Atoms

14 pages, 6252 KiB

Open AccessArticle

Simultaneous Observation of Tungsten Spectra of W⁰ to W⁴⁶⁺ Ions in Visible, VUV and EUV Wavelength Ranges in the Large Helical Device

by Tetsutarou Oishi, Shigeru Morita, Daiji Kato, Izumi Murakami, Hiroyuki A. Sakaue, Yasuko Kawamoto, Tomoko Kawate and Motoshi Goto

Atoms 2021, 9(3), 69; https://doi.org/10.3390/atoms9030069 - 17 Sep 2021

Cited by 8 | Viewed by 2670

Abstract

Spectroscopic studies for emissions released from tungsten ions have been conducted in the Large Helical Device (LHD) for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. Tungsten ions are [...] Read more.

Spectroscopic studies for emissions released from tungsten ions have been conducted in the Large Helical Device (LHD) for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. Tungsten ions are distributed in the LHD plasma by injecting a pellet consisting of a small piece of tungsten metal wire enclosed by a carbon tube. Line emissions from W⁰, W⁵⁺, W⁶⁺, W²⁴⁺–W²⁸⁺, W³⁷⁺, W³⁸⁺, and W⁴¹⁺–W⁴⁶⁺ are observed simultaneously in the visible (3200–3550 Å), vacuum ultraviolet (250–1050 Å), and extreme ultraviolet (5–300 Å) wavelength ranges and the wavelengths are summarized. Temporal evolutions of line emissions from these charge states are compared for comprehensive understanding of tungsten impurity behavior in a single discharge. The charge distribution of tungsten ions strongly depends on the electron temperature. Measurements of emissions from W¹⁰⁺ to W²⁰⁺ are still insufficient, which is addressed as a future task. Full article

(This article belongs to the Special Issue Atomic and Molecular Spectra in Magnetically Confined Torus Plasmas)

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13 pages, 3404 KiB

Open AccessArticle

Three-Photon Ionization with One-Photon Resonance between Excited Levels

by Aleksandr Gomonai, Eugene Remeta and Anna Gomonai

Atoms 2021, 9(3), 68; https://doi.org/10.3390/atoms9030068 - 17 Sep 2021

Viewed by 1763

Abstract

Within the framework of a three-level model, the process of three-photon ionization with one-photon resonance between two excited levels (with the lower one being initially unpopulated) is considered using the density matrix method. It is shown that such resonance can result in the [...] Read more.

Within the framework of a three-level model, the process of three-photon ionization with one-photon resonance between two excited levels (with the lower one being initially unpopulated) is considered using the density matrix method. It is shown that such resonance can result in the appearance of a maximum in the three-photon ionization spectrum when detuning between the resonance wavenumber and the wavenumber of the transition responsible for the lower excited level being populated exceeds the laser radiation linewidth by more than three orders of magnitude. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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10 pages, 686 KiB

Open AccessArticle

Simultaneous Excitation of Helium by Means of an Electron and a Photon: A Joined Experimental and Theoretical Study

by Imane Ajana, Driss Nehari, Driss Khalil, Abdelmalek Taoutioui, Hicham Agueny and Abdelkader Makhoute

Atoms 2021, 9(3), 67; https://doi.org/10.3390/atoms9030067 - 17 Sep 2021

Cited by 1 | Viewed by 1730

Abstract

We report on a joined experimental and theoretical study of differential cross-sections resulting from inelastic scattering of a monoenergetic electron by helium atoms in the presence of an intense carbon dioxide laser. In particular, we measured the signals of the scattered electrons during [...] Read more.

We report on a joined experimental and theoretical study of differential cross-sections resulting from inelastic scattering of a monoenergetic electron by helium atoms in the presence of an intense carbon dioxide laser. In particular, we measured the signals of the scattered electrons during the simultaneous electron–photon excitation of He 2

^{1}

P state for the first three microseconds of the laser pulse. The signals were measured for an incident electron energy of 45 eV and showed a structure that emerged at small scattering angles. The latter was found to be sensitive to the nature of the transferred photons, as well as the intensity of the laser field. The experimental findings were supported by quantum calculations based on the second-order Born approximation in which the correlated electron–electron interactions were taken into account. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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8 pages, 1738 KiB

Open AccessEditor’s ChoiceArticle

Revealing the Target Electronic Structure with Under-Threshold RABBITT

by Anatoli Kheifets

Atoms 2021, 9(3), 66; https://doi.org/10.3390/atoms9030066 - 13 Sep 2021

Cited by 13 | Viewed by 2376

Abstract

The process of reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) reveals the target atom electronic structure when one of the transitions proceeds from below the ionization threshold. Such an under-threshold RABBITT resonates with the target bound states and thus maps [...] Read more.

