Near-threshold study of the neon photoelectron satellites

Near-threshold photoionization of neon has been studied in the region of the 2s satellite states. Photoelectron spectra for various constant values of photoelectron energy, from zero to 0.4 eV, have been measured under high resolution revealing a rich structure due to satellite states, many of which are observed for the first time. Differential ionization cross sections for some of the satellite states, near their respective thresholds, have been obtained as continuous functions of photon energy, revealing the influence of resonant processes perturbing the direct ionization cross sections. The angular measurements of the satellite states have enabled their beta variations to be deduced over the same energy ranges. Cusp-like features at the double ionization potentials have also been observed in the threshold photoelectron spectra and these are discussed within the framework of Wannier theory.