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The momentum profiles from positron annihilation with core electrons in Al have been observed with a recently developed two-detector Doppler-broadening technique. Independent-particle-model (IPM) calculations are in good agreement with the experimental results beyond twice the Fermi momentum and suggest the absence of strong positron-electron correlation effects in this region. Comparisons of calculations with properly normalized momentum profiles indicate that high-momentum core contributions may provide information on the nature of vacancy-type defects and self-trapping effects., Physics

With use of bromine atoms, deposited on the surface of a silicon single crystal, the presence of x-ray standing waves above the crystal surface has been detected under conditions of strong Bragg diffraction., Physics

Interference effects have been observed when coherently related x-ray beams are Compton scattered from an atomic system. We use dynamical diffraction methods to prepare the initial x-ray state and observe the coherent Compton effect in both crosssection and profile measurements., Physics