Vibrational and rotational dynamics of the electronic states of nitrogen dioxide near and above the adiabatic ionization threshold

Studies of the higher Rydberg states of NO$\sb2$ have been restricted due to the poor Franck-Condon overlap between the ground state of the bent neutral molecule and the linear ion. A knowledge of these states is required so as to better understand the dynamics of the intermolecular relaxation in the system. The research in this thesis has overcome the Franck-Condon barrier through the use of multiresonant stepwise excitation of the molecule. Using this technique, we are able to examine the autoionizing Rydberg series built upon different rovibrational states of the core molecule. We find a definite correlation between the vibrational mode of the core and the efficiency of the autoionization. When this stepwise excitation scheme is combined with Zero Kinetic Energy Photoelectron Spectroscopy (ZEKE-PES), we are able to examine directly the various ionization thresholds of the molecule experimentally for the first time. In addition to the positions of the ZEKE resonances, the intensities of these resonances can provide information on the competition between different decay channels in the molecule. We find that the mechanism which governs autoionization efficiency also affects the direction of relaxation preferred by these near threshold states. A mechanism for coupling between rotational thresholds is also presented, as well as relative rovibrational ionization thresholds and spectroscopic constants of the ion