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Electron Scattering from Atoms, Ions and Molecules

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

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 21808

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Special Issue Editors

Prof. Dr. Rajesh Srivastava

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Guest Editor

Department of Physics, Indian Institute of Technology (IIT), Roorkee 247667, India
Interests: atomic and molecular collision physics; atomic and molecular structures; plasma diagnostics

Prof. Dr. Dmitry V. Fursa

E-Mail Website
Guest Editor

Department of Physics and Astronomy, Curtin University, Perth, WA 6845, Australia
Interests: electron, positron and photon collisions with atoms and molecules

Special Issue Information

Dear Colleagues,

The impact of electrons on the elastic and inelastic processes of atoms, ions, as well as molecules, have been the most extensively studied subjects in the field of atomic collision physics. The wide interest in such electron-induced fundamental processes has been due to its numerous and wide-ranging applications in various fields, e.g., plasma physics, astrophysics, laser physics, fusion research, etc. In collision physics, the experiment and theoretical modelling have been developing and supporting each other from their inception. With time, the quality and variety in experimental techniques have continuously progressed, revealing and providing us with new aspects of fundamental physics. The accurate experimental data allowed for comprehensive testing of theoretical models, which, in turn, led to the developments of sophisticated quantum mechanical computational techniques which have become recently feasible with significant advances in computational resources. Currently, comprehensive cross-section datasets are available for several collision systems and are actively used in plasma modelling applications. For this Special Issue, we invite original contributions covering all aspects of electron collisions with atoms, ions, and molecules, such as:

Relativistic and non-relativistic elastic scattering from atoms, ions and molecules;
Electron impact excitation and ionization of light and heavy atoms and ions;
Relativistic and non-relativistic atomic structure calculations;
Electron-molecule scattering, including rotational, vibrational and electronic excitations;
Correlation, polarization, and ionization in electron impact atomic and molecular collisions;
Electron impact inner shell excitations and Auger’s electron spectroscopy;
Plasma related optical emission spectroscopy (OES) measurements;
Application of electron impact atomic and molecular collision data in astrophysical and laboratory plasma modelling.

The contributions may include new experimental measurements and novel theoretical or computational approaches or calculations. Measurements and calculations of various electron impacts on atomic and molecular processes with different atomic systems are welcome. Our aim is to provide recent developments and new results in the area of electron initiated atomic and molecular collision physics and their related applications in plasma modelling.

Prof. Dr. Rajesh Srivastava
Prof. Dr. Dmitry V. Fursa
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 monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

electrons
atoms
ions
molecules
excitation
ionization
inner-shell excitations
atomic structure calculations
relativistic and non-relativistic theories
cross sections
optical emission spectroscopy
plasma modelling

Published Papers (12 papers)

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Editorial

Jump to: Research

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://0-doi-org.brum.beds.ac.uk/10.3390/atoms11020031 - 6 Feb 2023

Cited by 1 | Viewed by 1047

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)

Research

Jump to: Editorial

12 pages, 3298 KiB

Open AccessArticle

Time-Resolved Analysis of the Electron Temperature in RF Magnetron Discharges with a Pulsed Gas Injection

by Thibault Sadek, Pierre Vinchon, Antoine Durocher-Jean, Guillaume Carnide, Myrtil L. Kahn, Richard Clergereaux and Luc Stafford

Atoms 2022, 10(4), 147; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10040147 - 6 Dec 2022

Cited by 3 | Viewed by 1533

Abstract

Pulsed gas injection in a plasma can affect many fundamentals, including electron heating and losses. The case of an asymmetric RF magnetron plasma with a pulsed argon injection is analyzed by optical emission spectroscopy of argon 2p-to-1s transitions coupled with collisional-radiative modeling. For a fully detailed population model of argon 2p levels accounting for direct and stepwise electron-impact excitation in optically thick conditions, a rapid decrease in the electron temperature, T_e, is observed during each gas injection with the sudden pressure rise. The opposite trend, with unrealistic T_e values before and after each pulse, is observed for analysis based on simple corona models, thus emphasizing the importance of stepwise excitation processes and radiation trapping. Time-resolved electron temperature variations are directly linked to the operating parameters of the pulsed gas injection, in particular the injection frequency. Based on the complete set of data, it is shown that the instantaneous electron temperature monotonously decreases with increasing pressure, with values consistent with those expected for plasmas in which charged species are produced by electron-impact ionization of ground state argon atoms and lost by diffusion and recombination on plasma reactor walls. Full article

