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Atoms, Volume 11, Issue 12 (December 2023) – 10 articles

Cover Story (view full-size image): The interaction of strong laser fields with atoms and its application to generate high harmonics in gases has been extensively studied recently. The generated harmonics can be used for time-resolved spectroscopy to study fast physical and chemical processes; they can be utilized to seed X-ray and free electron lasers to improve their coherence and beam quality, and harmonic beams can be used for the next-generation EUV lithography. The pulses of the driver laser with a 0.8 µm wavelength and 40 fs ultrashort pulse duration were focused to generate harmonics in a long gas medium, which gave us an opportunity to exploit the nonlinear propagation effects in such a configuration. An intense harmonic source around 13.5 nm was successfully realized with broad spectral tunability. Numerical simulations aid us in understanding the observations. View this paper
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23 pages, 6236 KiB  
Review
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 1 | Viewed by 1488
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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16 pages, 3558 KiB  
Article
Reactions of CH2OO, CH3CHOO, and (CH3)2COO with Methane through the Formation of Intermediate Complex
by Yuri A. Dyakov, Sergey O. Adamson, Gennady V. Golubkov, Igor I. Morozov, Danil R. Nigmatullin, Oleg A. Olkhov, Pao K. Wang and Maxim G. Golubkov
Atoms 2023, 11(12), 157; https://doi.org/10.3390/atoms11120157 - 14 Dec 2023
Viewed by 1262
Abstract
Criegee intermediates, which are the products of the ozonolysis of alkenes, play a key role in many chemical and physical processes in the atmosphere. Their reactions with other atmospheric compounds are responsible for the formation of hydroxyl, methyl, hydrogen radicals, nitric and sulfuric [...] Read more.
Criegee intermediates, which are the products of the ozonolysis of alkenes, play a key role in many chemical and physical processes in the atmosphere. Their reactions with other atmospheric compounds are responsible for the formation of hydroxyl, methyl, hydrogen radicals, nitric and sulfuric acids, and others. Methane is an active greenhouse gas whose concentration has increased rapidly in the last several decades. In this work, we consider the interaction between these two important atmospheric compounds. We choose the three simple Criegee intermediate (CI) molecules: formaldehyde oxide (CH2OO), acetaldehyde oxide (CH3CHOO), and acetone oxide ((CH3)2COO). Some reactions between methane and these Cis have been studied earlier as possible pathways for deactivating methane as well as a source of methanol formation due to molecular collisions in the atmosphere. In the present study, we extend the consideration to the case when an intermediate energetically stable complex is formed after collision. We found that this complex could easily decompose to form an OH radical and another unstable fragment, which can quickly dissociate into CH3 radicals, atomic hydrogen, acetone, acetaldehyde, propaldehyde, methyl alcohol, water, and others, depending on the type of CI being reacted with. These compounds can actively interact with other atmospheric components and change their physical and chemical properties. In addition, CI with a methyl substituent is shown to have increased energy in transition states and minima, resulting in slower reaction rates. Full article
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5 pages, 213 KiB  
Editorial
Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules and Clusters
by Himadri S. Chakraborty and Hari R. Varma
Atoms 2023, 11(12), 156; https://doi.org/10.3390/atoms11120156 - 12 Dec 2023
Viewed by 1171
Abstract
Atomic, molecular, and optical (AMO) physics is a vastly important sub-discipline [...] Full article
40 pages, 3865 KiB  
Article
On Rayleigh–Taylor Dynamics
by Abdul Hasib Rahimyar, Des Hill, James Glimm and Snezhana Abarzhi
Atoms 2023, 11(12), 155; https://doi.org/10.3390/atoms11120155 - 08 Dec 2023
Viewed by 1229
Abstract
In this work, we theoretically and numerically investigate Rayleigh–Taylor dynamics with constant acceleration. On the side of theory, we employ the group theory approach to directly link the governing equations to the momentum model, and to precisely derive the buoyancy and drag parameters [...] Read more.
