J. Phys. I France
Volume 5, Numéro 2, February 1995
Page(s) 245 - 262
DOI: 10.1051/jp1:1995126
J. Phys. I France 5 (1995) 245-262

Coherent Bremsstrahlung and the Quantum Theory of Measurement

E.H. du Marchie van Voorthuysen

Nuclear Solid State Physics and Materials Science Centre, University of Groningen, Nijenborgh 4, NL 9747 AG Groningen, The Netherlands

(Received 29 December 1993, revised 21 September 1994, accepted 18 October 1994)

Coherent bremsstrahlung (CB) is the result of inelastic Bragg scattering of electrons of a few hundreds of keV, a collective effect of the whole crystal. In an electron microscope it is theoretically possible to determine the row of atoms where the electron was inelastically scattered. These statements are contradictory. Optical path calculations are made for 160 keV electrons inelastically scattered by a silicon [111] crystal and the results are compared with measured CB spectra. The results can be understood by application of Van Kampen's theory of quantum mechanical measurement. Experimental CB spectra turn out to be the result of coherent scattering of atoms within the same row, and incoherent summation of intensities from different rows, or, in other words, the electrons that cause CB are localised within atomic rows.

© Les Editions de Physique 1995