Article ID Journal Published Year Pages File Type
5425995 Surface Science 2006 8 Pages PDF
Abstract

The adsorption of CCl4 on Ag(1 1 1) has been investigated from 100 K to 300 K using absolute sticking probability measurement, temperature programmed desorption, Auger electron spectroscopy, low energy electron diffraction, ultra-violet photoelectron spectroscopy and X-ray photoelectron spectroscopy. At 100 K, CCl4 adsorbs molecularly with a sticking probability of 1.0, forming a (3 × 3) adsorption structure. At 300 K the following overall reaction occurs,2CCl4(g)→4Cl(chem)+C2Cl4(g),with an initial sticking probability of S0 = 0.25, indicating that activated dissociative adsorption is the initial step in the above reaction. The saturated surface at 300 K consists entirely of chemisorbed chlorine which undergoes an order/disorder transition to a sharp (√3 × √3)R30° structure on cooling below 180 K. Temperature programmed desorption of CCl4 adsorbed at 100 K shows a multilayer peak at 140 K and a first layer peak at 203 K, where part of the molecularly adsorbed CCl4 desorbs and the rest is converted to a surface carbene, :CCl2, and chemisorbed chlorine. At 248 K the adsorbed carbenes react to form C2Cl4 which promptly desorbs, as it is formed above its normal desorption temperature of 210 K.

Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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