Pumping K-Alpha Resonance Fluorescence by Monochromatic X-Ray Sources

TL;DR

This paper explores the theoretical and experimental aspects of K-alpha resonance fluorescence induced by monochromatic X-ray sources, proposing a more efficient excitation mechanism with potential biomedical applications.

Contribution

It introduces a novel approach to induce K-alpha resonance fluorescence using two monochromatic X-ray beams, reducing the required X-ray fluence compared to XFEL experiments.

Findings

Resonant absorption features match experimental observations in aluminum ions.

Predicted K-alpha resonances in titanium suggest feasible detection in 4.5-5.0 keV range.

Proposed excitation mechanism could enable less intense, targeted resonance fluorescence for biomedical uses.

Abstract

We demonstrate the correspondence between theoretically calculated K-shell resonances lying below the K-edge in multiple ionization states of an element (Pradhan et al. 2009), and recently observed K-alpha resonances in high-intensity X-ray free-electron laser (XFEL) plasmas (Vinko et al. 2012). Resonant absorptions in aluminum ions are computed and found to reproduce experimentally observed features. Results are also presented for titanium for possible observation of K-alpha resonances in the 4.5-5.0 keV energy range. A possibly sustainable excitation mechanism for K-alpha resonance fluorescence might be implemented using two monochromatic X-ray beams tuned to the K-edge and the K-alpha resonant energies simultaneously. This targeted ionization/excitation would create inner-shell vacancies via Auger decay, as well as pump K-alpha resonances. The required X-ray fluence to achieve resonance fluorescence would evidently be much less than in the XFEL experiments, and might enable novel biomedical applications.