Scattering in electron spectrometers, diagnosis and avoidance. II. Cylindrical mirror analysers

An analysis is made of the effects leading to an unwanted scattered background of electrons in cylindrical mirror analysers (CMAs). This work complements that given in Part I on concentric hemispherical analysers. It is shown that scattering from the middle region of the inner surface of the mirror electrode is significant but that the amount of scattering reaching the detector may be reduced by reducing the area of the output slit or by adding a deflection post filter to the optics as occurs in some commercial instruments. Internal scattering causes a higher background so that peak‐to‐background ratios are attenuated and transmission function calibrations involve a systematic error. Evidence for this error is a step in the calibration curves for I(E)/En(E) established earlier. The steps appearing in the curves for Cu and Ag reference samples give a direct measure of the scattering intensity. Calibration plots are established for this purpose. Results from previous interlaboratory comparisons are analysed showing that in commercial CMAs with large‐area energy selection slits the scattering may reach 35% of the copper true background at 950 eV, complicating the subsequent use of the data. Concentric hemispherical analysers and some commercial CMAs show very low scattering. In some CMAs the analogue detection systems cause a similar enhanced background in addition to scattering, boosting the above figure of 35% to 100%.