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MO: Fachverband Molekülphysik

MO 2: Elektronische Spektroskopie

MO 2.10: Talk

Monday, March 10, 2008, 18:45–19:00, 3F

Detection of dark states of porphyrins — •Andreas-Neil Unterreiner¹, Oliver Schalk¹, Helge Brands¹, and Silviu Balaban² — ¹Universität Karlsruhe (TH), Lehrstuhl für Molekulare Physikalische Chemie, 76128 Karlsruhe — ²Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021 Karlsruhe

Porphyrins are known to exhibit two absorbing bands, the B-band in the visible (500-650 nm) and the Soret-band in the UV (420 nm). In order to explain ultrafast dynamics after excitation to the Soret band, dark states in its vicinity have been postulated. Here, we present the first direct observation of these states in 5,10,15,20-tetra-p-tolyl-21H,23H-porphyrin (TTP-H₂) and 5,10,15,20-tetra-p-tolyl-porphyrinato zinc II (ZnTTP) by means of pump-probe and transient anisotropy experiments. After excitation to the Q-band, the molecules were probed by NIR-pulses in the range between 950 and 1350 nm in order to study states of gerade-symmetry. Examination of transient spectra and anisotropy revealed the energies of the two lowest so called dark states. The experimental results are compared with predictions from theoretical calculations.