W.-H. Sun

X-Ray Resonance in Crystal Cavities: Realization of Fabry-Perot Resonator for Hard X Rays

X-ray back diffraction from monolithic two silicon crystal plates of 25-150 microm thickness and a 40-150 microm gap using synchrotron radiation of energy resolution DeltaE = 0.36 meV at 14.4388 keV clearly show resonance fringes inside the energy gap and the total-reflection range for the (12 4 0) reflection. This cavity resonance results from the coherent interaction between the x-ray wave fields generated by the two plates with a gap smaller than the x-ray coherence length. This finding opens up new opportunities for high-resolution and phase-contrast x-ray studies, and may lead to new developments in x-ray optics.

Local environment surrounding S and Cd in CdS:O thin film photovoltaic materials probed by x-ray absorption fine structures

Local environments surrounding Cd and S in CdS:O thin films have been determined using extended x-ray absorption fine structure (EXAFS) and near-edge x-ray absorption fine structure (NEXAFS). As indicated by the Cd EXAFS, Cd atoms remain predominantly bonded with S. The S EXAFS and NEXAFS clearly demonstrate the presence of S–O bonds. The oxygen atoms actually combine with S to form SO3 and SO4 complexes. Combined with the transmission electron micrograph, these x-ray results suggest formation of oxygen-free CdS nanocrystals and provide an unambiguous explanation for the mystery of increased band gap that appears to violate the band anticrossing model.

Coherent trapping of x-ray photons in crystal cavities in the picosecond regime

We report on the trapping of 14keV photons in periods of 1.11–1.67ps by the 12 4 0 backdiffraction in two- and multiplate silicon single-crystal cavities of a few hundred micrometer size. The formation of standing waves inside the cavities ensures better coherence for the x rays. We anticipate that the transmitted x rays through this type of cavities can be used as a quasicoherent x-ray source for probing the dynamic structures of solids, liquids, and biological substances.

Direct Observation of Resonance Fringes in X-ray Cavity: A Diffraction Experiment

C431 P.15.01.1 Acta Cryst. (2005). A61, C431 Direct Observation of Resonance Fringes in X-ray Cavity: A Diffraction Experiment Shih-Lin Chang, Yuriy P. Stetsko, Mau-Tsu Tang, Yen-Ru Lee, Wen-Hsien Sun, Hsueh-Hung Wu, Makina Yabashi, Tetsuya Ishikawa, Department of Physics, National Tsing Hua University, Taiwan, R.O.C.. National Synchrotron Radiation Research Center Taiwan, R.O.C.. Spring-8/JASRI, Japan. Spring-8/RIKEN,Japan. Email: slchang@phys.nthu.edu.tw