Beam-foil lifetimes of highly ionized silicon

Abstract

Electronically excited states of Si ions are created by passing a 20MeV Si s+ beam through a thin carbon foil. The EUV-radiation (2= 13-61 nm) emitted by the beam is analyzed using a grazing-incidence spectrometer. From the decay curves, lifetimes of 24 low lying levels in Si VIII to Si XII and of the 4f and 5 g levels of Si XI and Si XII are derived. Cascades from doubly excited states turn out to be an important contribution to the radiation observed. The lifetime values of this work are compared to theoretical data mainly of Wiese, Sinano~lu and Dankwort/Trefftz. Most experimental values agree with at least one of the theoretical values. The decay time 560 ps of the 2s2p 3 3D~ state of Si IX is clearly longer than the theoretical prediction (highest value 455 ps by Sinano~lu).

Relativistic fine structure oscillator strengths for Li-like ions: C IV - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

“…The lifetimes of some levels of Li-like ions have been measured and can be obtained theoretically from the sum of the A values as mentioned above. Lifetime experiments have been carried out by, for example, Heckmann et al (1976), Pinnington et al (1974) for O VI, Traãbert et al (1977) for Si XII using beam-foil technique. However, present comparison is made mainly with individual A-values.…”

Beam-foil lifetimes of O VII in the 10?100 ps-range

“…Behind the f0il the radiation of the decaying O VI-O VIII ions is observed by means of a grazing-incidence spectrometer (McPherson 247, R = 2.2 m, 600 lines/mm, see Ref. 7 for further details) in single photon counting technique. Lifetime curves are obtained by moving the foil along the beam axis.…”

“…Differences between theoretical and experimental values and among measurements related to the same atomic level have decreased considerably in the past few years. Experimental [4] and evaluational [7] improvements now allow the determination of decay times as short as about 10ps from the measured decay curves with sufficient reliability. There still remain severe problems in EUV-beam-foil spectroscopy concerning lifetime experiments, some of which are discussed below: foil alteration, normalization, window function of the spectrometer, replenishment of levels by cascades, and blending of lines.…”

MCDHF Calculations and Beam-Foil EUV Spectra of Boron-Like Sodium Ions (Na VII)

“…In the late 1970s, the Bochum beam-foil spectroscopy group began to measure EUV spectra and decay curves of B-like ions of Si and P [18][19][20][21][22][23]; references to various earlier calculations of oscillator strengths and transition rates are given in those papers. In the 1990s, the Bochum group returned to measurements of detailed processes in B-like ions, such as the massive changes of multiplet line intensity patterns (away from the standard expectation of LS coupling that had been tabulated 80 years ago by White and Eliason [24]), due to the changes in level mixing along the isoelectronic sequence [25].…”