Electron impact excitation and ionization of laser-excited sodium atoms

Abstract

We have investigated the ejected-electron spectrum following impact excitation and ionization of laser-excited atoms by 1.5 keV electrons. By means of two-laser excitation and subsequent cascading transitions about 8% (4%) of the target atoms were in excited states with n > 3 (7d). The experimental ejected-electron spectrum due to the decay of Auger and autoionization states of laser-excited atoms with n = 4 - 7 has been fully interpreted by comprehensive calculations of the energies, cross sections and decay probabilities of the corresponding states. The various processes contributing to the ejected-electron spectrum are with decreasing magnitude: 2s ionization leading to Auger states, excitation leading to autoionization states and excitation leading to autoionization states.