 10 electrons is presented. The study includes exact analytical calculations of all the interaction terms, including direct Coulomb interactions and exchange interactions. Two alternative [...] Read more.

An extension of the variational approach for the study of atomic properties of ions and atoms containing up to 10 electrons is presented. The study includes exact analytical calculations of all the interaction terms, including direct Coulomb interactions and exchange interactions. Two alternative formulations are considered, with one and with two variational parameters. The exact and numerical values of these parameters are obtained and tabulated. The results of this study are compared with Hartree–Fock calculations. Sample applications to electron-atom scattering and energy losses of ions in Tokamak plasmas are presented. Full article

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

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9 pages, 1265 KiB

Open AccessArticle

Towards an Intrinsic Doppler Correction for X-ray Spectroscopy of Stored Ions at CRYRING@ESR

by Felix Martin Kröger, Günter Weber, Steffen Allgeier, Zoran Andelkovic, Sonja Bernitt, Alexander Borovik, Jr., Louis Duval, Andreas Fleischmann, Oliver Forstner, Marvin Friedrich, Jan Glorius, Alexandre Gumberidze, Christoph Hahn, Frank Herfurth, Daniel Hengstler, Marc Oliver Herdrich, Pierre-Michel Hillenbrand, Anton Kalinin, Markus Kiffer, Maximilian Kubullek, Patricia Kuntz, Michael Lestinsky, Bastian Löher, Esther Babette Menz, Tobias Over, Nikolaos Petridis, Philip Pfäfflein, Stefan Ringleb, Ragandeep Singh Sidhu, Uwe Spillmann, Sergiy Trotsenko, Andrzej Warczak, Binghui Zhu, Christian Enss and Thomas Stöhlker Show full author list Hide full author list

Atoms 2023, 11(2), 22; https://doi.org/10.3390/atoms11020022 - 28 Jan 2023

Cited by 1 | Viewed by 1270

Abstract

We report on a new experimental approach for the Doppler correction of X-rays emitted by heavy ions, using novel metallic magnetic calorimeter detectors which uniquely combine a high spectral resolution with a broad bandwidth acceptance. The measurement was carried out at the electron [...] Read more.

We report on a new experimental approach for the Doppler correction of X-rays emitted by heavy ions, using novel metallic magnetic calorimeter detectors which uniquely combine a high spectral resolution with a broad bandwidth acceptance. The measurement was carried out at the electron cooler of CRYRING@ESR at GSI, Darmstadt, Germany. The X-ray emission associated with the radiative recombination of cooler electrons and stored hydrogen-like uranium ions was investigated using two novel microcalorimeter detectors positioned under 0

^{\circ}

and 180

^{\circ}

with respect to the ion beam axis. This new experimental setup allowed the investigation of the region of the N, M → L transitions in helium-like uranium with a spectral resolution unmatched by previous studies using conventional semiconductor X-ray detectors. When assuming that the rest-frame energy of at least a few of the recorded transitions is well-known from theory or experiments, a precise measurement of the Doppler shifted line positions in the laboratory system can be used to determine the ion beam velocity using only spectral information. The spectral resolution achievable with microcalorimeter detectors should, for the first time, allow intrinsic Doppler correction to be performed for the precision X-ray spectroscopy of stored heavy ions. A comparison with data from a previous experiment at the ESR electron cooler, as well as the conventional method of conducting Doppler correction using electron cooler parameters, will be discussed. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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8 pages, 1811 KiB

Open AccessArticle

Electron Capture by Proton Beam in Collisions with Water Vapor

by Sanjeev Kumar Maurya, Abhijeet Bhogale and Lokesh C. Tribedi

Atoms 2023, 11(2), 21; https://doi.org/10.3390/atoms11020021 - 27 Jan 2023

Viewed by 1245

Abstract

In low energy ion-molecule collisions, electron capture is one of the most important channels. A new experimental setup was developed to study the electron capture process using low-energy ion beams extracted from an electron cyclotron resonance (ECR) plasma-based ion accelerator. Experiments were carried [...] Read more.

