Photoabsorption, Photoionization, and Photoelectron Spectroscopy explores photoabsorption processes involving individual, isolated molecules in the wavelength or photon energy range from the ionization thresholds of molecules (usually in the vacuum ultraviolet region) through the soft and hard X-ray region and beyond the "K edge." The interaction between electromagnetic radiation and isolated molecules based on photoabsorption, photoionization, and photoelectron spectroscopy studies is described, along with the techniques for measurement of total and partial cross sections. This book is comprised of eight chapters and examines the decomposition of molecules and molecular ions as well as mildly excited (valence shell excitation) and highly excited (inner shell excitation) molecules. After providing a general theoretical background, it discusses certain classes of atoms and molecules and considers electromagnetic interactions with gases. The following chapters focus on photoabsorption below the first ionization limit; quasi-discrete states above the first ionization potential; and the ionization continuum. Total photoabsorption and photoionization cross sections for selected molecules are also considered, and the angular distribution of photoelectrons is analyzed. The various measurement techniques are described in the last chapter. This monograph will be of interest to radiation chemists, radiation physicists, photochemists, mass spectrometrists, and perhaps radiation biologists.