Atoms

8895 KiB

Open AccessFeature PaperArticle

Electroweak Decay Studies of Highly Charged Radioactive Ions with TITAN at TRIUMF

by Kyle G. Leach, Iris Dillmann, Renee Klawitter, Erich Leistenschneider, Annika Lennarz, Thomas Brunner, Dieter Frekers, Corina Andreoiu, Anna A. Kwiatkowski and Jens Dilling

Atoms 2017, 5(1), 14; https://doi.org/10.3390/atoms5010014 - 21 Mar 2017

Cited by 9 | Viewed by 4714

Abstract

Several modes of electroweak radioactive decay require an interaction between the nucleus and bound electrons within the constituent atom. Thus, the probabilities of the respective decays are not only influenced by the structure of the initial and final states in the nucleus, but [...] Read more.

Several modes of electroweak radioactive decay require an interaction between the nucleus and bound electrons within the constituent atom. Thus, the probabilities of the respective decays are not only influenced by the structure of the initial and final states in the nucleus, but can also depend strongly on the atomic charge. Conditions suitable for the partial or complete ionization of these rare isotopes occur naturally in hot, dense astrophysical environments, but can also be artificially generated in the laboratory to selectively block certain radioactive decay modes. Direct experimental studies on such scenarios are extremely difficult due to the laboratory conditions required to generate and store radioactive ions at high charge states. A new electron-beam ion trap (EBIT) decay setup with the TITAN experiment at TRIUMF has successfully demonstrated such techniques for performing spectroscopy on the radioactive decay of highly charged ions. Full article

(This article belongs to the Special Issue Perspectives of Atomic Physics with Trapped Highly Charged Ions)

► Show Figures

Figure 1

235 KiB

Open AccessFeature PaperArticle

Direct Observation of the M1 Transition between the Ground Term Fine Structure Levels of W VIII

by Momoe Mita, Hiroyuki A. Sakaue, Daiji Kato, Izumi Murakami and Nobuyuki Nakamura

Atoms 2017, 5(1), 13; https://doi.org/10.3390/atoms5010013 - 8 Mar 2017

Cited by 24 | Viewed by 5209

Abstract

We present a direct observation of the M1 transition between the fine structure splitting in the

4 f^{13} 5 s^{2} 5 p^{6}

^{2} F

ground term of W VIII. The spectroscopic data of few-times ionized tungsten ions are important for [...] Read more.

We present a direct observation of the M1 transition between the fine structure splitting in the

4 f^{13} 5 s^{2} 5 p^{6}

^{2} F

ground term of W VIII. The spectroscopic data of few-times ionized tungsten ions are important for the future ITER diagnostics, but there is a serious lack of data. The present study is part of an ongoing effort to solve this problem. Emission from the tungsten ions produced and trapped in a compact electron beam ion trap is observed with a Czerny–Turner visible spectrometer. Spectra in the EUV range are also observed at the same time to help identify the previously-unreported visible lines. The observed wavelength

574.47 \pm 0.03

nm (air), which corresponds to the fine structure splitting of 17,402.5 ± 0.9 cm

^{- 1}

, shows reasonable agreement with the previously reported value 17,410 ± 5 cm

^{- 1}

obtained indirectly through the analysis of EUV spectra [Ryabtsev et al., Atoms 3 (2015) 273]. Full article

(This article belongs to the Special Issue Perspectives of Atomic Physics with Trapped Highly Charged Ions)

► Show Figures

Figure 1

2673 KiB

Open AccessFeature PaperReview

Spectral Analysis of Moderately Charged Rare-Gas Atoms

by Jorge Reyna Almandos and Mónica Raineri

Atoms 2017, 5(1), 12; https://doi.org/10.3390/atoms5010012 - 7 Mar 2017

Cited by 4 | Viewed by 4225

Abstract

This article presents a review concerning the spectral analysis of several ions of neon, argon, krypton and xenon, with impact on laser studies and astrophysics that were mainly carried out in our collaborative groups between Argentina and Brazil during many years. The spectra [...] Read more.

