Dynamics of higher photoexcited states in m-LPPP probed with sub-20 fs time resolution

We study the enhanced charge generation from higher excited states in a conjugated polymer via a modification of transient differential transmission spectroscopy. The first excited state S1 is reexcited via a second laser pulse towards a higher state Sn. The relaxation dynamics of Sn as well as the kinetics of the states created from Sn is revealed by a broad-band probe pulse. sh and probe durations below 20 fs allow the time-resolution of the Sn relaxation and enables us to identify the two main contributions to enhanced charge generation from Sn, energy migration and vibrational relaxation.