Ultrafast UV photon echo peak shift and fluorescence up conversion studies of non-polar solvation dynamics

The authors present photon echo peak shift and femtosecond fluorescence up-conversion studies of nonpolar solvation dynamics of a simple nonpolar dye p-terphenyl in EtOH and cyclohexane, using excitation in the UV range at 290 nm. The UV fluorescence up-conversion expts. were combined with a polychromatic detection and the results highlight the high sensitivity of this approach to fully characterize the excited state dynamics of the dye. The authors also demonstrate the feasibility of UV photon echo and transient grating and its sensitivity for the detection of nonpolar solvation dynamics by measuring the frequency correlation function of the dye in the ground state. While solvation dynamics in the picosecond regime is obsd. in EtOH, electronic coherence dephasing occurs on timescales faster than 100 fs in EtOH as well as in the nonpolar solvent cyclohexane.