Resonant Electron Impact Excitation of 3d Levels in Fe14+ and Fe15+
TL;DR: In this article, the experimental results are compared with theoretical cross sections calculated based on fully relativistic wave functions and the distorted wave approximation for the resonance strength of 3p-3d transitions in Fe14+ and Fe15+ excited with a mono-energetic electron beam.
Abstract: We present laboratory spectra of the 3p–3d transitions in Fe14+ and Fe15+ excited with a mono-energetic electron beam. In the energy-dependent spectra obtained by sweeping the electron energy, resonant excitation is confirmed as an intensity enhancement at specific electron energies. The experimental results are compared with theoretical cross sections calculated based on fully relativistic wave functions and the distorted wave approximation. Comparisons between the experimental and theoretical results show good agreement for the resonance strength. A significant discrepancy is, however, found for the non-resonant cross section in Fe14+. This discrepancy is considered to be the fundamental cause of the previously reported inconsistency of the model with the observed intensity ratio between the and transitions.
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TL;DR: In this article, the level structures of palladium-like ions and the behavior of their metastable states with an electron beam ion trap were studied and compared with theoretical simulations based on a collisional-radiative model.
Abstract: We study the level structures of palladium-like ${\mathrm{I}}^{7+}$ $(Z=53)$ and ${\mathrm{Ba}}^{10+}$ $(Z=56)$ and the behavior of their metastable states with an electron beam ion trap. The difference in the level structures between ${\mathrm{I}}^{7+}$ and ${\mathrm{Ba}}^{10+}$ arising from the configuration crossing between $4{d}^{\ensuremath{-}1}5p$ and $4{d}^{\ensuremath{-}1}4f$ around the atomic number $Z$ = 56 causes significant differences in the lifetimes of the metastable states. ${\mathrm{Ba}}^{10+}$ has several long-lived levels $(g{10}^{\ensuremath{-}3} \mathrm{s})$ in the electron configurations $4{d}^{\ensuremath{-}1}5s$ and $4{d}^{\ensuremath{-}1}4f$, whereas the lifetime of the same $4{d}^{\ensuremath{-}1}4f$ levels in ${\mathrm{I}}^{7+}$ is much shorter due to the appearance of deexcitation channels to a lower energy level in $4{d}^{\ensuremath{-}1}5p$. The extreme ultraviolet spectra identified through comparison with theoretical simulations based on a collisional-radiative model evince the level crossing between the $4{d}^{\ensuremath{-}1}5p$ and $4{d}^{\ensuremath{-}1}4f$ configurations in ${\mathrm{Ba}}^{10+}$. Additionally, we investigate the ionization processes from the metastable states in palladium-like ions by observing the electron energy dependence of the prominent visible line $(4{d}^{\ensuremath{-}1}:{^{2}\mathrm{D}}_{5/2}\text{\ensuremath{-}}{^{2}\mathrm{D}}_{3/2})$ of rhodium-like ${\mathrm{I}}^{8+}$ and ${\mathrm{Ba}}^{11+}$. The electron energy dependencies reflecting the properties of the metastable states show a difference between iodine and barium, which can be explained by the populations of the metastable states calculated with theoretical simulations.
8 citations
TL;DR: In this paper, the authors investigated experimentally and theoretically dielectronic recombination populating doubly excited configurations $3l3l'$ (LMM) in Fe XVII, the strongest channel for soft X-ray line formation in this ubiquitous species.
Abstract: We investigated experimentally and theoretically dielectronic recombination (DR) populating doubly excited configurations $3l3l'$ (LMM) in Fe XVII, the strongest channel for soft X-ray line formation in this ubiquitous species. We used two different electron beam ion traps and two complementary measurement schemes for preparing the Fe XVII samples and evaluating their purity, observing negligible contamination effects. This allowed us to diagnose the electron density in both EBITs. We compared our experimental resonant energies and strengths with those of previous independent work at a storage ring as well as those of configuration interaction, multiconfiguration Dirac-Fock calculations, and many-body perturbation theory. This last approach showed outstanding predictive power in the comparison with the combined independent experimental results. From these we also inferred DR rate coefficients, unveiling discrepancies from those compiled in the OPEN-ADAS and AtomDB databases.
