Photoionization and electron-impact ionization of Ar5+

Absolute cross sections for photoionization and electron-impact ionization of Ar5+ have been measured using two different interacting-beams setups. The spectra consist of measurements of the yield of products due to single ionization as a function of electron or photon energy. In addition, absolute photoionization and electron-impact ionization cross sections were measured to normalize the measured Ar6+ product-ion yield spectra. In the energy range from 90 to 111 eV, both electron-impact ionization and photoionization of Ar5+ are dominated by indirect 3s subshell excitation-autoionization. In the energy range from 270 to 285 eV, resonances due to 2p-3d excitation-autoionization are prominent in the photoionization spectrum. In the range from 225 to 335 eV, an enhancement due to 2p-nl (n>2) excitations are evident in the electron-impact ionization cross section. The electron and photon impact data show some features due to excitation of the same intermediate autoionizing states.