Time-resolved spectroscopy of the electrode region in a fluorescent lamp1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (5) ◽  
pp. 627-631
Author(s):  
Thomas Lennartsson ◽  
Sven Huldt
Keyword(s):  
Cross Sections ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Electron Collision ◽  
Fluorescent Lamp ◽  
Recombination Rates ◽  
Penning Ionization ◽  
Time Resolved ◽  
International Colloquium ◽  
Electrode Region

In this paper, the ongoing spectroscopic investigations of the plasma inside a fluorescent lamp at Lund Observatory is presented. The intensity of the spectral lines of neutral and singly ionized mercury and krypton in the electrode region in a fluorescent lamp are investigated, both as a function of current through the tube and time resolved during an AC cycle. The results show different dynamics for different spectral lines, which may be due to different population mechanisms and transport phenomena in the discharge. To correctly interpret the data, a model for the electrode region is necessary; however, for this purpose information on processes like electron collision cross-sections, Penning ionization rates, and recombination rates are needed.

scholarly journals Current Status and Developments of the Atomic Database on Rare-Earths at Mons University (DREAM)

Atoms ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 18 ◽  
Author(s):  
Pascal Quinet ◽  
Patrick Palmeri
Keyword(s):  
Rare Earths ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Current Status ◽  
Time Resolved ◽  
Hartree Fock ◽  
Lanthanide Atoms ◽  
Experimental Values ◽  
Theoretical Results ◽  
Good Agreement

The main purpose of the Database on Rare Earths At Mons University (DREAM) is to provide the scientific community with updated spectroscopic parameters related to lanthanide atoms (Z = 57–71) in their lowest ionization stages. The radiative parameters (oscillator strengths and transitions probabilities) listed in the database have been obtained over the past 20 years by the Atomic Physics and Astrophysics group of Mons University, Belgium, thanks to a systematic and extensive use of the pseudo-relativistic Hartree-Fock (HFR) method modified for taking core-polarization and core-penetration effects into account. Most of these theoretical results have been validated by the good agreement obtained when comparing computed radiative lifetimes and accurate experimental values measured by the time-resolved laser-induced fluorescence technique. In the present paper, we report on the current status and developments of the database that gathers radiative parameters for more than 72,000 spectral lines in neutral, singly-, doubly-, and triply-ionized lanthanides.

High accuracy radiative data for plasma opacities1This article is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 439-449 ◽  
Author(s):  
Sultana N. Nahar
Keyword(s):  
Cross Sections ◽  
Radiation Transport ◽  
High Energy ◽  
Oscillator Strengths ◽  
International Colloquium ◽  
Radiative Processes ◽  
Elemental Abundances ◽  
Ionization Cross Sections ◽  
Photo Ionization ◽  
Atomic Parameters

Opacity, which gives the measure of the radiation transport in plasmas, is caused by the repeated absorption and emission of the propagating radiation by the constituent plasma elements. Microscopically, opacity (κ) depends mainly on two radiative processes: (i) photo-excitation (bound-bound transition) and (ii) photo-ionization (bound-free transition) in addition to electron-photon scattering. The monochromatic opacity κ(ν) at photon frequency ν is determined by the atomic parameters, oscillator strengths (f), and photo-ionization cross sections (σPI). However, total monochromatic opacity is obtained from summed contributions of all possible transitions from all ionization stages of all elements in the source. The calculation of accurate parameters for such a large number of transitions has been the main problem for obtaining accurate opacities. The overall mean opacity, such as the Rosseland mean opacity (κR), depends also on the physical conditions, such as temperature, density, elemental abundances, and equation of state. The necessity for high-precision calculations for opacities may be exemplified by the existing problems, such as the determination of solar elemental abundances. With new computational developments under the Iron Project, we are able to calculate more accurate atomic parameters, such as oscillator strengths for large number of transitions using the relativistic Breit–Pauli R-matrix (BPRM) method. We are finding new features in photo-ionization, such as the existence of extensive and dominant resonant structures in the high-energy region not studied before. These new data should provide more accurate opacities in high-temperature plasmas and can be used to investigate the well-known solar abundance problem.

