X-ray Monochromator with 2 × 10⁸ Energy Resolution

An X-ray beam of 3 × 10⁷ photons s⁻¹ with 2 × 10⁸ relative energy resolution has been obtained at a third-generation synchrotron undulator X-ray source using the (13 13 13) Bragg reflection from a silicon perfect crystal. The production of these 25.70 keV X-rays with 450 ± 50 μeV bandpass opens up new possibilities in X-ray optics and spectroscopies.