Photo fragmentation of large dimers into singly charged ions via the knockout mechanism

TL;DR

This paper develops a theoretical model for photon-induced fragmentation of large dimers into singly charged ions, predicting efficiency differences among various dimers and validating the model with helium data.

Contribution

The study introduces a new theoretical framework for understanding photon-induced dimer fragmentation, including predictions for Li-He dimers where experimental data are lacking.

Findings

Good agreement with helium dimer experimental data

Li-He dimers show higher fragmentation efficiency than He$_2$

Reflection approximation is accurate for large dimers

Abstract

We study the fragmentation of very large dimers into two singly charged ions caused by absorption of a photon. In this process a photo electron emitted from one atom of the dimer has certain chances to hit the other atom knocking out one of its electrons. This results in the production of two singly charged ions and the consequent Coulomb explosion of the residual doubly charged system. We develop a theory of this process and apply it to calculate the fragmentation of $^4$He$_2$, $^7$Li - $^4$He and $^6$Li - $^4$He dimers. Our results for the helium dimer are in good agreement with available experimental data. For the Li-He dimers (where experimental data are still absent) our results predict that this fragmentation mechanism becomes much more efficient than in the case of He$_2$. We also show that, provided the recoil effects are of minor importance, the so called reflection approximation is very accurate also for large dimers.