Starting from the hypothesis of the modulation of energy of ions extracted by the high-frequency voltage one calculates the width and the form of the energy spectrum of these ions. The variation of the energy deviation of the ions in function of the extraction voltage is obtained by applying to the extraction system the double floating probe theory. These results are in agreement with the experimental results.

A thorough analysis of electron apedra measured at 80 keV in collisions between Ne8+(ls2) ions and helium and molecular hydrogen targets is presented. The Is'3lnl' and Is'41nl' lines are identified up to n =9. With helium, a fitting procedure for ls'31nI' lines (all the lines for n = 3 , 4 , and the first 3s51 ones), observed for the first time at different angles, make it possible to compare our experimental results with two different theoretical data sets: our own theoretical values for positions, autoionization and radiative probabilities obtained by the AUTOLSJ method, which are given in a companion paper, and those recently published by Baehau e1 01 using a Feshbach method with a madel potential. This allows us to test bath theoretical positions and lifetimes of (3, n ) states. The relative weight of the n = 3 . 4 and the first n = 5 states is often found to be angle dependent. The apparent, angle dependent, branching ratio for autoionization into the 2p and 2s continua of the ( 3 , 3 ) and the first (3,4) states is determined for several cases and discussed. Finally, dile:ca:ia! 2x6 :a!^! crass sectian: are given nnd co-pnrcd vi:h athcr ~.;zi!ab!c erpcri; mental results.

Positions, autoionization and radiative probabilities of Ne6*(ls23131'), Ne"(ls'3141')and some Neei(lsz4141') states have been calculated with the AUTOLSJ method and compared with other recent theoretical data. Thhese results will he comparzd with our experimental electron spectra in a companion paper.The theoretical basis of the electron spectra analysis discussed in lhe companion paper is also established. Various kinds of perturbations of the electron lineshapes and angular distributions (autoionization from a Stark state, post-collision effects and interferences) are oresented in a unified fashion and discussed.

By non-coincident electron spectroscopy, it is shown in N7++Ar that the electron spectrum allows an identification of double, triple and quadruple electron capture into autoionising multiply excited states of nitrogen. The contribution of double capture processes is discussed in great detail and a comparison with double capture electron spectra previously obtained in N 7 + + He, H, is made.The triply and quadruply excited nitrogen ions decay through autoionising cascades into doubly excited states. The origin of the observed doubly excited lines as well as of some satellite 31n'l' lines is discussed through possible decay modes of multiply excited states. All the experimental findings are compared with the predictions of Niehaus' classical overbarrier model as well as with a recent coincident energy gain spectrum of Roncin et al.

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