Influence of orbital symmetry on diffraction imaging with rescattering electron wave packets

TL;DR

This paper demonstrates that molecular orbital symmetry does not hinder laser-induced electron diffraction imaging of molecules, even when molecules are randomly oriented, thus overcoming previous limitations and expanding imaging capabilities.

Contribution

The study shows that molecular orbital symmetry does not prevent structure retrieval in electron diffraction, even for randomly oriented molecules with specific orbital symmetries.

Findings

Successful retrieval of molecular structures of O2 and C2H2 with different orbital symmetries.

Random molecular orientation does not impede diffraction imaging.

Unexpected strong backscattering from low-Z atoms observed.

Abstract

The ability to directly follow and time resolve the rearrangement of the nuclei within molecules is a frontier of science that requires atomic spatial and few-femtosecond temporal resolutions. While laser induced electron diffraction can meet these requirements, it was recently concluded that molecules with particular orbital symmetries (such as {\pi}g) cannot be imaged using purely backscattering electron wave packets without molecular alignment. Here, we demonstrate, in direct contradiction to these findings, that the orientation and shape of molecular orbitals presents no impediment for retrieving molecular structure with adequate sampling of the momentum transfer space. We overcome previous issues by showcasing retrieval of the structure of randomly oriented O2 and C2H2 molecules, with {\pi}g and {\pi}u symmetries, respectively, and where their ionisation probabilities do not maximise along their molecular axes. While this removes a serious bottleneck for laser induced diffraction imaging, we find unexpectedly strong back scattering contributions from low-Z atoms.