arXiv subjects

L. Kaiser

Publications and source records attributed to L. Kaiser.

4 recordsLinked to original sources

arXiv2025

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

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.

physics.atom-ph↗

arXiv2025

Probing Instantaneous Single-Molecule Chirality in the Planar Ground State of Formic Acid

We experimentally demonstrate that individual molecules of formic acid are chiral even when they are in the vibronic ground state, which has a planar equilibrium structure. We ionize the C 1s shell of the molecule and record the photoelectron in coincidence with positively charged fragments. This provides two consecutive measurements of the structure of one molecule, the first by photoelectron diffraction imaging and the second by Coulomb explosion imaging. We find that both measurements show the same handedness of the specific molecule. The phenomenon of being achiral on average but chiral at the level of individual molecules is general to most prochiral molecules and is a consequence of the three-dimensional zero-point delocalization of the nuclei in the vibrational ground state.

physics.atom-ph↗

arXiv2024

Role of the Coulomb Potential in Compton Scattering

We report a fully differential study of ionization of the Ne L-shell by Compton scattering of 20 keV photons. We find two physical mechanisms which modify the Compton-electron emission. Firstly, we observe scattering of the Compton electrons at their parent nucleus. Secondly, we find a distinct maximum in the electron momentum distribution close-to-zero momentum which we attribute to a focusing of the electrons by the Coulomb potential.

physics.atom-ph↗

arXiv2020

Revealing the Two-Electron Cusp in the Ground States of He and H2 via Quasifree Double Photoionization

We report on kinematically complete measurements and ab initio non-perturbative calculations of double ionization of He and H2 by a single 800 eV circularly polarized photon. We confirm the quasifree mechanism of photoionization for H2 and show how it originates from the two-electron cusp in the ground state of a two-electron target. Our approach establishes a new method for mapping electrons relative to each other and provides valuable insight into photoionization beyond the electric-dipole approximation.

physics.atom-ph↗