Production of characteristic x rays by low-energy protons

S>The cross sections for the production of characteristic x rays by targets bombarded with low-energy protons are measured for a number of elements. Scintillation counters capable of resolving x rays with energies as low as 2 kev are used as detectors. X rays from K, L, and M shells are observed and the behavior of the production cross section for these is measured as a function of incident proton energy. Proton beams with energies between 100 and 500 kev are used. The ionization cross sections for the shells are also computed using measured or extrapolated values of the appropriate fluorescence yields. The dependence of the K-shell ionization cross section on atomic number (Z) and on the energy of the bombarding protons is in accord with the theoretical predictions provided that the deflection of the bombarding particle by the Coulomb field of the nucleus is taken into account. The measured L-shell ionization cross sectlons are smaller than the values predicted by a Born approximation calculation in which Coulomb effects are neglected. Only a qualitative explanation of the behavior of M-shell ionization is presented. (auth)