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Photodetachment of negative ions with two active electrons
Abstract
Since the discovery of autoionization states in the 1960s, correlated two-electron dynamics has been the center for studies of electron-electron correlation. In the last three decades, a fairly complete understanding of low-lying two-electron resonance states was achieved, based on various quantum approximations which reveal the underlying symmetries of the problem and explain the regularity of two-electron resonances in the spectra. Photodetachment plus excitation of atomic negative ions is a fruitful means of observing and studying such states since there is no obscuring Rydberg series in the spectra. We present comprehensive studies for photodetachment of three negative ions, Li−, Na−, and He− , in the energy region below the n = 5 thresholds of the respective neutral atoms. Since this energy region is below the excitation of inner shell electrons, these negative ions can be adequately treated as two active electrons moving in a central field resulting from the nuclear charge and the frozen core electrons. Prediction of total and partial cross sections using the eigenchannel R-matrix method are presented and compared with other experimental and theoretical results. Excellent agreements with experimental measurements show the effectiveness of our approach in studying single escape processes of two-electron systems. Analyses of the resonance structures in the photodetachment spectra give parameters of all resonances that are accessible from the ground state negative ions according to dipole selection rules. Identifications of the corresponding doubly excited states provide insights into the dynamics of these quasi-two-electron systems. Studies of partial cross sections in the neighborhood of a resonance reveal two universal behaviors, mirroring and mimicking, which result from different resonance properties. More interesting, while mirroring behaviors are proved analytically to be a common feature in photo-fragmentation processes accompanied by high levels of excitation of the residual atom or ion, they reflect the intrinsic coherence of indistinguishable paths in quantum processes.
Subject Area
Atoms & subatomic particles
Recommended Citation
Liu, Chien-Nan, "Photodetachment of negative ions with two active electrons" (1999). ETD collection for University of Nebraska-Lincoln. AAI9942135.
https://digitalcommons.unl.edu/dissertations/AAI9942135