Angular Correlation of Electrons Emitted by Double Auger Decay of K-Shell Ionized Neon

Abstract

We have investigated in detail the $4$-body continuum state produced when core-ionized neon undergoes Double-Auger (\textsc{da}) decay, using COLd Target Recoil Ion Momentum Spectroscopy (\textsc{coltrims}). We conducted the experiment at the Lawrence Berkeley National Laboratory's Advanced Light Source (\textsc{lbnl-als}) beamline $11.0.2$. The synchrotron operated in $2$-bunch mode and outputted an elliptically polarized, pulsed photon beam ($h\nu{}$=$872.9eV$), sufficient to K-shell ionize neon just above threshold.

Our analysis supports research showing that Auger electrons tend to share energy asymmetrically. We qualitatively compared this result to Photo-Double Ionization (\textsc{pdi}) of helium. Further, we confirm research that shows how Auger electrons that share energy symmetrically can be modeled by the elastic-like knock-out process plus Post-Collision Interaction (\textsc{pci}) effects.

New observations include the angular correlation between the photo-electron and each respective Auger electron, for specific ranges of energy sharing. We identify a broad feature in the asymmetric case that shows a level of interaction between electrons that until recently, has disagreed with theory. Additionally, we consider the angular correlation between the photo-electron and the momentum sum of the Auger electrons. We observe that the angular correlation between this sum and the photo-electron in the highly asymmetric case is nearly identical to the correlation between just the fast-Auger and the photo-electron - as expected. In the case of symmetric energy sharing, the sum momentum vector appears to be isotropic, particularly for small angles of interaction.

Finally, we acknowledge two novel methods of calibration. The first, uses well known line-energies to calibrate the spectrometer. These lines correspond to the decay channels of core-excited neon, $Ne(1s^{-1}3p)$. The second, describes a method to statistically weight list-mode data in order to calibrate it to well known physical features (e.g., isotropic distributions).