Electronic dephasing studies of molecules in solution at room temperature by femtosecond degenerate four wave mixing

The electronic dephasing of two oxazine dyes dissolved in ethylene glycol at room temperature is investigated by femtosecond degenerate four wave mixing (DFWM) experiments. Both two-pulse and three-pulse DFWM with simultaneous detection of the signals at two distinct phase-matching directions permits detailed investigation of dephasing dynamics in a room temperature liquid. At least two stochastic processes are responsible for the observed electronic dephasing: one is treated empirically as an exponential decay; the second is regarded in the full analytic form of the Kubo relaxation function. Both fast and slow (inhomogeneous) dynamics are recovered. The slow dynamics is found to bring about spectral diffusion over the inhomogeneous distribution on the time scale around a picosecond.