TEMPERATURE AND PRESSURE-DEPENDENT OPTICAL DEPHASING OF PENTACENE IN TRICLINIC AND MONOCLINIC P-TERPHENYL

Temperature-dependent (4.3-10 K) photon echo measurements are presente d for pentacene doped p-terphenyl at variable high pressure (0-18 kbar ). The homogeneous electronic linewidth of pentacene in monoclinic p-t erphenyl is observed to narrow at high pressure due to an increase in the pseudolocal phonon frequency. In contrast, pressure induced change s in the Linewidth of pentacene in triclinic p-terphenyl appear to occ ur largely due to changes in the pseudolocal phonon lifetime. In addit ion, softening of the pseudolocal phonon frequency is observed near th e polymorphic phase transition pressure of 5.5 kbar and photosite spec ific dynamics are observed at high pressure.