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11 pages, 2109 KiB

Open AccessArticle

Simulation of Extreme Ultraviolet Radiation and Conversion Efficiency of Lithium Plasma in a Wide Range of Plasma Situations

by Xiangdong Li, Frank B. Rosmej and Zhanbin Chen

Atoms 2024, 12(3), 16; https://doi.org/10.3390/atoms12030016 - 12 Mar 2024

Viewed by 1669

Abstract

Based on the detailed term accounting approach, the relationship between extreme ultraviolet conversion efficiency and plasma conditions, which range from 5 to 200 eV for plasma temperature and from 4.63 × 10¹⁷ to 4.63 × 10²² cm⁻³ for plasma density, [...] Read more.

Based on the detailed term accounting approach, the relationship between extreme ultraviolet conversion efficiency and plasma conditions, which range from 5 to 200 eV for plasma temperature and from 4.63 × 10¹⁷ to 4.63 × 10²² cm⁻³ for plasma density, is studied for lithium plasmas through spectral simulations involving very extended atomic configurations, including a benchmark set of autoionizing states. The theoretical limit of the EUV conversion efficiency and its dependence on sustained plasma time are given for different plasma densities. The present study provides the necessary understanding of EUV formation from the perspective of atomic physics and also provides useful knowledge for improving EUV conversion efficiency with different technologies. Full article

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

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12 pages, 1539 KiB

Open AccessArticle

Energy Shift of the Atomic Emission Lines of He-like Ions Subject to Outside Dense Plasma

by Tu-Nan Chang, Te-Kuei Fang, Rui Sun, Chensheng Wu and Xiang Gao

Atoms 2024, 12(1), 4; https://doi.org/10.3390/atoms12010004 - 15 Jan 2024

Cited by 2 | Viewed by 1841

Abstract

We present an extension of our study of the energy shift of the atomic emissions subject to charged-neutral outside dense plasma following the good agreement between the experimental measurements and our recent theoretical estimates for the

α

and

β

emission lines of a [...] Read more.

We present an extension of our study of the energy shift of the atomic emissions subject to charged-neutral outside dense plasma following the good agreement between the experimental measurements and our recent theoretical estimates for the

α

and

β

emission lines of a number of H-like and He-like ions. In particular, we are able to further demonstrate that the plasma-induced transition energy shift could indeed be interpolated by the simple quasi-hydrogenic picture based on the application of the Debye–Hückel (DH) approximation for the

n = 3

to

n = 2

transitions of the He-like ions. Our theoretically estimated redshifts of those emissions may offer the impetus for additional experimental measurement to facilitate the diagnostic efforts in the determination of the temperature and density of the dense plasma. Full article

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

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10 pages, 764 KiB

Open AccessCommunication

Modeling Femtosecond Reduction of Atomic Scattering Factors in X-ray-Excited Silicon with Boltzmann Kinetic Equations

by Beata Ziaja, Michal Stransky, Konrad J. Kapcia and Ichiro Inoue

Atoms 2023, 11(12), 154; https://doi.org/10.3390/atoms11120154 - 7 Dec 2023

Viewed by 1681

Abstract

In this communication, we describe the application of Boltzmann kinetic equations for modeling massive electronic excitation in a silicon nanocrystal film after its irradiation with intense femtosecond hard X-ray pulses. This analysis was inspired by an experiment recently performed at the X-ray free-electron [...] Read more.

In this communication, we describe the application of Boltzmann kinetic equations for modeling massive electronic excitation in a silicon nanocrystal film after its irradiation with intense femtosecond hard X-ray pulses. This analysis was inspired by an experiment recently performed at the X-ray free-electron laser facility SACLA, which measured a significant reduction in atomic scattering factors triggered by an X-ray pulse of the intensity ∼

10^{19}

W/cm

^{2}

, occurring on a timescale comparable with the X-ray pulse duration (6 fs full width at half maximum). We show that a Boltzmann kinetic equation solver can accurately follow the details of the electronic excitation in silicon atoms caused by such a hard X-ray pulse, yielding predictions in very good agreement with the experimental data. Full article

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

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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

Viewed by 1537

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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9 pages, 3770 KiB

