Abstract
We have used resonance-Raman scattering to study the effects of hydrostatic pressure (to 80 kbar) on polyiodide chain vibrations in iodine-doped poly(vinyl alcohol) films. Two strong fundamental bands are observed along with overtone and combination bands. The low-energy band at 107 cm-1 is attributed to symmetric stretching of I3-. The higher lying band at 154 cm-1 is from symmetric stretching of the two end I2 units in I5-. The I3- and I5- are intermixed within the polyiodide chains. The combination band arises from exciton coupling between molecules within the chains. Three primary effects are observed with increasing pressure. First, the Raman band at 107 cm-1 blue shifts under pressure, while the band at 154 cm-1 shifts weakly. This latter is attributed to the competing effects of compression, enhanced interaction of the outer I2 with the central I- (which weakens the outer I−I bond), and attractive host−guest interactions which increase in strength with compression. The second effect observed in the...
Published Version
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