Atoms

12 pages, 984 KiB

Open AccessArticle

Electron and Positron Impact Ionization of SF_6−nH_n(n = 0 − 6); {SCl_n, SF_n−1Cl(n = 1 − 6)} and SF₅X(X = CN, CFO)

by S. Suriyaprasanth, Heechol Choi and Dhanoj Gupta

Atoms 2023, 11(10), 137; https://doi.org/10.3390/atoms11100137 - 21 Oct 2023

Cited by 1 | Viewed by 1259

We have calculated the electron and positron impact ionization of a set of molecules,

S F_{6 - n} H_{n} (n = 0 - 6)

,

S C l_{n} (n = 1 - 6)

, [...] Read more.

We have calculated the electron and positron impact ionization of a set of molecules,

S F_{6 - n} H_{n} (n = 0 - 6)

,

S C l_{n} (n = 1 - 6)

,

S F_{n - 1} C l (n = 1 - 6)

and

S F_{5} X (X = C N, C F O)

, for which there are much fewer data in the literature. We have optimized the targets, and their electric polarizability is calculated along with their orbital binding and kinetic energies within the Hartree–Fock approximation that serve as input to the Binary Encounter Bethe (BEB) model for both electron and positron ionization. Most of the targets are investigated for the first time, apart from

S F_{6}

, for which we compared our data with various experimental and theoretical data, giving us a good comparison. Full article

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

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6 pages, 677 KiB

Open AccessCommunication

The Excitation of the 3D and 4D States of Atomic Hydrogen by Electron Impact

by Anand K. Bhatia

Atoms 2023, 11(10), 136; https://doi.org/10.3390/atoms11100136 - 18 Oct 2023

Viewed by 1091

Abstract

The excitation cross-sections of the 3D and 4D states of atomic hydrogen at low incident energies (from 0.90 to 5.00 Ry) were calculated using the variational polarized orbital method, which is also called the hybrid theory. Up to 12 partial waves [...] Read more.

The excitation cross-sections of the 3D and 4D states of atomic hydrogen at low incident energies (from 0.90 to 5.00 Ry) were calculated using the variational polarized orbital method, which is also called the hybrid theory. Up to 12 partial waves (L = 2 to 13) were used to obtain converged cross-sections at high energies. The importance of the long-range forces near the threshold region and the behavior of the cross-sections in that region are indicated. The S, P, and D cross-sections are needed if the total excitation cross-sections are measured in addition to the elastic cross-sections. These cross-sections are also useful if the cascade from the D to the P to the S states is considered in the diagnostics of solar and astrophysical observations. Full article

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9 pages, 3770 KiB

Open AccessArticle

K-Edge Structure in Shock-Compressed Chlorinated Parylene

by David Bailie, Steven White, Rachael Irwin, Cormac Hyland, Richard Warwick, Brendan Kettle, Nicole Breslin, Simon N. Bland, David J. Chapman, Stuart P. D. Mangles, Rory A. Baggot, Eleanor R. Tubman and David Riley

Atoms 2023, 11(10), 135; https://doi.org/10.3390/atoms11100135 - 18 Oct 2023

Viewed by 1126

Abstract

We have carried out a series of experiments to measure the Cl K-absorption edge for shock-compressed samples of chlorinated parylene. Colliding shocks allowed us to compress samples up to four times the initial density with temperatures up to 10 eV. Red shifts in [...] Read more.

We have carried out a series of experiments to measure the Cl K-absorption edge for shock-compressed samples of chlorinated parylene. Colliding shocks allowed us to compress samples up to four times the initial density with temperatures up to 10 eV. Red shifts in the edge of about 10 eV have been measured. We have compared the measured shifts to analytical modelling using the Stewart–Pyatt model and adaptions of it, combined with estimates of density and temperature based on hydrodynamic modelling. Modelling of the edge position using density functional theory molecular dynamics (DFT-MD) was also used and it was found that good agreement was only achieved when the DFT simulations assumed conditions of lower temperature and slightly higher density than indicated by hydrodynamic simulations using a tabular equation of state. Full article

