Special Issue "Recent Advances in Ion-Impact Atomic Collisions: Experiment, Theory and Applications"

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

Deadline for manuscript submissions: closed (31 January 2019)

Special Issue Editors

Guest Editor
Prof. Dr. Tom Kirchner

Department of Physics & Astronomy, York University, 4700 Keele Street, Toronto, Ontario, Canada
Website | E-Mail
Interests: atomic scattering theory; quantum dynamics of few-body Coulomb systems; ion-atom and ion-molecule collisions; density functional theory approach to the many-body problem
Guest Editor
Prof. Dr. Michael Schulz

Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409, USA
Website | E-Mail
Interests: few-body problem; atomic scattering experiments; kinematically complete experiments; coherence effects; electron-electron correlation effects

Special Issue Information

Dear Colleagues,

Ion-impact atomic collision studies have shaped our understanding of the microscopic world and continue to play an important role in shedding light on fundamental properties and processes of atomic and molecular few-body systems. At the same time, they provide insight and data of relevance for more applied research directions such as the study of fusion plasmas, X-ray emissions of astrophysical objects, and radiation damage of biological tissue. For this special issue we invite original contributions covering all aspects of contemporary heavy-particle atomic collision physics, ranging from the development of new theoretical or computational approaches and experimental techniques to the calculation and measurement of cross section data for specific processes and the use of collisional data in plasma modeling and other areas. The goal is to provide a snapshot of current research in the field, of new insights, developments, and applications and of open problems.

Prof. Dr. Tom Kirchner
Prof. Dr. Michael Schulz
Guest Editors

Manuscript Submission Information

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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

  • basic processes in ion-atom, ion-molecule, and ion-cluster collisions
  • few-body dynamics
  • fragmentation of molecules and clusters by ion impact
  • postcollisional de-excitation processes (radiative vs. Auger)
  • ion-biomolecule interactions
  • laser-assisted collisions
  • coherence, electron-electron correlation, and relativistic effects
  • experimental techniques and instrumentation
  • applications of ion-impact collisions

Published Papers (7 papers)

