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We present 2D-IR spectra of a weak IR absorber, 13 C 15 N − dissolved in D 2 O, by means of heterodyne detected three-pulse photon echo experiments. Spectral dephasing of the stretch vibration of the cyanide ion is governed by two processes: A fast, inertial process which is essentially in the homogeneous limit, and which gives rise to the larger fraction of the total line-width of the transition (≈10 cm −1 ), and an additional slower spectral diffusion process with 5.3 cm −1 line-width and 2.9 ps time constant. We consider this molecule a benchmark system to optimize theoretical approaches to describe vibrational dephasing of strongly interacting solute–solvent systems.

We review recent work in the study of interfacial electronic states and electron–adsorbate interactions with time- and angle-resolved two-photon photoemission (2PPE) spectroscopy. Results for interfaces between noble-metal surfaces and organic as well as inorganic dielectric overlayers are presented. Layer structure and thickness have pronounced effects on the spatial extents, binding energies, and dynamics of image-potential states (IPS) and molecular orbitals. The transition from delocalized to localized states in the plane of the interface can also occur dynamically through electron-induced nuclear motion in the overlayer. An important example of this class of phenomenon is the formation of polaronic states from initially delocalized IPS, which occurs on sub-picosecond timescales. Dynamic energy relaxation through electron solvation by molecular dipoles, the analogue of the dynamic Stokes shift in bulk solvents, may also accompany localization on ultrafast timescales, and has become the focus of much recent experimental and theoretical interest. The interplay of a static layer structure and an evolving potential from the adsorbate creates a rich environment for interfacial electron dynamics, as evidenced by the alcohol/Ag(1 1 1), nitrile/Ag(1 1 1), and D 2 O/Cu(1 1 1) systems. We conclude with a discussion of recent attempts to determine the spatial extent of localization parallel to the interface for electrons following localization and solvation using experimental measurements of the photoelectron distribution in momentum space.

A fast, efficient numerical algorithm is used to study intermolecular zero-quantum coherences (iZQCs) and double-quantum coherences (iDQCs) in two applications where the three-dimensional structure of the magnetization is important: high-resolution NMR in inhomogeneous fields and contrast enhancement in MRI. Simulations with up to 2 million coupled volume elements (256 x 256 x 32) show that iZQCs can significantly narrow linewidths in the indirectly detected dimension of systems with inhomogeneous fields and explore the effects of shape and orientation of the inhomogeneities. In addition, this study shows that MR images from iZQC and iDQC CRAZED pulse sequences contain fundamentally new contrast, and a modified CRAZED pulse sequence (modCRAZED) can isolate the contrast from chemically inequivalent spins.