Multitime coherent spectroscopies of complex molecules: from infrared to X-ray
Femtosecond visible and infrared analogues of multiple-pulse NMR techniques provide novel snapshot probes into the structure and electronic and vibrational dynamics of complex molecular assemblies such as photosynthetic antennae, proteins, and hydrogen-bonded liquids. The response of complex molecules to a series of femtosecond optical laser pulses provides a multidimensional view into molecular structure as well as a vibrational motions, interactions, and relaxations. In complete analogy with NMR techniques, spreading the spectroscopic information in more than one dimension helps resolve congested spectra, eliminates certain static broadening mechanisms and provides structural and dynamical information unavailable from one-dimensional measurements. The basic concepts underlying these generalized techniques will be surveyed.