A mixture of naphthalene and 2-methylnaphthalene was deposited on a crystal of α-alumina. When optically pumped, the energy was transferred from the naphthalene to the 2-methylnaphthalene. Initially, only the excimer was observed. As the crystal was heated in a temperature programmed desorption experiment, the adlayer of the mixture exhibited a disorder-to-order transition and the fluorescence was primarily from the 2-methylnapthalene. The addition of a volatile, non-emitting molecule, 1-chlorohexane, to the adlayer composed of the mixture of fluorophores caused the adlayer to undergo structural relaxation that was much more pronounced. The rate constant of the laser induced fluorescence decay increased concomitantly with the percolation because of the available non-radiative pathways that were created by intermolecular interactions.
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