title: X-ray Bragg diffraction in asymmetric backscattering geometry.
abstract: We observe three effects in the Bragg diffraction of x rays in backscattering geometry from asymmetrically cut crystals. First, exact Bragg backscattering takes place not at normal incidence to the reflecting atomic planes. Second, a well-collimated (approximately 1 microrad) beam is transformed after the Bragg reflection into a strongly divergent beam (230 microrad) with reflection angle dependent on x-ray wavelength--an effect of angular dispersion. The asymmetrically cut crystal thus behaves like an optical prism, dispersing an incident collimated polychromatic beam. The dispersion rate is approximately 8.5 mrad/eV. Third, parasitic Bragg reflections accompanying Bragg backreflection are suppressed. These effects offer a radically new means for monochromatization of x rays not limited by the intrinsic width of the Bragg reflection.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA. shvydko@aps.anl.gov
authors.forename: Yu V
authors.initials: YV
authors.lastname: Shvyd'ko
authors.forename: M
authors.initials: M
authors.lastname: Lerche
authors.forename: U
authors.initials: U
authors.lastname: Kuetgens
authors.forename: H D
authors.initials: HD
authors.lastname: Rüter
authors.forename: A
authors.initials: A
authors.lastname: Alatas
authors.forename: J
authors.initials: J
authors.lastname: Zhao