Coincidence experiments Auger electron

Coincidences between 4d5/2 photoelectrons and Nj-Oj Oj 0 Auger electrons have been measured with the experimental set-up shown in Fig. 1.17. The photoelectrons were recorded with the monitor analyzer placed at a fixed position (0 = 90°, 1 = 150°), the Auger electrons were detected using both sectors of the rotatable double-sector CMA (0° = 90°, 0° variable). The relative transmission and detection efficiencies of these sectors were taken into account in order to use the signals from both sectors. For the coincidence experiment three modifications in the experimental set-up were necessary due to the points mentioned in Section 4.6.3 concerning optimization ... 

Following the general discussion in Section 4.6.2, the rates of true and accidental coincidences can be estimated. This possibility is of special interest because it allows better control of the experiment, and it can open ways to improve the experimental conditions further. Using subscript 1 for photoelectrons and subscript 2 for Auger electrons, in the present case the following parameters for such an estimation of coincidences are needed ... 

Autoionization spectra resulting from specific resonances can be obtained by electron-electron coincidence measurements (Haak et al. 1984 Ungier and Thomas 1983, 1984, 1985). To associate a fr.rgmentation pattern with a particular core hole excited state and a particular autoionization or Auger decay channel, a double-coincidence experiment must be done using electron impact excitation. The energy of the scattered electron must be determined, the energy of the emitted electron must be detennined, and the ions produced in coincidence with these two events must be determined. The difficulties inherent in these kinds of experiments have been aptly summarized by Hitchcock (1989), If you can do it by photons, don t waste your time with electron-coincidence techniques. ... 

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