Spectroscopy and dynamics of highly excited molecules

Abstract

This dissertation considers the high-lying electronic structure and fragmentation dynamics of the triatomics NO\sb2, N\sb2O, H\sb2O and the radical OH. The experimental techniques used to determine the high-lying electronic structure of N\sb2O include mass-selected resonantly-enhanced multi-photon ionization (REMPI) using coherent ultraviolet light. Dissociation dynamics are probed indirectly in N\sb2O through peak width analysis and directly in NO\sb2 by an additional laser which scanned the NO product. Photoionization dynamics and, in particular, the partitioning of angular momentum between the ionic core and the ejected electron, are studied with the aid of two powerful and practical techniques: (1) production of coherent vacuum ultraviolet radiation by frequency tripling the doubled output of a YAG-pumped dye laser in a free-jet expansion and (2) threshold photoionization by detecting electrons released via the application of a pulsed field. The major results include (1) newly assigned Rydberg states in N\sb2O where a valence picture was expected by some theoreticians to be appropiate, (2) the conclusion that rotational distributions of product NO from photodissociating NO\sb2 is independent of Rydberg structure in the dissociation continuum, (3) ionization potentials of significantly greater accuracy for N\sb2O, H\sb2O, and OH, and, finally, (4) significant evidence to support a theory of Rydberg state interactions which asymmetrically affect the photoionization rotational branch intensities