Studies of neonL-shell excitation by impact of highly ionized heavy ions

Abstract

Passage of foil-excited 1.4 MeV/A S and 1.1 MeV/A Cl ions of neon charge state ∼ 12⁺ through neon gas targets at pressure ∼100 mTorr has been found to be accompanied by copious production of Ne II–VIII excited states. Comparable excitation cross-sections ∼10⁻¹⁸ cm² are found for a large number of levels belonging to all of these charge states and corresponding to principal quantum numbersn=2, 3, 4. Vacancy distributions very similar to those found in beam-foil excitation of ∼1MeV neon beams are found. Because the Ne recoil velocities are small compared to the fast beam velocities characteristic of the beam-foil source, it is possible to reduce both Doppler shifts and spreads by 3–4 order of magnitude for equivalent collimation. It has also been found that there is an excitation cross-section change of a factor ∼5 for a corresponding projectile charge state change from 6⁺ to 12⁺, that efforts to classifyK x-ray satellite spectra byLshell vacancy labels (KL ⁰,KL ¹,...) are probably inaccurate due to extensive population ofn≧3 spectator levels, that both the recoil ion and beam-foil spectra exhibit few lines withn≧4, and that for the allowed transitions studied here, collisional excited states quenching effects due to the ∼100mTorr target gas pressures used are negligible.