Spectroscopy of Selected Molecules Using Excimer Lasers.

This thesis presents the results of approximately two years of work involving spectroscopy with the use of excimer lasers. In Chapter I, a brief introduction is given which provides some needed information concerning multiphoton spectroscopy. Also, a brief review of molecular photophysics is given with an emphasis made on small molecules, especially diatomics. In the following chapter, Chapter II, several theoretical aspects of multiphoton processes are discussed and some key derivations are outlined. Chapter III contains a discussion and comparison of the more commonly used excitation sources in the ultraviolet and the vacuum ultraviolet. The various experimental apparatus is described along with supporting equipment and electronics in Chapter IV. Also, the techniques used for obtaining optically clear liquids in the ultraviolet and the vacuum ultraviolet are outlined. The actual experiments themselves are discussed in Chapter's V through VIII. Chapter V is concerned with the excitation of rare gas liquids using excimer lasers. The positive identification of the KrXe continuum at 162.5 nm is made. Also, an interesting molecular energy transfer mechanism is discussed. Chapter VI is concerned with photodissociation of Nitrosyl Chloride at 193 nm. Quenching rates of the resultant NO by various rare gases are given. An interesting quenching mechanism, involving curve crossings, of NO by Cl atoms is also discussed. The photodissociation of Sulfur Dioxide at 248 nm is presented in Chapter VII. An interesting branching of the photodissociation products into SO + O and S + O(,2) is discussed. The effects of rare gases are also included. Chapter VIII is concerned with the photodissociation of Phosgene at 193 nm. An interesting intramolecular recombination process leading to the creation of neutral fragments from energy levels above the ionization limit is noted and described. The effects of the addition of rare gases described in this chapter is also notable. A general summary is presented in Chapter IX. Appendices A and B describe the results of some additional experiments using Rare Gas Halide lasers on the following molecules; C(,2)F(,6), CO(,2), N(,2)O, OCCl(,2), SF(,6), C(,2)N(,2) and ClCN.