Reference-free measurements of the1s2s2p2P1/2,3/2o→

Abstract

We have measured the widths and energies of the 1s2s2p 2 P 1/2,3/2 → 1s 2 2s 2 S 1/2 transitions in lithiumlike sulfur and argon, as well as the energies of the forbidden 1s2s2p 4 P 5/2 → 1s 2 2s 2 S 1/2 M2 transition in both elements. All measurements were performed with a double-flat-crystal spectrometer without the use of any reference line. The transition energy measurements have accuracies ranging from 2.3 to 6.4 ppm depending on the element and line intensity. The widths and the intensity ratios of the 1s2s2p 2 P 1/2,3/2 → 1s 2 2s 2 S 1/2 lines have also been measured. These are reference-free measurements of transitions in core-excited lithiumlike ions and have an accuracy comparable to the best relative measurements. We have also performed multiconfiguration Dirac-Fock calculations of the widths, energies, and intensity ratios. An extensive comparison between existing experimental results and theory is performed, and Bayesian techniques are employed to extract the energy of the 1s2p 2 4 P 1/2 → 1s 2 2p 2 P 1/2 transition in sulfur and identify contaminant transitions.

A Critical Compilation of Experimental Data on the 1s2$l$2$l^{\prime}$ Core-Excited States of Li-like Ions from Carbon to Uranium

“…Imprecision of the earlier calculations of wavelengths of the Li-like satellite lines led to misidentification of several observed lines. Nevertheless, the data of Dohmann and Mann were found to be usable after re-calibration with internal standards provided by high-precision calculations of Yerokhin and Surzhykov [115] for the He-like w line, measurements of Machado et al [64] for the Li-like q, r, and U lines, and measurements of Tarbutt et al [96] for the Li-like m line. Fitting the differences between the wavelengths reported by Dohmann and Mann and the reference wavelengths from the above sources revealed a systematic error varying linearly with wavelength.…”

Photoionization of Astrophysically Relevant Atomic Ions at PIPE

“…Considering the ppm accuracies that can be obtained at hard X-ray beamlines with crystal monochromators, this situation for soft X-rays seems unsatisfying and calls for better calibration standards. As proposed in [34] (see also below), few-electron ions could serve this purpose since the theoretical uncertainties of photoionization-resonance positions for such fundamental atomic systems are on the meV level if state-of-the-art atomic theory is applied (see, e.g., [34][35][36]).…”

Photoionization of astrophysically relevant atomic ions at PIPE

“…Considering the ppm accuracies that can be obtained at hard X-ray beamlines with crystal monochromators, this situation for soft X-rays seems unsatisfying and calls for better calibration standards. As proposed in [34] (see also below), few-electron ions could serve this purpose since the theoretical uncertainties of photoionization-resonance positions for such fundamental atomic systems are on the meV level if state-of-the-art atomic theory is applied (see, e.g., [34][35][36][37]).…”