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Volume 11
Issue 6
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Atoms, Volume 11, Issue 6 (June 2023) – 15 articles

Cover Story (view full-size image): This paper proposes a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy.
The functionality of this new technique was explored through dynamic, detailed gas and Monte Carlo atom-trajectory simulations, and the results are presented and discussed.
These calculation results show that the new double-nozzle technique has many advantages compared with conventional techniques which are currently used for the high-resolution laser spectroscopic study of the heaviest elements. View this paper
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9 pages, 2260 KiB  
Communication
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 854
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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7 pages, 398 KiB  
Communication
Measurement of the Tensor-Analyzing Power Component T20 for Incoherent Negative Pion Photoproduction on a Deuteron
by Anna Kuzmenko, Vyacheslav Gauzshtein, Eed Darwish, Alexander Fix, Matvey Kuzin, Michael Levchuk, Alexey Loginov, Dmitriy Nikolenko, Igor Rachek, Yuriy Shestakov, Dmitriy Toporkov, Arseniy Yurchenko, Bogdan Vasilishin and Sergey Zevakov
Atoms 2023, 11(6), 99; https://doi.org/10.3390/atoms11060099 - 15 Jun 2023
Cited by 1 | Viewed by 805
Abstract
New results for the T20-component of the tensor-analyzing power of the incoherent negative pion photoproduction are presented. The experiment was performed for the electron beam energy of 800 MeV at the VEPP-3 storage ring in 2021. To extract the T20 [...] Read more.
New results for the T20-component of the tensor-analyzing power of the incoherent negative pion photoproduction are presented. The experiment was performed for the electron beam energy of 800 MeV at the VEPP-3 storage ring in 2021. To extract the T20-component, we used asymmetry with respect to the change in the sign of the tensor polarization of the deuteron target. Identification of the reaction events was carried out by the detection of two protons in coincidence. Experimental data were compared with the results of statistical simulation, considering the interaction between the NN and πN subsystems in the final state of the reaction. Full article
(This article belongs to the Section Nuclear Theory and Experiments)
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21 pages, 9092 KiB  
Review
Neutron Interferometer Experiments Studying Fundamental Features of Quantum Mechanics
by Armin Danner, Hartmut Lemmel, Richard Wagner, Stephan Sponar and Yuji Hasegawa
Atoms 2023, 11(6), 98; https://doi.org/10.3390/atoms11060098 - 15 Jun 2023
Cited by 2 | Viewed by 1212
Abstract
Quantum theory provides us with the best account of microscopic components of matter as well as of radiation. It was introduced in the twentieth century and has experienced a wide range of success. Although the theory’s probabilistic predictions of final experimental outcomes is [...] Read more.
Quantum theory provides us with the best account of microscopic components of matter as well as of radiation. It was introduced in the twentieth century and has experienced a wide range of success. Although the theory’s probabilistic predictions of final experimental outcomes is found to be correct with high precision, there is no general consensus regarding what is actually going on with a quantum system “en route”, or rather the perceivable intermediate behavior of a quantum system, e.g., the particle’s behavior in the double-slit experiment. Neutron interferometry using single silicon perfect crystals is established as a versatile tool to test fundamental phenomena in quantum mechanics, where an incident neutron beam is coherently split in two or three beam paths with macroscopic separation of several centimeters. Here, we present quantum optical experiments with these matter-wave interferometers, studying the effect of the quantum Cheshire Cat in some variants, the neutron’s presence in the paths of the interferometer as well as the direct test of a commutation relation. To reduce disturbances induced by the measurement, the interaction strength is lessened and so-called weak interactions are exploited by employing pre- and post-selection procedures. All results of the experiments confirm the predictions of quantum theory; the observed behaviors of the neutron between the pre- and post-selection in space and time emphasize striking and counter-intuitive aspects of quantum theory. Full article
(This article belongs to the Special Issue Advances in and Prospects for Matter Wave Interferometry)
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11 pages, 3248 KiB  
Article
Pulse Cycle Dependent Nondipole Effects in Above-Threshold Ionization
by Danish Furekh Dar and Stephan Fritzsche
Atoms 2023, 11(6), 97; https://doi.org/10.3390/atoms11060097 - 12 Jun 2023
Viewed by 1108
Abstract
In this study, we employ strong field approximation (SFA) to investigate the influence of the number of pulse cycles on above-threshold ionization within the framework of nondipole theory. The SFA enables the analysis of the ionization process under the dominance of the electric [...] Read more.