(This article belongs to the Special Issue Atomic Physics in Dense Plasmas)

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13 pages, 981 KiB

Open AccessArticle

Multi-Reflection Time-of-Flight Mass Spectroscopy for Superheavy Nuclides

by Peter Schury, Yuta Ito, Toshitaka Niwase and Michiharu Wada

Atoms 2023, 11(10), 134; https://doi.org/10.3390/atoms11100134 - 17 Oct 2023

Cited by 1 | Viewed by 1398

Abstract

The atomic masses of isotopes of elements beyond fermium, which can presently only be produced online via fusion-evaporation reactions, have until recently been determined only from

α

decay chains reaching nuclides with known atomic masses. Especially in the case of lower-yield nuclides, for [...] Read more.

The atomic masses of isotopes of elements beyond fermium, which can presently only be produced online via fusion-evaporation reactions, have until recently been determined only from

α

decay chains reaching nuclides with known atomic masses. Especially in the case of lower-yield nuclides, for which the sufficiently detailed nuclear spectroscopy required to fully determine the nuclear structure is not possible, such indirect mass determinations may suffer systematic errors. For many superheavy nuclides, their decay chains end in spontaneous fission or in

β

-decay prior to reaching nuclides of known mass. To address this dearth of accurate atomic masses, we have developed a multi-reflection time-of-flight mass spectrograph that can make use of decay-correlations to accurately and precisely determine atomic masses for the very low-yield superheavy nuclides. Full article

(This article belongs to the Special Issue Advances in Ion Trapping of Radioactive Ions)

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19 pages, 995 KiB

Open AccessReview

Review of Rydberg Spectral Line Formation in Plasmas

by Andrey Yu. Letunov and Valery S. Lisitsa

Atoms 2023, 11(10), 133; https://doi.org/10.3390/atoms11100133 - 17 Oct 2023

Viewed by 1289

Abstract

The present review is dedicated to the problem of an array of transitions between highly-excited atomic levels. Hydrogen atoms and hydrogen-like ions in plasmas are considered here. The presented methods focus on calculation of spectral line shapes. Fast and simple methods of universal [...] Read more.

The present review is dedicated to the problem of an array of transitions between highly-excited atomic levels. Hydrogen atoms and hydrogen-like ions in plasmas are considered here. The presented methods focus on calculation of spectral line shapes. Fast and simple methods of universal ionic profile calculation for the

H_{n α}

(

Δ n = 1

) and

H_{n β}

(

Δ n = 2

) spectral lines are demonstrated. The universal dipole matrix elements formulas for the

H_{n α}

and

H_{n β}

transitions are presented. A fast method for spectral line shape calculations in the presence of an external magnetic field using the formulas for universal dipole matrix elements is proposed. This approach accounts for the Doppler and Stark–Zeeman broadening mechanisms. Ion dynamics effects are treated via the frequency fluctuation model. The accuracy of the presented model is discussed. A comparison of this approach with experimental data and the results of molecular dynamics simulation is demonstrated. The kinetics equation for the populations of highly-excited ionic states is solved in the parabolic representation. The population source associated with dielectronic recombination is considered. Full article

(This article belongs to the Special Issue Rydberg Atomic Physics)

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11 pages, 1588 KiB

Open AccessArticle

Quantum-Chemical Study of the Benzene Reaction with Fluorine

by Sergey O. Adamson, Daria D. Kharlampidi, Anastasia S. Shtyrkova, Stanislav Y. Umanskii, Yuri A. Dyakov, Igor I. Morozov and Maxim G. Golubkov

Atoms 2023, 11(10), 132; https://doi.org/10.3390/atoms11100132 - 17 Oct 2023

Viewed by 1306

Abstract

The reaction of benzene with fluorine atoms may be of interest as a source of phenyl and ipso-fluorocyclohexadienyl radicals or as a method for fluorobenzene gas phase synthesis. The structures and electronic energies of the equilibrium configurations and transition complexes of the [...] Read more.

