The surface chemistry of several small photoactive molecules adsorbed on an insulator surface: Cyanogen iodide, methyl iodide, carbon disulfide and iodine on magnesium oxide(100)

Understanding the surface chemistry of small photoactive molecules adsorbed on MgO(100) is necessary prior to surface photodissociation experiments so that the surface's contribution to the observed photochemistry can be determined. The photoactive molecules used in this study were selected on the basis of their gas phase photochemical properties, while MgO(100) was chosen as a substrate because of its low reactivity. The surface chemistry of MgO(100) is not well established, along with the surface chemistry of the small photoactive molecules studied.;Four surface sensitive analytical techniques were used in this study, temperature programmed desorption (TPD), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). TPD and XPS give information on the degree of surface-adsorbate interaction while AES and LEED were used to develop a cleaning procedure.;Iodine adsorption on MgO(100) results in I;Methyl iodide adsorption on MgO(100) at low coverage produces TPD behavior consistent with repulsive dipole-dipole interactions. Screening of methyl iodide dipoles by the MgO surface is impossible, due to the insulator characteristics of the surface. At higher coverages methyl iodide adsorption goes through a phase of cluster growth until completion of a multilayer.;Cyanogen iodide adsorption on MgO(100) has behavior similar to methyl iodide, at low coverages. At all coverages there is a partial decomposition of ICN which is due to its orientation on the surface. At high coverages zero order coverage dependence is observed. XPS indicates the ICN is intact on the surface at all coverages.;Carbon disulfide exhibits behavior consistent with a vacuum system pumping effect. TPD indicates that the CS...