Kubicek K, Braun J, Bruhns H, López-Urrutia J R Crespo, Mokler P H, Ullrich J
Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany.
Rev Sci Instrum. 2012 Jan;83(1):013102. 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) 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.
最近推出的一种用于高精度晶体X射线光谱中绝对波长测定的新技术已得到升级，达到了前所未有的精度。该方法将可见激光束与邦德方法相结合，在没有任何X射线参考线的情况下确定布拉格角（θ和-θ）。使用平面晶体，即使在低X射线通量下，该技术也能使绝对X射线波长测量变得可行。升级后的光谱仪已与关于类氦氩中1s2p(1)P(1) → 1s(2)(1)S(0) w线的首次实验结合使用。通过解析X射线谱线的微小曲率，精度达到了有史以来报道的最佳值1.5 ppm。该结果对双电子屏蔽和双光子辐射图水平上预测的二阶量子电动力学贡献敏感，并将首次能够在这种精度水平上对类氦离子的预测结合能进行基准测试。
