Autoionising state production in N+, O+, Ne+ and Ar+ scattering on clean and K covered Al(1 1 1) surfaces

We present a study of the autoionising state production in N, O, Ne and Ar ion collisions with a clean and potassium covered Al(1 1 1) surface in an energy range from 5 to 50 keV. In case of clean Al, we only observe production of 2p4nln′l′, 2s2p5nl, 2s2p6nl autoionising states for Ne+ projectiles; for N+, O+ and Ar+ scattering no sign of production of doubly excited states was found, although ion backscattering is known to occur. In case of K covered surfaces we in all cases observe production of sputtered excited K atoms in 3p54s2 autoionising states. For Ar+ the quasi-symmetric collision with K produces excitation of Ar in 3p44s2 states. For N+ scattering the electron spectra reveal a small structure which we attribute to the formation of metastable N− (1D). K adsorption does not lead to the appearance of any new Ne∗∗ related structures.