Studies of Fluorescence and Coherent Radiation Generated by Atoms and Molecules in Strong Laser Fields

New technology, developed in the past few years, has lead to the creation of an entirely new class of laser systems able to deliver peak powers up to one terawatt (10^{12} W) combined with a beam quality allowing focused intensities in excess of 10^{19} W/cm^2 . The generation of very high intensities allows for the investigation of the basic interactions of atoms and molecules with very strong fields. The simplest and, indeed, earliest experiments on atoms in strong fields consists of measuring what field strength is needed to ionize an atom to a particular charge state. Another type of experiment consists of measuring the kinetic energy spectrum of the electrons produced by the multiphoton ionization process. This thesis follows a third approach to studying the strong field interaction: measurement of the vacuum ultraviolet (VUV) radiation produced by atoms and molecules in strong fields. VUV radiation, in these experiments, comes from at least three main sources: (1) the plasma created by the multiphoton ionization process; (2) parametric processes, such as harmonic generation and wave mixing; and (3) fluorescence produced by the direct excitation of atoms and molecules. Except for parametric processes, very little work has been done on these sources. The object of the thesis is to (1) present new experimental data produced by each of the three sources listed above; (2) discuss the central role of the strong field for each; and (3) describe the significance or applications of each of the sources. As a result, the thesis covers a fairly wide range of phenomena and, thus, is intended to explore a new area of research, rather than concentrate on one narrow aspect of the field.