THE KINETICS OF EXCIMER FORMATION IN FLUID MEDIA.

The ratio of molecular to excimer fluorescence intensities has been measured as a function of temperature for concentrated solutions of 2-methylnaphthalene, 1-fluoronaphthalene, acenaphthene and 1,2-benzanthracene in low-viscosity solvents. Values of 5-6 kcalmole obtained for the heats of photoassociation are significantly lower than that of 11 kcalmole found for pyrene, and indicate that the repulsion energy between unexcited molecules in the excimer configuration is largely responsible for the red-shift of some 6000cm-1 to the-1 power of the excimer band with respect to the molecular spectrum. The corresponding entropies of photoassociation are estimated to lie within the range of -20 to -28 e.u.. Author