Coster-Kronig electrons from the autoionizing Rydberg states of 2 MeV u-1Si5+ions excited through a thin C-foil target

Several peaks have been observed, in the electron energy range up to 20 eV, due to Coster-Kronig electrons from the autoionizing Rydberg states emitted from 2 MeV u-1 Si5+ ions excited through a carbon foil. To obtain a better understanding of these low-energy electron spectra and their production mechanisms, we synthesize the expected electron spectrum which is compared with the observed electron spectrum. Two theoretical methods, namely the perturbation theory of Z-expansion (MZ code) and the multiconfiguration Hartree-Fock method (Cowan code), are used to calculate the necessary Auger electron energies and emission rates. It has been found that the 1s22pnl-1s22s 2S and 1s22s2pnl-1s22s2 1S decays give the most significant contributions to the observed electron spectrum from threshold up to the 20 eV region. The synthetic electron spectra have also been found to reproduce the observed electron spectra quite nicely when the charge distributions of the projectile Si ions after thin carbon foils are taken into account.