Special Issue "Photoionization of Atoms"

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: 31 December 2022 | Viewed by 3605

Special Issue Editors

Prof. Dr. Sultana N. Nahar
E-Mail Website
Guest Editor
Astronomy Department, The Ohio State University, Columbus, OH 43210, USA
Interests: photoionization; electron-ion recombination; photo-excitations; electron impact excitation; spectroscopy; X-ray spectroscopy for atomic processes and biomedical applications; database
Prof. Dr. Guillermo Hinojosa
E-Mail Website
Guest Editor
Instituto de Ciencias Físicas, National Autonomous University of Mexico (UNAM), Cuernavaca 62200, Mexico
Interests: atomic, molecular and optical physics; photoionization of ions; negative ions; fundamental processes in low temperature plasma

Special Issue Information

Dear Colleagues,

Photoionization of an atom or ion is one most common processes involving the interaction of a photon with an atom. It is one of the four most dominant atomic processes, along with photo-excitation, electron-ion recombination, and electron impact excitations, in astrophysical plasmas that produce the spectra and hence carries considerable information about the constituent elements and their abundances, plasma opacity, ionization fractions, etc. This special issue will present the precise underlying science of photoionization. Although direct photoionization via absorption of a photon by the atomic system happens, resonances form in the process as the energy of the photon-atom system matches to that of a doubly excited state, known as the autoionizing state, lying above the ionization threshold. It is inherent to study the process with inclusion of resonances. The objective of this issue is to advance the current understanding of atomic photoionization, both theoretically and experimentally, for complex atomic systems with demonstrations of various features in the low and high energy regions, that will impact the accuracy of photoionization environments, modeling of astrophysical and laboratory plasmas and their applications.

Prof. Dr. Sultana N. Nahar
Prof. Guillermo Hinojosa
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atoms is an international peer-reviewed open access quarterly journal published by MDPI.

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Keywords

  • photoionization
  • experimental features
  • theoretical features
  • benchmarking
  • astrophysical applications

Published Papers (4 papers)

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Research

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Article
Photoejection from Various Systems and Radiative-Rate Coefficients
Atoms 2022, 10(1), 9; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10010009 - 19 Jan 2022
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Abstract
Photoionization or photodetachment is an important process. It has applications in solar- and astrophysics. In addition to accurate wave function of the target, accurate continuum functions are required. There are various approaches, like exchange approximation, method of polarized orbitals, close-coupling approximation, R-matrix formulation, [...] Read more.
Photoionization or photodetachment is an important process. It has applications in solar- and astrophysics. In addition to accurate wave function of the target, accurate continuum functions are required. There are various approaches, like exchange approximation, method of polarized orbitals, close-coupling approximation, R-matrix formulation, exterior complex scaling, the recent hybrid theory, etc., to calculate scattering functions. We describe some of them used in calculations of photodetachment or photoabsorption cross sections of ions and atoms. Comparisons of cross sections obtained using different approaches for the ejected electron are given. Furthermore, recombination rate coefficients are also important in solar- and astrophysics and they have been calculated at various electron temperatures using the Maxwell velocity distribution function. Approaches based on the method of polarized orbitals do not provide any resonance structure of photoabsorption cross sections, in spite of the fact that accurate results have been obtained away from the resonance region and in the resonance region by calculating continuum functions to calculate resonance widths using phase shifts in the Breit–Wigner formula for calculating resonance parameters. Accurate resonance parameters in the elastic cross sections have been obtained using the hybrid theory and they compare well with those obtained using the Feshbach formulation. We conclude that accurate results for photoabsorption cross sections can be obtained using the hybrid theory. Full article
(This article belongs to the Special Issue Photoionization of Atoms)
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Article
Photoionization and Electron-Ion Recombination of n = 1 to Very High n-Values of Hydrogenic Ions
Atoms 2021, 9(4), 73; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms9040073 - 03 Oct 2021
Cited by 3 | Viewed by 549
Abstract
Single electron hydrogen or hydrogenic ions have analytical forms to evaluate the atomic parameters for the inverse processes of photoionization and electron-ion recombination (H I + hν H II + e) where H is hydrogen. Studies of these processes have continued [...] Read more.
Single electron hydrogen or hydrogenic ions have analytical forms to evaluate the atomic parameters for the inverse processes of photoionization and electron-ion recombination (H I + hν H II + e) where H is hydrogen. Studies of these processes have continued until the present day (i) as the computations are restricted to lower principle quantum number n and (ii) to improve the accuracy. The analytical expressions have many terms and there are numerical instabilities arising from cancellations of terms. Strategies for fast convergence of contributions were developed but precise computations are still limited to lower n. This report gives a brief review of the earlier precise methodologies for hydrogen, and presents numerical tables of photoionization cross sections (σPI), and electron-ion recombination rate coefficients (αRC) obtained from recombination cross sections (σRC) for all n values going to a very high value of 800. σPI was obtained using the precise formalism of Burgess and Seaton, and Burgess. αRC was obtained through a finite integration that converge recombination exactly as implemented in the unified method of recombination of Nahar and Pradhan. Since the total electron-ion recombination includes all levels for n = 1–∞, the total asymptotic contribution of n = 801–∞, called the top-up, is obtained through a n3 formula. A FORTRAN program “hpxrrc.f” is provided to compute photoionization cross sections, recombination cross sections and rate coefficients for any nl. The results on hydrogen atom can be used to obtain those for any hydrogenic ion of charge z through z-scaling relations provided in the theory section. The present results are of high precision and complete for astrophysical modelings. Full article
(This article belongs to the Special Issue Photoionization of Atoms)
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Review