In this work, we theoretically and numerically investigate Rayleigh–Taylor dynamics with constant acceleration. On the side of theory, we employ the group theory approach to directly link the governing equations to the momentum model, and to precisely derive the buoyancy and drag parameters for the bubble and spike in the linear, nonlinear, and mixing regimes. On the side of simulations, we analyze numerical data on Rayleigh–Taylor mixing by applying independent self-similar processes associated with the growth of the bubble amplitude and with the bubble merger. Based on the obtained results, we reveal the constituents governing Rayleigh–Taylor dynamics in the linear, nonlinear, and mixing regimes. We outline the implications of our considerations for experiments in plasmas, including inertial confinement fusion. Full article
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10 pages, 764 KiB  
Communication
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 - 07 Dec 2023
Viewed by 1211
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 ∼1019 W/cm2, 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, 3434 KiB  
Article
DFT Investigation on the Complexation of β-Cyclodextrin and Hydroxypropyl-β-Cyclodextrin as Recognition Hosts with Trichloroethylene
by Ahlem Benmerabet, Abdelaziz Bouhadiba, Youghourta Belhocine, Seyfeddine Rahali, Najoua Sbei, Mahamadou Seydou, Ihsene Boucheriha, Imane Omeiri and Ibtissem Meriem Assaba
Atoms 2023, 11(12), 153; https://doi.org/10.3390/atoms11120153 - 07 Dec 2023
Cited by 1 | Viewed by 1359
Abstract
In this investigation, the potential use of native β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) as encapsulating agents for trichloroethylene (TCE) was assessed. Various quantum chemical parameters, including HOMO, LUMO, and HOMO–LUMO gap, were calculated. The docking process was examined by considering different initial configurations. [...] Read more.
In this investigation, the potential use of native β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) as encapsulating agents for trichloroethylene (TCE) was assessed. Various quantum chemical parameters, including HOMO, LUMO, and HOMO–LUMO gap, were calculated. The docking process was examined by considering different initial configurations. The complexation energies were calculated at the molecular level using DFT/BLYP-D4 and PBEh-3c calculations to gain insight into TCE encapsulation within the β-CD and HP-β-CD cavities. We used the independent gradient model (IGM) and extended charge decomposition analysis (ECDA) approaches to examine non-covalent interactions and charge transfer within TCE@β-CD and TCE@HP-β-CD complexes. The calculated thermodynamic data and complexation energies exhibited negative values for both considered complexes, indicating a favorable complexation process. Weak Van der Waals intermolecular interactions were the main driving forces in stabilizing the formed complex. Additionally, Monte Carlo simulations were conducted for a better understanding of the inclusion process. Our results provide evidence for the use of β-CD and HP-β-CD as suitable macrocyclic hosts for complexing trichloroethylene. Full article
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23 pages, 3642 KiB  
Article
Photoionization Study of Neutral Chlorine Atom
by Momar Talla Gning and Ibrahima Sakho
Atoms 2023, 11(12), 152; https://doi.org/10.3390/atoms11120152 - 06 Dec 2023
Viewed by 1159
Abstract
Photoionization of neutral chlorine atom is investigated in this paper in the framework of the screening constant per unit nuclear charge (SCUNC) method. Resonance energies, quantum defects and effective charges of the 3s23p4 (3P2,1,0) [...] Read more.
Photoionization of neutral chlorine atom is investigated in this paper in the framework of the screening constant per unit nuclear charge (SCUNC) method. Resonance energies, quantum defects and effective charges of the 3s23p4 (3P2,1,0)ns and 3s23p4 (3P1,0)nd Rydberg series originating from both the 2P03/2 ground state and the 2P01/2 excited state of chlorine atom are reported. The present study believed to be the first theoretical investigation is compared with the recent experimental measurements (Yang et al., Astrophys. J. 810:132, 2015). Good agreements are obtained between theory and experiments. New SCUNC data are tabulated as useful references for interpreting astrophysical spectra from neutral atomic chlorine. Full article
(This article belongs to the Special Issue Photoionization of Atoms)
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11 pages, 881 KiB  
Article
Differential Studies of Argon Particle and Antiparticle Interactions: Present Status and Future Possibilities
by Robert D. DuBois and Károly Tőkési
Atoms 2023, 11(12), 151; https://doi.org/10.3390/atoms11120151 - 01 Dec 2023
Viewed by 1115
Abstract
Although the comparison of fully differential ionization data for particle and antiparticle impact provides the ultimate tests of theoretical models, only very low antiparticle beam intensities are available. Hence, few experiments of this type have been performed. Therefore, available experimentally obtained single and [...] Read more.
