Transient spectral investigations of two-photon absorption in poly(p-phenylenevinylene

A picosecond pump-probe technique has been used to study the position of the two-phonon state and an ‘ultrafast window’ (‘UW’) for the ultrafast χ(3) effect due to two-photon absorption in poly(p-phenylenevinylene thin films. We show that the peak of the two-photon absorption is at 3.58 eV, which is 1.22 eV above the lowest dipole-allowed excited state. In the picosecond time range there is a spectral region which we refer to as a ‘two-photon UW’ in which the transient two-photon absorption is not accompanied by a ‘slow’ one-photon absorption with a long-lived intermediate one-photon state.