INTERACTIONS OF UV PHOTONS AND LOW-ENERGY ELECTRONS WITH CHEMISORBED BENZENE ON AG(111)

The interactions of UV photons and low energy electrons with chemisorbed benzene (C6D6) on Ag(111) has been studied using temperature programmed desorption (TPD) and ultraviolet photoelectron spectroscopy (UPS). The adsorption and desorption of C6D6 on Ag(111) is completely reversible. No photoeffects are observed when chemisorbed C6D6(a) is exposed to UV photons generated from a high pressure Hg are lamp. Exposure to electrons results in decomposition of C6D6(a) to surface D atoms and phenyl fragments. The cross section for electron induced decomposition of C6D6(a) at one monolayer coverage is (1.9 ± 0.1) × 10-17 cm2 at 50 eV. It decreases with decreasing incident electron energy and has a threshold between 11 and 16 eV. Surface D atoms desorb as D2 at ~ 200 K. Phenyl fragments recombine and desorb as biphenyl at 375-390 K; they do not decompose. It is demonstrated that low energy electron induced decomposition of C6D6 on Ag(111) is an effective way to prepare surface phenyl fragments. © 1990.