Near L-edge Single and Multiple Photoionization of Singly Charged Iron Ions

Abstract

Absolute cross sections for m-fold photoionization (m = 1, . . . , 6) of Fe + by a single photon were measured employing the photon-ion merged-beams setup PIPE at the PETRA III synchrotron light source, operated by DESY in Hamburg, Germany. Photon energies were in the range 680-920 eV which covers the photoionization resonances associated with 2p and 2s excitation to higher atomic shells as well as the thresholds for 2p and 2s ionization. The corresponding resonance positions were measured with an uncertainty of ±0.2 eV. The cross section for Fe + photoabsorption is derived as the sum of the individually measured cross-sections for m-fold ionization. Calculations of the Fe + absorption cross sections have been carried out using two different theoretical approaches, Hartree-Fock including relativistic extensions and fully relativistic Multi-Configuration Dirac Fock. Apart from overall energy shifts of up to about 3 eV, the theoretical cross sections are in good agreement with each other and with the experimental results. In addition, the complex deexcitation cascades after the creation of inner-shell holes in the Fe + ion have been tracked on the atomic fine-structure level. The corresponding theoretical results for the product charge-state distributions are in much better agreement with the experimental data than previously published configuration-average results. The present experimental and theoretical results are valuable for opacity calculations and are expected to pave the way to a more accurate determination of the iron abundance in the interstellar medium.

Photoionization and photofragmentation of singly charged positive and negative Sc3N@C80 endohedral fullerene ions

“…Two permanent experimental installations were used, namely, the PIPE (Photon-Ion Spectrometer at PETRA III) endstation [30,31] of beamline P04 [32] and the IPB (Ion-Photon Beamline) endstation [33] of beamline 10.0.1. at the ALS. Several of the most recent publications of the present collaboration on photoprocesses of ions studied at the endstations at the ALS [13,[34][35][36][37] and at PETRA III [38][39][40][41][42][43] illustrate the experimental capabilities and the latest developments.…”

Near L-edge Single and Multiple Photoionization of Triply Charged Iron Ions

“…To help provide reliable iron L-shell photoabsorption data for these astrophysical environments, we have carried out a series of combined experimental and theoretical studies. Previously, we presented cross sections for single and multiple photoionization of Fe + ions in the range of L-shell photoexcitation and photoionization (Schippers et al 2017). Here, we present photoabsorption measurements for Fe 3+ .…”

“…Reliable atomic data for gas-phase Fe 3+ photoabsorption is needed to distinguish any gas-phase absorption from any solid-matter absorption and for the accurate determination of the iron abundance and its chemical environment. Benchmarking the relevant ionization cross sections by experimental laboratory studies is a prerequisite for such an analysis, as described in more detail by Schippers et al (2017).…”

Near-K-edge single, double, and triple photoionization ofC+ions

“…The partial widths for n-electron removal are readily obtained from Γ ne = S ne S Γ (A. 18) and the Auger decay rates for the emission of n electrons are…”