The process of reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) reveals the target atom electronic structure when one of the transitions proceeds from below the ionization threshold. Such an under-threshold RABBITT resonates with the target bound states and thus maps faithfully the discrete energy levels and the corresponding oscillator strengths. We demonstrate this sensitivity by considering the Ne atom driven by the combination of the XUV and IR pulses at the fundamental laser frequency in the 800 and 1000 nm ranges. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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15 pages, 84547 KiB

Open AccessArticle

In Silico Studies on Selected Neutral Molecules, CGa₂Ge₂, CAlGaGe₂, and CSiGa₂Ge Containing Planar Tetracoordinate Carbon

by Prasenjit Das and Pratim Kumar Chattaraj

Atoms 2021, 9(3), 65; https://doi.org/10.3390/atoms9030065 - 10 Sep 2021

Cited by 16 | Viewed by 3474

Abstract

Density functional theory (DFT) was used to study the structure, stability, and bonding in some selected neutral pentaatomic systems, viz., CGa₂Ge₂, CAlGaGe₂, and CSiGa₂Ge containing planar tetracoordinate carbon. The systems are kinetically stable, as [...] Read more.

Density functional theory (DFT) was used to study the structure, stability, and bonding in some selected neutral pentaatomic systems, viz., CGa₂Ge₂, CAlGaGe₂, and CSiGa₂Ge containing planar tetracoordinate carbon. The systems are kinetically stable, as predicted from the ab initio molecular dynamics simulations. The natural bond orbital (NBO) analysis showed that strong electron donation occurs to the central planar carbon atom by the peripheral atoms in all the studied systems. From the nucleus independent chemical shift (NICS) analysis, it is shown that the systems possess both σ- and π- aromaticity. The presence of 18 valence electrons in these systems, in their neutral form, appears to be important for their stability with planar geometries rather than tetrahedral structures. The nature of bonding is understood through the adaptive natural density partitioning analysis (AdNDP), quantum theory of atoms in molecules (QTAIM) analysis, and also via Wiberg bond index (WBI) and electron localization function (ELF). Full article

(This article belongs to the Special Issue Planar Tetracoordinate Carbon—Fifty Years and Beyond)

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11 pages, 365 KiB

Open AccessArticle

Vibrational Excitation Cross-Section by Positron Impact: A Wave-Packet Dynamics Study

by Luis A. Poveda, Marcio T. do N. Varella and José R. Mohallem

Atoms 2021, 9(3), 64; https://doi.org/10.3390/atoms9030064 - 9 Sep 2021

Cited by 4 | Viewed by 1661

Abstract

The vibrational excitation cross-section of a diatomic molecule by positron impact is obtained using wave-packet propagation techniques. The dynamics study was carried on a two-dimensional potential energy surface, which couples a hydrogenlike harmonic oscillator to a positron via a spherically symmetric correlation polarization [...] Read more.

The vibrational excitation cross-section of a diatomic molecule by positron impact is obtained using wave-packet propagation techniques. The dynamics study was carried on a two-dimensional potential energy surface, which couples a hydrogenlike harmonic oscillator to a positron via a spherically symmetric correlation polarization potential. The cross-section for the excitation of the first vibrational mode is in good agreement with previous reports. Our model suggests that a positron couples to the target vibration by responding instantly to an interaction potential, which depends on the target vibrational coordinate. Full article

(This article belongs to the Special Issue Electron Scattering in Gases –from Cross Sections to Plasma Modeling)

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10 pages, 2047 KiB

Open AccessArticle

Emission Lines in 290–360 nm of Highly Charged Tungsten Ions W²⁰⁺–W²⁹⁺

by Shota Era, Daiji Kato, Hiroyuki A. Sakaue, Toshiki Umezaki, Nobuyuki Nakamura and Izumi Murakami

Atoms 2021, 9(3), 63; https://doi.org/10.3390/atoms9030063 - 8 Sep 2021

Cited by 3 | Viewed by 2555

Abstract

Forbidden transitions in the near-UV and visible wavelength of highly charged tungsten (W) ions are potentially useful as novel tungsten diagnostics means of fusion plasmas. Emission lines in 290–360 nm from W

^{q +}

ions interacting with an electron beam of 540–1370 eV [...] Read more.

Forbidden transitions in the near-UV and visible wavelength of highly charged tungsten (W) ions are potentially useful as novel tungsten diagnostics means of fusion plasmas. Emission lines in 290–360 nm from W

^{q +}

ions interacting with an electron beam of 540–1370 eV are measured, using a compact electron-beam-ion-trap. The charge states of 64 lines are identified as W

^{20 +}

–W

^{29 +}

. A magnetic-dipole (M1) line of W

^{29 +}

between the excited states

(4 d^{8} 4 f) {[{(4 d_{5 / 2}^{- 2})}_{4} 4 f_{7 / 2}]}_{13 / 2} \to {[{(4 d_{5 / 2}^{- 2})}_{4} 4 f_{5 / 2}]}_{13 / 2}

is newly identified; the wavelength is determined as 351.03(10) nm in air. The theoretical wavelength calculated using the multiconfiguration Dirac–Hartree–Fock method is in a good agreement with the measurement. Full article

(This article belongs to the Special Issue Atomic and Molecular Spectra in Magnetically Confined Torus Plasmas)

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11 pages, 2406 KiB

Open AccessEditor’s ChoiceArticle

Cross Sections and Rate Coefficients for Vibrational Excitation of H₂O by Electron Impact

by Mehdi Ayouz, Alexandre Faure, Jonathan Tennyson, Maria Tudorovskaya and Viatcheslav Kokoouline

Atoms 2021, 9(3), 62; https://doi.org/10.3390/atoms9030062 - 6 Sep 2021

Cited by 8 | Viewed by 2522

Abstract

Cross-sections and thermally averaged rate coefficients for vibration (de-)excitation of a water molecule by electron impact are computed; one and two quanta excitations are considered for all three normal modes. The calculations use a theoretical approach that combines the normal mode approximation for [...] Read more.

