Date of this Version
PHYSICAL REVIEW A 83, 043412 (2011); DOI: 10.1103/PhysRevA.83.043412
Cross sections for single photoionization of Fe3+, Fe5+, and Fe7+ ions were measured at spectral resolutions of 0.04, 0.15, and 0.13 eV, respectively, by merging mass- and charge-selected ion beams with a beam of monochromatized synchrotron undulator radiation. The measurements span photon energy ranges beginning at the ionization thresholds and extending several tens of electron volts to include the most important resonant contributions due to 3p–nd transitions to autoionizing states. The photoion yield spectra are characterized by narrow resonances and also broad features in Fe3+ and Fe5+ that are believed to result from unresolved fast super- Coster-Kronig transitions following 3p–3d excitation. Absolute photoionization cross-section measurements were also performed using ion beams containing undetermined fractions of ions in their ground and metastable states. A Rydberg series attributed to 3p–nd transitions from the 2G1 metastablestate in Fe3+ was identified. The data are compared with recently published measurements on Fe3+ and Fe5+ using a similar technique at lower spectral resolution.