B Denne

Transitions in Multiply Excited FVI and FVII

The transitions 1s2s2p2 5P-1s2p3 5S0 in F VI and 1s2s2p 4P0-1s2p2 4P in F VII have been investigated using the method of beam-foil spectroscopy. The fine-structure separations have been determined for the 1s2s2p2 5P term in F VI and for both 4P terms in F VII. The results are compared with recent theoretical calculations of fine structure, based on relativistic wavefunctions, and with previous experimental data. Lifetime measurements are reported for the 1s2p2 4P5/2 level and the 1s2p3 5S20 level.

Transitions in Al-like, Mg-like and Na-like Kr and Mo, observed in the JET Tokamak

Spectra of highly ionized Kr and Mo, emitted from the JET tokamak plasmas, have been recorded in the region 30-355 ?. Detailed analysis of the n = 3, ?n = 0 transitions in Kr XXIV-XXVI and Mo XXX-XXXII has resulted in a number of new spectral classifications. Some isoelectronic regularities for Al-like and Mg-like ions are discussed.

Radiative Lifetimes and Hyperfine Induced Decay of the 1s 2p 3P2 and 3P0 Levels in Al XIII

The transitions 1s2s 3S1-1s2p 3P2 and 1s2s 3S1-1s2p 3P0 in He-like Al have been observed in a beam-foil experiment at 900 ± 1 A and 953 ± 1 A, respectively. The lifetimes of the upper levels have been determined to 5.4 ± 0.2 ns (3P2) and 4.8 ± 0.2 ns (3P0). We have observed a shortening of the 2p 3P0 lifetime in agreement with theories which consider hyperfine quenching effects, and we give an estimate of the quenching of the level. The wavelengths are compared with theoretical values which include Lamb shift.

Lifetimes of the 2s2p1P Level in Be-Like NIV and OV Obtained from Beam-Foil Experiments and Extensive Cascade Analyses

Lifetime measurements using the beam-foil method are reported for the 2s2p 1P level in Be-like N IV and O V. The results, 0.425 ± 0.015 ns in N IV and 0.338 ± 0.015 ns in O V, are in excellent agreement with the majority of recent theoretical results. The existing systematic discrepancy between theory and experiments in this sequence is thereby removed for these two ions. It is shown that this agreement is possible only when the most prominent cascades that repopulate the 2s2p 1P level, are explicitly included in the analysis through the application of the ANDC method. Lifetimes of these cascading levels are also reported and are found to be in good agreement with previous experimental and theoretical results.

Transition Probabilities for Allowed and Forbidden Transitions From the 1s2p 3P Levels in He-like O VII and F VIII

We have measured the lifetimes of the 1s2p 3P levels in O VII and F VIII. For O VII the following values (in ns) were found 12.10 ± 0.20 (3P2), 1.52 ± 0.08 (3P1) while the F VIII results are 10.44 ± 0.15 (3P2), 0.531 ± 0.020 (3P1) and 9.48 ± 0.20 (3P0). From these data we deduce experimental transition rates for the 1s2 1S0-1s2p 3P1 intercombination line, obtaining (5.80 ± 0.35) × 108 s-1 (O VII) and (17.8 ± 0.7) × 108 s-1 (F VIII) and for the nuclear-spin induced 1s2 1S0-1s2p 3P0 transition in 19F VIII, (0.142 ± 0.020) × 108 s-1. All results are in good agreement with recent theoretical data.

Beam-Foil Studies of Multiply Ionized Oxygen

Beam-foil spectra of oxygen have been recorded in the region 2000-4500 A with emphasis on good spectral resolution. Wavelengths for many hydrogenic transitions in O VI-O VII have been determined with ± 0.1-0.5 A uncertainties. The data are compared with predictions using polarization formulae. A few lifetimes are also reported.

Energies and lifetimes of the 4s4d 1D and 4p2 1D in Ga II

Abstract Four new classifications of 1 D and 1 S levels in Ga II have been made with a sliding spark source and the lifetimes of the 4s4d 1 D and levels have been measured using beam-foil excitation.

Lifetime Measurements for some Δ n = 0 Transitions in Cl XIII-Cl XV

A beam-foil investigation of chlorine at energies up to 48 MeV has been performed in the wavelength region 300-1100 A. Hydrogen-like transitions, as well as Δn = 0 transitions, belonging to Cl XII-Cl XV were observed. Radiative lifetimes and f-values are reported for some important Δn = 0 transitions, 2s 2S1/2-2p 2P3/2 and 2s 2S1/2-2p 2P1/2 in Cl XV, 2s2p 1P1-2p2 1D2 in Cl XIV and 2s2p2 2P3/2-2p3 2D5/2 in Cl XIII.

Wavelength of the 4s2 1S0-4s4p 3P1 intercombination line in Br VI

Abstract A beam-foil measurement of the wavelength of the Br VI 4s 2 1 S 0 -4s4p 3 P 1 intercombination transition has been made which corrects an earlier error. The new value of 946.3(2) A is 6.7 A longer than the previously accepted value, and the excitation energies of all triplet levels in Br VI should correspondingly be adjusted downward by 756 cm −1 .

Observation of strong orientation effects for levels in highly ionized oxygen

Abstract The method of beam-tilted-foil excitation has been applied to O IV and O VI at 4 MeV beam energy. Circular polarizations of nearly 30% have been observed and studied as a function of foil tilt angle. A new development for cascade-free lifetime measurements is discussed.