Cross-sections and thermally averaged rate coefficients for vibration (de-)excitation of a water molecule by electron impact are computed; one and two quanta excitations are considered for all three normal modes. The calculations use a theoretical approach that combines the normal mode approximation for vibrational states of water, a vibrational frame transformation employed to evaluate the scattering matrix for vibrational transitions and the UK molecular R-matrix code. The interval of applicability of the rate coefficients is from 10 to 10,000 K. A comprehensive set of calculations is performed to assess uncertainty of the obtained data. The results should help in modelling non-LTE spectra of water in various astrophysical environments. Full article

(This article belongs to the Special Issue Electron Scattering in Gases –from Cross Sections to Plasma Modeling)

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14 pages, 725 KiB

Open AccessArticle

Benchmark Angle-Differential Cross-Section Ratios for Excitation of the 4p5s Configuration in Krypton

by Ahmad Sakaamini, Jean-Baptiste Faure, Murtadha A. Khakoo, Oleg I. Zatsarinny and Klaus Bartschat

Atoms 2021, 9(3), 61; https://doi.org/10.3390/atoms9030061 - 2 Sep 2021

Cited by 3 | Viewed by 3001

Abstract

Benchmark intensity ratio measurements of the energy loss lines of krypton for excitation of the

4 p^{6}^{1} S_{0}

→

4 p^{5} 5 s {[3 / 2]}_{2}

, [...] Read more.

Benchmark intensity ratio measurements of the energy loss lines of krypton for excitation of the

4 p^{6}^{1} S_{0}

→

4 p^{5} 5 s {[3 / 2]}_{2}

,

4 p^{5} 5 s {[3 / 2]}_{1}

,

4 p^{5} 5 s^{'} {[1 / 2]}_{0}

, and

4 p^{5} 5 s^{'} {[1 / 2]}_{1}

transitions are reported, these being the lowest electronic excitations for krypton. The importance of these ratios as stringent tests of theoretical electron scattering models for the noble gases is discussed, as well as the role of spin-exchange and direct processes regarding the angular dependence of these ratios. The experimental data are compared with predictions from fully-relativistic B-spline R-matrix (close-coupling) calculations. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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18 pages, 2110 KiB

Open AccessArticle

Evaluation of Fe XIV Intensity Ratio for Electron Density Diagnostics by Laboratory Measurements

by Nagaaki Kambara, Tomoko Kawate, Tetsutarou Oishi, Yasuko Kawamoto, Hiroyuki A. Sakaue, Daiji Kato, Nobuyuki Nakamura, Hirohisa Hara and Izumi Murakami

Atoms 2021, 9(3), 60; https://doi.org/10.3390/atoms9030060 - 30 Aug 2021

Cited by 1 | Viewed by 3017

Abstract

The intensity ratio of Fe XIV 264.765A/274.203A is useful to determine the electron density of solar corona, and the relationship between the electron density and the intensity ratio obtained from a model should be evaluated using laboratory plasmas to estimate the electron density [...] Read more.

The intensity ratio of Fe XIV 264.765A/274.203A is useful to determine the electron density of solar corona, and the relationship between the electron density and the intensity ratio obtained from a model should be evaluated using laboratory plasmas to estimate the electron density more precisely. We constructed a new collisional–radiative model (CR-model) for Fe XIV (an Al-like iron ion) by considering the processes of proton-impact excitation and electron-impact ionization to the excited states of a Mg-like iron ion. The atomic data used in the CR-model were calculated using the HULLAC atomic code. The model was evaluated based on laboratory experiments using a compact electron beam ion trap, called CoBIT, and the Large Helical Device (LHD). The measured Fe XIV 264.785 Å/274.203 Å line intensity ratio with CoBIT was 1.869 ± 0.036, and it agreed well with our CR-model results. Concurrently, the measured ratio using LHD was larger than the results of our CR-model and CHIANTI. The estimated electron densities using our CR-model agreed with those from CHIANTI within a factor of 1.6–2.4 in the range of

n_{e} \approx 10^{10 - 11} {cm}^{- 3}

. Further model development is needed to explain the ratio in a high-electron density region. Full article

(This article belongs to the Special Issue Atomic and Molecular Spectra in Magnetically Confined Torus Plasmas)

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47 pages, 4057 KiB

Open AccessArticle

Relativistic Study on the Scattering of e^± from Atoms and Ions of the Rn Isonuclear Series

by Mahmudul H. Khandker, A. K. Fazlul Haque, M. M. Haque, M. Masum Billah, Hiroshi Watabe and M. Alfaz Uddin

Atoms 2021, 9(3), 59; https://doi.org/10.3390/atoms9030059 - 27 Aug 2021

Cited by 9 | Viewed by 2416

Abstract

Calculations are presented for differential, integrated elastic, momentum transfer, viscosity, inelastic, total cross sections and spin polarization parameters S, T and U for electrons and positrons scattering from atoms and ions of radon isonuclear series in the energy range from 1 eV–1 MeV. [...] Read more.

