Temperature-dependent resonance Raman study of iodine-doped poly(vinyl alcohol) films

The resonance Raman spectrum of iodine-doped poly(vinyl alcohol) films was studied as a function temperature from 77 t0 290 K. The main bands in the spectrum are assigned to fundamental and overtone bands of linear I3− and I5−. The presence of combination bands in the spectrum is attributed to exciton coupling between these species in polyiodide chains. The low-temperature measurements allowed us to resolve new spectral features. At 77 K, the spectrum showed evidence for minor amounts of I2 and isomers of the main polyiodide components. The optical properties of the PVA-iodine complex are not simple and cannot be assigned to any single polyiodide species.