X-ray reflectivity study of the surface of liquid gallium.

X-ray reflectivity from the surface of liquid gallium was measured under ultrahigh vacuum conditions using a novel technique for curved surfaces. The small deviations between the measured and theoretical Fresnel reflectivity for an ideally sharp flat interface for wave-vector transfer [approx lt]0.5 A[sup [minus]1] imply an interfacial width for the electron density profile of [approx lt]1.3[plus minus]0.2 A. This is consistent with a model of atomic close packing which lacks structure along the surface normal at length scales [gt]10 A.