Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 16: Electronic Structure and Spectroscopy II

CPP 16.1: Talk

Wednesday, March 29, 2006, 14:00–14:15, ZEU 160

Statistics of low energy weakly localized Frenkel exciton levels in one-dimensional disordered systems — •Mariusz Bednarz — Abteilung Theoretische Physik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany

A novel approach to probe the statistics of low energy levels of weakly localized Frenkel states in one-dimensional disordered systems will be shown. We analyze theoretically the spectral dynamics of excitons caused by the vibration-assisted hopping over localized states. The Pauli master equation is used as a tool to describe exciton hopping. Exciton fluorescence under very narrow spectral excitation conditions, resonant with the absorption band, is put forward to uncover the regularities of the exciton spectral dynamics. Under such conditions the fluorescence spectra are composed of a narrow peak at the excitation energy and a red shifted wing. This spectral structure has a simple explanation within the framework of the band-edge local level structure which has been proven to exist in the low-energy tail of the density of exciton states. The narrow peak results from the localized exciton states (mostly with large oscillator strength) created by the pump, while the wing is formed due to possible hopping of initially created excitons to the lower energy localized states, occurring within the same localization segment as well as between different ones. We show in a very detailed manner how the statistics of low energy levels can be extracted form the wing of such spectra at zero Kelvin. The effect of the localization due to spatial correlation of molecular energetic disorder on the energy level statistic also will be shown.