ULTRAFAST CHARGE SEPARATION IN A SUBSTITUTED POLYACETYLENE

Formation time of a soliton-antisoliton pair has been determined as 98 +/- 8 fs experimentally by femtosecond transient spectroscopy performed on a thin film of poly[(o-trimethylsilyl)phenylacetylene], a substituted polyacetylene. It agrees favourably with results of the numerical simulation based on the Su-Schrieffer-Heeger model. A temporal behavior of photoinduced absorption was fitted successfully by a sum of an exponentially and a power-law decaying components. This allowed one to determine separately the spectrum of the soliton-antisoliton pair and that of an exciton-polaron created by an intrachain photoexcitation.