Perfect crystals and imperfect neutrons

Neutron diffraction studies of perfect, non-absorbing crystals have been used to explore aspects of dynamical diffraction theory. The Pendellösung fringe patterns obtained from Laue transmitting crystals with full-spectrum incident radiation have been used to determine crystal structure factors with high precision. It has been established that spherical wave theory is called for, and small crystal curvature must be allowed for, in the interpretation of the fringe patterns. Novel information about the characteristics of the neutron wave packet becomes available from the experimental studies.