Although the comparison of fully differential ionization data for particle and antiparticle impact provides the ultimate tests of theoretical models, only very low antiparticle beam intensities are available. Hence, few experiments of this type have been performed. Therefore, available experimentally obtained single and double differential cross-sections, which are much easier to obtain, are compared in order to demonstrate differences when only the projectile mass or charge (+1 or −1) is changed. Included in the comparison are cross-sections calculated for positron and electron impact using a three-particle classical trajectory Monte Carlo method. The calculated cross-sections provide independent information about the ejected electron and the scattered projectile contributions, plus information about the impact parameters, all as functions of the collision kinematics. From these comparisons, suggestions as to where future investigations are both feasible and useful are provided. Full article
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10 pages, 3617 KiB  
Article
Spectral Shift and Split of Harmonic Lines in Propagation Affected High Harmonic Generation in a Long-Interaction Gas Tube
by Jozsef Seres, Enikoe Seres, Carles Serrat, Thanh-Hung Dinh, Noboru Hasegawa, Masahiko Ishino, Masaharu Nishikino and Shinichi Namba
Atoms 2023, 11(12), 150; https://doi.org/10.3390/atoms11120150 - 01 Dec 2023
Viewed by 1323
Abstract
While generating high harmonics in long media of helium gas, at certain laser intensities and chirp, the spectral shift and split of the harmonic lines were experimentally observed, sometimes exceeding one harmonic order. Beyond reporting these results, numerical simulations were performed to understand [...] Read more.
While generating high harmonics in long media of helium gas, at certain laser intensities and chirp, the spectral shift and split of the harmonic lines were experimentally observed, sometimes exceeding one harmonic order. Beyond reporting these results, numerical simulations were performed to understand the phenomenon. A 3D propagation model was solved under the strong field approximation. According to the simulations, the distortion of the laser beam profile during propagation and the consequently accused change in the conditions of phase matching are responsible for the observations. The observed phenomena can be an excellent tool to produce tunable narrow band harmonic sources covering a broad range around 13.5 nm for spectroscopy and for seeding X-ray lasers, and to understand non-desired detuning of the seed wavelength. Full article
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16 pages, 700 KiB  
Article
A Critical Analysis of Target Ionization and Projectile Electron Loss in Neutral– and Ion–Atom Collisions
by Michele A. Quinto, Nicolás J. Esponda, Maria F. Rojas, Roberto D. Rivarola and Juan M. Monti
Atoms 2023, 11(12), 149; https://doi.org/10.3390/atoms11120149 - 21 Nov 2023
Viewed by 1173
Abstract
Electron removal (target ionization and/or projectile electron loss) in neutral–atom collisions is theoretically studied for the impact of H0, He0 and He+ beams on noble gases (He, Ne and Ar). These reactions are investigated theoretically within the Continuum Distorted [...] Read more.
Electron removal (target ionization and/or projectile electron loss) in neutral–atom collisions is theoretically studied for the impact of H0, He0 and He+ beams on noble gases (He, Ne and Ar). These reactions are investigated theoretically within the Continuum Distorted Wave-Eikonal Initial State model. New features have been included in the theoretical model: (i) a scaled projectile charge depending on its velocity and charge, (ii) a dynamic projectile-effective-charge depending on the momentum transfer, and (iii) a dynamic target-effective-charge depending on the kinematics of the emitted electron. The energy and angular spectra of emitted electrons from the target and from the projectile are calculated and compared with the available experimental data. Also, the influence of each one of the corrections on the resulting spectra will be studied. Full article
(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)
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