ELECTRON-IMPACT EXCITATION AND IONIZATION OF LASER-EXCITED SODIUM ATOMS NA-ASTERISK(7D)

We have investigated the ejected-electron spectrum following impact ex citation and ionization of laser-excited Na (nl) atoms by 1.5 keV ele ctrons. By means of two-laser excitation 3s --> 3p(3/2) --> 7d and sub sequent cascading transitions about 8% (4%) of the target atoms were i n excited states with n > 3 (7d). The experimental ejected-electron sp ectrum due to the decay of Auger and autoionization states of laser-ex cited atoms Na(nl) with n = 4-7 has been fully interpreted by compreh ensive calculations of the energies, cross sections and decay probabil ities of the corresponding states. The various processes contributing to the ejected-electron spectrum are with decreasing magnitude: 2s ion ization leading to 2s2p(6)nl Auger states, 2p --> 3s excitation leadin g to 2p(5)3s(P-1)nl autoionization states and 2s --> 3l' excitation le ading to 2s2p(6)3l'(L-1)nl autoionization states.