Open AccessANOMALOUS TRANSMISSION OF X-RAYS UNDER ASYMMETRICAL REFLECTION CONDITION NEAR THE ABSORPTION EDGE
Author(s) -
Zhimeng Xu,
Chucai Guo,
Zhibing Zhao,
T. Fukamachi,
Riichirou Negishi
Publication year - 1998
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.47.1818
Subject(s) - poynting vector , bragg's law , physics , optics , scattering , reflection (computer programming) , diffraction , perfect crystal , crystal (programming language) , wave vector , plane wave , transmission coefficient , reflection coefficient , absorption (acoustics) , condensed matter physics , atomic physics , transmission (telecommunications) , quantum mechanics , magnetic field , computer science , programming language , electrical engineering , engineering , vacancy defect
Anomalous transmission of X-rays for plance-parallel perfect crystals under asymmetrical Bragg reflection condition near the atomic absorption edge is studied in detail. When diffraction is induced mainly by the imaginary part of atomic scattering factor, the nodes of the standing wave within the crystal lie on the atomic plane at the exact Bragg angle, which results in an anomalous transmission. The transmitted beam comes mainly from the wave-field with its Poynting vector Poynting toward the lower surface of the crystal (the entrance surface being the upper one). The effective absorption coefficient of this wave-field decreases with the asymmetrical factor a. Therefore, the transmitted coefficient of the whole crystal increases as a increases. For a given ratio between the contributions of the real and imaginary parts of atomic scattering factor to diffraction, the deviation of Poynting vector from the normal of the real part of the dispersion surface increases with the degree of asymmetrical reflection condition.