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Radiative lifetime measurements have been performed, with a time-resolved laser-induced fluorescence technique, for 20 odd-parity levels of La I belonging to the configurations 5d26p, 5d6s6p and 4f5d6s. The new results are compared with the few experimental data available in the literature and with theoretical calculations including configuration interaction effects. The agreement theory-experiment is generally satisfying but discrepancies are observed for some levels emphasizing the difficulty to get a reliable theoretical model in such a heavy and complex neutral element. [ABSTRACT FROM AUTHOR]

We report on a calculation of five lifetimes of metastable levels in Ar II, obtained with a relativistic Hartree-Fock method in which most of the intravalence correlation is represented within a configuration interaction scheme while core-valence correlation is described by a core-polarization model potential with a core-penetration corrective term. The quality of the calculation has been assessed through an experimental determination of the radiative lifetime of the metastable 3d4F9/2 level. The experiment was performed with a laser probing technique on a stored ion beam at the CRYRING of Stockholm. [ABSTRACT FROM AUTHOR]

New radiative lifetimes for 20 levels of Pr II have been measured using the time-resolved laser-induced fluorescence (LIF) technique. The combination of these experimental values with theoretical branching fractions (BF) obtained with the pseudo-relativistic Hartree-Fock (HFR) approach has allowed us to determine oscillator strengths and transition probabilities for about 150 lines appearing in the spectral region between 369.9 and 741.2 nm. A detailed discussion of our new results and comparisons with previous data are also given in the present paper. [ABSTRACT FROM AUTHOR]

The satellite structure of 1s2p[sup 1, 3]P[sub 1]–1s[sup 2 1]S[sub 0] lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree–Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Theoretical transition probabilities have been obtained for 54 n = 3 transitions depopulating the 3 s3 p1Po, 3p2 3P, 1D, 1S, 3 s3 d1D, 3D and 3 p3 d3Po, 3Do, 3Fo, 1Fo, 1Do, 1Po levels, including 14 transitions not yet observed. Some of these predictions have been compared with experimental lifetimes obtained by beam-foil spectroscopy for four n = 3 levels of K7+. An excellent agreement is observed between theory and experiment for all the levels. [ABSTRACT FROM AUTHOR]

Transitions between the five fine-structure levels in the 3 s23 p3 ground configuration of Fe XII (P-like) are of interest in astrophysics and terrestrial plasma diagnostics. The decay rates give rise to level lifetimes in the millisecond range, which have been measured recently at a heavy-ion storage ring. While most of the 3 s23 p23 d levels are short-lived, two of these levels have no E1 decay channels and may also have millisecond lifetimes. We present HFR and MCDF calculations of the E1, M1, E2 and M2 transition rates between the 3 s23 p3, 3s3p4 and 3 s23 p23 d levels and compare the lifetime results to most recent experimental data as well as to other predictions. [ABSTRACT FROM AUTHOR]

Lifetimes of three levels belonging to the configuration 4 f135 d with J = 1 in Yb III have been measured for the first time using the time-resolved laser-induced fluorescence method. Experimental transition probabilities have been deduced for the transitions between the levels studied and the ground state. The comparison of the experimental lifetimes with theoretical data, deduced within the relativistic Hartree-Fock (HFR) approach, underlines the dramatic importance of an adequate consideration of core-polarization effects in the theoretical model and the sensitivity of one of the lifetime values to small correlation effects. [ABSTRACT FROM AUTHOR]

The lifetimes of the 4 d2D 3/2,5/2 levels of Sr+ have been determined both experimentally and theoretically. The experiment was performed at an ion storage ring utilising collinear laser excitation. The calculation was performed by the Hartree-Fock method including relativistic effects and core polarisation. The obtained lifetimes (which are about 0.4 s) are discussed in detail and compared with earlier published results. In addition, calculated lifetimes of a large number of excited states in Sr+ are included. [ABSTRACT FROM AUTHOR]

Studies of hyperfine structure of metastable states are facilitated by storage rings and ion traps. Here we report on the development of a method to study metastable states of stored singly charged ions by laser excitation. The experiments were performed at the accelerator and storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm. We discuss means to improve the resolution and the possibility to extend the method to highly charged ions. [ABSTRACT FROM AUTHOR]

Previous works devoted to the Ne V spectrum are very fragmentary and yield a rather controversial picture of this ion. A lot of unidentified lines are still reported in these multiple studies. In the present paper, Hartree-Fock calculations and least-squares fits over the whole set of the available data (including the most recent ones) have been performed. As a result, a comprehensive view of the Ne V spectrum is presented. 10 new energy levels and 40 newly classified lines are proposed. An improved value of the ionisation potential of Ne V is also proposed. [ABSTRACT FROM AUTHOR]

