The effect of water and methanol on the laser induced fluorescence decay of 2-methoxynaphthalene that had been vapor deposited as a bilayer on a crystal of α-alumina was observed. At about 25 K before the desorption of the methanol and water, thermally induced percolation into the 2-methoxy-naphthalene adlayer disrupted the formation of excimers. Due to the resulting intermolecular interaction between the water or methanol and 2-methylnaphthalene, the rate constant of the laser induced fluorescence decay increased while at the same time, the intensity of the excimer decreased.