Selective Bond Breaking in CO$_2^{2+}$ Induced by Photoelectron Recoil

TL;DR

This study demonstrates that the recoil momentum of photoelectrons influences which bond in CO₂$^{2+}$ breaks during dissociation, revealing a directional control mechanism in molecular fragmentation.

Contribution

The paper provides experimental evidence that photoelectron recoil momentum can steer bond breaking in CO₂$^{2+}$, highlighting a nondipole effect in molecular dissociation.

Findings

Up to 25% asymmetry in bond cleavage depending on photoelectron emission direction

Recoil momentum influences which bond in CO₂$^{2+}$ breaks

O$^+$ fragments preferentially emitted opposite to light propagation

Abstract

After core-ionization of CO$_2$, typically an Auger-Meitner decay takes place, leading to the formation of a dicationic molecule that may dissociate into CO$^+$ and O$^+$. We demonstrate experimentally that the recoil momentum of the photoelectron steers, which of the two equivalent bonds breaks during the dissociation. At 20 keV photon energy, we observe an asymmetry of up to 25% for bond cleavage that depends on the emission direction of the photoelectron. Furthermore, we show that this effect leads to a significant nondipole effect in molecular dissociation in the laboratory frame: O$^+$ fragments are more likely to be emitted in the direction opposite to the light propagation than along it.