Oscillatory structure of laue case rocking curves

Perfect crystal Laue case (n, – n) rocking curves (i.e. convoluted intrinsic reflection curves) display pronounced oscillations provided both crystals have equal thickness and are rotated exactly through their parallel orientation. It is shown that the oscillations are directly related to the oscillatory structure of the intrinsic curves known from the dynamical diffraction theory, a fact which has been overlooked so far. Experimental oscillatory rocking curves agree very well with calculated curves and can neatly be used to extract the intrinsic distributions. A special feature of the “equal thickness” rocking curves is the extremely narrow central peak. For instance, with the silicon 440 reflection and AgKα X-rays, the central peak is less than 0.05″ of are wide. A possible application is in very sensitive small angle measurements with hard X-rays or thermal neutrons.