Atomic and molecular physics using synchrotron radiation - the early years.

The field of atomic and molecular photoionization has undoubtedly been transformed by the use of synchrotron radiation. In the mid-1960's the 180 MeV electron synchrotron at the National Bureau of Standards, Washington, DC, was used to discover many resonances in the photoionization continua of atoms and simple molecules. The resonances were characterized in terms of the excited states involved, their energies and lifetimes. This article concentrates on that period. As dedicated high-flux storage rings became available, the emphasis turned to the study of the products of the photoionization process in order to further understand the electron correlation effects that had been uncovered earlier; examples of these more sophisticated experiments are given.