Calculations are presented for differential, integrated elastic, momentum transfer, viscosity, inelastic, total cross sections and spin polarization parameters S, T and U for electrons and positrons scattering from atoms and ions of radon isonuclear series in the energy range from 1 eV–1 MeV. In addition, we analyze systematically the details of the critical minima in the elastic differential cross sections along with the positions of the corresponding maximum polarization points in the Sherman function for the aforesaid scattering systems. Coulomb glory is investigated across the ionic series. A short range complex optical potential, comprising static, polarization and exchange (for electron projectile) potentials, is used to describe the scattering from neutral atom. This potential is supplemented by the Coulomb potential for the same purpose for a charged atom. The Dirac partial wave analysis, employing the aforesaid potential, is carried out to calculate the aforesaid scattering observables. A comparison of our results with other theoretical findings shows a reasonable agreement over the studied energy range. Full article

(This article belongs to the Special Issue Electron Scattering in Gases –from Cross Sections to Plasma Modeling)

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11 pages, 2709 KiB

Open AccessArticle

Interferometry in an Atomic Fountain with Ytterbium Bose–Einstein Condensates

by Daniel Gochnauer, Tahiyat Rahman, Anna Wirth-Singh and Subhadeep Gupta

Atoms 2021, 9(3), 58; https://doi.org/10.3390/atoms9030058 - 25 Aug 2021

Cited by 7 | Viewed by 2990

Abstract

We present enabling experimental tools and atom interferometer implementations in a vertical “fountain” geometry with ytterbium Bose–Einstein condensates. To meet the unique challenge of the heavy, non-magnetic atom, we apply a shaped optical potential to balance against gravity following evaporative cooling and demonstrate [...] Read more.

We present enabling experimental tools and atom interferometer implementations in a vertical “fountain” geometry with ytterbium Bose–Einstein condensates. To meet the unique challenge of the heavy, non-magnetic atom, we apply a shaped optical potential to balance against gravity following evaporative cooling and demonstrate a double Mach–Zehnder interferometer suitable for applications such as gravity gradient measurements. Furthermore, we also investigate the use of a pulsed optical potential to act as a matter wave lens in the vertical direction during expansion of the Bose–Einstein condensate. This method is shown to be even more effective than the aforementioned shaped optical potential. The application of this method results in a reduction of velocity spread (or equivalently an increase in source brightness) of more than a factor of five, which we demonstrate using a two-pulse momentum-space Ramsey interferometer. The vertical geometry implementation of our diffraction beams ensures that the atomic center of mass maintains overlap with the pulsed atom optical elements, thus allowing extension of atom interferometer times beyond what is possible in a horizontal geometry. Our results thus provide useful tools for enhancing the precision of atom interferometry with ultracold ytterbium atoms. Full article

(This article belongs to the Special Issue Atomic Interferometry with Bose–Einstein Condensates)

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22 pages, 3583 KiB

Open AccessArticle

Constrained Molecular Dynamic Simulation of the Potential Mean Force of Lithium Bromide Ion Pairs in Acetonitrile

by Reinhardt Pinzón

Atoms 2021, 9(3), 57; https://doi.org/10.3390/atoms9030057 - 17 Aug 2021

Viewed by 2923

Abstract

Molecular dynamic simulations of Li⁺, and Br⁻ ions in acetonitrile were carried out. The simulated structural properties were compared to experimental data. The solvent potentials of Li⁺-Br⁻, Li⁺-Li⁺, and Br⁻-Br [...] Read more.

Molecular dynamic simulations of Li⁺, and Br⁻ ions in acetonitrile were carried out. The simulated structural properties were compared to experimental data. The solvent potentials of Li⁺-Br⁻, Li⁺-Li⁺, and Br⁻-Br⁻ were evaluated using constrained molecular dynamics (CMD) simulations, to determine the solvent contribution to the total force acting on the solute and estimate the liquid arrangements according to the potential of mean force (PMF) values. The PMF of friction kernels and the passage across the Li⁺-Br⁻ barrier was studied using the Grote–Hynes theory. The union-separation development happens in the polarization confining system. Full article

(This article belongs to the Section Quantum Chemistry, Computational Chemistry and Molecular Physics)

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15 pages, 4738 KiB

Open AccessArticle

Deep Minimum and a Vortex for Positronium Formation in Low-Energy Positron-Helium Collisions

by Albandari W. Alrowaily, Sandra J. Ward and Peter Van Reeth

Atoms 2021, 9(3), 56; https://doi.org/10.3390/atoms9030056 - 6 Aug 2021

Cited by 2 | Viewed by 2222

Abstract

We find a zero in the positronium formation scattering amplitude and a deep minimum in the logarithm of the corresponding differential cross section for positron–helium collisions for an energy just above the positronium formation threshold. Corresponding to the zero, there is a vortex [...] Read more.

