An x-ray reflectance study of the liquid–vapor interface of Cs

We report the results of a study of the angular dependence of the reflection of CrKα x rays from the liquid–vapor interface of cesium. It is shown that the data are consistent with the prediction, by D’Evelyn and Rice, that the liquid–vapor interface of cesium is stratified. Other theoretical models of the liquid–vapor interface are also compared with the experimental data. The Mon–Stroud model is shown to be inconsistent with those data. A model with a monotone density profile only 0.7 atomic diameters wide will fit the experimental data, but it is argued that this model is physically inconsistent, since the restriction of the outermost atoms to lie within ±0.35 diameters of a plane is likely to force stratification of the neighboring liquid for a few atomic diameters.