Ultrafast optical dephasing in a low-temperature organic glass

The optical dephasing of pentacene in an o-terphenyl glass at 1.5 K is examined with picosecond photon echo and fluorescence line narrowing experiments. The homogeneous T2 is found to be 1–3 ps, in contrast to all previous measurements on glass—chromophore systems in which the homogeneous T2are two to three orders of magnitude longer.