X-ray emission cross sections and spectral distributions for carbon bombarded with MeV C, N, and O ions

Abstract

X rays emitted by a thin target bombarded with C, N, and O ions with energies between 1 and 2.5 MeV are observed at an angle of 135\ifmmode^\circ\else\textdegree\fi{} with a Bragg crystal spectrometer having a resolution of 3 eV. The $\mathrm{KL}$ and $K{L}^{2}$ satellite lines of the carbon target are observed, as well as the diagram $K$ line. These peaks are superimposed on a broad x-ray distribution extending from 265 to 290 eV. The $K{L}^{2}$ line appears for N at low energies, but not for C. Projectile and target spectra involve the $K$ and $\mathrm{KL}$ lines in approximately equal amounts for C. These observations are interpreted as evidence for a molecular-orbital theory involving promotion of $L$ electrons of the colliding atoms, in which the momentum change of the promoted electron is taken into account. Cross sections for production of carbon $K$ x rays at energies below the carbon absorption edge in the Bragg pseudocrystal are obtained from the data. The cross sections rise monotonically with energy in the range studied and are smallest for oxygen ions, which have the largest atomic number.