Using intrinsic Ge as x-ray detector, $K$-shell ionization cross sections have been determined for Ho, Tm, Lu, Ta, W, Pt, Au, Pb, and Bi under bombardment with 40-110-MeV $\alpha$ particles. The target-atom $K$-shell ionization cross sections are compared with the predictions of different models. The agreement is considerably improved when relativistic effects are taken into account. Intensity ratios have also been measured and found to agree with previous determinations. X-ray satellite emission, following nuclear rearrangements, was also observed and a calculation made in the case of Ho to relate nuclear reactions and $K$ x-ray production cross sections. Small peaks in the spectra of Au, Pb, and Bi have been tentatively attributed to double $J$-shell ionization, and hypersatellite energy is given for these atoms.

• Received 21 March 1977

DOI:https://doi.org/10.1103/PhysRevA.16.1390