Ionization of one-electron ions and capture by bare and one-electron ions of C, N, O, and F on He

Abstract

Experimentally measured single-electron-transfer cross sections are presented for bare nuclei and one-electron ions of C, N, O, and F following collisions with a He-gas target in the energy range from \ensuremath{\sim}0.5-2.5 MeV / amu. Excellent agreement is found between the $K$-shell ionization cross sections (electron loss by one-electron ions) and a theoretical plane-wave-Born-approximation calculation without inclusion of Coulomb-deflection and binding-energy corrections. Comparisons are also made between the capture cross sections (electron gain) and previously measured total projectile x-ray cross sections. The ratio of the x-ray cross section to the total capture cross section is compared to the same ratio found through a Brinkman-Kramers (BK) calculation. The results of the comparison show that the single normalization constant for the capture to each state, which was used in the theoretical analysis of the x-ray cross section, is inadequate. In particular, the results show that the BK calculation underestimates the capture of the electron to the $1s \mathrm{and} 2s$ states as compared to the higher, x-ray-emitting states. The total capture cross sections are also given as a function of $\frac{E}{M}$ (MeV / amu). For a given velocity the capture is dependent only upon the charge state of the incident ion. Also, the similar velocity dependence with average ratios of 1:0.68:0.44 for the charge-changing processes $q\ensuremath{\rightarrow}q\ensuremath{-}1(q=8,7,\mathrm{and} 6)$ correspond to a ${q}^{3}$ dependence for the total cross section.