3 citations
TL;DR: The database contains numerical data of cross sections and rate coefficients for electron collision or ion collisions with atoms and molecules, attached with bibliographic information on their data sources, which are applicable to understand atomic and molecular processes in various plasmas.
Abstract: The National Institute for Fusion Science (NIFS) has compiled and developed atomic and molecular numerical databases for various collision processes and makes it accessible from the internet to the public. The database contains numerical data of cross sections and rate coefficients for electron collision or ion collisions with atoms and molecules, attached with bibliographic information on their data sources. The database system provides query forms to search data, and numerical data are retrievable. The graphical output is helpful to understand energy dependence of cross sections and temperature dependence of rate coefficients obtained by various studies. All data are compiled mainly from published literature, and data sources can be tracked by the bibliographic information. We also have data of sputtering yields and back-scattering coefficients for solid surfaces collided by ions in the database. All data in the database are applicable to understand atomic and molecular processes in various plasmas, such as fusion plasma, astrophysical plasma and applied plasma, as well as for understanding plasma–surface interaction in plasmas.
3 citations
TL;DR: In this article , the authors demonstrate hyperfine-structure-resolved laser spectroscopy of HCIs in an electron beam ion trap plasma, employing the magnetic-dipole transition in the 4 d 9 5 s state of 127 I 7+ .
Abstract: Abstract Hyperfine structures of highly charged ions (HCIs) are favourable spectroscopic targets for exploring fundamental physics along with nuclear properties. Recent proposals of HCI atomic clocks highlight their importance, especially for many-electron HCIs, and they have been theoretically investigated by refining atomic-structure calculations. However, developments in hyperfine spectroscopy of many-electron HCIs have not proceeded due to experimental difficulty. Here, we demonstrate hyperfine-structure-resolved laser spectroscopy of HCIs in an electron beam ion trap plasma, employing the magnetic-dipole transition in the 4 d 9 5 s state of 127 I 7+ . Ion-state manipulation by controlled electron collisions in the well-defined laboratory plasma enables laser-induced fluorescence spectroscopy of trapped HCIs. The observed spectrum of evaporatively cooled ions under low magnetic fields shows characteristic features reflecting the hyperfine structures. The present demonstration using combined optical and plasma approaches provides a benchmark for state-of-the-art atomic calculations of hyperfine structures in many-electron HCIs, and offers possibilities for a variety of unexploited experiments.
1 citations
TL;DR: In this article , the lifetime measurement of an electron-beam ion trap using pulsed laser excitation from a metastable state which is continuously populated by electron collisions is presented, which provides a new benchmark for relativistic atomic structure calculations with $d$-state electrons.
Abstract: We present the lifetime measurement of the ${(4{d}_{3/2}^{\ensuremath{-}1}5s)}_{J=2}$ state in Pd-like ${\mathrm{I}}^{7+}$, which predominantly decays to the $(4{d}^{10}{)}_{J=0}$ ground state by an electric-quadrupole transition modified by strong spin-orbit mixing. We measure this microsecond-order lifetime in an electron-beam ion trap using pulsed laser excitation from a metastable state which is continuously populated by electron collisions. The measured lifetime provides a new benchmark for relativistic atomic structure calculations with $d$-state electrons.
References
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TL;DR: The Atmospheric Imaging Assembly (AIA) as discussed by the authors provides multiple simultaneous high-resolution full-disk images of the corona and transition region up to 0.5 R ⊙ above the solar limb with 1.5-arcsec spatial resolution and 12-second temporal resolution.