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

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17 pages, 3471 KiB

Open AccessArticle

Diagnostics of Argon Plasma Using Reliable Electron-Impact Excitation Cross Sections of Ar and Ar⁺

by Neelam Shukla, Reetesh Kumar Gangwar and Rajesh Srivastava

Atoms 2022, 10(4), 118; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10040118 - 24 Oct 2022

Cited by 5 | Viewed by 1709

Abstract

Comprehensive collisional radiative (CR) models have been developed for the diagnostic of argon plasma using Ar and Ar⁺ emission lines. The present CR models consist of 42 and 114 fine-structure levels of Ar and Ar⁺, respectively. Various populating and depopulating mechanisms are incorporated in the model. A complete set of electron-impact fine-structure resolved excitation cross-sections for different excited levels in Ar and Ar⁺ are used, which are obtained by employing relativistic distorted wave theory. Along with this, the electron-impact ionization, radiation trapping, diffusion, and three-body recombination are also considered. Further, to demonstrate the applicability of the present CR model, we applied it to characterize the Helicon-plasma utilizing the optical emission spectroscopy measurements. The key plasma parameters, such as electron density and electron temperature, are obtained using their measured Ar and Ar⁺ emission line intensities. Our results are in reasonable agreement with their anticipated estimates. The matching of our calculated intensities of the different Ar and Ar⁺ lines shows excellent agreement with the measured intensities at various powers. Full article

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

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19 pages, 1774 KiB

Open AccessArticle

Electron Impact Ionization of Adenine: Partial Cross Sections

by Mohammad Atiqur Rehman and E. Krishnakumar

Atoms 2022, 10(4), 100; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10040100 - 23 Sep 2022

Cited by 4 | Viewed by 1397

Abstract

Electron ionization of a genetically important nucleobase, adenine, was investigated from threshold to 500 eV using crossed electron beam–effusive molecular beam geometry and time-of-flight mass spectrometry. We measured the complete set of absolute partial cross sections for adenine using the relative flow technique (RFT) up to an electron energy of 500 eV. Normalization to absolute values was performed using electron ionization cross sections for argon and the vapor pressure data of adenine. The total cross sections obtained by summing the partial cross sections were compared with the existing theoretical and experimental data. The appearance energies of various fragment ions were also measured and compared with the reported data. The prominence of ions with mass (HCN)_n⁺ (n = 1 to 5) indicated a possible pathway to form adenine in the interstellar medium through aggregation of HCN units. Analysis of the partial cross sections for various groups of fragment ions as a function of electron energy was found to give insights into their composition. Full article

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

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8 pages, 1808 KiB

Open AccessArticle

Dynamics of Site Selectivity in Dissociative Electron Attachment in Aromatic Molecules

by Vishvesh Tadsare, Sukanta Das, Samata Gokhale, E. Krishnakumar and Vaibhav S. S. Prabhudesai

Atoms 2022, 10(4), 98; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10040098 - 22 Sep 2022

Cited by 2 | Viewed by 1285

Abstract

Dissociative electron attachment has shown site selectivity in aliphatic molecules based on the functional groups present in them. This selectivity arises from the core excited resonances that have excited parent states localized to a specific site of the functional group. Here, we show that such site selectivity is also observed in the amine group when present in aromatic molecules. However, the proximity of the aromatic ring to the functional group under investigation has a substantial effect on the dissociation dynamics. This effect is evident in the momentum distribution of the hydride ions generated from the amine group. Our results unravel the hitherto unknown facets of the site selectivity in aromatic organic molecules. Full article

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

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Figure 1

16 pages, 420 KiB

Open AccessArticle

Constructing Electron-Atom Elastic Scattering Potentials Using Relativistic Coupled-Cluster Theory: A Few Case Studies

by Bijaya Kumar Sahoo

Atoms 2022, 10(3), 88; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10030088 - 6 Sep 2022