This article presents a review concerning the spectral analysis of several ions of neon, argon, krypton and xenon, with impact on laser studies and astrophysics that were mainly carried out in our collaborative groups between Argentina and Brazil during many years. The spectra were recorded from the vacuum ultraviolet to infrared regions using pulsed discharges. Semi-empirical approaches with relativistic Hartree–Fock and Dirac-Fock calculations were also included in these investigations. The spectral analysis produced new classified lines and energy levels. Lifetimes and oscillator strengths were also calculated. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

► Show Figures

Figure 1

1665 KiB

Open AccessFeature PaperArticle

Resonance Transitions in the Spectra of the Ag⁶⁺–Ag⁸⁺ Ions

by Alexander Ryabtsev and Edward Kononov

Atoms 2017, 5(1), 11; https://doi.org/10.3390/atoms5010011 - 4 Mar 2017

Cited by 2 | Viewed by 4450

Abstract

The spectrum of silver, excited in a vacuum spark, was recorded in the region 150–350 Å on a 3-m grazing incidence spectrograph. The resonance 4d^k–(4d^k−15p + 4d^k−14f + 4p⁵4d^k+1) was studied in the [...] Read more.

The spectrum of silver, excited in a vacuum spark, was recorded in the region 150–350 Å on a 3-m grazing incidence spectrograph. The resonance 4d^k–(4d^k−15p + 4d^k−14f + 4p⁵4d^k+1) was studied in the Ag⁶⁺–Ag⁸⁺ spectra (Ag VII–Ag IX) with k = 5–3, respectively. Several hundred lines were identified with the aid of the Cowan code and orthogonal operator technique calculations. The energy levels were found and the transition probabilities were calculated. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

► Show Figures

Figure 1

3953 KiB

Open AccessFeature PaperArticle

The Role of the Hyperfine Structure for the Determination of Improved Level Energies of Ta II, Pr II and La II

by Laurentius Windholz

Atoms 2017, 5(1), 10; https://doi.org/10.3390/atoms5010010 - 28 Feb 2017

Cited by 4 | Viewed by 4820

Abstract

For the determination of improved energy levels of ionic spectra of elements with large values of nuclear magnetic dipole moment (and eventually large values of nuclear quadrupole moments), it is necessary to determine the center of gravity of spectral lines from resolved hyperfine [...] Read more.

For the determination of improved energy levels of ionic spectra of elements with large values of nuclear magnetic dipole moment (and eventually large values of nuclear quadrupole moments), it is necessary to determine the center of gravity of spectral lines from resolved hyperfine structure patterns appearing in highly resolved spectra. This is demonstrated on spectral lines of Ta II, Pr II and La II. Blend situations (different transitions with accidentally nearly the same wave number difference between the combining levels) must also be considered. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

► Show Figures

Figure 1

2737 KiB

Open AccessFeature PaperArticle

The Cu II Spectrum

by Alexander Kramida, Gillian Nave and Joseph Reader

Atoms 2017, 5(1), 9; https://doi.org/10.3390/atoms5010009 - 24 Feb 2017

Cited by 19 | Viewed by 5378

Abstract

New wavelength measurements in the vacuum ultraviolet (VUV), ultraviolet and visible spectral regions have been combined with available literature data to refine and extend the description of the spectrum of singly ionized copper (Cu II). In the VUV region, we measured 401 lines [...] Read more.

New wavelength measurements in the vacuum ultraviolet (VUV), ultraviolet and visible spectral regions have been combined with available literature data to refine and extend the description of the spectrum of singly ionized copper (Cu II). In the VUV region, we measured 401 lines using a concave grating spectrograph and photographic plates. In the UV and visible regions, we measured 276 lines using a Fourier-transform spectrometer. These new measurements were combined with previously unpublished data from the thesis of Ross, with accurate VUV grating measurements of Kaufman and Ward, and with less accurate older measurements of Shenstone to construct a comprehensive list of ≈2440 observed lines, from which we derived a revised set of 379 optimized energy levels, complemented with 89 additional levels obtained using series formulas. Among the 379 experimental levels, 29 are new. Intensities of all lines observed in different experiments have been reduced to the same uniform scale by using newly calculated transition probabilities (A-values). We combined our calculations with published measured and calculated A-values to provide a set of 555 critically evaluated transition probabilities with estimated uncertainties, 162 of which are less than 20%. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

► Show Figures

Figure 1

235 KiB

Open AccessFeature PaperArticle

Calculation of Rates of 4p–4d Transitions in Ar II

by Alan Hibbert

Atoms 2017, 5(1), 8; https://doi.org/10.3390/atoms5010008 - 21 Feb 2017

Cited by 4 | Viewed by 3670

Abstract

Recent experimental work by Belmonte et al. (2014) has given rates for some 4p–4d transitions that are significantly at variance with the previous experimental work of Rudko and Tang (1967) recommended in the NIST tabulations. To date, there are no theoretical rates with [...] Read more.

