Chlorine adsorption on silver (111) at low temperatures

Two previously unreported low-temperature structures of chlorine on silver( lll) are discussed: the sharp Ag(111)-(root 3 x root 3)R30 degrees-Cl, whic h disorders above 195 K and a split spot pattern assigned as Ag(111)-(13 x 13)-Cl. The latter surface is also disordered at room temperature and gives a diffuse pattern reminiscent of a (root 3 x root 3) R30 degrees pattern. These patterns are discussed with reference to previous work and compared t o chlorine adsorption on other fee transition metal (111) surfaces. SEXAFS analysis of the sharp Ag(111)-(root 3 x root 3)R30 degrees-Cl surface revea ls a Cl-Ag bond length of 2.48 Angstrom, which disagrees with a previous SE XAFS bond length determination for chlorine on Ag(lll), but is in accordanc e with trends in metal-chlorine bond lengths for other fee metal (111) (roo t 3 x root 3) R30 degrees surfaces.