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Atomic transition probabilities for about 6400 allowed and forbidden lines of S I – S XV are tabulated based on a critical evaluation of recent literature sources. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes. These tables provide data of interest for astronomical as well as laboratory plasmas. They will also be useful for the diagnostics of plasmas encountered in fusion energy research.

Tables of wavelengths, line classifications, and transition probabilities have been critically compiled for ionized spectra of neon (Ne V-VIII), magnesium (Mg V-X), silicon (Si VI-XII), and sulfur (S VIII-XIV) in the 20 Å-170 Å region. The tables provide basic atomic data for about 3300 transitions in support of astronomical studies from the Chandra X-ray Observatory.

Tables of critically compiled wavelengths, energy levels, line classifications, and transition probabilities are given for spectra of ionized neon (Ne V–Ne VIII) in the region 55–170 A. These tables provide data of interest for the Emission Line Project in support of analysis of astronomical data from the Chandra X-Ray Observatory. They will also be useful for the diagnostics of plasma encountered in fusion energy research. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes.

Tables of critically compiled wavelengths, energy levels, line classifications, and transition probabilities are given for spectra of ionized silicon (Si VI–Si XII) in the region 25–170 A. These tables provide data of interest for the Emission Line Project in support of analyses of astronomical data from the Chandra X-ray Observatory. They will also be useful for the diagnostics of plasmas encountered in fusion energy research. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes.

Tables of critically compiled wavelengths, energy levels, line classifications, and transition probabilities are given for spectra of ionized magnesium (Mg V–Mg X) in the region 35–170 A. These tables provide data of interest for the Emission Line Project in support of analyses of astronomical data from the Chandra X-Ray Observatory. They will also be useful for the diagnostics of plasmas encountered in fusion energy research. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes.

Tables of critically compiled wavelengths, energy levels, line classifications, and transition probabilities are given for spectra of ionized sulfur (S VIII–S XIV) in the region 21–170 A. These tables provide data of interest for the Emission Line Project in support of the analysis of astronomical data from the Chandra X-Ray Observatory. They will also be useful for the diagnostics of plasmas encountered in fusion energy research. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes.

We have extended our critical review of the available experimental data on Stark widths and shifts for spectral lines of non‐hydrogenic neutral atoms and positive ions by one year, including the year 2000, so that we now cover the period from 1989 through the end of 2000. Our recently completed new review represents a continuation of earlier critical reviews up to 1988. Data tables containing the selected experimental Stark broadening parameters are presented with estimated accuracies. Guidelines for the accuracy estimates, developed during the previous reviews, are summarized. The data are arranged according to elements and spectra, and these are presented in alphabetical and numerical order, respectively. A total of 77 spectra are covered, and the material on multiply charged ions has significantly increased. Comparisons with comprehensive calculations based on semi‐classical theory are made whenever possible, since the comparison with theory has often been a principal motivation for the experiments.

Atomic transition probabilities for allowed and forbidden lines of Ba I and Ba II are tabulated, based on a critical evaluation of recent literature sources. The data are presented in multiplet format and are ordered by increasing excitation energies.

Emission experiments, performed at NIST and the Ruhr-University Bochum, have provided sensitive tests of recent atomic structure calculations. Somewhat surprisingly, numerous large discrepancies have been found between experiment and theory, and also between different sophisticated calculations. Some systematic trends for these large differences show up and are reviewed.

We have measured the relative transition probabilities of about $100 3s\ensuremath{-}3p$ and $3p\ensuremath{-}3d$ lines of neutral fluorine in the visible and near-infrared spectrum with a wall-stabilized high-current arc, which is operated under conditions very close to partial local thermodynamic equilibrium. The set of measured lines includes about 40 intersystem transitions. Our data have been placed on an absolute scale by normalizing several strong transitions to the results of the OPACITY Project calculations, which are expected to be quite accurate for such transitions. We estimate that the uncertainties of our absolute transition probability values are in the \ifmmode\pm\else\textpm\fi{}15% to \ifmmode\pm\else\textpm\fi{}20% range, while the uncertainties of the relative values do not exceed 6%, except for very weak transitions. Our results indicate that especially for $3p\ensuremath{-}3d$ transitions appreciable departures from LS coupling are encountered. Comparisons with other results indicate that earlier experimental data agree well with ours on a relative scale, but need to be renormalized.

