Momentum-space imaging of {\sigma}-orbitals for chemical analysis

TL;DR

This paper demonstrates that momentum-space imaging of {\sigma}-orbitals via photoemission orbital tomography can effectively analyze surface chemical reactions, especially for bonds involving local modifications, expanding the technique's applicability.

Contribution

It shows that {\sigma}-orbitals can be imaged over a broad energy range and that the plane wave approximation is valid for these orbitals, enhancing chemical analysis capabilities.

Findings

{\sigma}-orbitals are imageable across a broad energy spectrum.

Plane wave approximation holds well for {\sigma}-orbitals.

Successfully identified reaction products in surface chemical reactions.

Abstract

Tracing the modifications of molecules in surface chemical reactions benefits from the possibility to image their orbitals. While delocalized frontier orbitals with {\pi}-character are imaged routinely with photoemission orbital tomography, they are not always sensitive to local chemical modifications, particularly the making and breaking of bonds at the molecular periphery. For such bonds, {\sigma}-orbitals would be far more revealing. Here, we show that these orbitals can indeed be imaged in a remarkably broad energy range, and that the plane wave approximation, an important ingredient of photoemission orbital tomography, is also well fulfilled for these orbitals. This makes photoemission orbital tomography a unique tool for the detailed analysis of surface chemical reactions. We demonstrate this by identifying the reaction product of a dehalogenation and cyclodehydrogenation reaction.