We find a zero in the positronium formation scattering amplitude and a deep minimum in the logarithm of the corresponding differential cross section for positron–helium collisions for an energy just above the positronium formation threshold. Corresponding to the zero, there is a vortex in the extended velocity field that is associated with this amplitude when one treats both the magnitude of the momentum of the incident positron and the angle of the scattered positronium as independent variables. Using the complex Kohn variational method, we determine accurately two-channel K-matrices for positron–helium collisions in the Ore gap. We fit these K-matrices using both polynomials and the Watanabe and Greene’s multichannel effective range theory taking into account explicitly the polarization potential in the Ps-He⁺ channel. Using the fitted K-matrices we determine the extended velocity field and show that it rotates anticlockwise around the zero in the positronium formation scattering amplitude. We find that there is a valley in the logarithm of the positronium formation differential cross section that includes the deep minimum and also a minimum in the forward direction. Full article

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12 pages, 943 KiB

Open AccessArticle

Redistribution of the Rydberg State Population Induced by Continuous-Spectrum Radiation

by Anastasia S. Chervinskaya, Dmitrii L. Dorofeev and Boris A. Zon

Atoms 2021, 9(3), 55; https://doi.org/10.3390/atoms9030055 - 6 Aug 2021

Cited by 2 | Viewed by 2043

Abstract

We consider the redistribution of the Rydberg state population resulting from multistep cascade transitions induced by radiation with a continuous spectrum. The population distribution is analyzed within the space of quantum numbers n and l. The dynamics of the system are studied [...] Read more.

We consider the redistribution of the Rydberg state population resulting from multistep cascade transitions induced by radiation with a continuous spectrum. The population distribution is analyzed within the space of quantum numbers n and l. The dynamics of the system are studied using both the numerical solution of kinetic equations and the diffusion approximation based on the Fokker–Planck equation. The main path of the redistribution process is determined. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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22 pages, 7271 KiB

Open AccessArticle

Microwave Atom Chip Design

by William Miyahira, Andrew P. Rotunno, ShuangLi Du and Seth Aubin

Atoms 2021, 9(3), 54; https://doi.org/10.3390/atoms9030054 - 5 Aug 2021

Cited by 2 | Viewed by 2212

Abstract

We present a toolbox of microstrip building blocks for microwave atom chips geared towards trapped atom interferometry. Transverse trapping potentials based on the AC Zeeman (ACZ) effect can be formed from the combined microwave magnetic near fields of a pair or a triplet [...] Read more.

We present a toolbox of microstrip building blocks for microwave atom chips geared towards trapped atom interferometry. Transverse trapping potentials based on the AC Zeeman (ACZ) effect can be formed from the combined microwave magnetic near fields of a pair or a triplet of parallel microstrip transmission lines. Axial confinement can be provided by a microwave lattice (standing wave) along the microstrip traces. Microwave fields provide additional parameters for dynamically adjusting ACZ potentials: detuning of the applied frequency to select atomic transitions and local polarization controlled by the relative phase in multiple microwave currents. Multiple ACZ traps and potentials, operating at different frequencies, can be targeted to different spin states simultaneously, thus enabling spin-specific manipulation of atoms and spin-dependent trapped atom interferometry. Full article

(This article belongs to the Special Issue Atomic Interferometry with Bose–Einstein Condensates)

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3 pages, 2932 KiB

Open AccessObituary

A Tribute to Oleg Zatsarinny (1953–2021): His Life in Science

by Klaus Bartschat, Charlotte Froese Fischer and Alexei N. Grum-Grzhimailo

Atoms 2021, 9(3), 53; https://doi.org/10.3390/atoms9030053 - 5 Aug 2021

Cited by 3 | Viewed by 2329

Abstract

Oleg Ivanovich Zatsarinny (Figure 1) was born in the city of Uzhgorod, Ukraine, on 4 November 1953 [...] Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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19 pages, 3238 KiB

Open AccessEditor’s ChoiceArticle

Accurate Electron Drift Mobility Measurements in Moderately Dense Helium Gas at Several Temperatures

by Armando Francesco Borghesani

Atoms 2021, 9(3), 52; https://doi.org/10.3390/atoms9030052 - 4 Aug 2021

Cited by 9 | Viewed by 2366

Abstract

We report new accurate measurements of the drift mobility

μ

of quasifree electrons in moderately dense helium gas in the temperature range

26 K \leq T \leq 300 K

for densities lower than those at which states of electrons localized in bubbles appear. [...] Read more.

