Electron slow motion: Ion physics on the femtosecond scale

What are the reactions of different materials to an ion? In nuclear fusion research, when the walls of the fusion reactor are bombarded by high-energy ion beams, this is a question that plays an important role.

It is easy to look at the result of an ion impact. It's hard to understand the temporal sequence of such processes. A research group at TU Wien has succeeded in analyzing what happens to the individual particles when an ion is applied to a material. The temporal sequence of the processes can be reconstructed using the electrons that are emitted in the process. The results were chosen as an Editors Suggestion and have now been published.

The research group at the Institute of Applied Physics works with ionized particles. The xenon atoms that have 54 electrons in their neutral state are stripped of 20 to 40 electrons and directed onto a thin layer of material.

Anna Niggas is the first author of the current paper. We already knew that Graphene has intriguing properties. The electron transport in Graphene is very fast.

It isn't possible to observe the processes directly because the particles are so fast. Anna Niggas says that there are special tricks that can be used. "We were able to measure the number and energy of these electrons very precisely, compare the results with theoretical calculations contributed by our co- authors from Kiel University, and this allowed us to untangle what happens on a small scale."

Journey through Graphene.

The thin layer of material is first approached by the charged ion. The electrons of the material move in the direction of the impact site because of the electric field generated by it. The electric field gets so strong that electrons are torn out of the material and captured by the ion. The ion hit the surface and penetrated the material. A lot of energy is transferred from the ion to the material in a short time.

Positive charge remains if electrons aren't present. electrons move in from other areas of the material Strong currents form within the material on an atomic scale when this process is performed in Graphene. The process in Molybdenum disulfide is a bit slower. Fast electrons can leave the material, slower electrons can turn around, and do not end up in the detector.

One second is all it takes for the ion to penetrate a layer of Graphene. Ultra short laser pulse can be used to measure processes on short time scales, but in this case they deposit a lot of energy in the material and completely change the process. "With our method, we have found an approach that allows quite fundamental new insights," says Richard. The results help us understand how matter reacts to very short and very intense radiation exposure.

More information: Anna Niggas et al, Ion-Induced Surface Charge Dynamics in Freestanding Monolayers of Graphene and MoS2 Probed by the Emission of Electrons, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.086802 Journal information: Physical Review Letters Citation: Electron slow motion: Ion physics on the femtosecond scale (2022, August 22) retrieved 22 August 2022 from https://phys.org/news/2022-08-electron-motion-ion-physics-femtosecond.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.