Single-Electron Capture into Ar⁺ Excited States in Ar²⁺ +Na Collision below 12 keV I. Absolute Measurement of Emission Cross-Sections

Emission spectra between 2800 and 6000 Å have been observed at the ionic energies from 0.2 to 12 keV. Absolute measurements of emission cross-sections have been made for the emission lines coming from ArII excited states at 4 and 8 keV with a crossed-beam technique. Processes of single-electron capture into the ArII 4 p - and 4'-states, with exothermicity of a few eV, take place dominantly (∼10 -15 cm 2 ), while the endothermic processes producing ArII in the 4 d - and 5 s -states occur with small cross-sections. Sum of the cross-sections for electron capture into the excited states observed is comparable with the total single-electron capture cross-section estimated from attenuation measurements of ion currents. Possible errors and uncertainties are discussed.