Coherence in the excited states of multidimensional systems: Dimer and exciton dynamics in crystalline phenazine

Coherence in multidimensional excited systems was established using optical and zero-field magnetic resonance spectroscopy. High resolution phosphorescence microwave double resonance at the Larmor frequency of the excited phenazine dimer gave the dynamics of optical coherence while the magnetic resonance spectra at 1.6 K gave a coherence time which was shown to be at least 10^5 times that of the stochastic-markoffian limit and approximately 11000 of the radiative lifetime. These results indicate that the cross-chain interaction does not destroy the in-chain spin correlation