The effect of temperature on the parameters of the phosphorescence spectrum of naphthalene in glassy toluene

The temperature shift and the shape of the 0–0 band of the phosphorescence spectrum of naphthalene in glassy toluene are studied in the presence and absence of excitation migration over triplet levels. In the absence of excitation migration, an increase in the temperature from 77 to 110 K has no effect on the position of the maximum of the 0–0 band and on its shape, which is a Gaussian. In the presence of migration, the shape of the 0–0 band at 77 K is non-Gaussian; upon heating to 110 K, it becomes Gaussian, and the band maximum is shifted toward the short-wavelength range by 35 cm^?1. It is shown that the reason for this is thermal activation of excitation transfer, in the course of excitation migration, to high-lying triplet levels within the range of their inhomogeneous broadening.