Behavior of I2 and I3- molecular units near the crystal surface of CsI and related polyiodides. Raman-spectroscopic studies

Raman spectra of CsI3 and CS2I8 crystals were measured for the samples whose structures were carefully examined. The surface of CS2I8 samples was found to turn into CsI3 when they were kept in air. The heating effect of laser irradiation was shown to change the spectra of CS2I8 samples to those of CsI3. These results imply that diffusion of iodine molecules occurs in polyiodide crystals. Then, we monitored the reaction of CsI crystals with iodine vapor, and found that iodine makes the layers of CsI3 and CS2I8 on the surface of CsI crystals. It was also found that nearly free I3- ions are generated near the surface of samples during both the thermal decomposition of CS2I8 and the reaction of Csl with iodine vapor. © 1990 The Chemical Socity of Japan.