Identification of I-3(-) and I-5(-) clusters in irradiated KI by X-ray photoelectron, Raman and optical absorption spectroscopies

Raman and XPS measurements have been performed on KI crystals irradiated near 200 K. The Raman studies show I-3(-) and I-n(-) (n = 5, 7, - - -) clusters which anneal together with F- and V- centres at 338 K. A small development of (I-2)n aggregates occurs during the anneal; these decay near 378 K and are responsible for a broad and weak residual V-band. The I 3d(5/2) XPS peak has been fitted to reveal the presence of 3 components after low energy argon-ion bombardment. These are identified as due to normal lattice iodine, I-3(-) and I-5(-) whose behaviour is consistent with the Raman work.