Auger electron-threshold photoelectron coincidence spectrometer for studies of atomic and molecular dications

An Auger electron-threshold photoelectron coincidence spectrometer has been developed to obtain spectroscopic information on atomic and molecular dicationic states. The spectrometer consists of two electrostatic hemispherical analyzers. Auger electrons are detected by one of the analyzers with a position sensitive detector. The other analyzer captures threshold photoelectrons over a 4π sr solid angle with a penetrating electric field. The signal-accumulation circuit is based on a fast-slow coincidence technique. In order to demonstrate both the performance and advantages of this type of Auger electron spectrometer, the Kr MNN Auger transitions are investigated. Auger electron spectra associated with each 3d subshell are obtained by coincidence detection with the corresponding threshold photoelectrons, thus providing unambiguously assignments for the initial core-hole states of the Auger lines. The total energy resolution in a coincident Auger electron spectrum reaches 80 meV (FWHM), a value which corresponds to a sub-natural linewidth as the natural width of the Kr 3d core-hole states is 101 meV.