Photodouble ionization of atoms and molecules near threshold

New experimental techniques have been applied to the study of single-photon double ionization of atoms and molecules. A coincidence technique is described in which the spectra of nearly zero energy photoelectrons are recorded in two identical photoelectron energy analysers. The results are discussed in terms of the available theoretical calculations. New techniques for the measurement of double differential cross sections (DDCS) and triple differential cross sections (TDCS) are discussed. New results using these techniques are presented, in which DDCS and TDCS are measured as continuous functions of photon energy.