Recent experimental work by Belmonte et al. (2014) has given rates for some 4p–4d transitions that are significantly at variance with the previous experimental work of Rudko and Tang (1967) recommended in the NIST tabulations. To date, there are no theoretical rates with which to compare. In this work, we provide such theoretical data. We have undertaken a substantial and systematic configuration interaction calculation, with an extrapolation process applied to ab initio mixing coefficients, which gives energy differences in agreement with experiment. The length and velocity forms give values that are within 10%–15% of each other. Our results are in sufficiently close agreement with those of Belmonte et al. that we can confidently recommend that their results are much more accurate than the early results of Rudko and Tang, and should be adopted in place of the latter. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

327 KiB

Open AccessArticle

Core Effects on Transition Energies for 3d^k Conﬁgurations in Tungsten Ions

by Charlotte Froese Fischer, Gediminas Gaigalas and Per Jönsson

Atoms 2017, 5(1), 7; https://doi.org/10.3390/atoms5010007 - 8 Feb 2017

Cited by 19 | Viewed by 4294

Abstract

Allenergylevelsofthe3dk,k=1,2,...,8,9,conﬁgurationsfortungstenions,computedusing the GRASP2K fully relativistic code based on the variational multiconﬁguration Dirac–Hartree–Fock method, are reported. Included in the calculations are valence correlation where all 3s,3p,3d orbitals are considered to be valence orbitals, as well as core–valence and core–core effects from the 2s,2p subshells. [...] Read more.

Allenergylevelsofthe3dk,k=1,2,...,8,9,conﬁgurationsfortungstenions,computedusing the GRASP2K fully relativistic code based on the variational multiconﬁguration Dirac–Hartree–Fock method, are reported. Included in the calculations are valence correlation where all 3s,3p,3d orbitals are considered to be valence orbitals, as well as core–valence and core–core effects from the 2s,2p subshells. Results are compared with other recent theory and with levels obtained from the wavelengths of lines observed in the experimental spectra. It is shown that the core correlation effects considerably reduce the disagreement with levels linked directly to observed wavelengths, but may differ signiﬁcantly from the NIST levels, where an unknown shift of the levels could not be determined from experimental wavelengths. For low values of k, levels were in good agreement with relativistic many-body perturbation levels, but for 2 < k < 8, the present results were in better agreement with observation. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

► Show Figures

Figure 1

325 KiB

Open AccessArticle

JJ2LSJ Transformation and Unique Labeling for Energy Levels

by Gediminas Gaigalas, Charlotte Froese Fischer, Pavel Rynkun and Per Jönsson

Atoms 2017, 5(1), 6; https://doi.org/10.3390/atoms5010006 - 27 Jan 2017

Cited by 86 | Viewed by 5428

Abstract

The JJ2LSJ program, which is important not only for the GRASP2K package but for the atom theory in general, is presented. The program performs the transformation of atomic state functions(ASFs) from a jj-coupled CSF basis into an LSJ-coupled CSF basis. In addition, the [...] Read more.

The JJ2LSJ program, which is important not only for the GRASP2K package but for the atom theory in general, is presented. The program performs the transformation of atomic state functions(ASFs) from a jj-coupled CSF basis into an LSJ-coupled CSF basis. In addition, the program implements a procedure that assigns a unique label to all energy levels. Examples of how to use the JJ2LSJ program are given. Several cases are presented where there is a unique labeling problem. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

5238 KiB

Open AccessFeature PaperReview

High-Precision Measurements of the Bound Electron’s Magnetic Moment

by Sven Sturm, Manuel Vogel, Florian Köhler-Langes, Wolfgang Quint, Klaus Blaum and Günter Werth

Atoms 2017, 5(1), 4; https://doi.org/10.3390/atoms5010004 - 21 Jan 2017

Cited by 36 | Viewed by 7655

Abstract

Highly charged ions represent environments that allow to study precisely one or more bound electrons subjected to unsurpassed electromagnetic fields. Under such conditions, the magnetic moment (g-factor) of a bound electron changes significantly, to a large extent due to contributions from [...] Read more.

