Multidimensional femtosecond correlation spectroscopies of electronic and vibrational excitations

Femtosecond visible and infrared analogues of multiple-pulse nuclear magnet ic resonance techniques provide novel snapshot probes into the structure an d electronic and vibrational dynamics of complex molecular assemblies such as photosynthetic antennae, proteins, and hydrogen-bonded liquids. A classi cal-oscillator description of these spectroscopies in terms of interacting quasiparticles (rather than transitions among global eigenstates) is develo ped and sets the stage for designing new pulse sequences and inverting the multidimensional signals to yield molecular structures. Considerable comput ational advantages and a clear physical insight into the origin of the resp onse and the relevant coherence sizes are provided by a real-space analysis of the underlying coherence-transfer pathways in Liouville space.