A threshold electron analyser for use in coincidence experiments

A new design of threshold electron analyser is presented which takes advantage of chromatic aberrations in electron lenses. Calculations show it to be capable of both high resolution ( approximately 3.5 meV half-width) and high collection efficiency (100% for zero energy electrons) even though a high extraction field (20 V Cm -1 ) is used in order to extract ion fragments with equally high efficiency. It is therefore particularly suitable for use in electron-ion coincidence experiments. Representative results are shown for the photoionization of argon and oxygen by vacuum ultraviolet radiation from the Daresbury synchrotron radiation source. These demonstrate the potential of both the electron and ion analysers to be used for such coincidence experiments.