Title :

EUV Laser Photoelectron Spectroscopy of Mass Selected Neutral Clusters and Molecules

Abstract :

Over the past 15 years our research interests have focused on four main and related areas: 1. properties, chemistry, catalytic, and photo-catalytic behavior of neutral, inorganic, isolated clusters, MmM’nXpHq (M,M’ = metals, X = O, S, C); 2. initial release of stored chemical energy from isolated energetic molecules (e.g., RDX, HMX, CL -20, high N- content species, …); 3. small molecule, neutral clusters (e.g., (NH3)n, (H2O)n, (NH3BH3)n, (SO2)n, …) and their ion chemistry; and 4. structure, energetics, ion fragmentation reactions of “simple” bio-related molecules (e.g., amino acids, saccharides, neurotransmitters, and DNA bases). These studies have evolved from characterization of energy levels and intermolecular interactions, to ultrafast kinetics and dynamics of molecular cluster reactions, to the study of inhomogeneous catalytic and photo-catalytic cluster reactions. Clusters and molecules are identified through mass spectrometry, UV/Vis electronic spectroscopy, and most recently photo-electron spectroscopy (PES) employing visible, UV, VUV, extreme ultraviolet (EUV, soft x-ray) lasers. Decomposition reactions for the initial release of molecular stored chemical energy have been time resolved at less than 100 fs. In order to acquire, analyze, and interpret the experimental data obtained on these systems, we have had to develop an essential theoretical/calculational component for our program. This seminar reviews our initial synthesis and reaction studies through mass spectrometry of neutral catalytic and photo-catalytic inorganic clusters, small molecule cluster ion reactions, and generation of new cluster species. These results serve as motivation for constructing a new PES apparatus employing visible, UV, VUV, and EUV photons for photo-detachment of anionic and neutral species in order to acquire spectroscopic data on the systems of interest. We will discuss these new results for FexSyHz clusters, energetic materials, and bio-related saccharides and DNA bases. The importance of the new spectroscopic (PES) data for these systems is that they enable the evaluation of theoretical techniques in order that proper algorithms and approaches may be employed to generate results that are not presently experimentally accessible, such as cluster and molecular structure, reaction mechanisms, and general electronic state specific potential energy surfaces.