Optical dephasing in solution: a line shape and resonance light scattering study of azulene in isopentane and cyclohexane

Results of a line shape and resonance light scattering study of the S1←S0 and S2←S0 electronic transitions of azulene in isopentane and cyclohexane are reported. The results are analyzed using two different non-Markovian master equations that make different assumptions about the statistical properties of the bath. For both these origin transitions we find that the solution dynamics fall in the so-called intermediate modulation regime. If exponential decay is assumed for the bath correlation function we obtain a correlation time of the bath of 25 fs for the S1←S0 transition and of 13 fs for the S2←S0 transition at room temperature. From the frequency dependence of the ratio of fluorescence to Raman yields of the S1←S0 transition we calculate an excited state lifetime of 1.4 ± 0.2 ps using the parameters of the bath derived from the line shape analysis, and irrespective of which master equation is used.