A B S T R A C TBy a combination of radiative lifetimes measured using the fast-beam-laser method and experimental branching ratios deduced from Fourier transform spectrometer spectra, it has been possible to derive experimental f-values for Lu ii lines observed in the visible and nearultraviolet regions. These data are compared with relativistic Hartree±Fock calculations, taking core polarization effects into account, and a set of additional oscillator strengths of astrophysical interest is presented.

Lifetimes (the inverse of the total decay rates) of several 3p and 3d levels in Ca-, Ar-, Cl- and Si-like ions of Fe that decay only by electric-dipole-forbidden transitions have been measured optically using a heavy-ion storage ring, observing either near-UV or EUV light. In several cases, more than one decay contributes to a given decay curve, which complicates the analysis. The lifetime results, with a precision ranging from 0.8 to 10%, compare well with some theoretical predictions.

Studies of the LIF radiation from beams of Sr+ and Br+ ions have been used to measure the lifetimes of the 4f and 5p levels of Sr II, and of the 4f, 6p and 7p levels of Ba II. The lifetimes obtained for the 5p levels of Sr II and the 6p levels of Ba II are in good agreement with previous LIF measurements. The fine structure of the 4f2F degrees term in Sr II has been resolved for the first time, the observed splitting being -1.30+or-0.06 cm-1. The energies of the two 4f levels have been measured as 60991.3 cm-1 (j=5/2) and 60990.0 cm-1 (j=7/2). The LIF decay curves recorded using a detector sensitive in the visible region for the 7p levels in Ba II showed very strong growing-in cascading, demonstrating that LIF decay curves are not necessarily single-exponential for high-lying levels. The lifetime results are compared with Coulomb approximation and RHF calculations where available, the latter including semi-empirical polarization corrections.

Core-polarization and configuration interaction effects are investigated in singly ionized copper. It is shown that these effects are responsible, to a large extent, for the discrepancies observed between recent relativistic Hartree–Fock (HFR) and configuration-interaction (CIV3) calculations and accurate beam-laser experimental results. A new set of transition rates is obtained using the HFR + Core Polarization formalism leading to theoretical lifetime and transition probability values in fair agreement with the experiment. An indicative calculation performed with the configuration - interaction code SUPERSTRUCTURE demonstrates the importance of semi-empirical term energy corrections in producing reliable transition rates in a case like the present one.

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