A Study of the Propagation Mode for Metallic Vapors in Shadow-Casting by Vacuum Evaporation of Au198 and Cr51

Abstract

A special method is introduced for quantitatively determining the metal‐evaporation mechanism using metallic gold and chromium tagged with pile‐produced Au¹⁹⁸ and Cr⁵¹. This tracer method provides a powerful tool for the study of the distribution of minute amounts of the evaporated metal. Propagation and deposition of the vaporized metal are analyzed under a variety of conditions both in the normal evaporation process and for shadow‐casting conditions. It is shown that crucible size and shape determine the evaporation‐dispersion pattern. Computation of film thickness is by quantitative tracer methods with correlating observations by electron microscopy. Structure of these metal films correlates with observations by an earlier worker [R. W. G. Wyckoff, PSA Journal 13, 12 (1947)]. The probable error of the method is ±2 percent.