Atoms

18 pages, 284 KiB

Open AccessArticle

by Alexander Ryabtsev

Atoms 2023, 11(11), 148; https://doi.org/10.3390/atoms11110148 - 16 Nov 2023

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Using a sliding spark and a 6.65 m normal incidence vacuum spectrograph, the third spectrum of platinum was analyzed. The transitions involving high-lying levels were studied. A total of 241 Pt III lines of the transitions from the levels of the 5d⁷ [...] Read more.

Using a sliding spark and a 6.65 m normal incidence vacuum spectrograph, the third spectrum of platinum was analyzed. The transitions involving high-lying levels were studied. A total of 241 Pt III lines of the transitions from the levels of the 5d⁷6p + 5d⁶6s6p configurations in the region 728–2062 Å were classified, increasing the number of known Pt III lines to more than 1000. Ninety-one energy levels belonging mostly to the 5d⁶6s6p configuration were added to Pt III. The odd Pt III levels were theoretically interpreted by means of multiconfiguration Dirak–Fock calculations and a least-squares fit of the calculated to the observed levels in the framework of the orthogonal parameters technique. Full article

14 pages, 4850 KiB

Open AccessArticle

The Vortex Surface in a Three-Body Quantum System

by Tamara A. Guarda, Francisco Navarrete and Raúl O. Barrachina

Atoms 2023, 11(11), 147; https://doi.org/10.3390/atoms11110147 - 15 Nov 2023

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Abstract

Vortices are structures known in our daily lives and observed in a wide variety of systems, from cosmic to microscopic scales. Relatively recent studies showed that vortices could also appear in simple quantum systems. For instance, they were observed experimentally and theoretically as [...] Read more.

Vortices are structures known in our daily lives and observed in a wide variety of systems, from cosmic to microscopic scales. Relatively recent studies showed that vortices could also appear in simple quantum systems. For instance, they were observed experimentally and theoretically as isolated zeros in the differential cross section in atomic ionization processes by the impact of charged particles. In this work, we show that the appearance of these quantum vortices as point structures was not due to any intrinsic property of them, but to the use of restrictive geometries in their visualization. In particular, we show that by studying the fully differential cross section for hydrogen ionization by positron impact, these vortex points are actually a manifestation of a more complex and hitherto unexplored structure, a 3D “vortex surface”. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Atomic Collision and Atomic Spectroscopy)

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13 pages, 3325 KiB

Open AccessArticle

Pathways to the Local Thermodynamic Equilibrium of Complex Autoionizing States

by Frédérick Petitdemange and Frank B. Rosmej

Atoms 2023, 11(11), 146; https://doi.org/10.3390/atoms11110146 - 15 Nov 2023

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Abstract

The generally accepted pathway to Local Thermodynamic Equilibrium (LTE) in atomic physics, where collision rates need to be much larger than radiative decay rates, is extended to complex autoionizing states. It is demonstrated that the inclusion of the non-radiative decay (autoionization rate) on [...] Read more.

The generally accepted pathway to Local Thermodynamic Equilibrium (LTE) in atomic physics, where collision rates need to be much larger than radiative decay rates, is extended to complex autoionizing states. It is demonstrated that the inclusion of the non-radiative decay (autoionization rate) on the same footing, like radiative decay, i.e., the LTE criterion

n_{e, c r i t} \times C ≫ A + Γ

(

n_{e, c r i t}

is the critical electron density above which LTE holds,

C

is the collisional rate coefficient, and

A

is the radiative decay rate) is inappropriate for estimating the related critical density. An analysis invoking simultaneously different atomic ionization stages identifies the LTE criteria as a theoretical limiting case, which provides orders of magnitude too high critical densities for almost all practical applications. We introduced a new criterion, where the critical densities are estimated from the non-autoionizing capture states rather than from the autoionizing states. The new criterion is more appropriate for complex autoionizing manifolds and provides order of magnitude reduced critical densities. Detailed numerical calculations are carried out for Na-like states of aluminum, where autoionization to the Ne-like ground and excited state occurrences are in excellent agreement with the new criterion. In addition, a complex multi-electron atomic-level structure and electron–electron correlation are identified as simplifying features rather than aggravating ones for the concept of thermalization. Full article

