Electronic transitions at the surface of KI microcrystals. Part 2.—Excitations with charge transfer to the adsorbates

Abstract

The adsorption of iodine, carbon tetrachloride, methyl ethyl ketone, acetonitrile and ammonia onto KI microcrystals has been studied by means of the diffuse reflectance technique in the ultraviolet. In all cases, signals at energies lower than those of the starting excitons have been observed, i.e. electronic excitations at the surface involve the adsorbate in a charge transfer. Iodine reacts with surface I^– ions to yield I^–₃; carbon tetrachloride forms a charge-transfer complex I^–·CCl₄; in the other three cases, the nature of the transition is intermediate between the starting surface exciton and the excitation of I^– in the same substances as solvents.