Spectroscopic measurements on few-electron high-Z ions take guidance from isoelectronic trends of low-Z to mid-Z ions and from theory. Such wide-range extrapolations, however, are fraught with uncertainty. We discuss as examples some n = 3, Δn = 0 transitions in the EUV spectra of Na-, Mg- and Al-like ions of Au that have been observed by electron beam ion trap work and by heavy-ion accelerator based beam-foil spectroscopy. New insights are gained from notable recent progress of calculations.

A knowledge ion beam spectroscopy spectroscopy accelerator based highly stripped ions of the spectra of ionized atoms is of importance in many fields. A wide variety of light sources are available for the study of such spectra. In recent years, techniques coming under the broad headings of fast beams and ion traps have been used extensively for such studies. This chapter will consider the advantages each technique has for particular applications.

The Livermore electron beam ion trap facility has recently been moved to a new location within LLNL, and new instrumentation was added, including a 32-pixel microcalorimeter. The move was accompanied by a shift of focus toward in situ measurements of highly charged ions, which continue with increased vigor. Overviews of the facility, which includes EBIT-I and SuperEBIT, and the research projects are given, including results from optical spectroscopy, QED, and X-ray line excitation measurements.

The transition probability of the magnetic dipole (M1) transition 2s22p 2PoJ=1/2 to J′=3/2 (λ=574.19 nm) in the B-like ion Cl12+ has been measured using two different light sources, the Heidelberg heavy-ion storage ring TSR and the Livermore electron beam ion trap EBIT-I. Our results for the atomic level lifetime are (21.2±0.6) ms from the heavy-ion storage ring and (21.0±0.5) ms from the electron beam ion trap. Particular attention has been paid to systematic errors, using these measurements as well as recent measurements on Fe10+ and Fe13+ ions as examples.

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.

The transition probability of the electric dipole forbidden transition in the ground state of Fe XIV (Al-like), the "green coronal line" at 5302.86 Å, has been measured using the Livermore electron beam ion trap. Our result for the 3s23p2 2P atomic level lifetime is 16.74 ± 0.12 ms, which differs significantly from an earlier measurement, and is the most accurate one to date. The measured transition rate of 59.7 ± 0.4 s-1 corroborates some earlier calculations, but not all of the more recent ones.

The transition probability of the magnetic dipole (M1) transition 2s(2)2p P-2(o) J=1/2 to J(')=3/2 (lambda=574.19 nm) in the B-like ion Cl12+ has been measured using two different light sources, the Heidelberg heavy-ion storage ring TSR and the Livermore electron-beam ion trap EBIT-I. Our results for the atomic level lifetime are 21.2+/-0.6 ms from the heavy-ion storage ring and 21.0+/-0.5 ms from the Livermore electron-beam ion trap. Particular attention has been paid to systematic errors, making this experiment a common reference for atomic level lifetime measurements in the visible spectrum.

The radiative lifetime of the 2s2 2p4 1S0 level in Ne2+ ions has been measured by time-resolved observations of one of the electric-dipole forbidden decay branches, the magnetic dipole (M1) transition to the 2s2 2p4 3P1 level, on ions circulating in a heavy-ion storage ring. The result, a lifetime of 213 ± 4 ms, agrees within the mutual 2σ errors with that of a recent measurement using a radiofrequency ion trap, but is expected to suffer less from possible systematic error. It also compares very well with two calculations that have been semiempirically corrected for experimental transition energies. PACS Nos.: 32.70Cs, 39.90+d, 31.50+w, 35.80B

We report measurements of photon emission cross sections following electron capture of C2+, N3+, N4+ and O3+ ions (obtained from an ECR ion source) in collision with ground state lithium atoms at keV energies. We examine the sources of error and obtain best estimates of the relative values of the cross sections having accuracies in the range from 15% to 50%. The accuracy of the absolute cross sections may be lower for capture by N3+ and N4+ ions because of the uncertainty in the fraction of metastable ions. We discuss this problem.

Transition probabilities of three magnetic dipole (M1) transitions in multiply charged ions of potassium have been measured using the Livermore electron beam ion trap EBIT-2. Our results for the atomic level lifetimes are 4.44 +/- 0.10 ms for K XI (F-like) 2s(2) 2p(5) P-2(1/2)o, 4.47 +/- 0.10 ms for K xv (B-like) 2s(2) 2P P-2(3/2)o and 7.6 +/- 0.5 ms for K XVI (Be-like) 2s2p P-3(2)n. The results confirm the accuracy of most predictions to within 3% of ground-state and 7% of excited-state transitions.

