9510182 Page Theoretical research will be conducted on the nonlinear dynamics of solids and molecules. Three projects will be undertaken: (1) a new class of localized vibrational excitations which occur in nonlinear periodic lattices, Ointrinsic localized modes,O will be studied. These modes are generated by optical pumping in the infrared. The properties of these new modes and their occurrence in real three-dimensional crystals will be studied. Multistable vibrational energy transmission across interfaces between optically pumped organic crystals having a resonant anharmonic interlayer coupling will also be studied. (2) a related study of the anomalous infrared properties of the defect system potassium iodide with singly charged silver will be done. (3) finally, infrared and Raman spectroscopy of large amplitude anharmonic dynamics in biomolecules and fullerenes will be studied using first-principles quantum molecular dynamics. %%% This theoretical research program investigates the nonlinear properties of solids and molecules. These nonlinear vibrations are often optically active and hence the research will reveal new insights into the optical properties of molecules and solids. ***