Highly charged ions represent environments that allow to study precisely one or more bound electrons subjected to unsurpassed electromagnetic fields. Under such conditions, the magnetic moment (g-factor) of a bound electron changes significantly, to a large extent due to contributions from quantum electrodynamics. We present three Penning-trap experiments, which allow to measure magnetic moments with ppb precision and better, serving as stringent tests of corresponding calculations, and also yielding access to fundamental quantities like the fine structure constant α and the atomic mass of the electron. Additionally, the bound electrons can be used as sensitive probes for properties of the ionic nuclei. We summarize the measurements performed so far, discuss their significance, and give a detailed account of the experimental setups, procedures and the foreseen measurements. Full article

(This article belongs to the Special Issue Perspectives of Atomic Physics with Trapped Highly Charged Ions)

► Show Figures

Figure 1

1483 KiB

Open AccessFeature PaperArticle

Hyperfine Structure and Isotope Shifts in Dy II

by Dylan F. Del Papa, Richard A. Holt and S. David Rosner

Atoms 2017, 5(1), 5; https://doi.org/10.3390/atoms5010005 - 20 Jan 2017

Cited by 6 | Viewed by 5047

Abstract

Using fast-ion-beam laser-fluorescence spectroscopy (FIBLAS), we have measured the hyperfine structure (hfs) of 14 levels and an additional four transitions in Dy II and the isotope shifts (IS) of 12 transitions in the wavelength range of 422–460 nm. These are the first precision [...] Read more.

Using fast-ion-beam laser-fluorescence spectroscopy (FIBLAS), we have measured the hyperfine structure (hfs) of 14 levels and an additional four transitions in Dy II and the isotope shifts (IS) of 12 transitions in the wavelength range of 422–460 nm. These are the first precision measurements of this kind in Dy II. Along with hfs and IS, new undocumented transitions were discovered within 3 GHz of the targeted transitions. These atomic data are essential for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines. Lanthanide abundances are important in diffusion modeling of stellar interiors, and in the mechanisms and history of nucleosynthesis in the universe. Hfs and IS also play an important role in the classification of energy levels, and provide a benchmark for theoretical atomic structure calculations. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

► Show Figures

Figure 1

381 KiB

Open AccessFeature PaperArticle

Combining Multiconfiguration and Perturbation Methods: Perturbative Estimates of Core–Core Electron Correlation Contributions to Excitation Energies in Mg-Like Iron

by Stefan Gustafsson, Per Jönsson, Charlotte Froese Fischer and Ian Grant

Atoms 2017, 5(1), 3; https://doi.org/10.3390/atoms5010003 - 12 Jan 2017

Cited by 18 | Viewed by 4792

Abstract

Large configuration interaction (CI) calculations can be performed if part of the interaction is treated perturbatively. To evaluate the combined CI and perturbative method, we compute excitation energies for the

3 l 3 l^{'}

,

3 l 4 l^{'}

and [...] Read more.

Large configuration interaction (CI) calculations can be performed if part of the interaction is treated perturbatively. To evaluate the combined CI and perturbative method, we compute excitation energies for the

3 l 3 l^{'}

,

3 l 4 l^{'}

and

3 s 5 l

states in Mg-like iron. Starting from a CI calculation including valence and core–valence correlation effects, it is found that the perturbative inclusion of core–core electron correlation halves the mean relative differences between calculated and observed excitation energies. The effect of the core–core electron correlation is largest for the more excited states. The final relative differences between calculated and observed excitation energies is 0.023%, which is small enough for the calculated energies to be of direct use in line identifications in astrophysical and laboratory spectra. Full article

(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)

925 KiB

Open AccessArticle

An Investigation on the He⁻(1s2s² ²S) Resonance in Debye Plasmas

by Arijit Ghoshal and Yew Kam Ho

Atoms 2017, 5(1), 2; https://doi.org/10.3390/atoms5010002 - 11 Jan 2017

Cited by 3 | Viewed by 4069

Abstract

The effect of Debye plasma on the

1 s 2 s^{2}^{2} S

resonance states in the scattering of electron from helium atom has been investigated within the framework of the stabilization method. The interactions among the charged particles in Debye plasma [...] Read more.

The effect of Debye plasma on the

1 s 2 s^{2}^{2} S

resonance states in the scattering of electron from helium atom has been investigated within the framework of the stabilization method. The interactions among the charged particles in Debye plasma have been modelled by Debye–Huckel potential. The

1 s 2 s

excited state of the helium atom has been treated as consisting of a

H e^{+}

ionic core plus an electron moving around. The interaction between the core and the electron has then been modelled by a model potential. It has been found that the background plasma environment significantly affects the resonance states. To the best of our knowledge, such an investigation of