PHOTOCHEMISTRY OF IODOBENZENE ADSORBED ON SAPPHIRE(0001)

Iodobenzene (C6H5I) dosed on sapphire(0001) at 110 K adsorbs molecular ly and desorbs with a peak near 187 K, depending slightly on coverage. Irradiation with 193 nm photons induces dissociation attributable to photon absorption by C6H5I and C-I bond cleavage. A measurable fractio n of the products are ejected during irradiation. Normalized to the in itial intensities, the I XPS signal decays 2.5 times faster than the C signal. The cross sections for the loss of C6H5I, I, and C are (2.8 /- 0.3) x 10(-18), (6.6 +/- 0.7) x 10(-19), and (2.7 +/- 0.3) x 10(-19 ) cm(2), respectively. Benzene (C6H6) and biphenyl (C12H10) appear in TPD at temperatures consistent with desorption-limited processes.