J. Plasma Fusion Res. SERIES, Vol.7 (2006) 331-333

New Critical Compilations of Atomic Transition Probabilities
WIESE Wolfgang, FUHR Jeﬀrey, KELLEHER Daniel and PODOBEDOVA Larissa
National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA（Received: 4 October 2004 / Accepted: 17 March 2005）

Abstract
At the National Institute of Standards and Technology (NIST), we are continuing our critical evaluationand compilation work on atomic transition probabilities. We have recently concentrated our eﬀorts on thespectra of Na, Mg, Al, Si and S – for all stages of ionization – and on Fe I and Fe II. These new compilations
represent a drastic improvement in both quantity and quality over earlier NIST publications. We present a
number of graphical comparisons in support of our data selections.
Keywords:
atomic transition probability, atomic ion, oscillator strength, line strength, sodium, magnesium, aluminum,silicon, sulfur, ironlowed and forbidden) for which experimental energies
are known for both lower and upper energy levels. In
general we list only lines for which the line strengths
have estimated uncertainties of ±50% or less. Becauseof the very small amount of experimental results available for highly-charged ions, we had to use theoretical
data for most transitions.
A large source of data for Na, Mg, Al, Si and S is theOpacity Project” [2]. The Opacity Project R-matrix
computations, which generally span quantum numbers
up to n = 10 and l = 4, were performed in LS coupling. For the stronger transitions of many spectra,
good agreement exists between the OP data and datafrom more detailed calculations which consider spinorbit interactions. However, the agreement among theOP calculations and various relativistic calculations becomes worse for transitions between levels where one
or both are appreciably mixed due to the breakdown of
LS coupling. In general, the accuracy of computed line
strengths decreases as the spectra become more complex. The calculations of Froese Fischer and co-workers[3] remain quite accurate, though they only span levels
up to n = 3 (recently, some n = 4 levels have been included for Mg). These calculations were performed by
the multiconfiguration Hartree-Fock (MCHF) method,
including Breit-Pauli corrections, and some of those
spectra were also performed by the multiconfiguration
Dirac-Hartree-Fock (MCDHF) method. Another important source of reliable data is the configuration interaction code-version 3 (CIV3) method of Hibbert [4].
Transition probabilities computed using the many-body

The Atomic Spectroscopy Data Center at NIST has
been involved in publishing critically evaluated atomic
transition probabilities since the early 1960s. Ourpresent work involves tabulating data for the elements
sodium, magnesium, aluminum, silicon, sulfur and iron.
These species were already compiled by us quite sometime ago, but in the meantime, much new work has been
done which enlarges and improves the database, mostly
by sophisticated calculations. Thus, our new compilations contain about 5 10 times more transitions thanthe earlier NIST data volumes, and the uncertainties are
generally significantly smaller. Often, we have compiled up to 1000 lines per spectrum.
In our evaluation procedure, we start by considering
all published results. By applying certain general assessment criteria, we then narrow our considerations tothe sources with the most accurate results. Our final numerical value for each line strength is obtained by averaging among these best data sources (sometimes there
is only one clearly superior source), and an accuracy isassigned. NIST compilations are intended to be sourcesof standard reference data, so that data with large uncertainties are not included.
As a part of the NIST project of critically evaluating transition probabilities of elements from sodium tocalcium, we have produced compilations for Na, Mg,
Al, Si and S. For allowed transitions lying in the 20 –170 Å spectral range, which is of special interest for theChandra X-ray observatory, tables of transition probabilities for 24 ions of neon (Ne V – Ne VIII), magnesium (Mg V – Mg X), silicon (Si VI – Si XII) andsulfur (S VIII – XIV) have already been presented in[1]. In this new work, we consider all transitions (al-”C 2006 by The Japan Society of Plasma

Science and Nuclear Fusion Research

Corresponding author’s e-mail: wolfgang.wiese@nist.gov331

New Critical Compilations of Atomic Transition Probabilities

Fig. 2 Improvement in the f-value situation for Fe I andFe II from 1988 to 2004

Fig. 1 Comparison of line strengths from the CIV3 [5] calculation with the MCHF [3] calculation for the Nelike ion S VII. Allowed transitions.

perturbation theory with Breit-Pauli corrections are alsoquite accurate. Results from many other authors havebeen used as well.
In order to obtain reliable uncertainty estimates forthe transition probabilities, we made graphical and numerical comparisons of the results of the various advanced calculations for as many transitions as possible. We present such a comparison for the Ne-like sulfur spectrum, S VII. Because of the important relativistic eﬀects in this spectrum, we only considered calculations that include spin-orbit eﬀects. A comparison
for the allowed transitions between the CIV3 results ofHibbert et al. [5] and the MCHF data of Fischer [2] isgiven in Fig. 1. There is good agreement (within 10%)for most of these transitions.
For the spectra of Fe I and Fe II, we have mainly
utilized recent experimental data obtained by a combination of accurate lifetime and emission branching-ratio
measurements. These new compilations have been expanded to about 2400 lines for Fe I and 900 lines for Fe
II. As shown below in Fig. 2, the improvement in boththe quality and quantity of the data can be clearly seen.
For Fe I, our data choices relied heavily on the accurate
absorption data of Blackwell et al. [6] and the comprehensive emission/branching-ratio/lifetime data O’Brianet al. [7]. A comparison between these two data sources
is shown in Fig. 3. In the case of Fe II, we also utilized
data sources that combined lifetime measurements with
branching fraction determinations. Such references include a series of experiments done at the University ofWisconsin [8] and a very recent paper by Schnabel etal. [9]. Figure 4 shows a comparison between thesegroups and supports our choice of data selections forthis spectrum.
This work was supported in part by the U.S. Department of Energy, Oﬃce of Fusion Energy Sciences, andthe NASA Oﬃce of Space Science.

Fig. 3 Comparison between the emission/branchingratio/lifetime data of O’Brian et al. [7] and the absorption data of Blackwell and co-workers [6].

Fig. 4 Comparison between the emission experiments
by Schnabel et al. [9] and the University of Wisconsin group [8].

[1]

[2]
[3]

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