Photoionization cross sections for ions of the cerium isonuclear sequence

Authors

• M. Habibi, University of Nevada - Reno
• D. A. Esteves, University of Nevada - Reno
• R. A. Phaneuf, University of Nevada - RenoFollow
• A. L. D. Kilcoyne, Lawrence Berkeley National LaboratoryFollow
• A. Aguilar, Lawrence Berkeley National Laboratory
• C. Cisneros, Universidad Nacional Autonoma de MexicoFollow

Date of this Version

2009

Citation

Physical Review A 80, 033407 (2009); DOI: 10.1103/PhysRevA.80.033407

Abstract

Photoionization cross sections for Ce^q+ (1 ≤ q ≤ 9) ions were measured in the 105–180 eV energy range of the 4d inner-shell giant resonance by merging a mass-to-charge-ratio-selected ion beam with a beam of monochromatized synchrotron radiation. The Cowan atomic structure code was used as an aid to interpret the experimental data. Four Rydberg series for 4d→nf (n ≥ 4) and 4d→np (n ≥ 6) autoionizing excitations were assigned using the quantum-defect theory in the Ce³⁺ photoionization cross section. The experimental data show the collapse of the nf wave functions (n ≥ 4) with increasing ionization stage as outer-shell electrons are stripped from the parent ion. The nf orbital collapse occurs partially for Ce²⁺ and Ce³⁺ ions and completely for Ce⁴⁺, where these wave functions penetrate the core region of the ion. A strong contribution to the total oscillator strength was observed in multiple photoionization channels for Ce⁺, Ce²⁺, and Ce³⁺, whereas most of the 4d excitations of the higher charge states decay by ejection of one electron.