Coherent bremsstrahlung from kilovolt electrons in zone axis orientations

Abstract

Abstract New experimental results are reported for type B coherent bremsstrahlung (CB) radiation from kilovolt electrons traversing thin crystals in zone axis orientations, obtained using an electron microscope and energy dispersive X-ray detector, approximately at right angles to the beam. These results are interpreted using the three-dimensional Bloch wave theory of multiple coherent electron scattering, which predicts coherent bremsstrahlung ('weak-beam radiation'), channelling radiation ('Pendellösung radiation') and combinations thereof. Absent CB peaks are observed from Laue zones in which all structure factors are zero. Doppler broadening is found to make the observation of channelling radiation satellites on CB peaks difficult. Closed-form expressions for 'resonant' CB are given.