(This article belongs to the Special Issue Atomic Physics in Dense Plasmas)

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8 pages, 442 KiB

Open AccessArticle

Guiding as a General Consequence of the Charged Particle Interaction with the Inner Surface of an Insulator Capillary—Guiding of 1 MeV Proton Microbeam through Polytetrafluoroethylene Macrocapillary

by Károly Tőkési, István Rajta, Gyula Nagy and Réka Judit Bereczky

Atoms 2023, 11(11), 145; https://doi.org/10.3390/atoms11110145 - 15 Nov 2023

Viewed by 1121

Abstract

The transmission of energetic, 1 MeV proton microbeam through a single, cylindrical shaped, macrometer-sized polytetrafluoroethylene capillary was studied experimentally. The capillary axis was tilted with respect to the axis of the incident ion beam. The tilting, the aspect ratio of the capillary and [...] Read more.

The transmission of energetic, 1 MeV proton microbeam through a single, cylindrical shaped, macrometer-sized polytetrafluoroethylene capillary was studied experimentally. The capillary axis was tilted with respect to the axis of the incident ion beam. The tilting, the aspect ratio of the capillary and the small beam divergence disabled the geometrical transmission of the beam through the target. The intensity, energy, deflection and charge state of the transmitted beam were investigated. We found that the pure guided transmission of a MeV/amu energy ion beam is observable. We clearly identified three completely different stages during the guiding process according to the measured energy distribution of transmitted particles. At the beginning the transmission intensity was low and only inelastic contributions with energy lower than 1 MeV were found in the spectrum. Later, in the second stage, the elastic peak appeared and became more and more significant. Finally, when the stable transmission evolved, only the elastic peak was present and the inelastic area was totally absent as a direct consequence of the ion guiding and as a result of the charged particle interaction with a charged inner surface of the insulator capillary. Full article

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27 pages, 5680 KiB

Open AccessReview

Collisional Classical Dynamics at the Quantum Scale

by Sebastian Otranto

Atoms 2023, 11(11), 144; https://doi.org/10.3390/atoms11110144 - 09 Nov 2023

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Abstract

During the past five decades, classical dynamics have been systematically used to gain insight on collision processes between charged particles and photons with atomic and molecular targets. These methods have proved to be efficient for systems in which numerical intensive quantum mechanical methods [...] Read more.

During the past five decades, classical dynamics have been systematically used to gain insight on collision processes between charged particles and photons with atomic and molecular targets. These methods have proved to be efficient for systems in which numerical intensive quantum mechanical methods are not yet tractable. During the years, reaction cross sections for charge exchange and ionization have been scrutinized at the total and differential levels, leading to a clear understanding of the benefits and limitations inherent in a classical description. In this work, we present a review of the classical trajectory Monte Carlo method, its current status and the perspectives that can be envisaged for the near future. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Atomic Collision and Atomic Spectroscopy)

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2 pages, 1808 KiB

Open AccessCorrection

Correction: Cárdenas-Castillo, L.F.; Camacho-Guardian, A. Strongly Interacting Bose Polarons in Two-Dimensional Atomic Gases and Quantum Fluids of Polaritons. Atoms 2023, 11, 3

by Luis Fernando Cárdenas-Castillo and Arturo Camacho-Guardian

Atoms 2023, 11(11), 143; https://doi.org/10.3390/atoms11110143 - 07 Nov 2023

Cited by 1 | Viewed by 1064

Abstract

The authors wish to make the following corrections to their paper [...] Full article

(This article belongs to the Special Issue Recent Trends on Quantum Fluctuations in Ultra-Cold Quantum Gases)

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25 pages, 8162 KiB

Open AccessArticle

Study of Electron Impact Excitation of Na-like Kr Ion for Impurity Seeding Experiment in Large Helical Device

by Shivam Gupta, Tetsutarou Oishi and Izumi Murakami

Atoms 2023, 11(11), 142; https://doi.org/10.3390/atoms11110142 - 05 Nov 2023

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Abstract

In this work, a krypton gas impurity seeding experiment was conducted in a Large Helical Device. Emission lines from the Na-like Kr ion in the extreme ultraviolet wavelength region, such as 22.00 nm, 17.89 nm, 16.51 nm, 15.99 nm, and 14.08 nm, respective [...] Read more.