In this study, we employ strong field approximation (SFA) to investigate the influence of the number of pulse cycles on above-threshold ionization within the framework of nondipole theory. The SFA enables the analysis of the ionization process under the dominance of the electric field, compared to other factors such as the binding potential of an atom. Nondipole effects, including higher-order multipole fields, can significantly impact ionization dynamics. However, the interaction between nondipole effects and pulse cycles remains unclear. Therefore, we investigate the pulse cycle dependence of ionization and examine peak shifts in Kr and Ar atoms. Our findings have implications for comprehensively understanding the effects of electromagnetic fields on electron behavior. The insights gained from this study provide valuable guidance for future research in strong field ionization. Full article
(This article belongs to the Special Issue Recent Progress in Strong-Field Atomic and Molecular Physics)
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18 pages, 3729 KiB  
Article
Structure and Bonding Patterns in C5H4 Isomers: Pyramidane, Planar Tetracoordinate Carbon, and Spiro Molecules
by Sayon Satpati, Tarun Roy, Sandip Giri, Anakuthil Anoop, Venkatesan S. Thimmakondu and Subhas Ghosal
Atoms 2023, 11(6), 96; https://doi.org/10.3390/atoms11060096 - 10 Jun 2023
Cited by 2 | Viewed by 2668
Abstract
We have theoretically investigated nine unusual isomers of the molecular formula C5H4 using coupled cluster (CC) and density functional theory (DFT) methods. These molecules possess non-classical structures consisting of two pyramidanes, three planar tetracoordinate carbon (ptC), and four [...] Read more.
We have theoretically investigated nine unusual isomers of the molecular formula C5H4 using coupled cluster (CC) and density functional theory (DFT) methods. These molecules possess non-classical structures consisting of two pyramidanes, three planar tetracoordinate carbon (ptC), and four spiro types of isomers. Both the pyramidanes (tetracyclo-[2.1.0.01,3.02,5]pentane; py-1 and tricyclo-[2.1.0.02,5]pentan-3-ylidene; py-2) are minima on the potential energy surface (PES) of C5H4. Among the three isomers containing ptC, (SP4)-spiro [2.2]pent-1-yne (ptC-2) is a minimum, whereas isomer, (SP4)-spiro [2.2]pent-1,4-diene (ptC-1) is a fourth-order saddle point, and (SP4)-sprio[2.2]pent-1,4-diylidene (ptC-3) is a transition state. The corresponding spiro isomers spiro[2.2]pent-1,4-diene (spiro-1), sprio[2.2]pent-1,4-diylidene (spiro-3) and spiro[2.2]pent-4-en-1-ylidene (spiro-4) are local minima, except spiro[2.2]pent-1-yne (spiro-2), which is a second-order saddle point. All relative energies are calculated with respect to the global minimum (pent-1,3-diyne; 1) at the CCSD(T)/cc-pVTZ level of theory. Quantum chemical calculations have been performed to analyze the bonding and topological configurations for all these nine isomers at the B3LYP/6-311+G(d,p) level of theory for a better understanding of their corresponding electronic structures. ptC-2 was found to be thermodynamically more stable than its corresponding spiro counterpart (spiro-2) and possesses a high dipole moment (μ = 4.64 D). The stability of the ptC structures with their higher spin states has been discussed. Full article
(This article belongs to the Special Issue Planar Tetracoordinate Carbon—Fifty Years and Beyond)
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12 pages, 1157 KiB  
Article
Quasi-Static Lineshape Theory for Rydberg Excitations in High-Density Media
by Trevor Scheuing and Jesús Pérez-Ríos
Atoms 2023, 11(6), 95; https://doi.org/10.3390/atoms11060095 - 10 Jun 2023
Viewed by 1038
Abstract
This work presents a theoretical approach for lineshapes of Rydberg excitations in high-density media. In particular, we introduce the quasi-static lineshape theory, leading to a methodic and general approach, and its validity is studied. Next, using 84Sr as a prototypical scenario, we [...] Read more.
