Apparent Anomalous Absorption and Image Matching

Abstract

Visual matching of experimental and theoretical electron micrographs can be used to determine the apparent anomalous absorption constant. The method has been applied to a copper-silicon (8 at. % Si) alloy by matching experimental and theoretical images of a Shockley partial dislocation and the main and subsidiary fringes of the associated stacking fault. The value of 0·067 which is obtained is considerably less than the value of 0·1 usually assumed for metals and alloys. In foils approximately 3611 thick details of the image are very sensitive to the value ofthe anomalous absorption constant and the value of 0·1 is inadequate for image matching. However, in foils approximately 6611thick the general topological features of an image are little altered by varying the anomalous absorption constant over a wide range and the approximate value of O· 1 is adequate for image matching.