Multiple Photodetachment of Oxygen Anions via K-Shell Excitation and Ionization: Direct Double-Detachment Processes and Subsequent Deexcitation Cascades

TL;DR

This study measures and analyzes the cross sections for multiple photodetachment of oxygen anions via K-shell excitation and ionization, revealing direct double detachment processes and complex deexcitation cascades with theoretical and experimental agreement.

Contribution

It provides the first detailed experimental and theoretical investigation of multiple photodetachment of oxygen anions in the 525-1500 eV range, including direct double detachment and cascade modeling.

Findings

Experimental cross sections match empirical scaling laws.

Identification of direct double detachment signatures.

Theoretical charge-state distributions agree with experiments.

Abstract

Experimental cross sections for m-fold photodetachment (m=2-5) of oxygen anions via K-shell excitation and ionization were measured in the photon-energy range of 525-1500 eV using the photon-ion merged-beams technique at a synchrotron light source. The measured cross sections exhibit clear signatures of direct double detachment, including double K-hole creation. The shapes of the double-detachment cross sections as a function of photon energy are in accord with Pattard's [J. Phys. B 35, L207 (2002)] empirical scaling law. We have also followed the complex deexcitation cascades that evolve subsequently to the initial double-detachment events by systematic large-scale cascade calculations. The resulting theoretical product charge-state distributions are in good agreement with the experimental findings.