High-accuracy Measurements of Core-excited Transitions in Light Li-like Ions

Moto Togawa; Steffen Kühn; Chintan Shah; Vladimir A. Zaystev; Natalia S. Oreshkina; Jens Buck; Sonja Bernitt; René Steinbrügge; Jörn Seltmann; Moritz Hoesch; Christoph H. Keitel; Thomas Pfeifer; Maurice A. Leutenegger; José R. Crespo López-Urrutia

arXiv · 2408.12219

High-accuracy Measurements of Core-excited Transitions in Light Li-like Ions

Moto Togawa·Steffen Kühn·Chintan Shah·Vladimir A. Zaystev·Natalia S. Oreshkina·Jens Buck·Sonja Bernitt·René Steinbrügge·Jörn Seltmann·Moritz Hoesch·Christoph H. Keitel·Thomas Pfeifer·Maurice A. Leutenegger·José R. Crespo López-Urrutia

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Abstract

The transition energies of the two $1s$-core-excited soft X-ray lines (dubbed q and r) from $1s^2 2s ^1S_{1/2}$ to the respective upper levels $1s(^{2}S)2s2p(^{3}P) ^{2}P_{3/2}$ and $^{2}P_{1/2}$ of Li-like oxygen, fluorine and neon were measured and calibrated using several nearby transitions of He-like ions. The major remaining source of energy uncertainties in monochromators, the periodic fluctuations produced by imperfect angular encoder calibration, is addressed by a simultaneously running photoelectron spectroscopy measurement. This leads to an improved energy determination of 5 parts per million, showing fair agreement with previous theories as well as with our own, involving a complete treatment of the autoionizing states studied here. Our experimental results translate to an uncertainty of only 1.6\,km/s for the oxygen line qr-blend used to determine the outflow velocities of active galactic nuclei, ten times smaller than previously possible.

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Moto Togawa, Steffen Kühn, Chintan Shah, Vladimir A. Zaystev, Natalia S. Oreshkina, Jens Buck, Sonja Bernitt, René Steinbrügge, Jörn Seltmann, Moritz Hoesch, Christoph H. Keitel, Thomas Pfeifer, Maurice A. Leutenegger, José R. Crespo López-Urrutia. 2024-08-22. High-accuracy Measurements of Core-excited Transitions in Light Li-like Ions. https://arxiv.org/abs/2408.12219

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