In this work, a krypton gas impurity seeding experiment was conducted in a Large Helical Device. Emission lines from the Na-like Kr ion in the extreme ultraviolet wavelength region, such as 22.00 nm, 17.89 nm, 16.51 nm, 15.99 nm, and 14.08 nm, respective to

2 p^{6} 3 p (^{2} P_{1 / 2}^{o}) - 2 p^{6} 3 s (^{2} S_{1 / 2})

,

2 p^{6} 3 p (^{2} P_{3 / 2}^{o}) - 2 p^{6} 3 s (^{2} S_{1 / 2})

,

2 p^{6} 3 d (^{2} D_{3 / 2}) - 2 p^{6} 3 p (^{2} P_{3 / 2}^{o})

,

2 p^{6} 3 d (^{2} D_{5 / 2}) - 2 p^{6} 3 p (^{2} P_{3 / 2}^{o})

, and

2 p^{6} 3 d (^{2} D_{3 / 2}) - 2 p^{6} 3 p (^{2} P_{1 / 2}^{o})

transitions, are observed. In order to generate a theoretical synthetic spectrum, an extensive calculation concerning the excitation of the

{Kr}^{25 +}

ion through electron impact was performed for the development of a suitable plasma model. For this, the relativistic multiconfiguration Dirac–Hartree–Fock method was employed along with its extension to the relativistic configuration interaction method to compute the relativistic bound-state wave functions and excitation energies of the fine structure levels using the General Relativistic Atomic Structure Package-2018. In addition, another set of calculations was carried out utilizing the relativistic many-body perturbation theory and relativistic configuration interaction methods integrated within the Flexible Atomic Code. To investigate the reliability of our findings, the results of excitation energies, transition probabilities, and weighted oscillator strengths of different dipole-allowed transitions obtained from these different methods are presented and compared with the available data. Further, the detailed electron impact excitation cross-sections and their respective rate coefficients are obtained for various fine structure resolved transitions using the fully relativistic distorted wave method. Rate coefficients, calculated using the Flexible Atomic Code for population and de-population kinetic processes, are integrated into the collisional-radiative plasma model to generate a theoretical spectrum. Further, the emission lines observed from the

{Kr}^{25 +}

ion in the impurity seeding experiment were compared with the present plasma model spectrum, demonstrating a noteworthy overall agreement between the measurement and the theoretical synthetic spectrum. Full article

(This article belongs to the Special Issue Atomic Processes for Plasma Modeling Applications)

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28 pages, 8131 KiB

Open AccessArticle

Effects of Spiralling Trajectories on White Dwarf Spectra: High Rydberg States

by Spiros Alexiou

Atoms 2023, 11(11), 141; https://doi.org/10.3390/atoms11110141 - 01 Nov 2023

Viewed by 1073

Abstract

It has been recently suggested that white dwarf diagnostics could be in error and should be revised because of the effect of the magnetic field on spiralling trajectories of the plasma particles (mainly electrons), predicting a dramatic width increase for high densities of [...] Read more.

It has been recently suggested that white dwarf diagnostics could be in error and should be revised because of the effect of the magnetic field on spiralling trajectories of the plasma particles (mainly electrons), predicting a dramatic width increase for high densities of Balmer-

β

and especially for the

δ

and

ϵ

lines. These suggestions overlook important physics and are shown here to be incorrect. Specifically, exact calculations are carried out that can assess the importance of various physical effects neglected in the erroneous analysis mentioned. The net result of accounting for spiralling electron trajectories is typically a small to modest reduction in the line widths, at least for the parameters considered. Full article

(This article belongs to the Special Issue Rydberg Atomic Physics)

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8 pages, 1602 KiB

Open AccessOpinion

Isomers in the Cosmos

by Eric B. Norman

Atoms 2023, 11(11), 140; https://doi.org/10.3390/atoms11110140 - 26 Oct 2023

Cited by 1 | Viewed by 1058

Abstract

The nucleosynthesis of chemical elements has been established to be the result of a variety of different types of nuclear reactions in stars. Under the extreme temperatures and densities encountered in such environments, nuclear isomers can be populated and thus complicate our understanding [...] Read more.