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Research

Open AccessArticle
Frozen Core Approximation and Nuclear Screening Effects in Single Electron Capture Collisions
Received: 31 January 2019 / Revised: 28 March 2019 / Accepted: 4 April 2019 / Published: 12 April 2019
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Abstract
Differential cross sections (DCS) for single electron capture from helium by heavy ion impact are calculated using a frozen core 3-body model and an active electron 4-body model within the first Born approximation. DCS are presented for H+, He2+, [...] Read more.
Differential cross sections (DCS) for single electron capture from helium by heavy ion impact are calculated using a frozen core 3-body model and an active electron 4-body model within the first Born approximation. DCS are presented for H+, He2+, Li3+, and C6+ projectiles with velocities of 1 MeV/amu and 10 MeV/amu. In general, the DCS from the two models are found to differ by about one to two orders of magnitude with the active electron 4-body model showing better agreement with experiment. Comparison of the models reveals two possible sources of the magnitude difference: the inactive electron’s change of state and the projectile–target Coulomb interaction used in the different models. Detailed analysis indicates that the uncaptured electron’s change of state can safely be neglected in the frozen core approximation, but that care must be used in modeling the projectile–target interaction. Full article
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Open AccessArticle
Distortion of the Ionization Cross Section of He by the Coherence Properties of a C6+ Beam
Received: 31 January 2019 / Revised: 20 February 2019 / Accepted: 26 February 2019 / Published: 1 March 2019
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Abstract
We analyze the influence of the coherence of the projectile’s beam in scattering phenomena. We focus our study in the ionization of He by C6+ projectiles at 100 MeV/amu. We assess the influence of this effect by performing a Born initial [...] Read more.
We analyze the influence of the coherence of the projectile’s beam in scattering phenomena. We focus our study in the ionization of He by C 6 + projectiles at 100 MeV/amu. We assess the influence of this effect by performing a Born initial state and continuum distorted wave final state (CDW-B1) calculation together with a rigorous procedure to account for the initial coherence properties of the projectile’s beam. These calculations, which had been previously performed for only the scattering and perpendicular collision planes and within the First Born approximation (FBA), were repeated for an ampler set of collision planes. Additionally, a more refined method to describe the applicability of the aforementioned procedure, is used. We achieve a better qualitative agreement with the experimental results. Full article
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Open AccessArticle
Charge-Exchange Emission from Hydrogen-Like Carbon Ions Colliding with Water Molecules
Received: 14 January 2019 / Revised: 27 January 2019 / Accepted: 29 January 2019 / Published: 1 February 2019
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Abstract
Absolute Extreme Ultraviolet emission cross-sections have been measured for collisions between C5+ and H2O in the range of 0.113 to 3.75 keV/amu (170–979 km/s). These results are used to derive velocity-dependent triplet-to-singlet ratios and emission cross-sections of the C [...] Read more.
Absolute Extreme Ultraviolet emission cross-sections have been measured for collisions between C 5 + and H 2O in the range of 0.113 to 3.75 keV/amu (170–979 km/s). These results are used to derive velocity-dependent triplet-to-singlet ratios and emission cross-sections of the Cv K-series following single-electron capture. Comparison with existing measurements of integral charge-changing cross-sections indicates that auto-ionizing multi-electron capture is a significant reactions channel. This reaction may indirectly populate the n = 2 states and thus add strength to the K α emission of Cv ions thereby co-determining the hardness ratio of K-series emission of Cv. Full article
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Open AccessArticle
Capture Cross Sections and Radiative Emission-Line Strengths for Slow Ne8+ Collisions with He and H2
Received: 20 December 2018 / Revised: 17 January 2019 / Accepted: 19 January 2019 / Published: 23 January 2019
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Abstract
The Ne8+–He and –H2 collision systems are examined at impact speeds ranging between 0.17 and 0.4 a.u. Transition probabilities for electron capture are obtained using the two-center basis generator method performed within the independent-electron model. The aim of calculating capture [...] Read more.
The Ne8+–He and –H2 collision systems are examined at impact speeds ranging between 0.17 and 0.4 a.u. Transition probabilities for electron capture are obtained using the two-center basis generator method performed within the independent-electron model. The aim of calculating capture cross sections for these collision systems is to provide new theoretical verification of previously reported experimental data and to provide aid for astrophysical X-ray studies. This study also examines the applicability of the independent-electron model with effective potentials to describe two-electron capture for these two systems. Comparisons of capture cross sections and radiative-emission counts with the available experimental and theoretical data show an overall good agreement. Full article
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Open AccessArticle
Transverse Momentum Transfer Distributions Following Single Ionization in 3.6 MeV/amu Au53+ + He Collisions: A 4-Body Classical Treatment
Received: 4 October 2018 / Revised: 27 November 2018 / Accepted: 29 November 2018 / Published: 3 December 2018
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Abstract
A four-body classical model based on the resolution of Hamilton equations of motion was used here to determine and analyze ionization doubly-differential cross sections following 3.6 MeV/amu Au53+ + He collisions. Our calculation was not able to reproduce the binary peaks experimentally [...] Read more.
A four-body classical model based on the resolution of Hamilton equations of motion was used here to determine and analyze ionization doubly-differential cross sections following 3.6 MeV/amu Au53+ + He collisions. Our calculation was not able to reproduce the binary peaks experimentally observed in the transverse momentum distributions for electron emission energies larger than 10 eV. Surprisingly, by introducing a large number of free or quasi-free electrons that followed the projectile at the same velocity, the agreement between the experiment and our calculation was improved, since our model reproduced, at least qualitatively, the experimental binary peaks. The origin of the presence of such electrons is discussed. Full article
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Open AccessArticle
Mixed-State Ionic Beams: An Effective Tool for Collision Dynamics Investigations
Received: 29 October 2018 / Revised: 22 November 2018 / Accepted: 26 November 2018 / Published: 29 November 2018
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Abstract
The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like (1s21S,1s2s3,1S) mixed-state beams, the spectrum contributions of the [...] Read more.
The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like ( 1 s 2 1 S , 1 s 2 s 3 , 1 S ) mixed-state beams, the spectrum contributions of the 1 s 2 s 3 S metastable beam component is effectively separated and clearly identified. This is performed with a technique that exploits two independent spectrum measurements under the same collision conditions, but with ions having quite different metastable fractions, judiciously selected by varying the ion beam charge-stripping conditions. Details of the technique are presented together with characteristic examples. In collisions of 4 MeV B 3 + with H 2 targets, the Auger electron spectrum of the separated 1 s 2 s 3 S boron beam component allows for a detailed analysis of the formation of the 1 s 2 s ( 3 S ) n l 2 L states by direct n l transfer. In addition, the production of hollow 2 s 2 p 1 , 3 P doubly- and 2 s 2 p 2 2 D triply-excited states, by direct excitation and transfer-excitation processes, respectively, can also be independently studied. In similar mixed-state beam collisions of 15 MeV C 4 + with H 2 , He, Ne and Ar targets, the contributions of the 1 s 2 , 1 s 2 s 3 , 1 S beam components to the formation of the 2 s 2 p 3 , 1 P states by double-excitation, 1 s 2 p excitation and transfer-loss processes can be clearly identified, facilitating comparisons with theoretical calculations. Full article
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Open AccessArticle
Coherence-Length Effects in Fast Atom Diffraction at Grazing Incidence
Received: 24 October 2018 / Revised: 16 November 2018 / Accepted: 20 November 2018 / Published: 27 November 2018
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Abstract
Coherence properties of projectiles, found relevant in ion-atom collisions, are investigated by analyzing the influence of the degree of coherence of the atomic beam on interference patterns produced by grazing-incidence fast-atom diffraction (GIFAD or FAD). The transverse coherence length of the projectiles, which [...] Read more.
Coherence properties of projectiles, found relevant in ion-atom collisions, are investigated by analyzing the influence of the degree of coherence of the atomic beam on interference patterns produced by grazing-incidence fast-atom diffraction (GIFAD or FAD). The transverse coherence length of the projectiles, which depends on the incidence conditions and the collimating setup, determines the overall characteristics of GIFAD distributions. We show that for atoms scattered from a LiF(001) surface after a given collimation, we can modify the interference signatures of the angular spectra by varying the total impact energy, while keeping the normal energy as a constant. Also, the role played by the geometry of the collimating aperture is analyzed, comparing results for square and circular openings. Furthermore, we study the spot-beam effect, which is due to different focus points of the impinging particles. We show that when a region narrower than a single crystallographic channel is coherently illuminated by the atomic beam, the spot-beam contribution strongly affects the visibility of the interference structures, contributing to the gradual quantum-classical transition of the projectile distributions. Full article
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