ADSORBATE-SUBSTRATE DYNAMICS FOR C(2X2)CL NI(100) - A SEXAFS STUDY/

Temperature and angle dependent surface extended X-ray absorption fine structure (SEXAFS) measurements are reported for c(2 x 2)Cl/Ni(100). A complete dynamic analysis including SEXAFS Debye-Waller factor and m ean cubic relative displacement is presented for nearest neighbour (n. n.) and for the first time next nearest neighbour (n.n.n.) Cl-Ni coord inations and compared with the data available on c(2 x 2)S/Ni(100). Th e Cl-Ni bonding to the second layer Ni atoms seems to be stronger than for S-Ni. Einstein temperatures for the first and second Cl-Ni coordi nations suggest that in the present system vibrations associated with longer out-of-plane bonds are more anharmonic than the shorter and rel atively stronger in-plane bonds.