Absolute photon emission cross sections following electron capture reactions have been measured for C2+, N3+, N4+, and O3+ ions colliding with Li(2s) atoms at keV energies. The results are compared with calculations using the extended classical over-the-barrier model by Niehaus. We explore the limits of our experimental method and present a detailed discussion of experimental errors.

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.

By 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 near-ultraviolet 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.

The lifetimes of 16 levels in Tm if have been measured using the fast-beam-laser technique to resolve the disagreement between time-resolved laser-induced fluorescence measurements recently published by Anderson, en Hartog, and Lawler [J. Opt. Soc. Am. B 13, 2382 (1996)] and a new relativistic Hartree-Fock calculation by Quinet, Palmeri, and Biemont [J. Quant. Spectrosc. Radiat. Transf. 62, 625 (1999)]. In all cases except one, our results support the previous measurement, but with a higher precision. [S1050-2947(99)02811-5].

The spectrum of iodine was photographed in the 400-2100 Å region on a 3 m normal incidence spectrograph at the Antigonish laboratory using a triggered spark source. The , 5s5p5d and 5s5p6s configurations of four-times ionized iodine (I V) were identified for the first time in the In I isoelectronic sequence. 34 of the 35 possible levels of these odd parity configurations have been established. 176 additional lines have been classified in the I V spectrum. The relativistic Hartree-Fock and least-squares-fitting calculations were carried out using the Cowan code to interpret the observed spectrum. The new observations also lead to the revision of the levels to and respectively.

The decay by magnetic dipole and electric quadrupole (M1 and E2) transitions of the 2s22p2 1D2 level in the ground complex of the C-like ion Si8+ and the 2s22p4 1D2 level in the O-like ion Si6+ have been optically observed with ions circulating in a storage ring. The measured natural level lifetimes of (38.3 ± 0.3) ms for Si8+ and (636 ± 0.7) ms for Si6+ corroborate theoretical data for such forbidden decays in multicharged ions of astrophysical interest. PACS Nos.: 32.70.Cs, 32.30.Jc, 34.50.Fa

The spectrum of iodine was photographed in the 400-2100 Angstrom region on a 3 m normal incidence spectrograph at the Antigonish laboratory using a triggered spark source. The 5p(3), 5s5p5d and 5s5p6s configurations of four-times ionized iodine (I v) were identified for the first time in the In I isoelectronic sequence. 34 of the 35 possible levels of these odd parity configurations have been established. 176 additional lines have been classified in the I v spectrum. The relativistic Hartree-Fock and least-squares-fitting calculations were carried out using the Cowan code to interpret the observed spectrum. The new observations also lead to the revision of the 5d D-2(3/2), D-2(5/2) levels to 154 049.5 cm(-1) and 155 461.5 cm(-1) respectively.

The slow electric-dipole intercombination decay of the 2s2p(3) S-5(2)0 level in the C-like ion N+, which appears in the auroral airglow spectrum, has been optically observed from ions circulating in a storage ring. A result of 5.88 +/- 0.03 ms was obtained for the natural lifetime of this level. This represents an improvement in precision by a factor of 10 compared to previous radio-frequency and electrostatic ion trap work and is in slight disagreement with the latest theoretical values. [S1050-2947(98)02812-1].

The slow electric-dipole intercombination decay of the ${2s2p}^{3}{}^{5}{S}_{2}^{o}$ level in the C-like ion ${\mathrm{N}}^{+},$ which appears in the auroral airglow spectrum, has been optically observed from ions circulating in a storage ring. A result of $5.88\ifmmode\pm\else\textpm\fi{}0.03 \mathrm{ms}$ was obtained for the natural lifetime of this level. This represents an improvement in precision by a factor of 10 compared to previous radio-frequency and electrostatic ion trap work and is in slight disagreement with the latest theoretical values.

The spectrum of iodine was photographed on a 3-m normal incidence spectrograph at the Antigonish laboratory using a triggered spark source in the 300-1200 Å region. Eleven out of twelve levels of the 5p5d configuration and all four levels of the 5p6s configuration of I VI have been established. The missing level 5p2 1S0 has been located and two levels 5s5d 1D2 and 5s6s 1S0 reported earlier have been revised. The beam foil spectra obtained at the University of Alberta in Edmonton complemented the spark data. The least-square-fitting (LSF) and Hartree-Fock calculations were carried out to interpret the level scheme. Sixty-six new lines have been classified in this spectrum.