The chemical composition of the sun1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 327-331 ◽  
Author(s):  
N. Grevesse ◽  
M. Asplund ◽  
A.J. Sauval ◽  
P. Scott
Keyword(s):  
Chemical Elements ◽  
Molecular Data ◽  
Solar Neighborhood ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Solar Photosphere ◽  
International Colloquium ◽  
Laboratory Plasmas ◽  
Selection Of

We have very recently re-determined the abundances of nearly all the available chemical elements in the solar photosphere, from lithium to thorium (Asplund et al. Annu. Rev. Astron. Astrophys. 47, 481 (2009)). This new complete and homogeneous analysis results from a very careful selection of spectral lines of all the indicators of the abundances present in the solar photospheric spectrum, from a discussion of the atomic and molecular data, and from an analysis of these lines based on a new 3D model of the solar outer layers, taking non-LTE effects into account when possible. We present these new results, compare them with other recent solar data as well as with recent results for the solar neighborhood, and discuss some of their most important implications as well as some of the atomic data we still urgently need.

Nonequilibrium Carrier Recombination in Highly Excited Bulk SiC Crystals

2010 ◽  
Vol 645-648 ◽  
pp. 215-218 ◽  
Author(s):  
Kęstutis Jarašiūnas ◽  
Patrik Ščajev ◽  
Vytautas Gudelis ◽  
Paul B. Klein ◽  
Masashi Kato
Keyword(s):  
Cross Sections ◽  
Free Carrier Absorption ◽  
Decay Kinetics ◽  
Recombination Rates ◽  
Time Resolved ◽  
Carrier Recombination ◽  
A Value ◽  
Numerical Fitting ◽  
Carrier Absorption ◽  
Linear And Nonlinear

We applied time-resolved free carrier absorption (FCA) to monitor non-equilibrium carrier dynamics in 4H epilayers and 3C SiC bulk crystals at excess carrier densities in the N = 1017 - 1019 cm-3 range. The numerical fitting of FCA decay kinetics provided the linear and nonlinear carrier recombination rates in the 40-390 K range and the absorption cross-sections eh at 1064 nm. In 4H, the decrease of the bulk lifetime (800 ns) with excitation provided the bimolecular and Auger coefficients B=(1.2±0.4)×10-12 cm3/s and C=(7±4)×10-31cm6/s, respectively, at room temperature. These values for 3C were 55-150 ns, (2.0±0.4)×10-12 cm3/s, and (2±1)×10-32 cm6/s, respectively. The rate of linear and nonlinear recombination increased at lower temperatures. A value of eh =4.4×10-18 cm2 for 3C SiC at 1.064 m was found 2.3 times smaller than that for 4H SiC.

scholarly journals Atomic Physics for Hot Plasmas

1988 ◽  
Vol 102 ◽  
pp. 279-282
Author(s):  
L.A. Vainshtein
Keyword(s):  
Atomic Physics ◽  
Cross Sections ◽  
Experimental Test ◽  
Dielectronic Recombination ◽  
Spectral Lines ◽  
Isoelectronic Sequence ◽  
Recombination Rates ◽  
Theoretical Methods ◽  
Laboratory Plasmas ◽  
Charged Ions

This report treats some aspects of how to obtain and apply main atomic characteristics responsible for the intensities and satellite structures of spectral lines in hot plasmas.The experimental test, of theoretical methods and calculated cross- sections σ is often possible only in a plasma, especially for highly charged ions. In this case the rates < υσ >, rather than σ, are measured for different temperature values. Another difficulty is linked to the analysis of a large number of processes which have to be taken into account simultaneously.In laboratory plasmas (usually during an ionization stage) the ionization, excitation and dielectronic recombination rates are measured for numerous ions with Z ≤ 25. They are discussed in the report by H. Griem at this Colloquium. Unfortunately, in some cases the results are not consistent along the isoelectronic sequence and deviate considerably (up to a factor of 1.5 - 2) from those yielded by cross-beam methods, or calculations.

scholarly journals New atomic data for trans-iron elements and their application to abundance determinations in planetary nebulae1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 379-385 ◽  
Author(s):  
N.C. Sterling ◽  
M.C. Witthoeft ◽  
D.A. Esteves ◽  
R.C. Bilodeau ◽  
A.L.D. Kilcoyne ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Cross Sections ◽  
Dielectronic Recombination ◽  
Elemental Abundance ◽  
Oscillator Strengths ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Element Abundance ◽  
International Colloquium ◽  
Stellar Spectra

