The Diffraction of X-Rays by Argon in the Liquid, Vapor, and Critical Regions

The x-ray diffraction pattern of argon has been obtained for 26 different conditions of pressure and temperature ranging from 0. 8 atmos. and 84. 35^ to 51. 1 atmos. and 168^ with a variation in density from 1. 401 g/cc to 0. 038 g/cc. The intensity in each case is given in electron units. The patterns for argon of high density show sharp maxima while those of low density show much less pronounced maxima or none at all. It is noted that there is considerable small angle scattering in patterns for argon near the saturated vapor curve and at moderate or high pressures and temperatures. Six liquid patterns and one vapor pattern have been analyzed for the atomic distribution. At higher pressure and temperature along the saturated vapor curve, the liquid structure gradually becomes less pronounced, and the structure of liquid and vapor near the critical point are generally similar in nature.