This work presents a theoretical approach for lineshapes of Rydberg excitations in high-density media. In particular, we introduce the quasi-static lineshape theory, leading to a methodic and general approach, and its validity is studied. Next, using 84Sr as a prototypical scenario, we discuss the role of the thermal atoms and core–perturber interactions, generally disregarded in Rydberg physics. Finally, we present a characterization of the role of Rydberg–core perturber interactions based on the density and principal quantum number that, beyond affecting the lineshape, could potentially apply to chemi-ionization reactions responsible for the decay of Rydberg atoms in high-density media. Full article
(This article belongs to the Section Cold Atoms, Quantum Gases and Bose-Einstein Condensation)
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14 pages, 5827 KiB  
Article
Improved Line Intensity Analysis of Neutral Helium by Incorporating the Reabsorption Processes in a Helium Collisional-Radiative Model
by Keren Lin, Motoshi Goto and Hiroshi Akatsuka
Atoms 2023, 11(6), 94; https://doi.org/10.3390/atoms11060094 - 08 Jun 2023
Cited by 1 | Viewed by 1046
Abstract
In this study, eight emission lines in the visible wavelength range of neutral helium were used to diagnose the electron density and temperature of the Large Helical Device (LHD) helium plasma instead of the conventional three-line method. The collisional-radiative (CR) model for low-pressure [...] Read more.
In this study, eight emission lines in the visible wavelength range of neutral helium were used to diagnose the electron density and temperature of the Large Helical Device (LHD) helium plasma instead of the conventional three-line method. The collisional-radiative (CR) model for low-pressure helium plasma was revised to include the optical escape factors for spontaneous transition from the n1P states to the ground state so that the influence of the absorption effect under optically thick conditions could be considered. The developed algorithm was based on fitting the number densities of eight excited states obtained using optical emission spectroscopy (OES). The electron density, electron temperature, ground-state density, and optical escape factors were selected as the fitting parameters. The objective function was set as the summation of the residual errors between the number densities measured in the experiment and those calculated using the revised model. A regularization term was introduced for the optical escape factor and optimized through bias and variance analyses. The results show that the agreement between the number density calculated by the algorithm and its counterpart measured in the experiment was generally improved compared to the method using three lines. Full article
(This article belongs to the Special Issue Plasma Spectroscopy and Plasma Diagnostics: From Classical to Sophisticated Methods)
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3 pages, 5769 KiB  
Editorial
Editorial of the Special Issue “General Relativistic Atomic Structure Program—GRASP”
by Jacek Bieroń, Charlotte Froese Fischer and Per Jönsson
Atoms 2023, 11(6), 93; https://doi.org/10.3390/atoms11060093 - 06 Jun 2023
Cited by 2 | Viewed by 1191
Abstract
The year 2022 marked the 10th anniversary not only of the ATOMS journal but also of the international collaboration on Computational Atomic Structure [...] Full article
(This article belongs to the Special Issue The General Relativistic Atomic Structure Package—GRASP)
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24 pages, 6178 KiB  
Article
Modification of Vibrational Parameters of a CO2 Molecule by a Laser Field: Impact on Tunnel Ionization
by Aleksei S. Kornev and Vladislav E. Chernov
Atoms 2023, 11(6), 92; https://doi.org/10.3390/atoms11060092 - 05 Jun 2023
Viewed by 1068
Abstract
In this paper, we theoretically study the laser-induced modification of the vibrational parameters of a carbon dioxide molecule regarding its tunnel ionization. Our study predicts a 5% increase in the ionization rate in anti-Stokes channels that corresponds to pumping the Σu mode [...] Read more.
In this paper, we theoretically study the laser-induced modification of the vibrational parameters of a carbon dioxide molecule regarding its tunnel ionization. Our study predicts a 5% increase in the ionization rate in anti-Stokes channels that corresponds to pumping the Σu mode up to vai=10. The molecule is imparted with an additional energy from the pre-pumped vibrational states, which is absorbed during ionization. As a result, the tunneling rate increases. This amplification of tunnel ionization of the CO2 gas target can potentially be used for the laser separation of carbon isotopes. Full article
(This article belongs to the Special Issue Recent Progress in Strong-Field Atomic and Molecular Physics)
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12 pages, 1042 KiB  
Article
High-Order Above-Threshold Ionization Using a Bi-Elliptic Orthogonal Two-Color Laser Field with Optimal Field Parameters
by Abdulah S. Jašarević, Elvedin Hasović and Dejan B. Milošević
Atoms 2023, 11(6), 91; https://doi.org/10.3390/atoms11060091 - 05 Jun 2023
Viewed by 1072
Abstract
In the present paper, we study the high-order above-threshold ionization of noble-gas atoms using a bi-elliptic orthogonal two-color (BEOTC) field. We give an overview of the SFA theory and calculate the differential ionization rate for various values of the laser field parameters. We [...] Read more.