Investigations of neutron(n)-capture element nucleosynthesis and chemical evolution have largely been based on stellar spectroscopy. However, the recent detection of these elements in several planetary nebulae (PNe) indicates that nebular spectroscopy is a promising new tool for such studies. In PNe, n-capture element abundance determinations reveal details of s-process nucleosynthesis and convective mixing in evolved low-mass stars, as well as the chemical evolution of elements that cannot be detected in stellar spectra. Only one or two ions of a given trans-iron element can typically be detected in individual nebulae. Elemental abundance determinations thus require corrections for the abundances of unobserved ions. Such corrections rely on the availability of atomic data for processes that control the ionization equilibrium of nebulae (e.g., photoionization cross sections and rate coefficients for various recombination processes). Until recently, these data were unknown for virtually all n-capture element ions. For the first six ions of Se, Kr, and Xe — the three most widely detected n-capture elements in PNe — we are calculating photoionization cross sections and radiative and dielectronic recombination rate coefficients using the multi-configuration Breit–Pauli atomic structure code AUTOSTRUCTURE. Charge transfer rate coefficients are being determined with a multichannel Landau–Zener code. To calibrate these calculations, we have measured absolute photoionization cross sections of Se and Xe ions at the Advanced Light Source synchrotron radiation facility. These atomic data can be incorporated into photoionization codes, which we will use to derive ionization corrections (hence abundances) for Se, Kr, and Xe in ionized nebulae. Using Monte Carlo simulations, we will investigate the effects of atomic data uncertainties on the derived abundances, illuminating the systems and atomic processes that require further analysis. These results are critical for honing nebular spectroscopy into a more effective tool for investigating the production and chemical evolution of trans-iron elements in the Universe.

Recent progress in spectroscopy of tungsten1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (5) ◽  
pp. 551-570 ◽  
Author(s):  
A. Kramida
Keyword(s):  
Energy Levels ◽  
Experimental Studies ◽  
Theoretical Data ◽  
Theoretical Work ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
International Colloquium ◽  
10Th International Colloquium ◽  
Laboratory Plasmas ◽  
Data Tables

This contribution reviews experimental and theoretical work on spectroscopy of tungsten published since the last critical compilation of the energy levels and spectral lines of highly ionized tungsten (Kramida and Shirai. At. Data Nucl. Data Tables, 95, 305 (2009)). Since then, 18 new experimental studies were published, which resulted in new identifications and (or) significantly improved wavelengths of spectral lines and energy levels of Li-like through As-like and Pm-like tungsten. A few tens of theoretical studies of tungsten spectra were published since 2008. A number of them report on high-precision calculations of energy levels, transition wavelengths, and radiative rates for tungsten spectra, such as neutral tungsten, Yb-like, Rh-like through Rb-like, Ag-like, Ga-like, Zn-like, Ni-like, Ca-like, Al-like, Mg-like, Na-like, Ne-like, B-like, Be-like, and Li-like. These developments are reviewed. Based on new experimental data, systematic errors are removed from some of the earlier measurements. Some new data are obtained by analyzing publications of other authors. Based on new published theoretical data, some old experimental results were confirmed and assessed. Revised and extended tables of energy levels and spectral lines of highly ionized tungsten are presented.

Analysis of the core polarization effects in the calculated atomic parameters of Hg iii

2020 ◽  
Vol 493 (1) ◽  
pp. 288-298
Author(s):  
I de Andrés-García ◽  
C Colón
Keyword(s):  
Stark Effect ◽  
Transition Probabilities ◽  
Stellar Atmosphere ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Electron Collision ◽  
Core Polarization ◽  
Polarization Effects ◽  
The Core ◽  
Starting Point

ABSTRACT The presence of Hg iii in the stellar atmosphere in the stars HgMn χ Lupi and HR7775 was reported by Leckrone et al. and Proffitt et al. In this last work, the authors indicate that the intensities of the spectral lines of 1360.50, 1647.48, and 1738.54 Å of Hg iii are relatively strong compared to the intensities of the spectral lines of Hg ii. Although the explanation given by the authors in their conclusions should be correct, the values of the oscillator strengths used by the authors in some cases were not consistent with the experimental lifetimes obtained by Henderson et al. In addition, some of the lines studied by the authors are widely overlapped with intense lines of Hg iii of the same multiplet. In this paper, we present values of transition probabilities and line broadening by electron collision (Stark effect) of several lines of Hg iii in order to clarify the problems indicated above. Since Hg iii is a heavy element, we include the core polarization effects (using the Cowan’s code) in our calculations. Several values of polarizability, taking Fraga values for Hg iv as a starting point, have been considered in this study in order to obtain theoretical values of those parameters close to the experimental ones. The theoretical values of the lifetimes obtained in this study, close to the experimental ones, were obtained for a polarizability value of 3.5 au.

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