Cited by 2 | Viewed by 1587

Abstract

In light of the immense interest in understanding the impact of an electron on atoms in the low-energy scattering phenomena observed in laboratories and astrophysical processes, we propose an approach to construct potentials using relativistic coupled-cluster (RCC) theory for the determination of electron-atom (e-A) elastic scattering cross-sections (eSCs). The net potential of an electron, scattered elastically by an atom, is conveniently expressed as the sum of the static (

V_{s t}

) and exchange (

V_{e x}

) potentials due to interactions of the scattered electron with the electrons of the atom and potentials due to polarization effects (

V_{p o l}

) on the scattered electron by the atomic electrons. The

V_{s t}

and

V_{e x}

potentials for the e-A eSC problems can be constructed with a knowledge of the electron density function of the atom, while the

V_{p o l}

potential can be obtained using the polarizabilities of the atom. In this paper, we present the electron densities and electric polarizabilties of Be, Mg, Ne and Ar atoms using two variants of the RCC method. Using these quantities, we construct potentials for e-A eSC problems. To obtain

V_{p o l}

accurately, we evaluate the second- and third-order electric dipole and quadrupole polarizabilities using a linear response approach. Full article

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

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24 pages, 886 KiB

Open AccessArticle

Cross Sections for Electron Scattering from Atomic Tin

by Haadi Umer, Igor Bray and Dmitry V. Fursa

Atoms 2022, 10(3), 78; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10030078 - 27 Jul 2022

Cited by 5 | Viewed by 2254

Abstract

The relativistic convergent close-coupling method is applied to calculate cross sections for electron scattering from atomic tin. We present integrated and momentum-transfer cross sections for elastic scattering from the ground and the first four excited states of tin for projectile energies ranging from [...] Read more.

5 p^{2}

5 p 6 s

5 p 5 d

and

5 p 6 p

manifolds from the ground state. The total ionisation cross sections are calculated from the ground and the first four excited states, accounting for the direct ionisation of the

5 p

valence shell and the closed

5 s

shell and the indirect contributions from the excitation–autoionisation. The presented results are compared with previous theoretical predictions and an experiment where available. For the total ionisation cross sections, we find good agreement with the experiment and other theories, while for excitation cross sections, the agreement is mixed. Full article

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

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22 pages, 7362 KiB

Open AccessArticle

An Investigation of the Resonant and Non-Resonant Angular Time Delay of e-C₆₀ Elastic Scattering

by Aiswarya R. and Jobin Jose

Atoms 2022, 10(3), 77; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10030077 - 25 Jul 2022

Cited by 3 | Viewed by 1682

Abstract

Time delay in electron scattering depends on both the scattering angle

θ

and scattered electron energy E. A study on the angular time delay of e-C₆₀ elastic scattering was carried out in the present work. We employed the annular square well [...] Read more.

Time delay in electron scattering depends on both the scattering angle

θ

and scattered electron energy E. A study on the angular time delay of e-C₆₀ elastic scattering was carried out in the present work. We employed the annular square well (ASW) potential to simulate the C₆₀ environment. The contribution from different partial waves to the total angular time delay profile was examined in detail. The investigation was performed for both resonant and non-resonant energies, and salient characteristics in the time delay profile for each case were studied. Full article

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

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17 pages, 1185 KiB

Open AccessArticle

Magnetic Sublevel Independent Magic and Tune-Out Wavelengths of the Alkaline-Earth Ions

by Jyoti, Harpreet Kaur, Bindiya Arora and Bijaya Kumar Sahoo

Atoms 2022, 10(3), 72; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10030072 - 11 Jul 2022

Cited by 1 | Viewed by 1998

Abstract

Light shift in a state due to the applied laser in an atomic system vanishes at tune-out wavelengths (

λ_{T}

s). Similarly, differential light shift in a transition vanishes at the magic wavelengths (

λ_{m a g i c}

s). In [...] Read more.

