Fluorescence self-quenching in aromatic vapours; the role of excited dimers

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Abstract
At temperatures sufficiently high to produce an appreciable pressure of 9, 10-diphenylanthracene, perylene or pyrene, the quantum yield of fluorescence is found to be independent of vapour pressure. The negative temperature coefficient of self-quenching in anthracene vapour is explained in terms of the dissociation of an excited dimer which is also responsible for delayed fluorescence. The pressure-dependence of the excited dimer lifetime at low pressures is shown to be consistent with a pressure-independent quenching constant if the second-order dissociation of the excited dimer becomes first-order at higher pressures.