Ground-state aggregation

The Effect of Ground-State Aggregation on Fluorescence Spectra. 132... 

Excitation spectra of HPC-Py/26 in water revealed a red-shift in the excimer species relative to monomer. This, along with the lack of a detectable rise time in the fluorescence decay profile of the excimer species, indicated that the excimers exist predominantly as ground-state aggregates. This result is a very significant indication of the nature of the aggregates as well as the association mechanism. 

Otten, I.G., Yeh, C.S., Byrn, S., and Morrison, H., Solution phase photodimerization of tetrame-thyluracil. Further studies on the photochemistry of ground-state aggregates, J. Am. Chem. Soc., 99, 6353, 1977. 

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