Time-resolved photoinduced absorption of orientedtrans-polyacetylene in the picosecond to microsecond range

The polarization dependence of the photoinduced absorption in oriented trans-(CH${)}_{\mathrm{x}}$ has been investigated by the picosecond and nanosecond time-resolved spectroscopies. In the nanosecond range, the transient absorption at 1.4 eV is more strongly induced by the excitation light polarized perpendicular to the chains. It is due to polarons induced by the interchain photoexcitation which generates an electron and a hole in different chains. A relaxation model of the photoexcitations (solitons and polarons) in trans-polyacetylene previously proposed by two of the authors (M.Y. and T.K.) is consistent with the present results.