J H Blanke

Beam-foil lifetime study of Al-like titanium, iron and nickel

The lifetimes of the resonance levels in the Al-like ions Ti X, Fe XIV and Ni XVI have been obtained from beam-foil measurements using a variety of analytical techniques. The spectral analysis and identification of cascade transitions necessary for application of the ANDC procedure have been aided by recent observations of laser-produced plasmas. The lifetime values obtained from ANDC analyses for the 3s 3p2 doublet levels agree well with predictions based on semi-empirical Hartree-Fock calculations. However, the ANDC results for the 3s2 3d levels fall between the values obtained using multi-exponential curve-fitting and from the calculations.

Quartet Term Systems of C3+?F6+ Ions

The C IV, N V, O VI and F VII quartet term systems have been investigated using the beam-foil method, Wavelengths of more than 70 lines associated with these systems are reported. They are compared to theoretical predictions and to data on analogous transitions in singly excited four-electron ions. Certain details of the term structure are discussed as are fine structure splittings and the separations of quartet terms arising from electron configuration 1s2p3p, 1s2p3d, and 1s2p4d. In the isoelectronic comparison the effect of configuration mixing becomes apparent for the last case.

The 2p4 3s, 3p and 3d Configurations of Thirteen Times Ionized Titanium, Ti XIV

The spectrum of Ti XIV has been observed in the wavelength region 80-550 A using the fast ion beam spectroscopy method. 47 lines have been identified as transitions between the 2p4 3s, 3p, and 3d configurations in the 360-540 A interval. The level identifications are supported by comparisons between observations and Hartree-Fock calculations along the F I isoelectronic sequence.

Identification of the 3s 2 3p 2 3 P 1,2 ? 3s3p 3 5 S 2 0 intercombination transition in siliconlike Ni14+

The3P1, 2−5S2o intercombination lines in Ni14+ have been identified in the EUV spectrum emitted by foil-excited Ni ion beams. The wavelengths are close to the theoretically predicted values. The relative intensities of the lines confirm the predicted branching ratios.In a most recent paper Ellis and Martinson [1] give predicted wavelengths and transition rates for the 3s23p23P1,2 — 3s3p35S2o, intercombination transition in siliconlike ions with 16≤Z≤28. The data were obtained theoretically (and compared with other theoretical data by Huang [2]) but adjusted to match the known wavelengths of this transition in the first three ions of the sequence and the finestructure intervals of the3P state which are known for a few more ionization stages.

Intercombination lines in Zn-like, Ga-like and Ge-like Nb

Using beam-foil spectroscopy and comparing prompt spectra (recorded close to the foil) with delayed ones we have observed the n = 4, Δn = 0 spin-forbidden transitions 4s2 1S0-4s4p 3P1o in Zn-like Nb XII, 4s24p 2Po- 4s4p2 4P in Ga-like Nb XI and 4s24p2 3P-4s4p3 5So in Ge-like Nb X. Lifetime measurements support the spectroscopic assignments. The experimental transition probabilities for the 4s2 1S0-4s4p 3P10 intersystem line in the Zn I sequence are compared with the rather differenct results of various theoretical calculations.

Wavelength measurements in the quartet term system of doubly excited OVI and FVII

In the emission spectra of beam-foil excited oxygen and fluorine, it has been possible to assign lines to the quartet term systems of doubly excited three electron ions. A comparison with known spectra of singly excited four-electron systems turned out to be useful for line identification. The measured wavelengths are compared to theoretical predictions.

Search for intercombination lines in few-electron spectra of rare-earth sequence ions of Os through Au

The eventual reordering along the isoelectronic sequences of the atomic shells of ions with 61 to 64 electrons (Pm I- to Gd I-like) into systems with one to four electrons outside the closed 4f14 electronic shell has been predicted by theory. However, this prediction provides a formidable challenge for an experimental proof, since very line-rich spectra are associated with ions with so many electrons. The possibilities and problems of a beam-foil spectroscopic approach which combines wavelength and lifetime measurements are discussed, and the results of a search for the intercombination lines expected in such few-electron spectra are presented for ions of Os, Pt and Au. Tentative identifications are given for intercombination lines in the Sm I- and Eu I-like spectra.

Experimental transition probability for theE1 intercombination transition in Be-like Xe50+

The 2s21S0 — 2s2p3P°1 intercombination transition in Be-like Xe50+ has been observed and the intensity decay with time has been measured using a foil-excited fast ion beam. The transition wavelength value is found to be λ = (9.81±0.05) nm and the upper level lifetime to be τ = (0.47±0.05) ns. Both values agree with recent theoretical predictions.

First results of experimental and theoretical investigations on sextet states of doubly-excited five-electron ions

In continuation of our previous work on doubly-excited ions with three and four electrons we present the first results on optical transitions in the term system of doubly-excited ions with five electrons. Transitions between such sextet states were identified in beam-foil spectra of the ions nitrogen, oxygen and fluorine. Assignments were first established by comparison with Multi-Configuration Dirac-Fock calculations. Later assignments were aided by Multi-Configuration Hartree-Fock calculations (see the contribution by G. Miecznik et al. in this issue). Decay curves were recorded for all six candidate lines. The lifetime results are compared to theoretical values which confirm most of the assignments qualitatively.

Satellite lines in the EUV spectrum of foil-excited lithium

The EUV spectrum of lithium in the wavelength range 10-28 nm has been recorded with high spectral resolution. About one hundred lines of Li III, singly and doubly excited Li II and doubly excited Li I have been identified. The line-rich spectrum obtained after foil excitation is contrasted with the spectrum obtained after He gas excitation of Li+ ions. The lifetimes of three core-excited states have been determined and found to agree with theoretical predictions.