Photochromic effect in molybdenum-oxide cluster systems

The photochromic effect under UV illumination has been studied in cluster s ystems of molybdenum oxides in aqueous solutions of citric acid. This paper reports the first observation of two types of systems exhibiting different photochromism. Systematic measurements of the optical characteristics, pro ton concentration, and photogalvanic emf have been carried out as functions of composition. A model is proposed for the molybdenum-oxide-cluster-citri c-acid complex, in which intramolecular electron transfer occurs under UV i llumination. (C) 1999 American Institute of Physics. [S1063-7834(99)04207-0 ].