Singlet-triplet excitation ratios in NeIII, ArIII and NII under ion impact

Peculiar properties of ion-atom collision systems, in particular deviations from statistical populations of singlet and triplet levels, can be studied by optical spectroscopy. We have extended earlier studies hy VUV spectrosc opy of a number of collision systems at various collision energies in the 0 .01-MeV/nucleon to 1-MeV/nucleon range, involving H-2(+), H+, He+, He2+, Ne +, Ar+, and N-2(+) as projectiles and Ne, Ar, and and N-2 as target gases. Statistically significant deviations of the relative intensities of singlet and tripler lines from simple ratios are observed in the displaced terms o f the? valence shell of NeIII, corroborating and extending earlier work. Fo r ArIII, the energy dependences of singlet-to-triplet excitation ratios are very different for different projectiles. For NII, in contrast, all observ ed line ratios are practically independent of the projectile energy.