Light shift in a state due to the applied laser in an atomic system vanishes at tune-out wavelengths (

λ_{T}

s). Similarly, differential light shift in a transition vanishes at the magic wavelengths (

λ_{m a g i c}

s). In many of the earlier studies, values of the electric dipole (E1) matrix elements were inferred precisely by combining measurements and calculations of

λ_{m a g i c}

. Similarly, the

λ_{T}

values of an atomic state can be used to infer the E1 matrix element, as it involves dynamic electric dipole (

α

) values of only one state whereas the

λ_{m a g i c}

values require evaluation of

α

values for two states. However, both the

λ_{m a g i c}

and

λ_{T}

values depend on angular momenta and their magnetic components (M) of states. Here, we report the

λ_{m a g i c}

and

λ_{T}

values of many

S_{1 / 2}

and

D_{3 / 2, 5 / 2}

states, and transitions among these states of the Mg

^{+}

, Ca

^{+}

, Sr

^{+}

and Ba

^{+}

ions that are independent of M values. It is possible to infer a large number of E1 matrix elements of the above ions accurately by measuring these values and combining with our calculations. Full article

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

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10 pages, 439 KiB

Open AccessArticle

Semiempirical Calculations on Low-Energy Electron Scattering by Zn and Cd Atoms

by Felipe Arretche, Wagner Tenfen and Bijaya K. Sahoo

Atoms 2022, 10(3), 69; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10030069 - 29 Jun 2022

Cited by 4 | Viewed by 1946

Abstract

Since total cross section measurements for electron scattering by Zn and Cd performed in the 1970s, the existence of p-wave shape resonances below 1 eV are well established in the literature. It was suggested that a second d-wave shape resonance could exist in both systems at an energy slightly higher than the one recorded for the p-wave but still below the inelastic threshold. We report elastic scattering calculations for electron collisions with Zn and Cd atoms below 4 eV using a semiempirical approach, as well the scattering length for both targets. Our results show that, indeed, the d-wave shape resonance is found in Zn but absent in Cd. In fact, our cross sections and the few other ones available for this energy range are in discrepancy with the available experimental total cross sections for Cd. Full article

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

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16 pages, 820 KiB

Open AccessArticle

Inclusion of Electron Interactions by Rate Equations in Chemical Models

by Laurence Campbell, Dale L. Muccignat and Michael J. Brunger

Atoms 2022, 10(2), 62; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020062 - 10 Jun 2022

Cited by 2 | Viewed by 1716

Abstract

The concept of treating subranges of the electron energy spectrum as species in chemical models is investigated. This is intended to facilitate simple modification of chemical models by incorporating the electron interactions as additional rate equations. It is anticipated that this embedding of fine details of the energy dependence of the electron interactions into rate equations will yield an improvement in computational efficiency compared to other methods. It will be applicable in situations where the electron density is low enough that the electron interactions with chemical species are significant compared to electron–electron interactions. A target application is the simulation of electron processes in the D-region of the Earth’s atmosphere, but it is anticipated that the method would be useful in other areas, including enhancement of Monte Carlo simulation of electron–liquid interactions and simulations of chemical reactions and radical generation induced by electrons and positrons in biomolecular systems. The aim here is to investigate the accuracy and practicality of the method. In particular, energy must be conserved, while the number of subranges should be small to reduce computation time and their distribution should be logarithmic in order to represent processes over a wide range of electron energies. The method is applied here to the interaction by inelastic and superelastic collisions of electrons with a gas of molecules with only one excited vibrational level. While this is unphysical, it allows the method to be validated by checking for accuracy, energy conservation, maintenance of equilibrium and evolution of a Maxwellian electron spectrum. Full article

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

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11 pages, 3185 KiB

Open AccessArticle

TDCS Calculation for the Ionization of Nitrogen Molecule by Electron Impact

by Alpana Pandey and Ghanshyam Purohit

Atoms 2022, 10(2), 50; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020050 - 18 May 2022

Cited by 3 | Viewed by 2139

Abstract

Triple differential cross section (TDCS) results are reported for the electron impact ionization of nitrogen molecules. The TDCSs have been calculated in distorted wave Born formalism using orientation averaged molecular orbital (OAMO) approximation. The TDCS results are presented as average and weighted sum [...] Read more.

3 σ_{g}

1 π_{u}

2 σ_{u}

and the inner

2 σ_{g}

molecular orbital. The obtained theoretical TDCSs are compared with the available measurements. The results are analysed in terms of the positions and relative intensities of binary and recoil peaks. Within a first order model and for a complex molecule, a reasonable agreement is obtained with the experimental data in the binary peak region with certain discrepancies in position and magnitude in the recoil peak region. Full article

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

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