In this project in the Experimental Physical Chemistry Program of the Chemistry Division, Knee will apply picosecond pump-probe photoelectron spectroscopy to the measurement of vibrational energy redistribution in polyatomic systems, including vibrational predissociation in van der Waals molecules. The main technique to be used, zero energy photoelectron spectroscopy, is an ideal method for doing many different kinds of studies. Also included in this work are experiments on ion vibrational spectroscopy. %%% Studies of the dynamics which occurs during the course of simple chemical reactions are important in order to be able to understand the fundamental processes of chemical change and energy redistribution which are involved. In particular, experiments on vibrational excitation of weakly bound species, such as van der Waals molecules, allow studies to be made at low energies, where vibrational modes are uncoupled and well understood.