G. Möller

A beam-foil study of the 3s3p3d 4F levels in the Al-like ions of Ti, Fe and Ni

The decays of the high angular momentum, high spin 4F0 states of the electron configuration 3s3p3d in aluminium-like ions (with three electrons outside a closed shell) have been identified in delayed spectra of foil excited Ti, Fe and Ni ion beams. The line identifications were aided by HXR, MCHF, and MCDF calculations and are corroborated by lifetime measurements which demonstrate the differential longevity of the fine structure levels. A search for the related case of 1s2p3d 4F0 level decays in Li-like ions of Si, P and S failed.

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.

EUV-spectroscopy of beam-foil excited 14.25 MeV/u Xe52+...Xe49+-ions

Abstract14.25 MeV/u Xe — ions with chargesq=52, 51, 50 and 49 were sent through carbon foils of 50 µg/cm2. Beam — foil spectra between 6 nm and 14 nm were registered using the GSI 5 m grazing incidence spectrometer. The spectra are dominated by Rydberg transitions from levels withn from 12 to 7. As weak features, 2s − 2p transitions in Li- and Be-like ions were observed. Their wavelengths were determined with an accuracy of 0.02 nm using modelled Rydberg lines for the wavelength scale calibration. Very good agreement with experimental and theoretical results was obtained. The present limitation for the use of Rydberg lines for an in-situ Doppler shift corrected calibration is emphasized.

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.

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.

Beam-foil lifetime study of then=3 complex in al-like Ti9+

The beam-foil spectrum obtained using a beam of Ti3+ ions of energy 10 MeV has been studied over the wavelength range from 14 nm to 80 nm. New assignments are suggested for 18 levels belonging to the levels of the 3p3, 3s 3p 3d and 3s2 4p configurations. The lifetimes of these levels, as determined from conventional multi-exponential curve fitting of their intensity decay curves, are typically about 30% longer than is forecast by theory. The same decay curves have also been used to represent the effect of cascade repopulation on the decay curves obtained for the resonance doublet levels of the 3s 3p2 and 3s2 3d configurations. A discussion is given of the possible techniques for cascade correction in beam-foil lifetime measurements, and of the inclusion of a window function to represent the vignetting effect close to the foil. Lifetimes obtained using these techniques for the 3s2 3d levels (38±6 ps for J=3/2, 36±5 ps for J=5/2), and the 3s3p22S level (99±6 ps),2P levels (60±15 ps for J=1/2, 50±15 ps for J=3/2) and2D levels (820±30 ps for j=3/2, 870±40 ps for J=5/2) are in good agreement with theoretical predictions.

Quest for experimental M1 and E1-intercombination transition probabilities in few-electron Xe ions

The experimental access to M1 transition probabilities within thens2npk (1 ≦k ≦ 5) ground state configurations of highly ionized atoms is outlined. A test experiment on Xe(45–50)+ yielded first spectra and decay curves of the 2s21S0 − 2s2p3P10 intercombination transition in Xe50+ and of M1 transitions within the 2s2 2pk (1 ≦k ≦ 5) ground configurations. The data compare well only with theoretical predictions which take the Lamb shift into account. Problems and prospects for better measurements are discussed.

Wavelengths and transition probabilities of intercombination lines in the spectra of Ga- and Ge-like Ag ions

Prompt and delayed EUV spectra of foil-excited Ag have been recorded at ion energies of 19 and 25 MeV. The recent identifications of intercombination transitions in Ga- and Ge-like Ag ions are corroborated by spectra recorded with higher resolution than before and by lifetime measurements. Lifetime results for the resonance transitions of Cu-like ions and for the intercombination transitions in Zn- to Ge-like ions are compared with theoretical predictions.

Study of 3d - 4f and 3d - 5f quartet and doublet transitions of doubly excited three-electron ions

We present the first observation of optical transitions between doubly excited doublet states in the term systems N V, O VI and F VII. The spectra were produced by foil excitation of fast ion beams. The assignment of the spectral lines was made by comparison with the results of MCDF calculations along the isoelectronic sequence. The same method also led to the identification of two 3d – 4f quartet transitions in Mg X.