In low energy ion-molecule collisions, electron capture is one of the most important channels. A new experimental setup was developed to study the electron capture process using low-energy ion beams extracted from an electron cyclotron resonance (ECR) plasma-based ion accelerator. Experiments were carried out with the proton beam colliding with water vapor in the energy range of 70–300 keV. Capture events were detected using a position-sensitive detection system comprising micro channel plates (MCPs) and a delay line detector (DLD). These e-capture events can be a result of pure capture reactions as well as transfer ionization. The capture cross section was found to decrease sharply with the beam energy and agreed well with previous measurements. The setup was also used to detect the events that gave rise to the single and multiple e-capture (integrated over all recoil-ion charge states) of C⁴⁺ ions. The capture cross-sections for one, two, three, and four electrons were measured for 100 keV C⁴⁺ ions. The ratio of multielectron capture yield to that for single e-capture decreased with the number of captured electrons. Full article

(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)

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11 pages, 1157 KiB

Open AccessArticle

Manifestations of Rabi Dynamics in the Photoelectron Energy Spectra at Resonant Two-Photon Ionization of Atom by Intense Short Laser Pulses

by Nenad S. Simonović, Duška B. Popović and Andrej Bunjac

Atoms 2023, 11(2), 20; https://doi.org/10.3390/atoms11020020 - 23 Jan 2023

Cited by 4 | Viewed by 1205

Abstract

We study the Rabi flopping of the population between the ground and excited 2p states of the hydrogen atom, induced by intense short laser pulses of different shapes and of carrier frequency

ω = 0.375

a.u. which resonantly couples the two states, and [...] Read more.

We study the Rabi flopping of the population between the ground and excited 2p states of the hydrogen atom, induced by intense short laser pulses of different shapes and of carrier frequency

ω = 0.375

a.u. which resonantly couples the two states, and manifestations of this dynamics in the energy spectra of photoelectrons produced in the subsequent ionization of the atom from the excited state. It is found that, for Gaussian, half-Gaussian and rectangular pulses, characterized by the same pulse area, the final populations take the same values and the spectra consist of similar patterns having the same number of peaks and approximately the same separation between the prominent edge (Autler–Townes) peaks. The additional analysis in terms of dressed states showed that the mechanism of formation of multiple-peak structures during the photoionization process is the same regardless of the pulse shape. These facts disprove the hypothesis proposed in earlier studies with Gaussian pulse, that the multiple-peak pattern appears due to dynamic interference of the photoelectrons emitted with a time delay at the rising and falling sides of the pulse, since the hypothesis is not applicable to either a half-Gaussian pulse that has no rising part or a rectangular pulse whose intensity is constant. Full article

(This article belongs to the Special Issue Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules, and Clusters)

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13 pages, 1761 KiB

Open AccessArticle

Proton and Electron Irradiations of CH₄:H₂O Mixed Ices

by Duncan V. Mifsud, Péter Herczku, Béla Sulik, Zoltán Juhász, István Vajda, István Rajta, Sergio Ioppolo, Nigel J. Mason, Giovanni Strazzulla and Zuzana Kaňuchová

Atoms 2023, 11(2), 19; https://doi.org/10.3390/atoms11020019 - 22 Jan 2023

Cited by 2 | Viewed by 2083

Abstract

The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules [...] Read more.

The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules under conditions that simulate interstellar space. Several of these regions, such as dense molecular cores, are exposed to ionizing radiation in the form of galactic cosmic rays, which may act as an important driver of molecular destruction and synthesis. In this paper, we report the results of a comparative and systematic study of the irradiation of CH₄:H₂O ice mixtures by 1 MeV protons and 2 keV electrons at 20 K. We demonstrate that our irradiations result in the formation of a number of new products, including both simple and complex daughter molecules such as C₂H₆, C₃H₈, C₂H₂, CH₃OH, CO, CO₂, and probably also H₂CO. A comparison of the different irradiation regimes has also revealed that proton irradiation resulted in a greater abundance of radiolytic daughter molecules compared to electron irradiation, despite a lower radiation dose having been administered. These results are important in the context of the radiation astrochemistry occurring within the molecular cores of dense interstellar clouds, as well as on outer Solar System objects. Full article

(This article belongs to the Special Issue Interaction of Electrons with Atoms, Molecules and Surfaces)

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6 pages, 225 KiB

Open AccessEditorial

“Atoms” Special Issue (Many-Electron and Multiphoton Atomic Processes: A Tribute to Miron Amusia)

by Anatoli S. Kheifets, Gleb Gribakin and Vadim K. Ivanov

Atoms 2023, 11(2), 18; https://doi.org/10.3390/atoms11020018 - 20 Jan 2023

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Abstract

The late Professor Miron Amusia was a key figure in theoretical atomic physics on the international stage for more than five decades [...] Full article

