The influence of the projectile velocity on the ${\mathrm{m}}_{\mathrm{\ell }}$ distributions of the ${\mathrm{Ar}}^{7+}$ excited states produced by electron capture during ${\mathrm{Ar}}^{8+}$-Li(2s) collisions is studied experimentally between 1.5 and 4.5 keV ${\mathrm{amu}}^{\mathrm{-}1}$ by measuring the polarization of the emitted light, and theoretically between 1 and 4 keV ${\mathrm{amu}}^{\mathrm{-}1}$ by using the classical trajectory Monte Carlo (CTMC) method. We investigate the 7${\mathrm{\ell }}^{|\mathrm{I}\mathrm{H}}$-8ℓ and 8${\mathrm{\ell }}^{|\mathrm{I}\mathrm{H}}$-9ℓ radiative transitions subsequent to the decay of the 8ℓ and 9ℓ sublevels of Ar VIII, which are preferentially populated by the single electron capture process. A small but not negligible effect is seen for the experimental polarization ratios relating to transitions from sublevels of large ℓ values, showing a slight increase of the component parallel to the incident ion beam as the projectile energy increases. Theoretical polarization ratios obtained from CTMC calculated ${\mathrm{m}}_{\mathrm{\ell }}$ distributions are in excellent agreement with the measured polarization ratios. Electronic energy curve calculations are then presented in order to discuss these results in terms of dynamical couplings.

• Received 30 May 1996

DOI:https://doi.org/10.1103/PhysRevA.55.1088