We report new accurate measurements of the drift mobility

μ

of quasifree electrons in moderately dense helium gas in the temperature range

26 K \leq T \leq 300 K

for densities lower than those at which states of electrons localized in bubbles appear. By heuristically including multiple-scattering effects into classical kinetic formulas, as previously done for neon and argon, an excellent description of the field E, density N, and temperature T dependence of

μ

is obtained. Moreover, the experimental evidence suggests that the strong decrease of the zero-field density-normalized mobility

μ_{0} N

with increasing N from the low up to intermediate density regime is mainly due to weak localization of electrons caused by the intrinsic disorder of the system, whereas the further decrease of

μ_{0} N

for even larger N is due to electron self-trapping in cavities. We suggest that a distinction between weakly localized and electron bubble states can be done by inspecting the behavior of

μ_{0} N

as a function of N at intermediate densities. Full article

(This article belongs to the Special Issue Electron Scattering in Gases –from Cross Sections to Plasma Modeling)

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25 pages, 5029 KiB

Open AccessArticle

High Sensitivity Multi-Axes Rotation Sensing Using Large Momentum Transfer Point Source Atom Interferometry

by Jinyang Li, Gregório R. M. da Silva, Wayne C. Huang, Mohamed Fouda, Jason Bonacum, Timothy Kovachy and Selim M. Shahriar

Atoms 2021, 9(3), 51; https://doi.org/10.3390/atoms9030051 - 3 Aug 2021

Cited by 6 | Viewed by 2581

Abstract

A point source interferometer (PSI) is a device where atoms are split and recombined by applying a temporal sequence of Raman pulses during the expansion of a cloud of cold atoms behaving approximately as a point source. The PSI can work as a [...] Read more.

A point source interferometer (PSI) is a device where atoms are split and recombined by applying a temporal sequence of Raman pulses during the expansion of a cloud of cold atoms behaving approximately as a point source. The PSI can work as a sensitive multi-axes gyroscope that can automatically filter out the signal from accelerations. The phase shift arising from the rotations is proportional to the momentum transferred to each atom from the Raman pulses. Therefore, by increasing the momentum transfer, it should be possible to enhance the sensitivity of the PSI. Here, we investigate the degree of enhancement in sensitivity that could be achieved by augmenting the PSI with large momentum transfer (LMT) employing a sequence of many Raman pulses with alternating directions. We analyze how factors such as Doppler detuning, spontaneous emission, and the finite initial size of the atomic cloud compromise the advantage of LMT and how to find the optimal momentum transfer under these limitations, with both the semi-classical model and a model under which the motion of the center of mass of each atom is described quantum mechanically. We identify a set of realistic parameters for which LMT can improve the PSI by a factor of nearly 40. Full article

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14 pages, 763 KiB

Open AccessEditor’s ChoiceArticle

Towards B-Spline Atomic Structure Calculations

by Charlotte Froese Fischer

Atoms 2021, 9(3), 50; https://doi.org/10.3390/atoms9030050 - 31 Jul 2021

Cited by 6 | Viewed by 2433

Abstract

The paper reviews the history of B-spline methods for atomic structure calculations for bound states. It highlights various aspects of the variational method, particularly with regard to the orthogonality requirements, the iterative self-consistent method, the eigenvalue problem, and the related sphf, dbsr-hf, [...] Read more.

The paper reviews the history of B-spline methods for atomic structure calculations for bound states. It highlights various aspects of the variational method, particularly with regard to the orthogonality requirements, the iterative self-consistent method, the eigenvalue problem, and the related sphf, dbsr-hf, and spmchf programs. B-splines facilitate the mapping of solutions from one grid to another. The following paper describes a two-stage approach where the goal of the first stage is to determine parameters of the problem, such as the range and approximate values of the orbitals, after which the level of accuracy is raised. Once convergence has been achieved the Virial Theorem, which is evaluated as a check for accuracy. For exact solutions, the V/T ratio for a non-relativistic calculation is −2. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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3 pages, 2226 KiB

Open AccessObituary

Scientific Activities of Oleg Zatsarinny in the Ukraine

by Oleksandr Borovik and Lyudmila Bandurina

Atoms 2021, 9(3), 49; https://doi.org/10.3390/atoms9030049 - 26 Jul 2021

Viewed by 1822

Abstract

These memoirs about Oleg Ivanovich Zatsarinny (1953–2021) concentrate on his scientific activities in the Ukraine. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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10 pages, 265 KiB

Open AccessArticle

New Transition and Energy Levels of Three-Times Ionized Krypton (Kr IV)

by M. Raineri, M. Gallardo, J. Reyna Almandos, A. G. Trigueiros and C. J. B. Pagan

Atoms 2021, 9(3), 48; https://doi.org/10.3390/atoms9030048 - 23 Jul 2021

Viewed by 1968

Abstract

A capillary pulsed-discharge and a theta-pinch were used to record Kr spectra in the region of 330–4800 Å. A set of 168 transitions of these spectra were classified for the first time. We extended the analysis to twenty-five new energy levels belonging to [...] Read more.

