Coherence in electronically excited dimers. The observation of coherent dimers and its relationship to coherent excitons

Abstract

The coherent nature of molecular excited dimers in their triplet states is unequivocally established by a series of low temperature optically detected magnetic resonance experiments in zero field. The results clearly establish that a minimum coherence time for the dimer ψ(+) state in 1,2,4,5-tetrachlorobenzene (≈ 1.7 K) is longer than 5 × 10^(−7) s while the exchange time in these systems is approximately 16 × 10^(−12) s. This implies that the coherence persists for a time approximately 10^5 times that associated with the stochastic limit. The coherence time could, however, be even longer. Moreover, these new results clearly demonstrate that there is a direct and quantitative relationship between coherent properties of dimers and the coherent properties of triplet Frenkel excitons.

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