The reaction of benzene with fluorine atoms may be of interest as a source of phenyl and ipso-fluorocyclohexadienyl radicals or as a method for fluorobenzene gas phase synthesis. The structures and electronic energies of the equilibrium configurations and transition complexes of the C₆H₆F system are calculated in the density functional approximation. It was found that the interaction of benzene with atomic fluorine can proceed via two channels: hydrogen abstraction with the phenyl radical formation, and hydrogen substitution with the ipso-fluorocyclohexadienyl radical as primary product. Then the dissociation of the ipso-fluorocyclohexadienyl radical leads to creation of fluorobenzene and atomic hydrogen. The initiation of this reaction requires the activation energy near 27 kcal/mol, which indicates the low probability of this process, occurring at temperatures close to the standard (298 K). The calculations of the fluorocyclohexadienyl isomers and their cations also indicate that the formation of fluorobenzene as a product of secondary reactions is unlikely. The conclusions are confirmed by experimental data. Full article

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

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Graphical abstract

20 pages, 781 KiB

Open AccessArticle

Quantum Dielectric Model for Energy Loss of Particles in Astrophysical Plasmas

by Claudio D. Archubi and Nestor R. Arista

Atoms 2023, 11(10), 131; https://doi.org/10.3390/atoms11100131 - 16 Oct 2023

Viewed by 1092

Abstract

We present the results obtained using a novel quantum approach to describe the interaction of charged particles with the astrophysical type of plasmas, based on the dielectric plasma-wave-packet model (PWPM) together with a full description of statistical effects on energy exchange processes. We [...] Read more.

We present the results obtained using a novel quantum approach to describe the interaction of charged particles with the astrophysical type of plasmas, based on the dielectric plasma-wave-packet model (PWPM) together with a full description of statistical effects on energy exchange processes. We use this formulation to calculate the energy loss moments for protons, positrons, and electrons traversing different stellar plasmas on a wide range of projectile velocities and plasma densities and temperatures. We consider special quantum restrictions for the cases of positrons and electrons, including relativistic corrections for high-velocity particles. We analyze and compare the results for different cases of main interest, from dilute solar-corona plasma to cases of increasing densities in the interior of the sun and in the dense regions of giant stars. Full article

(This article belongs to the Special Issue Atomic and Molecular Data in Astronomy and Astrophysics)

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18 pages, 27874 KiB

Open AccessReview

Review of the 1^st EUV Light Sources Code Comparison Workshop

by John Sheil, Oscar Versolato, Vivek Bakshi and Howard Scott

Atoms 2023, 11(10), 130; https://doi.org/10.3390/atoms11100130 - 13 Oct 2023

Cited by 1 | Viewed by 1572

Abstract

We review the results of the 1

^{st}

Extreme Ultraviolet (EUV) Light Sources Code Comparison Workshop. The goal of this workshop was to provide a platform for specialists in EUV light source plasma modeling to benchmark and validate their numerical codes using well-defined [...] Read more.

We review the results of the 1

^{st}

Extreme Ultraviolet (EUV) Light Sources Code Comparison Workshop. The goal of this workshop was to provide a platform for specialists in EUV light source plasma modeling to benchmark and validate their numerical codes using well-defined case studies. Detailed consideration of a plethora of atomic collisional and radiative processes is required for modeling EUV light source plasmas. Eight institutions spanning four countries contributed data to the workshop. Two topics were addressed, namely (i) the atomic kinetics and radiative properties of tin plasmas under EUV-generating conditions and (ii) laser absorption in a fully ionized, one-dimensional hydrogen plasma. In this paper, we summarize the key findings of the workshop and outline plans for future iterations of the code comparison activity. Full article

(This article belongs to the Special Issue Atomic Processes for Plasma Modeling Applications)

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11 pages, 603 KiB

Open AccessArticle

The St. Benedict Facility: Probing Fundamental Symmetries through Mixed Mirror β-Decays

by William S. Porter, Daniel W. Bardayan, Maxime Brodeur, Daniel P. Burdette, Jason A. Clark, Aaron T. Gallant, Alicen M. Houff, James J. Kolata, Biying Liu, Patrick D. O’Malley, Caleb Quick, Fabio Rivero, Guy Savard, Adrian A. Valverde and Regan Zite

