Time behaviour of transient spectra

The time behaviour of transient spectra is very essential for the assignment of these spectra to energy levels or species. If possible, independent experimental methods should be used to gain data of the time behaviour. Therefore, we performed time resolved fluorescence measurements on the oligothiophenes and obtained the fluorescence lifetimes of T [3]. Today other references are also available [11]. 

The obtained lifetimes for the Al band agree with the fluorescence lifetimes [3, 11], as demonstrated in Tab. 17.1. 

From these facts we conclude for all oligothiophenes that Al is an absorption from the excited fluorescing state Si. 

The development of A2 could be observed at all the longer oligothiophenes (n = 3-6). The A2 spectra are detectable after the decay of Al and F in times of about 100 ps (for 3T) 

The formation of triplets is demonstrated for 3T. According to Fig. 17.8 we consider the decay processes after 5-like excitation with simple rate equations (Eqs. 2 and 3) for the number density of the excited singlet SI and triplet TI. The solutions (Eqs. 4 and 5) yield the time behaviour of the excited states. 

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