In the present paper, we study the high-order above-threshold ionization of noble-gas atoms using a bi-elliptic orthogonal two-color (BEOTC) field. We give an overview of the SFA theory and calculate the differential ionization rate for various values of the laser field parameters. We show that the ionization rate strongly depends on the ellipticity and the relative phase between two field components. Using numerical optimization, we find the values of ellipticity and relative phase that maximize the ionization rate at energies close to the cutoff energy. To explain the obtained results, we present, to the best of our knowledge, for the first time the quantum-orbit analysis in the BEOTC field. We find and classify the saddle-point (SP) solutions and study their contributions to the total ionization rate. We analyze quantum orbits and corresponding velocities to explain the contribution of relevant SP solutions. Full article
(This article belongs to the Special Issue Recent Progress in Strong-Field Atomic and Molecular Physics)
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6 pages, 1490 KiB  
Opinion
The Spin-Orbit Interaction: A Small Force with Large Implications
by Steven T. Manson
Atoms 2023, 11(6), 90; https://doi.org/10.3390/atoms11060090 - 02 Jun 2023
Viewed by 1001
Abstract
The spin-orbit interaction is quite small compared to electrostatic forces in atoms. Nevertheless, this small interaction can have large consequences. Several examples of the importance of the spin-orbit force in atomic photoionization are presented and explained. Full article
(This article belongs to the Special Issue Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules, and Clusters)
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13 pages, 7522 KiB  
Article
Signatures of Quantum Chaos of Rydberg-Dressed Bosons in a Triple-Well Potential
by Tianyi Yan, Matthew Collins, Rejish Nath and Weibin Li
Atoms 2023, 11(6), 89; https://doi.org/10.3390/atoms11060089 - 31 May 2023
Cited by 1 | Viewed by 1179
Abstract
We studied signatures of quantum chaos in dynamics of Rydberg-dressed bosonic atoms held in a one-dimensional triple-well potential. Long-range nearest-neighbor and next-nearest-neighbor interactions, induced by laser dressing atoms to strongly interacting Rydberg states, drastically affect mean-field and quantum many-body dynamics. By analyzing the [...] Read more.
We studied signatures of quantum chaos in dynamics of Rydberg-dressed bosonic atoms held in a one-dimensional triple-well potential. Long-range nearest-neighbor and next-nearest-neighbor interactions, induced by laser dressing atoms to strongly interacting Rydberg states, drastically affect mean-field and quantum many-body dynamics. By analyzing the mean-field dynamics, classical chaos regions with positive and large Lyapunov exponents were identified as a function of the potential well tilting and dressed interactions. In the quantum regime, it was found that level statistics of the eigen-energies gain a Wigner–Dyson distribution when the Lyapunov exponents are large, giving rise to signatures of strong quantum chaos. We found that both the time-averaged entanglement entropy and survival probability of the initial state have distinctively large values in the quantum chaos regime. We further showed that population variances could be used as an indicator of the emergence of quantum chaos. This might provide a way to directly probe quantum chaotic dynamics through analyzing population dynamics in individual potential wells. Full article
(This article belongs to the Special Issue Cold and Rydberg Atoms for Quantum Technologies)
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22 pages, 11184 KiB  
Article
Proposal of a New Double-Nozzle Technique for In-Gas-Jet Laser Resonance Ionization Spectroscopy
by Victor Varentsov
Atoms 2023, 11(6), 88; https://doi.org/10.3390/atoms11060088 - 28 May 2023
Cited by 1 | Viewed by 1173
Abstract
This paper proposes a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy. We explored the functionality of this new technique through detailed gas dynamic and Monte Carlo atom-trajectory simulations, in which results are presented and discussed. The results of similar computer simulations [...] Read more.
