Resonant X-Ray Scattering from the Surface of a Dilute Hg-Au Alloy
  We present the first resonant x-ray reflectivity measurements from a liquid surface. The surface structure of the liquid Hg-Au alloy system just beyond the solubility limit of 0.14at% Au in Hg had previously been shown to exhibit a unique surface phase characterized by a low-density surface region with a complicated temperature dependence. In this paper we present reflectivity measurements near the Au LIII edge, for 0.2at% Au in Hg at room temperature. The data are consistent with a concentration of Au in the surface region that can be no larger than about 30at%. These results rule out previous suggestions that pure Au layers segregate at the alloy surface. 
Elaine DiMasi, Holger Tostmann, Oleg G. Shpyrko, Patrick Huber,   Benjamin M. Ocko, Peter S. Pershan, Moshe Deutsch and Lonn...