We have measured the atomic transition probabilities of two weak $E1$ multiplets in neutral oxygen for which advanced atomic structure calculations have encountered problems due to severe cancellation of positive and negative parts of the transition integrand. Measurements were made in emission from a wall-stabilized arc. Our results differ significantly from those of all recent calculations.

With a wall-stabilized arc source, we have measured the relative line strengths for various neutral carbon lines between electronic states with angular momentum quantum numbers l = 0, 1, 2 (s, p, d) and principal quantum numbers 3, 4 and 5, in order to provide some experimental data on the spectroscopic coupling situation for this spectrum. C I is of interest because it is the first element in the periodic table for which calculations have predicted significant departures from LS-coupling line strengths for prominent transitions, while lighter atoms and ions adhere quite closely to the LS-coupling scheme. We have found indeed that for 3p-4d and 3p-5s lines the deviations of the measured line strengths from LS-coupling values become large, while the agreement with recent intermediate coupling calculations is very good.

We have measured the relative line strengths for a fairly large number of lines of the 3s-3p and 3p-3d transition arrays of N II with a wall-stabilized arc source in order to test the quality of recent advanced atomic structure calculations. We have observed significant deviations from LS coupling for weaker 3p-3d lines and have found that our measurements agree much better with recent intermediate coupling results. Also, fairly strong intersystem, or spin-forbidden, lines occur for the N II ion due to a near coincidence of the 3s${\mathrm{}}^{1}$${\mathit{P}}^{\mathit{o}}$ and 3s${\mathrm{}}^{3}$${\mathit{P}}^{\mathit{o}}$ levels. We provide experimental comparison data for two recent calculations that differ by a factor of 2 for these intersystem lines. \textcopyright{} 1996 The American Physical Society.

During the course of critical compilations of atomic oscillator strengths at the National Institute of Standards and Technology over the last 30 years, we have developed and refined a general scheme to assess the accuracy of the pertinent experimental and theoretical data. To arrive at the accuracy ratings, we have utilized general assessments of the various approaches, the attention the authors give to the critical factors of their method, the authors' uncertainty estimates, extensive data comparisons, and fits into systematic trends. Some examples will be shown which indicate that accuracy estimates in the literature are often too optimistic.

The branching ratio technique for radiometric calibrations in the vacuum ultraviolet spectral region is briefly reviewed. Lists of transitions suitable for use with the technique are given for nitrogen-like species (N I, O II, and Ne IV) along with pertinent data for their application.

Critically evaluated wavelengths, energy levels, ionization energies, line classifications, oscillator strengths, and atomic transition probabilities for Mn VII to Mn XXV are tabulated. A short review of the line identifications and wavelength measurements is given for each stage of ionization. Grotrian diagrams are also presented to provide graphical overviews. The literature has been surveyed to December 1991.

Wavelengths, energy levels, ionization energies, line classifications, oscillator strengths, and atomic transition probabilities for Cr v to Cr XXIV are tabulated. A short review of the line identifications and wavelength measurements is given for each stage of ionization. Grotrian diagrams are given to provide graphical overviews. The literature has been surveyed through December 1991. §

The Stark broadening tables for hydrogen Lyman, Balmer and Paschen lines published in the early seventies give accurate results for the widths of the β lines down to relatively low electron densities, and for the far line wings in general. However, the half-widths of the α lines can be in error by as much as a factor of 30, particularly at intermediate densities. Modern theoretical methods are capable of producing accurate values over the entire density range. Recent developments in the Stark broadening of non-hydrogenic species are also considered.

