Spectrally resolved fs-CARS as a probe of the vibrational dynamics of a large polyatomic molecule: magnesium octaethylporphyrin

We report on the investigation of the electronic ground state vibrational d ynamics of a large, biologically relevant molecule (magnesium octaethylporp hyrin) using femtosecond time-resolved coherent anti-Stokes Raman scatterin g (CARS). By detecting the spectrum of the coherent anti-Stokes signal as a function of the delay time in a pump- and probe-type experiment, a detaile d mapping of the dynamics of the vibrational coherence in the spectral regi on of the modes of the porphyrin macro-cycle is achieved. The method is cap able to simultaneously give insight on the dephasing timescales and to prov ide spectral information on the vibrational mode structure. (C) 2001 Elsevi er Science B.V. All rights reserved.