Ultrafast optical dynamics of HITCI in ethylene glycol. A non-Markovian Brownian oscillator description

Femtosecond photon echo, chirped four-wave mixing and pump-probe experiments are reported, using a 13 fs cavity-dumped Ti: sapphire laser for excitation. It is shown that the optical dynamics of HITCI in ethylene glycol occurs on distinctly different time scales. The ultrafast solvent response is modelled by a non-Markovian solvent oscillator, while the slow diffusional solvent motions are represented by an overdamped Markovian oscillator. With this model an oscillator-bath time correlation function is obtained that exhibits a bimodal behaviour: an initial fast Gaussian decay is followed by a slower, long exponential tail.