Nature of the 1385.6 and 1438 eV Positive Glitches in the Transmission Function of the YB₆₆ Soft-X-ray Monochromator

In the course of the development of the YB₆₆ 004 monochromator for soft-X-ray spectroscopy in the 1-2 keV region, two positive glitches at 1385.6 and 1438 eV have been observed in the transmission function of this material in a double-crystal configuration. The nature of these glitches has been elucidated using a combination of photoemission experiments, reflectivity measurements and anomalous scattering calculations. Analyses of these results show that these positive glitches are due to the transmission at an energy 3/2 times higher than the 004 reflection and correspond to the yttrium L_III and L_II absorption edges at 2080 and 2156 eV, respectively. Reflectivity measurements and structure-factor calculations for the 006 reflection confirm that these glitches are caused by the sharp reflectivity increases associated with anomalous scattering for the 006 reflection at the yttrium L_III and L_II absorption edges.