Atoms 2023, 11(10), 129; https://doi.org/10.3390/atoms11100129 - 11 Oct 2023

Viewed by 1190

Abstract

Precise measurements of nuclear beta decays provide a unique insight into the Standard Model due to their connection to the electroweak interaction. These decays help constrain the unitarity or non-unitarity of the Cabibbo–Kobayashi–Maskawa (CKM) quark mixing matrix, and can uniquely probe the existence [...] Read more.

Precise measurements of nuclear beta decays provide a unique insight into the Standard Model due to their connection to the electroweak interaction. These decays help constrain the unitarity or non-unitarity of the Cabibbo–Kobayashi–Maskawa (CKM) quark mixing matrix, and can uniquely probe the existence of exotic scalar or tensor currents. Of these decays, superallowed mixed mirror transitions have been the least well-studied, in part due to the absence of data on their Fermi to Gamow-Teller mixing ratios (

ρ

). At the Nuclear Science Laboratory (NSL) at the University of Notre Dame, the Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) is being constructed to determine the

ρ

for various mirror decays via a measurement of the beta–neutrino angular correlation parameter (

a_{β ν}

) to a relative precision of 0.5%. In this work, we present an overview of the St. Benedict facility and the impact it will have on various Beyond the Standard Model studies, including an expanded sensitivity study of

ρ

for various mirror nuclei accessible to the facility. A feasibility evaluation is also presented that indicates the measurement goals for many mirror nuclei, which are currently attainable in a week of radioactive beam delivery at the NSL. Full article

(This article belongs to the Special Issue Advances in Ion Trapping of Radioactive Ions)

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10 pages, 5166 KiB

Open AccessArticle

The Fingerprints of Periodic Electric Fields on Line Shapes Emitted in Plasmas

by Ibtissem Hannachi and Roland Stamm

Atoms 2023, 11(10), 128; https://doi.org/10.3390/atoms11100128 - 08 Oct 2023

Viewed by 1044

Abstract

Periodic electric fields are found in many kinds of plasmas and result from the presence of collective fields amplified by plasma instabilities, or they are created by external sources such as microwave generators or lasers. The spectral lines emitted by atoms or ions [...] Read more.

Periodic electric fields are found in many kinds of plasmas and result from the presence of collective fields amplified by plasma instabilities, or they are created by external sources such as microwave generators or lasers. The spectral lines emitted by atoms or ions in a plasma exhibit a frequency profile characteristic of plasma conditions, such as the temperature and density of charged particles. The fingerprints of periodic electric fields appear clearly on the line shape for a large range of frequencies and magnitudes of the oscillating electric field. Satellite structures appear near to multiples of the oscillation frequency and redistribute the intensity of the line far from the line center. The modeling of the simultaneous effects of the plasma microfield and of a periodic electric field has been active since the seventies, but it remains difficult to be conducted accurately since the quantum emitter is submitted to several time-dependent electric fields, each with their own characteristic time. We describe here a numerical approach which couples a simulation of the motion of charged plasma particles with an integration of the emitter Schrödinger equation. Resulting hydrogen line shapes are presented for different plasmas and periodic fields encountered in laboratory and astrophysical plasmas. Full article

(This article belongs to the Special Issue Atomic Physics in Dense Plasmas)

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16 pages, 6966 KiB

Open AccessArticle

Status of CHIP-TRAP: The Central Michigan University High-Precision Penning Trap

by Matthew Redshaw, Ramesh Bhandari, Nadeesha Gamage, Mehedi Hasan, Madhawa Horana Gamage, Dakota K. Keblbeck, Savannah Limarenko and Dilanka Perera

Atoms 2023, 11(10), 127; https://doi.org/10.3390/atoms11100127 - 07 Oct 2023

Cited by 1 | Viewed by 1364

Abstract

Precise and accurate atomic mass data provide crucial information for applications in a wide range of fields in physics and beyond, including astrophysics, nuclear structure, particle and neutrino physics, fundamental symmetries, chemistry, and metrology. The most precise atomic mass measurements are performed on [...] Read more.

