von laue diffraction Laue diffraction For different incidence directions. the Single stal N b(co$。-cosp)=k dcosyo -cosy)=D. Laues the Bragg Condition of Crystal Diffraction Experiments Einstein AStrong reflection of the incident wave will occur for regards this the set of incident angles that satisfy the bragg (a)show its four-fold axis (b)show its three-fold axis Geometry of Bragg Diffraction Braggs Law ni=2dh sine a When xrays are scattered from a crystal lattice eaks of tensity are observe correspond to the following condition a The angle of incidence angle of scattering e The pathlength difference is equal to an inte The conditions for maximum intensity contained in B saw to calculate details about the crystal structure, or if the crystal Path difference for diffraction of rays from structure is known, to determine the wavelength adjacent planes is 2dhksinO, which must of the x rays incident upon the crystal correspond to ni for constructive interference2 von Laue Diffraction ß For different incidence directions, the diffraction patterns are different g - g = l b - b = l a - a = l c(cos cos ) l b(cos cos ) k a(cos cos ) h 0 0 0 Laue Diffraction Single crystal Laue¢s Experiments Laue Images of Zincblende ZnS (a)show its four-fold axis，(b)show its three-fold axis Einstein regards this experiment as the most beautiful one in physics. Nobel Prize winner of 1914 the Bragg Condition of Crystal Diffraction d q l Strong reflection of the incident wave will occur for the set of incident angles that satisfy the Bragg condition: 2dsinq =nl the index n defines the path difference between waves i & ii when the diffraction occurs … for a given value of n this path difference is nl. Geometry of Bragg Diffraction Path difference for diffraction of rays from adjacent planes is 2dhklsinq, which must correspond to nl for constructive interference. q q dhklsinq dhklsinq q q nl = 2dhkl sinq Bragg's Law When x-rays are scattered from a crystal lattice, peaks of scattered intensity are observed which correspond to the following conditions: The angle of incidence = angle of scattering The pathlength difference is equal to an integer number of wavelengths. The conditions for maximum intensity contained in Bragg's law above allow us to calculate details about the crystal structure, or if the crystal structure is known, to determine the wavelength of the x-rays incident upon the crystal