(This article belongs to the Special Issue Many-Electron and Multiphoton Atomic Processes: A Tribute to Miron Amusia)

13 pages, 868 KiB

Open AccessArticle

Binary Encounter Electrons in Fast Dressed-Ion–H₂ Collisions: Distorted Wave Theories and Experiment

by Nicolás J. Esponda, Stefanos Nanos, Michele A. Quinto, Theo J. M. Zouros, Roberto D. Rivarola, Emmanouil P. Benis and Juan M. Monti

Atoms 2023, 11(2), 17; https://doi.org/10.3390/atoms11020017 - 20 Jan 2023

Cited by 1 | Viewed by 1178

Abstract

We report measurements of double differential cross section for zero-degree binary encounter electrons emitted in collisions of 4.9 MeV and 13 MeV B

^{(2 - 5) +}

ions with H₂ targets. The corresponding calculations based on continuum distorted-wave (CDW) theories [...] Read more.

We report measurements of double differential cross section for zero-degree binary encounter electrons emitted in collisions of 4.9 MeV and 13 MeV B

^{(2 - 5) +}

ions with H₂ targets. The corresponding calculations based on continuum distorted-wave (CDW) theories are critically compared to the measurements. CDW in its post form exhibits a very good agreement with the measurements in all cases. The CDW theories utilized along with the well-known eikonal-initial-state (CDW-EIS) approximation are also examined and their results are compared to both the measurements and the CDW calculations. In particular, CDW-EIS using a recently proposed dynamic effective charge for the final channel projectile distortion exhibits a substantial improvement in comparison with an effective net-charge approximation. Full article

(This article belongs to the Special Issue Interaction of Electrons with Atoms, Molecules and Surfaces)

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10 pages, 3889 KiB

Open AccessArticle

Electron-Impact Ionization of Carbon

by Nicolás Bachi, Sebastian Otranto and Karoly Tőkési

Atoms 2023, 11(2), 16; https://doi.org/10.3390/atoms11020016 - 20 Jan 2023

Cited by 4 | Viewed by 1308

Abstract

We present ionization cross-sections of collisions between electrons and carbon atoms using the classical trajectory Monte Carlo method. Total cross-sections are benchmarked against the reported experimental data and the predictions of numerically intensive theoretical methods as well as pioneering calculations for this collision [...] Read more.

We present ionization cross-sections of collisions between electrons and carbon atoms using the classical trajectory Monte Carlo method. Total cross-sections are benchmarked against the reported experimental data and the predictions of numerically intensive theoretical methods as well as pioneering calculations for this collision system. At impact energies greater than about 100 eV, the present results are in very good agreement with the generalized oscillator strength formulation of the Born approximation as well as with the experimental data. Limitations inherent to a purely classical description of the electron impact ionization process at low impact energies are detected and analyzed, suggesting a clear route for future studies. Full article

(This article belongs to the Special Issue Interaction of Electrons with Atoms, Molecules and Surfaces)

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12 pages, 599 KiB

Open AccessArticle

Differential Analysis of the Positron Impact Ionization of Hydrogen in Debye Plasmas

by Emiliano Acebal, Sergio Hernan Martínez and Sebastian Otranto

Atoms 2023, 11(2), 15; https://doi.org/10.3390/atoms11020015 - 18 Jan 2023

Cited by 1 | Viewed by 1232

Abstract

In this work, a theoretical differential analysis of the positron impact ionization of hydrogen embedded in weakly coupled plasmas at an impact energy of 80 eV is developed. While the total and singly differential cross sections are analyzed within the classical trajectory Monte [...] Read more.

In this work, a theoretical differential analysis of the positron impact ionization of hydrogen embedded in weakly coupled plasmas at an impact energy of 80 eV is developed. While the total and singly differential cross sections are analyzed within the classical trajectory Monte Carlo method, a Born-3DW model for screened environments, recently introduced by the authors, is used to provide a fully differential view of the process. The present results suggest that the electron emission spectra are strongly affected by the level of screening of the surrounding medium, mainly due to the loss of the postcollisional interaction mechanism. Full article

(This article belongs to the Special Issue Interaction of Electrons with Atoms, Molecules and Surfaces)

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