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Review
Measurement of Photoionization Cross-Section for the Excited States of Atoms: A Review
Atoms 2022, 10(2), 39; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020039 - 14 Apr 2022
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Abstract
A review of experimental studies of the measurement of the photoionization cross-section for the excited states of the alkali atoms, alkaline earth atoms, and rare-gas atoms is presented, with emphasis on using multi-step laser excitation, ionization, and the saturation technique. The dependence of [...] Read more.
A review of experimental studies of the measurement of the photoionization cross-section for the excited states of the alkali atoms, alkaline earth atoms, and rare-gas atoms is presented, with emphasis on using multi-step laser excitation, ionization, and the saturation technique. The dependence of the photoionization cross-section from different intermediate states populated in the first step and ionized in the second step are discussed, including results on the photoionization cross-sections measured above the first ionization threshold. Results based on different polarizations of the exciting and the ionizing dye lasers are also discussed. Examples are provided, illustrating the photoionization cross-sections measured using thermionic diode ion detector, atomic beam apparatus in conjunction with a time-of-flight mass spectrometer and DC/RF glow discharge cell as an optogalvanic detection. Full article
(This article belongs to the Special Issue Photoionization of Atoms)
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Review
Atomic Processes, Including Photoabsorption, Subject to Outside Charge-Neutral Plasma
Atoms 2022, 10(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10010016 - 29 Jan 2022
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Abstract
We present in this review our recent theoretical studies on atomic processes subject to the plasma environment including the α and β emissions and the ground state photoabsorption of the one- and two-electron atoms and ions. By carefully examining the spatial and temporal [...] Read more.
We present in this review our recent theoretical studies on atomic processes subject to the plasma environment including the α and β emissions and the ground state photoabsorption of the one- and two-electron atoms and ions. By carefully examining the spatial and temporal criteria of the Debye–Hückel (DH) approximation based on the classical Maxwell–Boltzmann statistics, we were able to represent the plasma effect with a Debye–Hückel screening potential VDH in terms of the Debye length D, which is linked to the ratio between the plasma density N and its temperature kT. Our theoretical data generated with VDH from the detailed non-relativistic and relativistic multiconfiguration atomic structure calculations compare well with the limited measured results from the most recent experiments. Starting from the quasi-hydrogenic picture, we were able to show qualitatively that the energy shifts of the emission lines could be expressed in terms of a general expression as a function of a modified parameter, i.e., the reduced Debye length λ. The close agreement between theory and experiment from our study may help to facilitate the plasma diagnostics to determine the electron density and the temperature of the outside plasma. Full article
(This article belongs to the Special Issue Photoionization of Atoms)
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