This paper proposes a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy. We explored the functionality of this new technique through detailed gas dynamic and Monte Carlo atom-trajectory simulations, in which results are presented and discussed. The results of similar computer simulations for JetRIS setup (as a typical representative of the conventional in-gas-jet technique nowadays) are also presented and discussed. The direct comparison of calculation results for the proposed new technique with the conventional one shows that the double-nozzle technique has many advantages compared with the one used in the JetRIS setup at GSI for future high-resolution laser spectroscopic study of heaviest elements. To fully implement the proposed new technique in all existing (or under construction) setups for in-gas-jet laser resonance ionization spectroscopy, it will be enough to replace the used supersonic nozzle with the miniature double-nozzle device described in the paper. Full article
(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)
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22 pages, 433 KiB  
Article
Transitional Strength under Plasma: Precise Estimations of Astrophysically Relevant Electromagnetic Transitions of Ar7+, Kr7+, Xe7+, and Rn7+ under Plasma Atmosphere
by Swapan Biswas, Anal Bhowmik, Arghya Das, Radha Raman Pal and Sonjoy Majumder
Atoms 2023, 11(6), 87; https://doi.org/10.3390/atoms11060087 - 25 May 2023
Viewed by 979
Abstract
The growing interest in atomic structures of moderately stripped alkali-like ions in the diagnostic study and modeling of astrophysical and laboratory plasma makes an accurate many-body study of atomic properties inevitable. This work presents transition line parameters in the absence or presence of [...] Read more.
The growing interest in atomic structures of moderately stripped alkali-like ions in the diagnostic study and modeling of astrophysical and laboratory plasma makes an accurate many-body study of atomic properties inevitable. This work presents transition line parameters in the absence or presence of plasma atmosphere for astrophysically important candidates Ar7+, Kr7+, Xe7+, and Rn7+. We employ relativistic coupled-cluster (RCC) theory, a well-known correlation exhaustive method. In the case of a plasma environment, we use the Debye Model. Our calculations agree with experiments available in the literature for ionization potentials, transition strengths of allowed and forbidden selections, and lifetimes of several low-lying states. The unit ratios of length and velocity forms of transition matrix elements are the critical estimation of the accuracy of the transition data presented here, especially for a few presented for the first time in the literature. We do compare our findings with the available recent theoretical results. Our reported data can be helpful to the astronomer in estimating the density of the plasma environment around the astronomical objects or in the discovery of observational spectra corrected by that environment. The present results should be advantageous in the modeling and diagnostics laboratory plasma, whereas the calculated ionization potential depression parameters reveal important characteristics of atomic structure. Full article
(This article belongs to the Special Issue Photon and Particle Impact Spectroscopy and Dynamics of Atoms, Molecules, and Clusters)
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30 pages, 2791 KiB  
Article
Carbon Elastic and Inelastic Stopping-Power Components for Heavy Ions at Bohr and Higher Velocities
by Roman N. Sagaidak
Atoms 2023, 11(6), 86; https://doi.org/10.3390/atoms11060086 - 24 May 2023
Viewed by 820
Abstract
Carbon stopping power (SP) data for heavy ions (HIs), obtained around Bohr velocities, revealed remarkably lower values than those predicted using the SRIM/TRIM calculations/simulations. An attempt was made to extract the elastic (collisional) and inelastic (electronic) components from the available SP data obtained [...] Read more.
Carbon stopping power (SP) data for heavy ions (HIs), obtained around Bohr velocities, revealed remarkably lower values than those predicted using the SRIM/TRIM calculations/simulations. An attempt was made to extract the elastic (collisional) and inelastic (electronic) components from the available SP data obtained in experiments. A problem is that essentially, total SP is measured in experiments, whereas electronic SP values, usually presented as the results, are derived via the subtraction of the calculated collisional component from the measured values. At high HI reduced velocities (V/v0)/ZHI2/3≳0.3 (V and v0 are HI and Bohr velocities, respectively, and ZHI is the HI atomic number), the collisional component can be neglected, whereas at Bohr velocities it becomes comparable to the electronic one. These circumstances were used to compare the experimental SP data with the SRIM/TRIM calculations/simulations and to empirically obtain corrections to the collisional and inelastic SP components. Full article
(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)
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