Picosecond (Coherent) Transients in Molecular Mixed Crystals

Abstract

Results of picosecond photon echo and pump-probe experiments on pentacene in naphthalene and p-terphenyl are reported. The photon echoes are detected by optical mixing of the echo with a synchronized probe pulse in an ADP crystal. From the temperature dependence of the photon echo it is concluded that the pure electronic transition of pentacene in both naphthalene and p-terphenyl is relaxed by phonon scattering off a resonant phonon. Time-resolved absorption measurements on some selected excited state vibrations of pentacene in naphthalene show that drastic differences exist in vibrational relaxation times.