Site effect on radiative and non-radiative relaxation paths of naphthalene in low-temperature matrices Original Research Article

Fluorescence and phosphorescence spectra and decay times are recorded for naphthalene in Ne, N2, CH4, Ar, Kr and Xe matrices upon a selective excitation of different sites. Beside the usual frequency shifts we observe significant differences in the relative intensities of the “allowed” and “forbidden” transitions in the fluorescence spectra and in the S1 and T1 decay times (i.e. S1∼→T1 and T1∼→S0 intersystem crossing rates) between different families of sites in the same host. These effects are discussed in terms of the medium induced molecular deformations and of the variation of the external heavy atom effect on the S1↔T1 coupling with position of the perturber.