Excimer formation of pyrene as a probe to investigate the recombination of geminate pairs: ODESR and fluorescence study of dilute pyrene in squalane

It is shown that the monomer fluorescence and the excimer fluorescence from a dilute pyrene solution in squalane at room temperature are mainly from “delayed” geminate pairs (Py−, S+) and (Py−, Py+), respectively, from the ODESR spectra observed at the monomer and the excimer fluorescence. The recombination time of the former pair is found to be much shorter than that of the latter from analysis of these ODESR amplitudes. This indicates that the hole (S+) hops between the solvent molecules towards the solute anion.