Quantum Confinement of Translational Motion of Excitons in α-Perylene and Pyrene Microcrystals

Abstract

We observed that (1) the luminescence spectra of α-perylene shifted by 440 cm^-1 as much as the change in the excitation photon energy, from 22100 cm^-1 (452.5 nm) to 22540 cm^-1 (443.7 nm), whereas the luminescence spectrum of pyrene shifted by 100 cm^-1 according as the excitation photon energy in an energy region from 26940 cm (371.2nm) to 26730cm^-1(374.1nm), (2) for pyrene microcrystals the luminescence decay under resonant excitation increased as the excitation energy increased, (3) in both materials intense fsee-exciton luminescence was observed but self-trapped exciton luminescence was not. We concluded that in both materials (1) quantum confinement of translational motion of excitons occurs, and (2) excitons in microcrystals are not self-trapped.