COHERENT BREMSSTRAHLUNG AND THE QUANTUM-THEORY OF MEASUREMENT

Coherent bremsstrahlung (CB) is the result of inelastic Bragg scatteri ng of electrons of a few hundreds of keV, a collective effect of the w hole crystal. In an electron microscope it is theoretically possible t o determine the row of atoms where the electron was inelastically scat tered. These statements are contradictory. Optical path calculations a re made for 160 keV electrons inelastically scattered by a silicon [11 1] crystal and the results are compared with measured CB spectra, The results can be understood by application of Van Kampen's theory of qua ntum mechanical measurement. Experimental CB spectra turn out to be th e result of coherent scattering of atoms within the same row, and inco herent summation of intensities from different rows, or, in other word s, the electrons that cause CB are localised within atomic rows.