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Abstract

We have measured the intensities and polarizations of fine-structure lines in the N=9-8 manifolds of Ne viii and Ar viii spectra produced in collisions of Ne8+ and Ar8+ (v=0.05–0.15 a.u.) with atomic sodium, and determined alignment and partial cross sections for electron capture as functions of projectile velocity. At low velocity the partial cross section for capture into the S levels is significantly higher than for capture into higher L levels, and at higher velocities the higher-L partial cross sections increase for Ar viii and dominate for Ne viii. The low-L-level cross sections are in fair agreement with multichannel-Landau-Zener calculations, while the high-L-level cross sections are in qualitative disagreement. For the neon projectiles, the polarization of the Bohr line is approximately 0.3 and independent of velocity; for argon projectiles, the polarization is approximately 0.15 and increases with increasing velocity. A qualitative theoretical interpretation is offered.