Twist dynamics of 9-(N-carbazolyl)-anthracene: Effects of intramolecular vibrational redistribution and non-adiabatic transitions in coupled bright and dark states

The twist dynamics of 9-(N-carbazolyl)-anthracene (C9A) in the electronically excited bright and dark states S-1 and S-X is investigated theoretically. Effects of Intramolecular Vibrational Redistribution (IVR) as well as the diabatic transition S-1 --> S-X are taken into account. Based on a model hamiltonian and IVR-rates, which have been derived earlier from laser induced fluorescence spectra and life times observed by Monte et al. [1], the Liouville-von Neumann equation is integrated with a dissipative Liouvillian in Lindblad form. The resulting time dependent density matrix yields nearly coherent twist dynamics of this rather large molecule, at least on a timescale of several ps. The corresponding pump-probe spectra are predicted following the approach proposed by Manz et al. [2].