A capillary pulsed-discharge and a theta-pinch were used to record Kr spectra in the region of 330–4800 Å. A set of 168 transitions of these spectra were classified for the first time. We extended the analysis to twenty-five new energy levels belonging to 3s²3p²4d, 3s²3p²5d even configurations. We calculated weighted transition probabilities (gA) for all of the experimentally observed lines and lifetimes for new energy levels using a relativistic Hartree–Fock method, including core-polarization effects. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

8 pages, 286 KiB

Open AccessArticle

Relativistic B-Spline R-Matrix Calculations for Electron Collisions with Ytterbium

by Kathryn R. Hamilton, Klaus Bartschat and Oleg Zatsarinny

Atoms 2021, 9(3), 47; https://doi.org/10.3390/atoms9030047 - 23 Jul 2021

Cited by 2 | Viewed by 2348

Abstract

We have applied the full-relativistic Dirac B-Spline R-matrix method to obtain cross sections for electron scattering from ytterbium atoms. The results are compared with those obtained from a semi-relativistic (Breit-Pauli) model-potential approach and the few available experimental data. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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8 pages, 303 KiB

Open AccessArticle

Spectra of Ga-Like to Cu-Like Praseodymium and Neodymium Ions Observed in the Large Helical Device

by Chihiro Suzuki, Fumihiro Koike, Izumi Murakami, Tetsutarou Oishi and Naoki Tamura

Atoms 2021, 9(3), 46; https://doi.org/10.3390/atoms9030046 - 14 Jul 2021

Cited by 4 | Viewed by 2348

Abstract

Extreme ultraviolet (EUV) spectra of highly charged praseodymium (Pr) and neodymium (Nd) ions have been investigated in optically thin high-temperature plasmas produced in the Large Helical Device (LHD), a magnetically confined torus device for fusion research. Discrete spectral lines emitted mainly from highly [...] Read more.

Extreme ultraviolet (EUV) spectra of highly charged praseodymium (Pr) and neodymium (Nd) ions have been investigated in optically thin high-temperature plasmas produced in the Large Helical Device (LHD), a magnetically confined torus device for fusion research. Discrete spectral lines emitted mainly from highly charged ions having 4s or 4p outermost electrons were observed in plasmas with electron temperatures of 0.8–1.8 keV. Most of the isolated lines of Ga-like to Cu-like Nd ions were identified by a comparison with the recent data recorded in an electron beam ion trap (EBIT). The isolated lines of Pr ions corresponding to the identified lines of Nd ions were easily assigned from a similarity of the spectral feature for these two elements. As a result, some of the lines of Pr ions have been newly identified experimentally for the first time in this study. Full article

(This article belongs to the Special Issue Atomic and Molecular Spectra in Magnetically Confined Torus Plasmas)

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38 pages, 887 KiB

Open AccessArticle

EUV Beam-Foil Spectra of Titanium, Iron, Nickel, and Copper

by Elmar Träbert

Atoms 2021, 9(3), 45; https://doi.org/10.3390/atoms9030045 - 13 Jul 2021

Cited by 3 | Viewed by 2703

Abstract

Beam–foil spectroscopy offers the efficient excitation of the spectra of a single element as well as time-resolved observation. Extreme-ultraviolet (EUV) beam–foil survey and detail spectra of Ti, Fe, Ni, and Cu are presented, as well as survey spectra of Fe and Ni obtained [...] Read more.

Beam–foil spectroscopy offers the efficient excitation of the spectra of a single element as well as time-resolved observation. Extreme-ultraviolet (EUV) beam–foil survey and detail spectra of Ti, Fe, Ni, and Cu are presented, as well as survey spectra of Fe and Ni obtained at an electron beam ion trap. Various details are discussed in the context of line intensity ratios, yrast transitions, prompt and delayed spectra, and intercombination transitions. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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9 pages, 519 KiB

Open AccessArticle

One-Electron Energy Spectra of Heavy Highly Charged Quasimolecules: Finite-Basis-Set Approach

by Artem A. Kotov, Dmitry A. Glazov, Vladimir M. Shabaev and Günter Plunien

Atoms 2021, 9(3), 44; https://doi.org/10.3390/atoms9030044 - 13 Jul 2021

Cited by 7 | Viewed by 2310

Abstract

The generalized dual-kinetic-balance approach for axially symmetric systems is employed to solve the two-center Dirac problem. The spectra of one-electron homonuclear quasimolecules are calculated and compared with the previous calculations. The analysis of the monopole approximation with two different choices of the origin [...] Read more.

The generalized dual-kinetic-balance approach for axially symmetric systems is employed to solve the two-center Dirac problem. The spectra of one-electron homonuclear quasimolecules are calculated and compared with the previous calculations. The analysis of the monopole approximation with two different choices of the origin is performed. Special attention is paid to the lead and xenon dimers, Pb

^{82 +}

–Pb

^{82 +}

–e

^{-}

and Xe

^{54 +}

–Xe

^{54 +}

–e

^{-}

, where the energies of the ground and several excited

σ

-states are presented in the wide range of internuclear distances. The developed method provides the quasicomplete finite basis set and allows for the construction of perturbation theory, including within the bound-state QED. Full article

(This article belongs to the Special Issue Accelerator-Based Atomic Physics: Fast Ion–Atom and Ion–Molecule Collisions)

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11 pages, 3122 KiB

Open AccessArticle

On the Electron Impact Integral Cross-Sections for Butanol and Pentanol Isomers

by Nafees Uddin, Paresh Modak and Bobby Antony

Atoms 2021, 9(3), 43; https://doi.org/10.3390/atoms9030043 - 13 Jul 2021

Cited by 4 | Viewed by 2609

Abstract

The need for a reliable and comprehensive database of cross-sections for many atomic and molecular species is immense due to its key role in R&D domains such as plasma modelling, bio-chemical processes, medicine and many other natural and technological environments. Elastic, momentum transfer [...] Read more.

