Fluorine 1s correlation states in the photoionization of hydrogen fluoride: Experiment and theory

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Abstract
The x-ray photoemission spectrum of the F 1s region of gaseous HF was measured using Al Kα1,2 radiation. Several satellite (’’shakeup’’) peaks were observed at ∼25–35 eV higher binding energy than the main F 1s peak. The spectrum was interpreted in terms of a many-electron theory that includes configuration interaction (CI) in both the hole state and the ground state. A CI calculation yielded eleven physically meaningful excited states based on the HF+ (F 1s hole) state. Six were predicted to have intensities over 0.1% that of the main peak. The four most intense of these were clearly present by visual inspection of the spectrum. Six were readily fitted by the addition of constraints. Derived intensities were in very good agreement with theory if ground-state CI was included. The four most intense peaks can be crudely interpreted as arising from 3σ to 4σ, 1π to 2π, and 1π to 3π excitations, but careful inspection of the orbitals shows that these designations are oversimplified.