Open AccessArticle

K-Edge Structure in Shock-Compressed Chlorinated Parylene

by David Bailie, Steven White, Rachael Irwin, Cormac Hyland, Richard Warwick, Brendan Kettle, Nicole Breslin, Simon N. Bland, David J. Chapman, Stuart P. D. Mangles, Rory A. Baggot, Eleanor R. Tubman and David Riley

Atoms 2023, 11(10), 135; https://doi.org/10.3390/atoms11100135 - 18 Oct 2023

Viewed by 1485

Abstract

We have carried out a series of experiments to measure the Cl K-absorption edge for shock-compressed samples of chlorinated parylene. Colliding shocks allowed us to compress samples up to four times the initial density with temperatures up to 10 eV. Red shifts in [...] Read more.

We have carried out a series of experiments to measure the Cl K-absorption edge for shock-compressed samples of chlorinated parylene. Colliding shocks allowed us to compress samples up to four times the initial density with temperatures up to 10 eV. Red shifts in the edge of about 10 eV have been measured. We have compared the measured shifts to analytical modelling using the Stewart–Pyatt model and adaptions of it, combined with estimates of density and temperature based on hydrodynamic modelling. Modelling of the edge position using density functional theory molecular dynamics (DFT-MD) was also used and it was found that good agreement was only achieved when the DFT simulations assumed conditions of lower temperature and slightly higher density than indicated by hydrodynamic simulations using a tabular equation of state. Full article

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

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10 pages, 5166 KiB

Open AccessArticle

The Fingerprints of Periodic Electric Fields on Line Shapes Emitted in Plasmas

by Ibtissem Hannachi and Roland Stamm

Atoms 2023, 11(10), 128; https://doi.org/10.3390/atoms11100128 - 8 Oct 2023

Viewed by 1352

Abstract

Periodic electric fields are found in many kinds of plasmas and result from the presence of collective fields amplified by plasma instabilities, or they are created by external sources such as microwave generators or lasers. The spectral lines emitted by atoms or ions [...] Read more.

Periodic electric fields are found in many kinds of plasmas and result from the presence of collective fields amplified by plasma instabilities, or they are created by external sources such as microwave generators or lasers. The spectral lines emitted by atoms or ions in a plasma exhibit a frequency profile characteristic of plasma conditions, such as the temperature and density of charged particles. The fingerprints of periodic electric fields appear clearly on the line shape for a large range of frequencies and magnitudes of the oscillating electric field. Satellite structures appear near to multiples of the oscillation frequency and redistribute the intensity of the line far from the line center. The modeling of the simultaneous effects of the plasma microfield and of a periodic electric field has been active since the seventies, but it remains difficult to be conducted accurately since the quantum emitter is submitted to several time-dependent electric fields, each with their own characteristic time. We describe here a numerical approach which couples a simulation of the motion of charged plasma particles with an integration of the emitter Schrödinger equation. Resulting hydrogen line shapes are presented for different plasmas and periodic fields encountered in laboratory and astrophysical plasmas. Full article

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

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13 pages, 3652 KiB

Open AccessArticle

Extreme Ultraviolet Radiation Sources from Dense Plasmas

by Klaus Bergmann

Atoms 2023, 11(9), 118; https://doi.org/10.3390/atoms11090118 - 31 Aug 2023

Cited by 2 | Viewed by 1641

Abstract

The concept of dense and hot plasmas can be used to build up powerful and brilliant radiation sources in the soft X-ray and extreme ultraviolet spectral range. Such sources are used for nanoscale imaging and structuring applications, such as EUV lithography in the [...] Read more.

The concept of dense and hot plasmas can be used to build up powerful and brilliant radiation sources in the soft X-ray and extreme ultraviolet spectral range. Such sources are used for nanoscale imaging and structuring applications, such as EUV lithography in the semiconductor industry. An understanding of light-generating atomic processes and radiation transport within the plasma is mandatory for optimization. The basic principles and technical concepts using either a pulsed laser or a gas discharge for plasma generation are presented, and critical aspects in the ionization dynamics are outlined within the framework of a simplified atomic physics model. Full article

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

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9 pages, 2260 KiB

Open AccessCommunication

Scattering of X-ray Ultrashort Laser Pulses on Bound Electrons in Dense Plasma

by Egor Sergeevich Khramov and Valery Alexandrovich Astapenko

Atoms 2023, 11(6), 100; https://doi.org/10.3390/atoms11060100 - 16 Jun 2023

Cited by 1 | Viewed by 1217

Abstract

We considered the resonance scattering of ultrashort laser pulses (USLP) on the bound electrons of hydrogen-like ions in a dense plasma. A process description was proposed in terms of full scattering probability during the time of pulse action. Dense plasma’s effect was demonstrated [...] Read more.

