Electron capture to continuum states of bare projectile ions

Relative cross sections for electron capture to continuum states by bare projectile ions H⁺, C⁺⁶, O⁺⁸, and Si⁺¹⁴, have been measured for beam energies between 0.70-3.86 MeV/u with helium, neon, and argon targets. The relative cross sections have been made absolute by linking them to recently published absolute cross s sections from several other sources. The projectile charge, Z₁, and velocity dependences of these cross sections, as well as the experimentally observed shape of the forward electron peak which arises from electron capture to continuum processes, have been studied and compared with predictions from several theoretical treatments.

The absolute cross sections found here for 0.7-2.0 MeV H⁺ on neon and argon are consistent with those measured by Cranage and Lucas¹⁶ and Rødbro and Andersen ²⁷ for 0.7-1.7 MeV/uH⁺ incident on the same targets. The Z₁³, cross section scaling predicted by most theories has been shown to fail for Z₁-Ar, in this range of Z₁^2.3±0.3, and at these ion velocities, 2.3 ± 0.3 has been measured. The error represents the range in several measurements.

The experimental forward electron peak shapes show previously unpredicted target and projectile dependences. In particular, a large dependent asymmetry with respect to the central peak velocity, which had not been reported before, has been measured.