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The critical voltage effect in transmission electron microscopy . VII. The Influence of Absorption
Author(s) -
David M.,
Gevers R.,
Serneels R.
Publication year - 1977
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220790122
Subject(s) - absorption (acoustics) , eigenvalues and eigenvectors , symmetry (geometry) , transmission electron microscopy , acceleration voltage , condensed matter physics , physics , observable , voltage , electron , transmission (telecommunications) , optics , bloch wave , matrix (chemical analysis) , molecular physics , chemistry , materials science , quantum mechanics , mathematics , cathode ray , geometry , electrical engineering , engineering , chromatography
Abstract The influence is studied of the absorption on the dynamical behaviour of a linear ( 2N + 1)‐beam system close to the second order Bragg orientation and around the critical voltage. When a small imaginary potential is introduced into the dynamical matrix for such situations, the eigenvalues and the eigenvectors of the latter are drastically altered. In particular the mechanism of symmetry exchange of the first two Bloch waves, and its consequences on the vanishing of the second order DF bend contour are examined. A qualitative effect of absorption on the behaviour of the bend contour with varying voltage, seems unlikely to be observable in most materials. However, one finds that absorptionless calculations may underestimate the critical voltage of heavy materials by an amount of the order of 50 kV.