Wavelength-resolved stimulated photon echoes: Direct observation of ultrafast intramolecular vibrational contributions to electronic dephasing

Novel wavelength-resolved stimulated photon echo measurements on a dye mole cule in solution are presented. Data are simulated within the multimode Bro wnian oscillator model using the spectral density of de Boeij [J. Phys. Che m. 100, 11806 (1996)] for the same solute-solvent system. For photon echo p opulation times < 50 fs there are considerable differences between the meas ured and calculated data. Aided by further simulations, we conclude that th ese discrepancies result from dephasing dynamics of high frequency intramol ecular vibrational modes not included in the previously derived spectral de nsity. (C) 1999 American Institute of Physics. [S0021-9606(99)51427-X].