We operated a high-current wall-stabilized arc to generate a low-temperature, steady-state plasma in nitrogen, with admixtures of argon, helium, and oxygen. We measured the relative atomic transition probabilities for several strong and weak 3s-3p and 3p-3d lines of neutral nitrogen and placed them on an absolute scale with experimental lifetime data available in the literature. We obtained good agreement with recent advanced calculations and an earlier measurement for the strong transitions but encountered appreciable discrepancies for weak transitions.

We have critically compiled the atomic transition probabilities of Ar ii lines by combining recent high‐accuracy lifetime data with branching‐ratio emission measurements. We present several comparisons of the various literature data, including theoretical results, and we discuss our assessment procedure in detail. On the basis of this procedure, we present an extension list of critically evaluated transition probabilities with uncertainty estimates.

The branching-ratio technique for radiometric calibrations in the vacuum ultraviolet is briefly reviewed. A list of transitions suitable for use of the technique is given for boron-like ions, along with pertinent data for their application.

We have examined regularities in plasma-produced line shifts (Stark shifts) by a comprehensive analysis of literature data. Since the shifts are the result of atomic collision processes, regularities are expected from general atomic structure considerations. Specifically, systematic behavior should occur for spectral series and for corresponding transitions in homologous atoms and isoelectronic ions. Also, Stark shifts should be similar for lines within multiplets and, to a lesser degree, within supermultiplets and transition arrays. Numerous examples show conclusively that the measured data exhibit these predicted regularities. When pronounced irregularities occur, they are readily explainable in terms of special circumstances in the atomic structure.

Wavelengths, energy levels, level designations, oscillator strengths, and atomic transition probabilities for the vanadium ions V VI to V XXIII are tabulated. A short review of the line identifications and wavelength measurements is given for each stage of ionization. Grotrian diagrams are also presented to provide graphical overviews. The literature has been surveyed to September 1991.

Wavelengths, energy levels, level classifications, oscillator strengths, and atomic transition probabilities for the cobalt ions Co VIII to Co XXVII are tabulated. A short review is given for the wavelength measurements on each stage of ionization. Grotrian diagrams are also presented to provide graphical overviews. The literature has been surveyed to March 1990.

An overview of plasma diagnostic techniques based on atomic spectroscopy is given. Two widely used spectroscopic techniques-the Boltzmann-plot or slope method for excitation temperature measurements and Stark width determinations for electron density measurements-are discussed in detail. Since these techniques depend critically on the availability of accurate atomic data, especially transition probabilities and Stark broadening parameters, the numerical data are reviewed with respect to availability and quality. For the important spectra of Ar I and Fe I, tables of the most accurate transition probabilities-typically with uncertainties of ±10% or less-are given, which are based on very recent critical compilations. Some specific data needs are pointed out which would significantly contribute to improve the accuracy of the diagnostic techniques.

A critical review of the available experimental data on Stark widths and shifts for spectral lines of non‐hydrogenic neutral atoms and positive ions has been carried out. The review covers the period from 1983 through the end of 1988 and represents a continuation of earlier critical reviews up to 1982. Data tables containing the selected experimental Stark broadening parameters are presented with estimated accuracies. Guidelines for the accuracy estimates have been done developed during the previous reviews and are summarized. The data are arranged according to elements and spectra, and these are presented in alphabetical and numerical order, respectively. Comparisons with comprehensive calculations based either on the semiclassical theory, or—for multiply ionized atoms—on the modified semiempirical approximation, are made whenever possible, since the comparison with theory has often been a principal motivation for the experiments.

Wavelengths, energy levels, level classifications, oscillator strengths, and atomic transition probabilities of the iron ions Fe viii to Fe xxvi are critically reviewed and tabulated. Grotrain diagrams are also presented to provide graphical overviews. The literature has been surveyed to March 1988.

This paper summarizes work at the National Institute of Standards and Technology (NIST) in support of the International Atomic Energy Agency (IAEA) Coordinated Research Project on "Light Element Atom, Molecule and Radical Behaviour in the Divertor and Edge Plasma Regions." It includes numerical data on radiative transition rates for ions of fluorine and neon critically compiled at NIST.

