The ${\mathrm{Ar}}^{9+}-\mathrm{He}$ charge-exchange collision system is studied at low kinetic energy $(E=2.25\mathrm{}\mathrm{k}\mathrm{e}\mathrm{V}/\mathrm{a}\mathrm{m}\mathrm{u}),$ using two complementary instrumental techniques: x-ray and vacuum ultraviolet photon spectroscopy and Auger-electron spectroscopy. It is shown that single capture populates mostly $n=4\mathrm{}$ and 5 in Ne-like argon ${1s}^2{2s}^2{2p}^5\mathrm{nl}.\mathrm{}$ The analysis and identification of the lines show the cascade population of ${1s}^2{2s2p}^{6}3l$ states. These are not expected to be seen since in the entrance channel the projectile has the core ${1s}^2{2s}^2{2p}^5{}^2{P}_J^o.$ They are identified by photon emission. Double capture populates mostly Na-like core excited states corresponding to the configurations ${1s}^2{2s}^2{2p}^5{3l5l}^{\prime }.$ They are identified and it is seen that the continuum ${2p}^6{}^1{S}_0$ to which they Auger decay is the only one available in this case.

• Received 2 May 2002

DOI:https://doi.org/10.1103/PhysRevA.66.052707