Spectra of argon recoil ions in the 9-85 nm wavelength range have been measured by impact of a heavy-ion beam on a neutral target. These spectra were analyzed by comparison with experimentally observed transitions, interpolations or extrapolations in isoelectronic sequences, theoretically calculated energy levels and quantum defect calculations. This led to identification of 417 lines and to determination of 75 new transitions, especially in argon VI and VII.

The effect of the velocity of the incident ions in the n -distributions for n = 8 and 9 of the electron capture in collisions of highly charged Ar 8+ ions with a lithium target is studied in the 0.1-1 keV amu −1 energy range. The experimental n -distributions are deduced from the measured emission cross sections of all lines corresponding to 7 -8 and 8 -9 transitions. The results of theoretical calculations using the three-body classical trajectory Monte Carlo (CTMC) method are presented for the Ar 8+ -Li(2s) system and also for the O 8+ -Li(2s) system in order to show the influence of the Ar 8+ core electrons on the final n -distributions. The experimental and theoretical results are found to be in fair agreement except for the 9s and 9p cross sections. The presence of the projectile core electrons strongly affects the population and the collision energy dependence of low-values produced in the electron capture reaction. In particular, the σ (n ) partial cross sections (n = 8, 9 and = 0, 1, 2) increase with decreasing energies and go through a maximum for σ (8s) and σ (8p). Electronic energy curve calculations for the (Ar 7+ + Li) + and (O 7+ + Li) + systems allow us to discuss the results in terms of dynamical couplings.

The effect of the velocity of the incident ions in the nl-distributions of the electron capture in collisions of highly charged Ar8+ ions with a lithium target is studied. These Ar8+-Li(2s) collisions are experimentally studied by means of near UV and visible photon spectroscopy (200-600 nm) in the 1.5-4.5 keV amu-1 energy range and theoretically analysed by means of the three-body classical trajectory Monte-Carlo method. The presence of projectile core-electrons strongly affects the population and collision energy dependence of low l values produced in the electron capture reaction. It is shown that the sigma (nl) partial cross sections (n=8, 9 and l=0, 1, 2) increase with decreasing energies.

Charge exchange collisions at 105 keV between Ar7+ ions and lithium atoms have been studied by photon spectroscopy in the 2000-6000 Å wavelength range. A large number of new lines in Ar VII have been identified with the help of ab initio pseudo-relativistic Hartree-Fock calculations taking into account electrostatic interactions between 3snl (n = 6–10), 3 pnl (n = 4–6) and 3dnl (n = 4) configurations. They correspond to transitions 3snl–3sn'l' with n = 7, 8, 9 and Δn = 1 and 2. Lines in Ar VI were also observed and identified as transitions 3s2nl–3s2n'l' and 3s3pnl–3s3pn'l'(n = 6, 7) and Δn = 1.

A spectroscopic analysis of light emitted in the 200-6OOnm wavelength range by Ar", Ar6+ and AT5+ ions after charge exchange in 120keV Ar*+-Li collisions is performed. Transitions with An = 1 and An = 2 for n = 8, 9, 10 and 11 states of Ar VI11 following single electron capture are identified and the production cross sections for n = 8 and n = 9 are deduced from emission cross sections and compared with those calculated by the three-body classical trajectory Monte-Carlo method. Lines due to double capture process were observed and identified as Rydberg transitions 3snI-3sn'f' (n = 7, 8 and 9) in Ar VII. Lines due to triple electron capture process were found and identified as transitions 3s3nf-3s3n'l' and 3s3pnI-3s3pn'f' (n = 7, 8) in Ar VI. The configurations produced during the collision provides evidence that electron4ectron interaction play an important role in double and triple charge exchange processes.