The polarizability of triplet excitons on oligothiophene chains

The excess polarizability volume, Delta V-p, associated with the formation of the T-1 states of oligothiophenes, OTn with n from 2 to 12, has been determined by measuring the change in the imaginary component of the complex microwave conductivity resulting on flash-photolysis of dilute solution. Delta V-p gives a direct measure of the additional electronic delocalization associated with the half-filled HOMO and LUMO orbitals of these states. Delta V-p increases with increasing length of the oligomer chain from 5 Angstrom(3) for n=2 to 59 Angstrom(3) for the dodecamer. The increased delocalization in T-1 is discussed in terms or coupling with higher states in the triplet manifold.