Heidelberg 2015 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 9: Femtosecond Spectroscopy 2
MO 9.6: Vortrag
Dienstag, 24. März 2015, 16:00–16:15, PH/HS1
Identification of an Ultrafast Triplet Transition Discovered by Pump-Depletion-Probe Experiments — •Julia Herz1, Fabian Paulus2, Tiago Buckup1, Uwe Bunz2, and Marcus Motzkus1 — 1Physikalisch-Chemisches Institut — 2Organisch-Chemisches Institut, Ruprecht-Karls-Universität, D-69120 Heidelberg, Germany
Pump-depletion-probe experiments were carried out in order to disentangle the excited state dynamics of TIPS-pentacene. In particular the singlet fission process, in which an excited molecule reacts with a neighbor in its ground state producing two excited triplet species in an overall spin-conserved process, is important. The formed triplet state shows two transitions, one in the visible (T1->T3) and one in the NIR spectral region (T1->T2). Measurements in these two spectral ranges can provide insight into the interplay of the triplet manifold and help to unravel additional singlet fission channels. Applying a depletion pulse resonant with the triplet absorption in the visible leads to a loss of signal in the NIR, however, the evolution of the NIR signal does not follow the dynamics observed in the visible. Our results are explained by an ultrafast relaxation channel (ca. 90 fs) between the triplet states (T3->T2). A rate model simulation of the depletion effect supports this finding and gives further evidence, within our experimental time resolution, that both triplet transitions in the NIR and VIS probe the same triplet state (T1).