Precise and accurate atomic mass data provide crucial information for applications in a wide range of fields in physics and beyond, including astrophysics, nuclear structure, particle and neutrino physics, fundamental symmetries, chemistry, and metrology. The most precise atomic mass measurements are performed on charged particles confined in a Penning trap. Here, we describe the development, status, and outlook of CHIP-TRAP: the Central Michigan University high-precision Penning trap. CHIP-TRAP aims to perform ultra-high precision (∼1 part in 10

^{11}

fractional precision) mass measurements on stable and long-lived isotopes produced with external ion sources and transported to the Penning traps. Along the way, ions of a particular

m / q

are selected with a multi-reflection time-of-flight mass separator (MR-TOF-MS), with further filtering performed in a cylindrical capture trap before the ions are transported to a pair of hyperbolic measurement traps. In this paper, we report on the design and status of CHIP-TRAP and present results from the commissioning of the ion sources, MR-TOF-MS, and capture trap. We also provide an outlook on the continued development and commissioning of CHIP-TRAP. Full article

(This article belongs to the Special Issue Advances in Ion Trapping of Radioactive Ions)

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20 pages, 4321 KiB

Open AccessArticle

Applications of Machine Learning and Neural Networks for FT-ICR Mass Measurements with SIPT

by Scott E. Campbell, Georg Bollen, Alec Hamaker, Walter Kretzer, Ryan Ringle and Stefan Schwarz

Atoms 2023, 11(10), 126; https://doi.org/10.3390/atoms11100126 - 28 Sep 2023

Viewed by 1089

Abstract

The single-ion Penning trap (SIPT) at the Low-Energy Beam Ion Trapping Facility has been developed to perform precision Penning trap mass measurements of single ions, ideal for the study of exotic nuclei available only at low rates at the Facility for Rare Isotope [...] Read more.

The single-ion Penning trap (SIPT) at the Low-Energy Beam Ion Trapping Facility has been developed to perform precision Penning trap mass measurements of single ions, ideal for the study of exotic nuclei available only at low rates at the Facility for Rare Isotope Beams (FRIB). Single-ion signals are very weak—especially if the ion is singly charged—and the few meaningful ion signals must be disentangled from an often larger noise background. A useful approach for simulating Fourier transform ion cyclotron resonance signals is outlined and shown to be equivalent to the established yet computationally intense method. Applications of supervised machine learning algorithms for classifying background signals are discussed, and their accuracies are shown to be ≈65% for the weakest signals of interest to SIPT. Additionally, a deep neural network capable of accurately predicting important characteristics of the ions observed by their image charge signal is discussed. Signal classification on an experimental noise dataset was shown to have a false-positive classification rate of 10.5%, and 3.5% following additional filtering. The application of the deep neural network to an experimental ⁸⁵Rb⁺ dataset is presented, suggesting that SIPT is sensitive to single-ion signals. Lastly, the implications for future experiments are discussed. Full article

(This article belongs to the Special Issue Advances in Ion Trapping of Radioactive Ions)

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13 pages, 5848 KiB

Open AccessArticle

Quadrupole Effects in the Photoionisation of Sodium 3s in the Vicinity of the Dipole Cooper Minimum

by Nishita M. Hosea, Jobin Jose, Hari R. Varma, Pranawa C. Deshmukh and Steven T. Manson

Atoms 2023, 11(10), 125; https://doi.org/10.3390/atoms11100125 - 28 Sep 2023

Viewed by 1119

Abstract

A procedure to obtain relativistic expressions for photoionisation angular distribution parameters using the helicity formulation is discussed for open-shell atoms. Electric dipole and quadrupole transition matrix elements were considered in the present work, to study the photoionisation dynamics of the 3s electron of [...] Read more.

