Multiple capture in N⁷⁺+Ar investigated by electron spectroscopy (70 keV,θlab=10')

By non-coincident electron spectroscopy, it is shown in N 7+ +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 2 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 3ln'l' lines is discussed through possible decay modes of multiply excited states. All the experimental findings are compared with the predictions of Niehaus' (1986) classical overbarrier model as well as with a recent coincident energy gain spectrum of Roncin et al. (1987).