L-subshell ionization of heavy elements by carbon and nitrogen ions of energy 0.4-1.8 MeV/amu.

Abstract

L-shell x-ray production and subshell ionization cross sections have been measured for 0.4--1.8-MeV/amu carbon and nitrogen ions for selected heavy elements with 72\ensuremath{\le}${\mathit{Z}}_{2}$\ensuremath{\le}90. The results are compared with the predictions of the ECPSSR theory [perturbed-stationary-state (PSS) theory with energy-loss (E), Coulomb deflection (C), and relativistic (R) corrections] describing both direct ionization and electron-capture processes and the semiclassical approximation (SCA) calculations for direct ionization. For both theories significant deviations are found for ${\mathit{L}}_{2}$-subshell ionization in the low-energy range. The multiple ionization of outer shells was studied by comparing L x-ray intensity ratios measured for heavy ions and protons. The ionization probabilities of the ${\mathit{N}}_{4}$ subshell at zero impact parameter was extracted from these data. Measured ionization probabilities are compared with the predictions of the SCA theory and the ``geometrical model.'' The influence of multiple ionization on the measured L-subshell cross sections is discussed.