Projectile velocity dependence of emission line polarization degrees following slowAr8+-Li(2s) state-selective electron-capture collisions

Abstract

The influence of the projectile velocity on the m{sub scr(l)} distributions of the Ar{sup 7+} excited states produced by electron capture during Ar{sup 8+}-Li(2s) collisions is studied experimentally between 1.5 and 4.5 keV amu{sup {minus}1} by measuring the polarization of the emitted light, and theoretically between 1 and 4 keV amu{sup {minus}1} by using the classical trajectory Monte Carlo (CTMC) method. We investigate the 7scr(l){sup {prime}}-8scr(l) and 8scr(l){sup {prime}}-9scr(l) radiative transitions subsequent to the decay of the 8scr(l) and 9scr(l) 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 scr(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 m{sub scr(l)} 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. {copyright} {ital 1997} {ital The American Physical Society}