Abstract: The Atmospheric Imaging Assembly (AIA) provides multiple simultaneous high-resolution full-disk images of the corona and transition region up to 0.5 R ⊙ above the solar limb with 1.5-arcsec spatial resolution and 12-second temporal resolution. The AIA consists of four telescopes that employ normal-incidence, multilayer-coated optics to provide narrow-band imaging of seven extreme ultraviolet (EUV) band passes centered on specific lines: Fe xviii (94 A), Fe viii, xxi (131 A), Fe ix (171 A), Fe xii, xxiv (193 A), Fe xiv (211 A), He ii (304 A), and Fe xvi (335 A). One telescope observes C iv (near 1600 A) and the nearby continuum (1700 A) and has a filter that observes in the visible to enable coalignment with images from other telescopes. The temperature diagnostics of the EUV emissions cover the range from 6×104 K to 2×107 K. The AIA was launched as a part of NASA’s Solar Dynamics Observatory (SDO) mission on 11 February 2010. AIA will advance our understanding of the mechanisms of solar variability and of how the Sun’s energy is stored and released into the heliosphere and geospace.
4,321 citations
TL;DR: The CHIANTI database as mentioned in this paper is a set of atomic data and transition probabilities necessary to calculate the emission line spectrum of astrophysical plasmas, including atomic energy levels, atomic radiative data such as wavelengths, weighted oscillator strengths and A values, and electron collisional excitation rates.
Abstract: CHIANTI consists of a critically evaluated set of atomic data and transition probabilities necessary to calculate the emission line spectrum of astrophysical plasmas. The data consist of atomic energy levels, atomic radiative data such as wavelengths, weighted oscillator strengths and A values, and electron collisional excitation rates. A set of programs that use these data to calculate the spectrum in a desired wavelength range as a function of temperature and density is also provided. A suite of programs has been developed to carry out plasma diagnostics of astrophysical plasmas. The state-of-the-art contents of the CHIANTI database will be described and some of the most important results obtained from the use of the CHIANTI database will be reviewed.
2,116 citations
TL;DR: In this paper, a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...
Abstract: We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionizatio...
1,055 citations
TL;DR: The CHIANTI spectral code as mentioned in this paper consists of two parts: an atomic database and a suite of computer programs in Python and IDL, together, they allow the calculation of the optically thin spectrum of astrophysical objects and provide spectroscopic plasma diagnostics for the analysis of the astrophysical spectra.
Abstract: The CHIANTI spectral code consists of two parts: an atomic database and a suite of computer programs in Python and IDL. Together, they allow the calculation of the optically thin spectrum of astrophysical objects and provide spectroscopic plasma diagnostics for the analysis of astrophysical spectra. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, ionization, and recombination rate coefficients, as well as data to calculate free-free, free-bound, and two-photon continuum emission. Version 7.1 has been released, which includes improved data for several ions, recombination rates, and element abundances. In particular, it provides a large expansion of the CHIANTI models for key Fe ions from Fe VIII to Fe XIV to improve the predicted emission in the 50-170 A wavelength range. All data and programs are freely available at http://www.chiantidatabase.org and in SolarSoft, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net.
570 citations
TL;DR: H ULLAC as mentioned in this paper, an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes, is based on relativistic quantum mechanical calculations including configuration interaction.
Abstract: We describe H ULLAC , an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes. This code evolved and has been used over the years, but so far, there was no coherent, comprehensive, and in-depth presentation of it. It is based on relativistic quantum mechanical calculations including configuration interaction. The collisional cross sections are calculated in the distorted wave approximation. The theory and code are presented, emphasizing the various novel methods that has been developed to obtain accurate results very efficiently. In particular we describe the parametric potential method used for both bound and free orbitals, the factorization–interpolation method applied in the derivation of collisional rates, the phase amplitude approach for calculating the continuum orbitals and the N JGRAF graphical method used in the calculation of the angular momentum part of the matrix elements. Special effort has been made to insure the simplicity of use, which is demonstrated in an example.
437 citations