Multiple photoionization for the 2p subshell in the iron atom

Multiple photoionization is investigated for the 2p subshell in the iron atom. Study of the single photoionization with subsequent radiative and Auger cascade includes levels corresponding to the ground configuration. This work reveals that the quadruple photoionization dominates over other multiple-photoionization processes. Analysis of the partial photoionization cross sections to configurations of the produced ions shows that the excited long-lived configurations accumulate the main population of the Fe4+ ion. The main decay branches of the radiative and Auger cascade produced after a creation of the 2p subshell vacancy in the iron atom are identified. The ion yields for the photoionization and cascade obtained by considering level-to-level transitions are compared to the previous configuration average calculations

Multiple photoionization cross sections for Fe

Multiple photoionization cross sections from the K shell are studied for all levels of the Fe2+ 3d6 configuration. The study shows that the quadruple photoionization leads to the largest cross sections. A large variation in the multiple photoionization cross sections is determined among the levels of the Fe2+ 3d6 configuration. Main decay branches of radiative and Auger cascades, following the photoionization of the K shell for the ground configuration of the Fe2+ ion, are identified. The radiative and Auger cascade is studied by considering transitions among energy levels and subconfigurations. The obtained data for ion yields are compared with previous calculations produced for configuration averages

Electron-impact ionization of Fe

Electron-impact ionization cross sections and Maxwellian rate coefficients are presented for the Fe8+ ion by considering processes from the ground and metastable levels. The lifetimes of the levels for the 3s2 3p5 3d configuration were analysed using the extended basis of interacting configurations. Convergence of the cross sections for the indirect process due to excitations to the high-nl subshells was investigated. We demonstrate that excitations to the subshells with orbital quantum number l = 3 with subsequent autoionization dominate up to electron energies of ∼700 eV for the ground and metastable levels. Modelling of theoretical cross sections obtained for the ground and metastable levels to produce the best fit to the measurements shows that 15% of ions reach the reaction zone in the metastable state. The obtained results contradict the previous work that showed ∼30% for the metastable fraction

Multiple photoionization for the K shell in the Fe atom

Multiple photoionization for the K shell in the Fe atom is studied for all levels of the ground configuration. The study shows that sextuple-photoionization cross sections dominate for all levels of the 3d64s2 configuration. The cross sections strongly depend on the initial level for which the photoionization is investigated. The partial photoionization cross sections to the configurations of the produced ions are determined. The main sequences of the radiative and Auger cascade following the photoionization of the K shell in the Fe atom are identified. Presented ion yields for subconfigurations and levels are compared with the previous calculations for configuration averages, revealing that they strongly overestimate ion yields for the Fe7+–Fe10+ ions

Excitation of the 6<i>d</i> ²<i>D</i> → 6<i>p</i> ²<i>P</i>^o Radiative Transitions in the Pb⁺ Ion by Electron Impact

Results of experimental and theoretical investigation of electron-impact excitation of the 6s26d D2→6s26p P2o spectral transitions from the ground 6s26p P21/2o level in the Pb+ ion are presented. The experimental excitation functions for the transitions, measured by a VUV spectroscopy method, using the crossed electron and ion beams technique, reveal a rather distinct resonance structure resulting mainly from the electron decay of both atomic and ionic autoionizing states. The absolute values of the emission cross-sections, obtained by normalizing the experimental data at the incident electron energy 100 eV by those calculated using the Flexible Atomic Code software package, were found to be (0.35 ± 0.17) × 10–16 cm2 for the 6s26d D23/2 → 6s26p P21/2o (λ143.4 nm) transition and (0.19 ± 0.09) × 10–16 cm2 for the 6s26d D25/2 → 6s26p P23/2o (λ182.2 nm) transition