Beam - foil study of the lifetimes of levels in Na-like Ca X, Mg-like Ca IX and Si-like Ca VII

Abstract

Levels of Ca ions with one, two or four electrons in the n = 3 shell have been studied for their decay properties and lifetimes. For the 3p 2 P o 1/2,3/2 levels of Ca X and the 3s3p 1 P o 1 level of Ca IX, arbitrarily normalized decay curve (ANDC) and cascade model analyses yield results with precisions of 10% and less and with low systematic uncertainties. The measured lifetime of the Ca IX 3s3d 1 D 2 level confirms the need to include relativistic effects in the calculation. The lifetime results are compared to other, experimental and theoretical, data available for the isoelectronic sequences.

Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities: An Experimenter’s View

“…Well, I have run lifetime measurements on Na-like ions of various elements, and among those of Ca [32], some results differed significantly from the isoelectronic trend and from theory predictions that were beyond doubt. Although seasoned beam-foil colleagues from various countries tried their individual pet evaluation techniques, in the end we all agreed on the same numbers that differed from prediction-yet we stated in our publication that we recognized the difference and could not explain it.…”

“…For example, with increasing nuclear charge Z, there increases the probability of a spin-changing decay branch of the 2p 2 1 D 2 level to the 2s2p 3 P o 1,2 levels. (A corresponding case, the 3p 2 1 D 2 level decay, also with in-system and intercombination decay channels, occurs in the Mg isoelectronic sequence [32,133].) One might expect that any atomic structure code operating in intermediate coupling would include this decay branch automatically, but the scarcity of literature data and the scatter of the results of the few available computations tell a different story.…”

Multiconfiguration approach in the study of atomic spectra

“…There they demonstrate quite good agreement. This table also contains the available experimental data [69] and the theoretical results of the method of the optimized potential model (MOPM) [70], as well as the many body perturbation theory (MBPT) [71]. As mentioned before for the lifetimes of configuration 2s 2 2p N −1 3p, in this case the twoelectron transitions are also very important for the lifetimes of levels from which these transitions may occur.…”

Calcium and Potassium Spectra in the EUV

“…A number of studies have addressed the EUV spectra of multiply charged ions of calcium (for references see [1,[3][4][5]). This work focuses on the charge state ions from Ca 6+ to Ca 12+ .…”

“…Here we will discuss Ca data that precede those in [16,21]. Parts of the data have been published before [3,4]. The data have been obtained by beam-foil spectroscopy at the Bochum Dynamitron tandem accelerator laboratory, more than two decades ago.…”