Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 5: Focus: Structural Ordering and Electronic Transport II (joint focus with HL)
CPP 5.7: Vortrag
Montag, 26. März 2012, 17:00–17:15, ER 270
Intermolecular torsional motion of a π-aggregated dimer probed by two dimensional spectroscopy — •Joachim Seibt1 and Alexander Eisfeld1,2 — 1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden — 2Department of Chemistry and Chemical Biology Harvard University, 12 Oxford Street, Cambridge, MA 02138
The energetic splitting of the two exciton states of a molecular dimer depends strongly on the relative orientation of the monomers with respect to each other. The curvature of the corresponding adiabatic potential energy surfaces can lead to torsional motion of the monomers. It has been suggested recently that this torsional motion could provide a possible relaxation mechanism for the upper state which proceeds via a crossing of the two excited state potentials. Another, competing, relaxation mechanism is provided by coupling to the environment, leading to direct exciton relaxation. Here we examine theoretically the combined dynamics of torsional motion and excitonic relaxation for a π-aggregated dimer. Using two dimensional (2D) spectroscopy it is shown how torsional motion through a crossing of the adiabatic excitonic potential surfaces could be distinguished from direct relaxation. For the calculations a mixed quantum/classical approach is used, where the torsional motion is treated by an Ehrenfest type of equation, while the excitonic dynamics including dephasing and direct relaxation is described by a quantum master equation.