An investigation of dynamics and intermolecular interactions in molecular solid state systems. Picosecond and subpicosecond nonlinear experiments combined with ultrahigh resolution spectroscopy, conventional optical spectroscopy and theory are used to study isolated molecules in crystals and glasses, weakly interacting molecules in impurity band systems, and strongly interacting molecules in pure crystal exciton systems. In glasses by combining photon echo and other optical coherence experiments with optical holeburning experiments, acoustic measurements and heat capacities, a new and detailed picture of dynamics and intermolecular interactions in these nonequilibrium systems is emerging. In the impurity band problem, photon echo experiments are shown to be a direct observable for the concentration dependent delocalization of electronic excitations in mixed crystal systems. The application of phase related pulse sequences, particularly the optical dipolar echo, to the impurity band problem is described using a new approach for generating picosecond pulses with well defined phase relationships. The applications of picosecond transient grating techniques to the investigation of exciton transport and polariton effects in pure molecular crystals are discussed. A combination of photon echo experiments and polarization grating techniques are used to examine the relationship between the mechanical motions of molecules and coupling to electronic states as observed by optical dephasing.
