Towards weighing individual atoms by high-angle scattering of electrons

TL;DR

This paper explores the theoretical possibility of using high-angle electron scattering to identify individual atoms and isotopes by analyzing energy loss signals, with initial experiments showing mass-based separation of gold and carbon.

Contribution

It introduces a theoretical framework for atom-by-atom mass identification via high-angle electron scattering and demonstrates initial experimental proof-of-concept for mass-based separation.

Findings

Energy loss correlates with nuclear mass and atomic vibrations.

Peak position shifts can identify isotopes despite broadening.

Gold and carbon can be distinguished based on mass-related signals.

Abstract

We consider theoretically the energy loss of electrons scattered to high angles when assuming that the primary beam can be limited to a single atom. We discuss the possibility of identifying the isotopes of light elements and of extracting information about phonons in this signal. The energy loss is related to the mass of the much heavier nucleus, and is spread out due to atomic vibrations. Importantly, while the width of the broadening is much larger than the energy separation of isotopes, only the shift in the peak positions must be detected if the beam is limited to a single atom. We conclude that the experimental case will be challenging but is not excluded by the physical principles as far as considered here. Moreover, the initial experiments demonstrate the separation of gold and carbon based on a signal that is related to their mass, rather than their atomic number.