Phase-locked heterodyne-detected stimulated photon echo. A unique tool to study solute—solvent interactions

Heterodyne-detected phase-locked femtosecond stimulated photon echo (HSPE) and pump—probe (PLPP) experiments were accomplished on a dye dissolved in ethylene glycol. It is shown that all four Liouville pathways are needed in a proper description of the observed phenomena. By measurement of the real and imaginary part of the PLPP signal the short-time (⩽ 60 fs) solvation dynamics can be probed, but none was found in ethylene glycol. Time-resolved and conventional stimulated photon echo experiments were also performed. The fastest solvation step in ethylene glycol seems to occur on a time scale of 300 fs.