Ultrafast spectroscopy of even-parity states in π-conjugated polymers

Relaxation dynamics of even parity (A,) states in poly(p-phenylene vinylene) derivatives are studied using a novel fsec transient spectroscopy, in which two different excitation pulses successively generate odd parity (1 B-1(u)) excitons at 2.2 eV and then reexcite them to higher A(g) states. For reexcitation energies h omega < 1.1 eV ultrafast internal conversion hack to 1(1)B(u) takes place in accordance with Vavilov-Kasha's rule. However, for h omega > 1.1 eV the decay occurs in a nonemissive state identified as a polaron pair, showing that the A, states above 3.3 eV mediate charge transfer.