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4.2. Radiative Transition Probabilities

A general bibliography of forbidden transitions was prepared by Biemont and Zeippen, in proceedings of the Meudon Atomic Data Workshop (1989) published in Journal de Physique, Vol.1, Coll.1, Suppl. II, No. 3, 1991 (Ed: C.J. Zeippen and M. LeDourneuf). This volume (hereafter referred to as ZLD) also contains a review by Wiese.

Several evaluated compilations, including the data, are:

1. ``Forbidden lines in ns2 npk ground configuration and nsnp excited configurations of Beryllium through Molybdenum atoms and ions'', Victor Kaufman and Jack Sugar , J. Phys. Chem. Ref. Data, 15, 321 (1986). This work is complemented by additional compilations in J. Phys. Chem. Ref. Data 16 Suppl. 3, and 17 Suppl. 4, by J.R. Fuhr, W.C. Martin and W.L. Wiese.

2. ``Atomic transition probabilities'', J. Fuhr and W. Wiese in the CRC Handbook of Chemistry and Physics, 71st Edition, 1990. This is a critical compilation including both forbidden and allowed lines.

3. ``Atomic data for resonance absorption lines I. wavelengths longward of the Lyman limit'', D.C. Morton, ApJSupp, 77, 119 (1991).

4. TOPBASE contains a large number of oscillator strengths (A-values may also be obtained) for dipole transitions between LS multiplets for all isoelectronic sequences up to Si-like ions, with Z leq 26. The TOPBASE data is with calculated (not observed) wavelengths, and does not include fine structure components within the multiplets. Future revisions of TOPBASE intend to include such data.

Some of the Opacity Project data has been extended to incorporate fine structure through algebraic transformation, from LS multiplet to LSJ components, and using experimentally observed energy levels: Si I, S III, Ar V and Ca VII (Nahar 1993) and Fe II (Nahar 1994); the Fe II data includes 21,587 fine structure transitions. Another calculation using the R-matrix method is by Bell et al. (1994, ApJS in press) for 26 dipole fine structure transitions in O II.

An updated version of the old NBS tables is in preparation at the National Institute for Standards and Technology (NIST). This is an evaluated compilation with some data from experiments and other sources, but primarily incorporating the Opacity Project data for some of the light elements (with fine structure included as in Nahar's work). The preliminary reference is: ``Atomic Transition Probabilities of Carbon, Nitrogen, and Oxygen - A Critical Data Compilation'', W.L. Wiese, J.R. Fuhr, and T.M. Deters, Monograph Series of J. Phys. Chem. Ref. Data, 1995.

Experimental measurements are relatively few. Among the recent works are the intersystem A-values measured by the Harvard-Nevada groups for several ions (Smith and Parkinson, paper presented at this meeting); dipole transitions in Si I and Fe II using the laser resonance-fluorescence method (e.g. O'Brian and Lawler 1991), and for dipole allowed transitions in O II, O III and other ions using Beam-Foil spectroscopy (Engström 1993). The experimental techniques employed by these groups are highly accurate, with uncertainties within a few percent for lifetimes and A-values.

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