SURFACE LAYERING IN LIQUID GALLIUM - AN X-RAY REFLECTIVITY STUDY

Surface-induced atomic layering in liquid gallium has been observed us ing x-ray reflectivity, ultrahigh vacuum conditions, and sputtered cle an surfaces. Reflectivity data, collected on a supercooled liquid samp le to momentum transfers as large as q(z) = 3.0 Angstrom(-1), exhibit a strong maximum near 2.4 Angstrom(-1) indicating a layer spacing that is comparable to its atomic dimensions. The amplitude of the electron density oscillations decays with a characteristic length of 6 Angstro m. This is unexpectedly twice that of recent results for Hg, and the d ifference may be related to covalent bonding or supercooling.