Cross section for aluminumK-shell ionization by oxygen ions

Experimental $\mathrm{Al}\mathrm{}\left(K\right)\mathrm{}$ x-ray production cross sections are reported for atomic oxygen projectiles incident on solid aluminum targets with kinetic energy $E$ in the range $0.15\le E\le 91$ MeV from which Al $K$-shell ionization cross sections are deduced for the projectile energy range $1\le E\le 91$ MeV. For $E\lesssim 1$ MeV nearly all observed x rays are caused by the recoiling aluminum atoms. The results are compared with theories of Coulomb ionization to the target continuum. Differences between experiment and these theories are examined with respect to contributions to inner-shell ionization from electon capture and Pauli excitation. It is found that Coulomb ionization is the dominant process for projectile velocities ${\nu }_1>4\mathrm{}$ a.u., while Pauli excitation dominates when ${\nu }_1<4\mathrm{}$ a.u. Electron-capture processes are significant at high energies, but are negligible for ${\nu }_1<4\mathrm{}$ a.u. for this projectile target system.