Electron impact ionization and excitation of laser-excited atoms: investigation by means of electron spectrometry

We have measured the electron spectra following the excitation and ionizati on of laser-excited atoms by impact of 1.5 keV electrons: 2p excitation and 2s ionization of Na(3p(3/2)), Is excitation of Li(2p(3/2)) and 5p ionizati on of Ba(6s5d D-1.3). Except for Ba the intensities of ejected electrons ar e directly proportional to the cross sections of Anger and autoionizing sta tes. Theoretical excitation cross sections (Na 2p, Li 1s) are obtained in f irst Born approximation including the full relaxation of the atomic electro ns. Relative ionization cross sections (Na 2s, Ba 5p) are evaluated in sudd en approximation as a two-step process: pure 2s(5p) ionization plus relaxat ion of the rest of the atomic electrons. The experimental spectra are compa red to theoretical spectra. (C) 1999 Elsevier Science B.V. All rights reser ved.