Exciton Dynamics in β-9,10-Dichloroanthracene

Abstract

Flaky crystals of β-dichloroanthracene are grown by sublimation method. Polarized absorption and luminescence spectra have been examined over the temperature range from 300 K to 6 K. The lowest singlet exciton absorption band is confirmed to be located at 23370±20 cm -1 at 6.5 K. The exciton-phonon coupling strength is estimated to be 1.66. Vibronic luminescence bands have been observed at temperatures below 37 K and above 180 K and are assigned as due to radiative annihilation of free excitons. Adiabatic potential energy curves are proposed to explain those luminescence spectra and the parameters are obtained as follows: The self-trap depth=-1400±200 cm -1 . The half-width of the free exciton band=2100±300 cm -1 . The self-trapping barrier height=75±5 cm -1 . Possibility of the presence of two kinds of self-trapped exciton states is briefly discussed.