Production ofKX Rays by 160-MeV Protons

$K$-shell ionization cross sections have been measured for elements between $Z=26\mathrm{}$ and $Z=92\mathrm{}$ using 160-MeV protons as incident projectiles. The results are compared with two theoretical models, the plane-wave-Born-approximation calculations of Khandelwal, Choi, and Merzbacher and the binary-encounter model of Garcia. The results are in qualitative agreement with both these nonrelativistic models. The necessity for a relativistic theory is emphasized by comparison with recent high-energy-electron measurements.