Universal feature of weighted density of states of vibrational modes in dye-doped polymers

Abstract

Laser-induced fluorescence spectra have been measured, including narrow resonance fluorescence lines appearing at the same energy as the exciting light, for several dye molecules doped in various polymers at low temperatures. The fluorescence spectra of dye molecules in a single site have been determined by a numerical method using the experimentally obtained site-energy distribution functions. The weighted density of states of low-frequency vibrational modes has been also determined from the single-site fluorescence spectrum obtained for each combination of a guest molecule and a host polymer. Thus determined weighted density of states has been found to depend on host polymers but not on guest molecules. By employing the scales normalized by the peak frequency and intensity, it has been found that there exists a universality in the spectra of the weighted density of states for all the samples examined.