Photoionization of the Cerium Isonuclear Sequence and Cerium Endohedral Fullerene
Loading...
Authors
Habibi, Mustapha
Issue Date
2009
Type
Dissertation
Language
Keywords
Cerium , endohedral fullerene , photofragmentation , Photoionization
Alternative Title
Abstract
This dissertation presents an experimental photoionization study of the cerium isonuclear sequence ions in the energy range of the 4d inner-shell giant resonance. In addition, single and double photoionization and photofragmentation cross sections of the cerium endohedral ion Ce$@$C$_{82}^{+}$ were also measured and studied in the 4d excitation-ionization energy range of cerium.Relative and absolute cross-section measurements were performed at undulator beamline 10.0.1 of the Advanced Light Source (ALS) for nine parent cerium ions: Ce$^{+}$ -- Ce$^{9+}$. Double-to-single ionization cross-section ratios were measured for photoionization of the endohedral Ce$@$C$_{82}^{+}$ and empty fullerene C$_{82}^{+}$ molecular ions. The merged ion and photon beams technique was used to conduct the experiments. Multiconfiguration Hartree-Fock calculations were performed as an aid to interpret the experimental data. Four Rydberg series for 4d $\rightarrow$ nf (n $\geq$ 4) and 4d $\rightarrow$ np (n $\geq$ 6) autoionizing excitations were assigned using the quantum defect theory for the Ce$^{3+}$ photoionization cross section. The experimental data show the collapse of the nf wavefunctions (n $\geq$ 4) with increasing ionization stage as outer-shell electrons are stripped from the parent ion. The nf orbital collapse occurs partially for Ce$^{2+}$ and Ce$^{3+}$ ion and completely for Ce$^{4+}$, where these wavefunctions penetrate the core region of the ion. A strong contribution to the total oscillator strength was observed in the double and triple photoionization channels for low charge states ( Ce$^{+}$, Ce$^{2+}$, and Ce$^{3+}$), whereas most of the 4d excitations of the higher charge states decay by ejection of one electron.
Description
Citation
Publisher
License
In Copyright(All Rights Reserved)