Femtosecond transient absorption spectroscopy in alpha-sexithienyl thin films

The electroactive and photoactive properties of conjugated systems have att racted the interest of many laboratories, both for a basic understanding of their photophysics as well as for possible applications in organic-based o ptoelectronic devices. alpha-sexithienyl has been recognized as a model com pound for a basic understanding of the electronic properties of conjugated materials. We report on ultrafast pump-probe measurements on ultra-high vac uum deposited thin films of a-sexithienyl. Femtosecond transient spectrosco py experiments were performed at low temperatures and over a wide wavelengt h range of the probe beam (from 420 nm up to 680 nm). The dynamics of the p hotoexcited species are discussed in the frame of the excitonic model.