  Resonant x-ray reflectivity measurements from the surface of liquid Bi22In78
find only a modest surface Bi enhancement, with 35 atomic % Bi in the first
atomic layer. This is in contrast to the Gibbs adsorption in all liquid alloys
studied to date, which show surface segregation of a complete monolayer of the
low surface tension component. This suggests that surface adsorption in Bi-In
is dominated by attractive interactions that increase the number of Bi-In
neighbors at the surface. These are the first measurements in which resonant
x-ray scattering has been used to quantify compositional changes induced at a
liquid alloy surface.
