Picosecond Photoinduced Dichroism inTrans-(CH)x: Direct Measurement of Soliton Diffusion

Abstract

Photoinduced dichroism caused by bleaching of the interband transition in trans-${\left(\mathrm{CH}\right)}_x$ was observed in the picosecond time domain. The bleaching is induced instantaneously and decays with time as $t^{-\frac{1}{2}}$, changing to a lower power after ∼50 psec. Although the photoinduced bleaching persists to long times, polarization memory is lost after ∼${10}^{-9\mathrm{}}$ sec. The results provide a measurement of the diffusion constant of the charged excitations; $D\simeq 2\times {10}^{-2\mathrm{}}$ ${\mathrm{cm}}^2$ ${\sec }^{-1\mathrm{}}$ at 300 and 80 K.