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, which 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 to 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 reveals a Cl-Ag bond length of 2.48 Angstrom, which disagrees with a previous SEXAFS bond length determination for chlorine on Ag(lll), but is in accordance with trends in metal-chlorine bond lengths for other fee metal (111) (root 3 x root 3) R30 degrees surfaces.