Properties and operation of a 90° spherical deflector as photoelectron energy analyzer in connection with spin-polarization measurements by Mott scattering

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Abstract
We discuss the electron-optical properties of the 90 degrees spherical analyzer. A nearly parallel electron beam which can be extracted from a magnetic photocathode in an external magnetic field under suitable conditions is focused to the exit plane of the analyzer. Electron spin polarization detection using Mott scattering can be advantageously combined with such a 90 degrees electron spectrometer so as to achieve energy analysis in spin-polarized photoemission. In this case the diaphragms of the Mott scattering detector play the role of virtual exit slits of the electron spectrometer. Thereby, the limits for variations of the apparatus asymmetry of the Mott scattering setup become reduced, eliminating the need of measuring this quantity in separate measurements.