High-precision laser-assisted absolute determination of x-ray diffraction angles

• Published in: Review of scientific instruments 2012-01, Vol.83 (1), p.013102-013102-8
• Main Authors: Kubiček, K., Braun, J., Bruhns, H., Crespo López-Urrutia, J. R., Mokler, P. H., Ullrich, J.
• Format: Article
• Language: English
• Subjects: ACCURACY; ARGON; BENCHMARKS; BINDING ENERGY; BRAGG REFLECTION; CRYSTALS; ELECTRONS; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; LASERS; PHOTON BEAMS; PHOTONS; QUANTUM ELECTRODYNAMICS; SCREENING; WAVELENGTHS; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.3662412

A novel technique for absolute wavelength determination in high-precision crystal x-ray spectroscopy recently introduced has been upgraded reaching unprecedented accuracies. The method combines visible laser beams with the Bond method, where Bragg angles (θ and −θ) are determined without any x-ray reference lines. Using flat crystals this technique makes absolute x-ray wavelength measurements feasible even at low x-ray fluxes. The upgraded spectrometer has been used in combination with first experiments on the 1s2p 1 P 1 → 1s 2 1 S 0 \documentclass[12pt]{minimal}\begin{document}$w{\rm {\text -}line}$\end{document} w - line in He-like argon. By resolving a minute curvature of the x-ray lines the accuracy reaches there the best ever reported value of 1.5 ppm. The result is sensitive to predicted second-order QED contributions at the level of two-electron screening and two-photon radiative diagrams and will allow for the first time to benchmark predicted binding energies for He-like ions at this level of precision.