We considered the resonance scattering of ultrashort laser pulses (USLP) on the bound electrons of hydrogen-like ions in a dense plasma. A process description was proposed in terms of full scattering probability during the time of pulse action. Dense plasma’s effect was demonstrated at the resonance scattering cross-section spectrum, and the probability dependence on USLP carrier frequency and duration was obtained for the cases of isolated ions and ions in a dense plasma. Full article

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

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Review

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55 pages, 2293 KiB

Open AccessFeature PaperReview

Atomic Models of Dense Plasmas, Applications, and Current Challenges

by Robin Piron

Atoms 2024, 12(4), 26; https://doi.org/10.3390/atoms12040026 - 17 Apr 2024

Cited by 1 | Viewed by 1647

Abstract

Modeling plasmas in terms of atoms or ions is theoretically appealing for several reasons. When it is relevant, the notion of atom or ion in a plasma provides us with an interpretation scheme of the plasma’s internal functioning. From the standpoint of quantitative [...] Read more.

Modeling plasmas in terms of atoms or ions is theoretically appealing for several reasons. When it is relevant, the notion of atom or ion in a plasma provides us with an interpretation scheme of the plasma’s internal functioning. From the standpoint of quantitative estimation of plasma properties, atomic models of plasma allow one to extend many theoretical tools of atomic physics to plasmas. This notably includes the statistical approaches to the detailed accounting for excited states, or the collisional-radiative modeling of non-equilibrium plasmas, which is based on the notion of atomic processes. This paper is focused on the theoretical challenges raised by the atomic modeling of dense, non-ideal plasmas. It is intended to give a synthetic and pedagogical view on the evolution of ideas in the field, with an accent on the theoretical consistency issues, rather than an exhaustive review of models and experimental benchmarks. First we make a brief, non-exhaustive review of atomic models of plasmas, from ideal plasmas to strongly-coupled and pressure-ionized plasmas. We discuss the limitations of these models and pinpoint some open problems in the field of atomic modeling of plasmas. We then address the peculiarities of atomic processes in dense plasmas and point out some specific issues relative to the calculation of their cross-sections. In particular, we discuss the modeling of fluctuations, the accounting for channel mixing and collective phenomena in the photoabsorption, or the impact of pressure ionization on collisional processes. Full article

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

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23 pages, 6236 KiB

Open AccessReview

A Study of the Atomic Processes of Highly Charged Ions Embedded in Dense Plasma

by Alok Kumar Singh Jha, Mayank Dimri, Dishu Dawra and Man Mohan

Atoms 2023, 11(12), 158; https://doi.org/10.3390/atoms11120158 - 15 Dec 2023

Cited by 3 | Viewed by 2019

Abstract

The study of atomic spectroscopy and collision processes in a dense plasma environment has gained a considerable interest in the past few years due to its several applications in various branches of physics. The multiconfiguration Dirac-Fock (MCDF) method and relativistic configuration interaction (RCI) [...] Read more.

The study of atomic spectroscopy and collision processes in a dense plasma environment has gained a considerable interest in the past few years due to its several applications in various branches of physics. The multiconfiguration Dirac-Fock (MCDF) method and relativistic configuration interaction (RCI) technique incorporating the uniform electron gas model (UEGM) and analytical plasma screening (APS) potentials have been employed for characterizing the interactions among the charged particles in plasma. The bound and continuum state wavefunctions are determined using the aforementioned potentials within a relativistic Dirac-Coulomb atomic structure framework. The present approach is applied for the calculation of electronic structures, radiative properties, electron impact excitation cross sections and photoionization cross sections of many electron systems confined in a plasma environment. The present study not only extends our knowledge of the plasma-screening effect but also opens the door for the modelling and diagnostics of astrophysical and laboratory plasmas. Full article

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

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