| Abstract |
This thesis discusses results of photoabsorption experiments for four halogenated molecules and a chemical reaction. The technique used is Ion & Photoelectron Velocity Mapping, which measures simultaneously the energy and angular distribution of selected photofragments or photoelectrons. The text is divided into seven chapters. Chapter 1 is an introduction to photodissociation and Ion Imaging principles. The experimental setup is described in Chapter 2. The following chapters contain experimental results and their discussion. Specifically the photolysis of Cl2 following single photon absorption between 310 and 470 nm is discussed in Chapter 3. From the energy and angular distributions we extracted the contributions of excited states in Cl2 absorption spectrum, we observed non adiabatic crossing between them and found Cl(2P3/2) fragments to be aligned. In Chapter 4 we describe the rich dynamics of multiphoton excitation of Br2 in the region 430-475 nm. Through energy and angular distributions of ions and photoelectrons we observed excitation of Br2 to a Rydberg state, Br2 + ion formation, its excitation to higher excited levels and predissociation to excited Br atoms. We also confirmed previous conclusions about the branching ratio of Br spin orbit states produced by single photon dissociation of Br2. The single-photon photolysis of CH3Br in the 215-250 nm region is discussed in chapter 5 and the contribution of its excited states to the absorption spectrum as well as the kind and extent of CH3 internal excitation are extracted from fragment angular and energy distributions. In Chapter 6 the results of CH3I excitation to the A band continuum by 15 ns, 5 ps, 500fs (5 eV energy) laser pulses are presented. From I+, CH3 + and photoelectron images we observed the competition between single-photon photolysis and multiphoton ionization of CH3I. Finally in Chapter 7 we present the results of applying Image Mapping to the measurement of differential reaction cross sections in the case of Cl +C2H6 reaction for 0.36 eV collision energy.
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Μελέτες δυναμικής για φωτοδιάσπαση και αντιδράσεις αλογονούχων μορίων