The need for a reliable and comprehensive database of cross-sections for many atomic and molecular species is immense due to its key role in R&D domains such as plasma modelling, bio-chemical processes, medicine and many other natural and technological environments. Elastic, momentum transfer and total cross-sections of butanol and pentanol isomers by the impact of 6–5000 eV electrons are presented in this work. The calculations were performed by employing the spherical complex optical potential formalism along with single-centre expansion and group additivity rule. The investigations into the presence of isomeric variations reveal that they are more pronounced at low and intermediate energies. Elastic, total cross-sections (with the exception of n-pentanol) and momentum transfer cross-sections for all pentanol isomers are reported here for the first time, to the best of our knowledge. Our momentum transfer cross-sections for butanol isomers are in very good agreement with the experimental and theoretical values available, and in reasonable consensus for other cross-sections. Full article

(This article belongs to the Special Issue Electron Scattering in Gases –from Cross Sections to Plasma Modeling)

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19 pages, 1208 KiB

Open AccessArticle

A Fully Relativistic Approach to Photon Scattering and Photoionization of Alkali Atoms

by Adam Singor, Dmitry Fursa, Igor Bray and Robert McEachran

Atoms 2021, 9(3), 42; https://doi.org/10.3390/atoms9030042 - 8 Jul 2021

Cited by 3 | Viewed by 2560

Abstract

A fully relativistic approach to calculating photoionization and photon-atom scattering cross sections for quasi one-electron atoms is presented. An extensive set of photoionization cross sections have been calculated for alkali atoms: lithium, sodium, potassium, rubidium and cesium. The importance of relativistic effects and [...] Read more.

A fully relativistic approach to calculating photoionization and photon-atom scattering cross sections for quasi one-electron atoms is presented. An extensive set of photoionization cross sections have been calculated for alkali atoms: lithium, sodium, potassium, rubidium and cesium. The importance of relativistic effects and core polarization on the depth and position of the Cooper minimum in the photoionization cross section is investigated. Good agreement was found with previous Dirac-based B-spline R-matrix calculations of Zatsarinny and Tayal and recent experimental results. Full article

(This article belongs to the Special Issue A Tribute to Oleg Zatsarinny (1953–2021) and His Science–Fees Are Waived)

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5 pages, 855 KiB

Open AccessCommunication

Classical Description of Resonant Charge Exchange Involving the Second Flavor of Hydrogen Atoms

by Eugene Oks

Atoms 2021, 9(3), 41; https://doi.org/10.3390/atoms9030041 - 7 Jul 2021

Cited by 4 | Viewed by 2101

Abstract

We studied the consequences of the existence of the second flavor of hydrogen atoms (SFHA)—the existence proven by atomic experiments and evidenced by astrophysical observations—on the resonant charge exchange. We found analytically that there is indeed an important difference in the corresponding cross-sections [...] Read more.

We studied the consequences of the existence of the second flavor of hydrogen atoms (SFHA)—the existence proven by atomic experiments and evidenced by astrophysical observations—on the resonant charge exchange. We found analytically that there is indeed an important difference in the corresponding cross-sections for the SFHA compared to the usual hydrogen atoms. This difference could serve as an additional tool for distinguishing between the two kinds of hydrogen atoms in future experiments/observations. We also show that the SFHA does not exhibit any Stark effect—whether in a uniform or a non-uniform electric field—in any order of the perturbation theory. Full article

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21 pages, 1390 KiB

Open AccessTutorial

Classical and Quantum Collective Recoil Lasing: A Tutorial

by Nicola Piovella, Angel Tarramera Gisbert and Gordon R. M. Robb

Atoms 2021, 9(3), 40; https://doi.org/10.3390/atoms9030040 - 6 Jul 2021

Cited by 1 | Viewed by 2631

Abstract

Collective atomic recoil lasing (CARL) is a process during which an ensemble of cold atoms, driven by a far-detuned laser beam, spontaneously organize themselves in periodic structures on the scale of the optical wavelength. The principle was envisaged by R. Bonifacio in 1994 [...] Read more.

Collective atomic recoil lasing (CARL) is a process during which an ensemble of cold atoms, driven by a far-detuned laser beam, spontaneously organize themselves in periodic structures on the scale of the optical wavelength. The principle was envisaged by R. Bonifacio in 1994 and, ten years later, observed in a series of experiments in Tübingen by C. Zimmermann and colleagues. Here, we review the basic model of CARL in the classical and in the quantum regime. Full article

(This article belongs to the Special Issue Collective Atomic and Free-Electron Lasing)

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