A procedure to obtain relativistic expressions for photoionisation angular distribution parameters using the helicity formulation is discussed for open-shell atoms. Electric dipole and quadrupole transition matrix elements were considered in the present work, to study the photoionisation dynamics of the 3s electron of the sodium atom in the vicinity of the dipole Cooper minimum. We studied dipole–quadrupole interference effects on the photoelectron angular distribution in the region of the dipole Cooper minimum. Interference with quadrupole transitions was found to alter the photoelectron angular distribution, even at rather low photon energies. The initial ground and final ionised state discrete wavefunctions of the atom were obtained in the present work using GRASP, and we employed RATIP with discrete wavefunctions, to construct continuum wavefunctions and to calculate transition amplitudes, total cross-sections and angular distribution asymmetry parameters. 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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15 pages, 1098 KiB

Open AccessArticle

Single Ionization of Helium by Protons of Various Energies in the Parabolic Quasi-Sturmians Approach

by Alexander S. Zaytsev, Darya S. Zaytseva, Sergey A. Zaytsev, Lorenzo U. Ancarani, Ochbadrakh Chuluunbaatar, Konstantin A. Kouzakov and Yury V. Popov

Atoms 2023, 11(10), 124; https://doi.org/10.3390/atoms11100124 - 28 Sep 2023

Viewed by 1295

Abstract

The parabolic quasi-Sturmian approach, recently introduced for the calculation of ion–atom ionizing collisions, is adapted and applied here to the single ionization of helium induced by an intermediate-energy proton impact. Within the method, the ionization amplitude is represented as the sum of the [...] Read more.

The parabolic quasi-Sturmian approach, recently introduced for the calculation of ion–atom ionizing collisions, is adapted and applied here to the single ionization of helium induced by an intermediate-energy proton impact. Within the method, the ionization amplitude is represented as the sum of the products of the basis amplitudes associated with the asymptotic behavior of the continuum states of the two noninteracting hydrogenic subsystems

(e^{-}, {He}^{+})

and

(p^{+}, {He}^{+})

. The

p - e

interaction is treated as a perturbation in the Lippmann–Schwinger-type (LS) equation for the three-body system

(e^{-}, {He}^{+}, p^{+})

. This LS equation is solved numerically using separable expansions for the proton–electron potential. We examine the convergence behavior of the transition amplitude expansion as the number of terms in the representation of the

p - e

interaction is increased and find that, for some kinematic regimes, the convergence is poor. This difficulty, which is absent for a higher proton energy impact, is solved by varying the momentum of the auxiliary proton plane wave introduced into the basis function. Fully differential cross-sections are calculated and compared with experimental data for 75 keV protons and the results obtained with the 3C model. Full article

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

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15 pages, 4378 KiB

Open AccessArticle

The Double-Nozzle Technique Equipped with RF-Only Funnel and RF-Buncher for the Ion Beam Extraction into Vacuum

by Victor Varentsov

Atoms 2023, 11(10), 123; https://doi.org/10.3390/atoms11100123 - 22 Sep 2023

Viewed by 1000

Abstract

This study is a further development of our “Proposal of a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy” paper published in the journal Atoms earlier this year. Here, we propose equipping the double-nozzle technique with the RF-only funnel and RF-buncher placed [...] Read more.

This study is a further development of our “Proposal of a new double-nozzle technique for in-gas-jet laser resonance ionization spectroscopy” paper published in the journal Atoms earlier this year. Here, we propose equipping the double-nozzle technique with the RF-only funnel and RF-buncher placed in a gas-jet chamber at a 70 mm distance downstream of the double-nozzle exit. It allows for highly effective extraction into vacuum heavy ion beams, produced in two-steps laser resonance ionization in the argon supersonic jet. We explored the operation of this new full version of the double-nozzle technique through detailed gas dynamic and Monte Carlo trajectory simulations, with the results presented and discussed. In particular, our calculations showed that more than 80% of all nobelium-254 neutral atoms, extracted by argon flow from the gas-stopping cell, can then be extracted into vacuum in a form of pulsed ion beam having low transverse and longitudinal emittance. Full article

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

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