PHOTODOUBLE IONIZATION OF ATOMS AND MOLECULES NEAR-THRESHOLD

New experimental techniques have been applied to the study of single-p hoton double ionization of atoms and molecules. A coincidence techniqu e is described in which the spectra of nearly zero energy photoelectro ns are recorded in two identical photoelectron energy analysers. The r esults are discussed in terms of the available theoretical calculation s. New techniques for the measurement of double differential cross sec tions (DDCS) and triple differential cross sections (TDCS) are discuss ed. New results using these techniques are presented, in which DDCS an d TDCS are measured as continuous functions of photon energy.