Photoinduced Infrared Activity in Polyacetylene

Photoexcitation of trans - but not cis -polyacetylene, results in the appearance of strongly-ir-active local modes at 1370 and 1260 ${\mathrm{cm}}^{-1\mathrm{}}$. This observation demonstrates that the photogeneration of self-localized charge carriers is unique to the trans isomer. In spite of their localization the kinetic mass of these photocarriers is small, $M_c\simeq \mathrm{}(1-2.5)m$, a result which is in quantitative agreement with calculations based on single-chain models.