Atomic and molecular spectroscopic data are essential for the analysis of astronomical spectra and for modelling conditions in astronomical objects where photon-induced processes are important. In order to assess the atomic and molecular data required for analyzing spectroscopic observations from existing and planned orbiting observatories, and to provide space astronomers with a current inventory of atomic and molecular data compilations, a meeting was held as part of the XXIst General Assembly of the International Astronomical Union in Buenos Aires, Argentina, in July of 1991. This book comprises written versions of the majority of the presentations made at the meeting. This chapter reviews, in general terms, the use of atomic and molecular spectroscopic data in astrophysics and discusses current state of laboratory capabilities for obtaining these data.

Parmi les 3 quantites principales qui caracterisent les raies spectrales, les probabilites de transition atomique sont bien moins connues que les longueurs d'onde ou les niveaux d'energie. L'etat de la precision des donnees des probabilites de transition est passe en revue

Three atomic spectroscopic databases of the U.S. National Institute of Standards and Technology are reviewed. First, our principal spectroscopic database, the Atomic Spectra Database (ASD), is discussed, which will soon be put on the internet in a new, entirely redesigned and expanded version 3.0. This new edition will include several additional critical compilations that were recently completed at NIST. Furthermore, two new smaller specialized databases will be reviewed, — a handbook of basic atomic spectroscopic data and a tabulation of data for soft x‐ray lines, tailored to the needs of x‐ray space observatories. Finally, an overview of our plans for new critical data compilations during the next two‐to‐three years will be presented.

Summary from only given. High efficiency electrical light sources used in lighting applications are based on electrical discharges in plasmas. The systematic search for improved lighting plasmas increasingly relies on plasma discharge modeling with computers and requires better and more comprehensive knowledge of basic atomic data such as radiative transition probabilities and collision cross sections. NIST has ongoing research programs aimed at the study of thermal equilibrium plasmas such as high pressure electric arcs and non-equilibrium plasmas in radio-frequency discharges and high current hollow cathode lamps. In emission experiments we have measured branching fractions and determined absolute transition probabilities for spectral lines in Ne I, Ne II, F I, O I and O II. In case of the Ne measurements the line radiation emitted by a high current hollow cathode lamp was analyzed with a 2 m monochromator. In addition, the spectra of Ne I and Ne II were measured with a UV Fourier transform spectrometer at very high spectral resolution. The line intensities were subsequently calibrated to absolute radiances. Where complete sets of transitions from an upper level could be observed, recent lifetime data for these levels were used to determine absolute transition probabilities. The accuracy of our branching fraction data is 5% for the stronger lines.

A critical review and tabulation of the available experimental data on Stark widths and shifts for spectral lines non‐hydrogenic neutral atoms and positive ions has been carried out. The review covers the period from 1983 through the end of 1988 and represents a continuation of earlier critical reviews through the year 1982.

The status of experimental studies of the plasma broadening and shifts of non-hydrogenic neutral atom and positive ion spectral lines is reviewed, and the results of comparisons with theory are discussed. Advances in the experimental techniques and diagnostic procedures are also reviewed.

With a wall-stabilized high-current arc, we have measured the transition probabilities of several multiplet pairs of C I, N I, and O I. Pairs have been selected for which two recent ab initio calculations have produced widely different results. All chosen multiplets are among the prominent, strong features of their respective spectra, and the pairing is in each case done for multiplets that hardly differ in their excitation energies. Our results do not favor either of the calculations, but are consistent with an earlier experiment.

A summary of the contents and features of the new NIST Atomic Spectra Database is presented. All material in this large database has been obtained from critical data assessments done over the last 30 years. Only reference data, i.e., data fulfilling certain quality requirements, are included. For each spectral line and energy level, one numerical value—the “best” available value—is tabulated.

A new database has been created that makes a wealth of information on spectra, energy levels, and transition probabilities for atoms and atomic ions easily available via the World Wide Web. These data will be a valuable resource for interpretation of solar and other astrophysical spectra obtained from ground-based and space observations.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.