ABSTRACT
Double photoionization (DPI) of an atom by a single photon is a direct consequence of electron-electron interactions within the atom. We have measured the evolution of the K-shell DPI from threshold up in transition metals by high-resolution x-ray emission spectroscopy of the Kh alpha hypersatellites, photoexcited by monochromatized synchrotron radiation. The measured evolution of the single-to-double photoionization cross-section ratio with excitation energy was found to be universal. Theoretical fits suggest that near threshold DPI is predominantly a semiclassical knockout effect, rather than the purely quantum-mechanical shake-off observed at the infinite photon energy limit.
ABSTRACT
We review recent, and some less recent, measurements of several emission spectra of copper. The results are discussed with special emphasis on elucidating the structure of the Kα 1,2 and Kß 1,3 diagram lines and their underlying transitions. These lines are found to contain ≈30 % contribution from 3d spectator hole transitions. Other multielectronic transitions, the 2p spectator hole (satellites) and 1s spectator hole (hypersatellites) transitions were also measured. They are discussed paying special attention to the evolution of the lineshapes and intensities from the excitation threshold to saturation. Trends in the measured quantities depending on the spectator hole's shell and subshell are also discussed.
ABSTRACT
High-resolution Fe K(h) beta(1,3) and K(h) alpha(1,2) hypersatellite spectra were measured, using monochromatized synchrotron radiation photoexcitation. The lines' energies, splitting, excitation thresholds, and the K(h) alpha(1)/K(h) alpha(2) intensity ratio were derived with high accuracy. Having both spectra, not hitherto available for any atom with high resolution, allows separating out the energy shifts of the outer levels caused by a K shell spectator vacancy. Comparison with ab initio relativistic multiconfigurational Dirac-Fock calculations reveals that while the influence of relativity and QED effects is mostly accounted for, discrepancies remain in the lines' intensity ratio, which sensitively measures the intermediacy of the coupling. Similar discrepancies, of unknown origin, are found in the energy shifts of the outer levels due to the final-state K shell spectator vacancy.
ABSTRACT
The first pure high-resolution photoexcited K(h)alpha(1,2) hypersatellite spectrum from a hollow Cu atom is measured. Its K(h)alpha(2)- Kalpha(1) shift and the K(h)alpha(1,2) lines' splitting, widths, and intensity ratio are accurately determined. Such spectra are uniquely suited to study relativistic correlation effects, transition from LS to intermediate coupling, and the Breit-Wigner interaction. The threshold energy and the spectrum's evolution with excitation energy are also measured. The roles of relativity and Breit interaction are explored by comparison with ab initio Dirac-Fock calculations.
ABSTRACT
A complex set of social, economic, cultural and environmental circumstances affecting native Canadians in northern regions has resulted in the dietary replacement of indigenous foods with marketed products not always of equivalent nutritional value. This article examines the current food supply in three northern Manitoba Cree communities by looking at the availability and preservation of traditional foods, the price of marketed foods and perceptions of the food supply. Data were obtained by questionnaire from older adults (over 55 years) and younger women (16-45 years) in each community. The food supply comprised a mix of traditional and marketed foods, with limited use of traditional methods of food preservation. Marketed food prices were high in communities without all-weather road access. Respondents expressed a desire for more traditional food. Promotion of traditional foods could increase nutrient intake, decrease food costs and contribute to a revival of interest in Cree culture.
