Differential energy measurement between He- and Li-like uranium intra-shell transitions

• Published in: Physica scripta 2011-06, Vol.2011, p.014003
• Main Authors: Trassinelli, M, Kumar, A, Beyer, H F, Indelicato, P, Märtin, R, Reuschl, R, Kozhedub, Y S, Brandau, C, Bräuning, H, Geyer, S, Gumberidze, A, Hess, S, Jagodzinski, P, Kozhuharov, C, Liesen, D, Spillmann, U, Trotsenko, S, Weber, G, Winters, D F A, Stöhlker, Th
• Format: Article
• Language: English
• Subjects: Atomic Physics; Physics
• ISSN: 1402-4896; 0031-8949; 1402-4896
• DOI: 10.1088/0031-8949/2011/T144/014003

We present the first clear identification and highly accurate measurement of the intra-shell transition $1s2p\, ^3\!P_2 \to 1s2s\, ^3\!S_1$ of He-like uranium performed via X-ray spectroscopy. The present experiment has been conducted at the gas-jet target of the ESR storage ring in GSI (Darmstadt, Germany) where a Bragg spectrometer, with a bent germanium crystal, and a Ge(i) detector were mounted. Using the ESR deceleration capabilities, we performed a differential measurement between the $1s2p\, ^3\!P_2 \to 1s2s\, ^3\!S_1$ He-like U transition energy, at 4510 eV, and the $1s^22p\ ^2\!P_{3/2 } \to 1s^22s\, ^2\!S_{1/2}$ Li-like U transition energy, at 4460 eV. By a proper choice of the ion velocities, the X-ray energies from the He- and Li-like ions could be measured, in the laboratory frame, at the same photon energy. This allowed for a drastic reduction of the experimental systematic uncertainties, principally due to the Doppler effect, and for a comparison with the theory without the uncertainties arising from one-photon QED predictions and nuclear size corrections.