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The critical voltage effect in transmission electron microscopy. III. Influence of weak beams on degeneracy
Author(s) -
Gevers R.,
David M.,
Serneels R.
Publication year - 1975
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.2220690229
Subject(s) - degeneracy (biology) , perturbation (astronomy) , voltage , cathode ray , physics , beam (structure) , perturbation theory (quantum mechanics) , crystal (programming language) , optics , fourier series , electron , excitation , condensed matter physics , atomic physics , quantum mechanics , mathematics , mathematical analysis , computer science , bioinformatics , biology , programming language
In previous papers a theory of the critical voltage effect has been proposed based on a three‐beam treatment. The influence of further supplementary beams is considered using a general perturbation treatment. Two cases are considered: (i) the supplementary beams are all weak; (ii) there is a single non‐systematic strong perturbing beam. It is shown that the degeneracy may be retained, provided one changes in a proper way the illumination conditions, i.e. the accelerating voltage and possibly the crystal orientation. Perturbation calculus enables to obtain the shift of the critical voltage and of the excitation errors, as the sums of series in ascending powers of the Fourier coefficients (of the crystal potential) associated with the supplementary beams.