The Auger spectra in argon induced by electron impact – new measurements with high resolution

The Auger spectrum of argon in the kinetic energy region (135-235 eV) has been measured using a non-monochromatic electron beam (incident energy from 313 to 2019 eV) at two ejection angles of 60 degrees and 90 degrees with a high resolution electrostatic analyzer. The electron impact energies of 313 and 323 eV have been used in order to disentangle the contribution of the ionization and decay of the 2s state. The systematic analysis of the measured spectra shows the dominance of the Coster-Kronig transitions from the 2s ionization in the energy region 135-159 eV and 208-235 eV, while the Auger transitions from the 2p ionization are dominant in the energy region 160-208 eV. The high resolution of the present work led to the observation of a certain number of new features in two energy regions 135-159 and 208-235 eV, respectively. Recent literature data on the cascade Auger processes and threshold formation of Ar2+ satellite states allow the assignment of some of them, while other have been left without assignments. The influence of the PCI effect on the line-shape, width and energy position of the features in the kinetic energy region 200-208 eV has been also investigated and the PCI shift versus excess energy above threshold compared with previous data and theoretical predictions.