Oligothiophenes occupied states

The electronic structure of oligothiophenes is characterized by UPS and MO calculations for the occupied states and by a variety of optical techniques for the transition between occupied and unoccupied levels. Because of the vast number of papers on optical measurements, only a selection demonstrating the most important features can be presented here. 

Another process which has to be considered is the conformation change from the nonrelaxed nonplanar to the planar excited state, which could be connected with a fast increase of absorption. The most important radiationless decay process in oligothiophenes is ISC. Therefore, a fast channel of ISC was suggested, which is effective before the lowest vibronic state of Si is occupied. The fast decay of the AD(f) kinetics is caused by an effective formation of triplets. 

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