Microscopic Surface Structure of Liquid Alkali Metals

TL;DR

This study uses x-ray scattering to analyze the microscopic surface structure of a liquid alkali metal alloy, revealing surface layering behavior and its resistance to oxidation and hydride formation.

Contribution

It provides the first detailed x-ray scattering analysis of liquid alkali metal surfaces, showing surface layering and stability against oxidation.

Findings

Surface follows capillary wave roughness

Surface layering is less pronounced than in other metals

Oxide and hydride do not form under experimental conditions

Abstract

We report an x-ray scattering study of the microscopic structure of the surface of a liquid alkali metal. The bulk liquid structure factor of the eutectic K67Na33 alloy is characteristic of an ideal mixture, and so shares the properties of an elemental liquid alkali metal. Analysis of off-specular diffuse scattering and specular x-ray reflectivity shows that the surface roughness of the K-Na alloy follows simple capillary wave behavior with a surface structure factor indicative of surface induced layering. Comparison of thelow-angle tail of the K67Na33 surface structure factor with the one measured for liquid Ga and In previously suggests that layering is less pronounced in alkali metals. Controlled exposure of the liquid to H2 and O2 gas does not affect the surface structure, indicating that oxide and hydride are not stable at the liquid surface under these experimental conditions.