The nucleosynthesis of chemical elements has been established to be the result of a variety of different types of nuclear reactions in stars. Under the extreme temperatures and densities encountered in such environments, nuclear isomers can be populated and thus complicate our understanding of these processes. In this paper, I have chosen to discuss five cases that illustrate how nuclear isomers can play important roles in the nucleosynthesis of chemical elements. Full article

(This article belongs to the Special Issue Over a Century of Nuclear Isomers: Challenges and Prospects)

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10 pages, 5137 KiB

Open AccessCommunication

A Radio-Frequency Ion Trap System for the Multi-Reflection Time-of-Flight Mass Spectrometer at SHANS and Its Offline Commissioning

by Jun-Ying Wang, Wen-Xue Huang, Yu-Lin Tian, Yong-Sheng Wang, Yue Wang, Wan-Li Zhang, Yuan-Jun Huang, Zai-Guo Gan and Hu-Shan Xu

Atoms 2023, 11(11), 139; https://doi.org/10.3390/atoms11110139 - 26 Oct 2023

Viewed by 1344

Abstract

To precisely measure atomic masses and select neutron-deficient isotopes produced by fusion evaporation reactions, an MRTOF-MS (multi-reflection time-of-flight mass spectrometer) at the SHANS (Spectrometer for Heavy Atom and Nuclear Structure) is being developed. One of the key parts, an RF ion trap system [...] Read more.

To precisely measure atomic masses and select neutron-deficient isotopes produced by fusion evaporation reactions, an MRTOF-MS (multi-reflection time-of-flight mass spectrometer) at the SHANS (Spectrometer for Heavy Atom and Nuclear Structure) is being developed. One of the key parts, an RF ion trap system with the aim to provide brilliant ion pulses with a low energy spread and narrow pulse width for ion preparation prior to injection into the MRTOF mass analyzer, has been constructed and commissioned offline successfully. The principle, construction details and test results are reported. Pulsed beams of

^{39}

K

^{1 +}

,

^{85, 87}

Rb

^{1 +}

and

^{133}

Cs

^{1 +}

ions have been tested and the amplitudes and frequencies of the RF signals, DC voltages, helium gas pressure and time parameters have been scanned. The corresponding time spreads have reached 0.252 µs, 0.394 µs and 0.450 µs, respectively. Full article

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

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13 pages, 3453 KiB

Open AccessArticle

Fragmentation of Multiply Charged C₁₀H₈ Isomers Produced in keV Range Proton Collision

by Meloottayil V. Vinitha, Pragya Bhatt, Cholakka P. Safvan, Sarita Vig and Umesh R. Kadhane

Atoms 2023, 11(11), 138; https://doi.org/10.3390/atoms11110138 - 25 Oct 2023

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Abstract

The dissociation of multiply charged C₁₀H₈ isomers produced in fast proton collisions (velocities between 1.41 and 2.4 a.u.) is discussed in terms of their fundamental molecular dynamics, in particular the processes that produce different carbon clusters in such a collision. [...] Read more.

The dissociation of multiply charged C₁₀H₈ isomers produced in fast proton collisions (velocities between 1.41 and 2.4 a.u.) is discussed in terms of their fundamental molecular dynamics, in particular the processes that produce different carbon clusters in such a collision. This aspect is assessed with the help of a multi-hit analysis of daughter ions detected in coincidence with the elimination of H

^{+}

and CH_n⁺ (n = 0 to 3). The elimination of H

^{+}

/C

^{+}

is found to be significantly different from CH₃⁺ loss. The loss of CH₃⁺ proceeds through a cascade of momentum-correlated dissociations with the formation of heavy ions such as C₉H₅⁺, C₉H₅²⁺ and C₇H₃⁺. The structure of such large fragment ions is predicted with the help of their calculated ground state electronic energies and the multi-hit time-of-flight (ToF) correlation between the second and third hit fragments if detected. Furthermore, we report experimentally the super-dehydrogenation of naphthalene and azulene targets, with evidence of complete dehydrogenation in a single collision. 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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Atoms, Volume 11, Issue 11 (November 2023) – 11 articles

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