Since Moore published her well-known tables of atomic and ionic energy levels (in 1949-1951), the number of observed lines of the light atoms and their ions has grown significantly. The lack of complete and consistent up-to-date tables of spectral lines and energy levels, particularly of the neon-ions spectra, notably reduces possibilities of interpretation of astrophysical and laboratory spectra. In the present paper, all optical spectral lines of Ne IV observed in 24 previous works have been systematised together with recent observations made by means of the beam-foil method at Liège University. As a result of our extended analysis of the whole set of available data, 35 new energy levels have been found and 90 newly classified spectral lines have been listed for the Ne IV spectrum, only a few of them having been reported previously. A complete table of observed and classified spectral lines has been built, and the list of optimised energy levels has been derived from it in a consistent way. A new, improved, ionisation potential of Ne IV has been deduced from the experimental data. [ABSTRACT FROM AUTHOR]

Spectra and decay curves of boron-like (Na VII) and beryllium-like (Na VIII) sodium ions produced by beam-foil excitation have been recorded in the 30-60 nm spectral range and the radiative lifetimes of seven n=2 levels have been measured. The experimental results are compared with the available theoretical values and with new results obtained in the framework of two theoretical approaches: the Relativistic Hartree-Fock approximation and the Multiconfiguration Dirac-Fock method. Corroborated by the fair agreement of the new theory data with experiment, a new set of accurate transition probabilities for the 2s22p-2s2p2 and 2s2p2-2p3 transitions of Na VII is presented. [ABSTRACT FROM AUTHOR]

Oscillator strengths have been obtained for the first time for 12 transitions of Tb ii. Solar implications based on these f-values and on recent hyperfine structure data are discussed. More especially, a detailed investigation of a weak absorption feature located around λ 3658 is presented. [ABSTRACT FROM AUTHOR]

Oscillator strengths calculated by the STF method for selected transitions of V i and Co i have permitted to deduce, from an LTE study of weak lines, photospheric abundances in agreement with those obtained from carbonaceous chondrites. A summary of results is also presented for all the iron-group elements. [ABSTRACT FROM AUTHOR]

A new value of the solar photospheric abundance of iron, independent of line-shape parameters, is derived. Our analysis is based on a study of 40 weak infrared lines (0.85< λ<2.5 μ) for which theoretical oscillator strengths (calculated with configuration interactions taken into account) have recently been computed by Kurucz (1974). The abundance obtained, A = 7.57±0.11 (in the usual scale where log N = 12.00) is in agreement with the 'high' solar values recently reported in the literature and with the meteoritic abundance. [ABSTRACT FROM AUTHOR]

Absolute oscillator strengths are computed by the STF method for selected lines of Sc i.The lifetimes deduced from these values are in satisfactory agreement with recent beam-foil measurements. From a study of 10 selected lines, a new value of the solar photospheric abundance is derived (log N = 3.04) in agreement with the meteoritic value. [ABSTRACT FROM AUTHOR]

Oscillator strengths are calculated for 259 lines of Ti i by taking configuration interaction into account in a somewhat simplified treatment. Radial integrals are obtained by an adaptation of the scaled Thomas-Fermi method. The great majority of selected lines originate from slightly perturbed terms. From a satisfactory comparison of our g $${\text{f}}$$ -values with recent experimental data and with solar results in the visible region, we have been able to extend the work for some infrared lines. Very few transition probabilities were known for Ti i in that spectral range. On the basis of our oscillator strengths, a mean value log N = 4.88 ± 0.12 (in the usual scale), is proposed for the solar photospheric abundance, in agreement with the meteoritic value. [ABSTRACT FROM AUTHOR]

Radiative lifetimes of the highly exited states s and d of neutral sulphur have been measured using time-resolved laser-induced fluorescence. The sulphur atoms were generated in a laser-produced plasma. The investigated states were populated through a two-step process involving a two-photon excitation to the lowest excited triplet state of even parity , followed by a one-photon excitation to the investigated state. We obtained ns and ns. These values are much longer than theoretically predicted ones and much shorter than those indirectely inferred from astronomical data. [ABSTRACT FROM AUTHOR]

Absolute transition probabilities are calculated for 2 p( P) nd − 2 p( P) n′f transitions of C i (1 ⩽ λ ⩽ 3 μ). Pair coupling expressions for line strengths are used and the radial wavefunctions are obtained through the use of the Coulomb approximation. A description of the occurrence of these lines in the solar photospheric spectrum is presented and 47 new identifications are proposed. [ABSTRACT FROM AUTHOR]

The aim of the new database D.R.E.A.M. is to supply the astrophysicists with accurate atomic data (wavelengths, energy levels, oscillator strengths, radiative lifetimes) of neutral, singly or multiply ionized lanthanides. Up to now, it contains about 50000 lines but it will be updated and extended in the near future. [ABSTRACT FROM AUTHOR]