Proceedings

EPJ D Highlight - Buckyballs release electron-positron pairs in forward directions

Impacting positrons release positronium from C60. Credit: Benjah-bmm27, public domain.

Theoretical calculations reveal that when impacted by positrons of particular energies, spherical nanoparticles release unstable electron-positron pairs, with signals dominating in the same direction as the incoming positrons.

When electrons collide with positrons, their antimatter counterparts, unstable pairs can form in which both types of particle orbit around each other. Named ‘positronium’, physicists have now produced this intriguing structure using a diverse range of positron targets – from atomic gases to metal films. However, they have yet to achieve the same result from vapours of nanoparticles, whose unique properties are influenced by the ‘gases’ of free electrons they contain in well-defined, nanoscopic regions. In new research published in EPJ D, Paul-Antoine Hervieux at the University of Strasbourg, France and Himadri Chakraborty at Northwest Missouri State University, USA, reveal the characteristics of positronium formation within football-shaped nanoparticles, C60, for the first time. At specific positron impact energies, they show that positronium emission dominates in the same direction as the incoming antiparticles.

Commonly known as buckminsterfullerene, or ‘buckyballs’, C60 is stable, easily synthesised and sustainable at room temperatures. Thanks to these useful properties, Hervieux and Chakraborty’s findings could have important implications for fields including astrophysics, materials physics, and pharmaceutical research. In particular, they could offer improvements in tests of how antimatter responds to gravity, which can involve structures including dipositronium and antihydrogen atoms; each of which feature positronium in the first steps of their fabrication processes.

When positrons of certain energies approach buckyballs at angles of up to 10 degrees, the physicists showed that a series of narrow, forward-facing positronium signals resulted from the ‘diffraction resonance’ of the particles. The effect is comparable to how light is diffracted by microscopic spherical obstructions; showing variation with larger fullerene molecules like C240, and when particles are excited to higher energy levels. Hervieux and Chakraborty modelled these properties through theoretical calculations of how diffraction resonance affected the angles over which positronium is emitted, as a function of positron impact energy. Their results offer important insights for the wide variety of researchers who use these short-lived structures. In future studies, the duo now hopes to further explore their potential for use in real experiments.

This was our first experience of publishing with EPJ Web of Conferences. We contacted the publisher in the middle of September, just one month prior to the Conference, but everything went through smoothly. We have had published MNPS Proceedings with different publishers in the past, and would like to tell that the EPJ Web of Conferences team was probably the best, very quick, helpful and interactive. Typically, we were getting responses from EPJ Web of Conferences team within less than an hour and have had help at every production stage.
We are very thankful to Solange Guenot, Web of Conferences Publishing Editor, and Isabelle Houlbert, Web of Conferences Production Editor, for their support. These ladies are top-level professionals, who made a great contribution to the success of this issue. We are fully satisfied with the publication of the Conference Proceedings and are looking forward to further cooperation. The publication was very fast, easy and of high quality. My colleagues and I strongly recommend EPJ Web of Conferences to anyone, who is interested in quick high-quality publication of conference proceedings.

On behalf of the Organizing and Program Committees and Editorial Team of MNPS-2019, Dr. Alexey B. Nadykto, Moscow State Technological University “STANKIN”, Moscow, Russia. EPJ Web of Conferences vol. 224 (2019)

ISSN: 2100-014X (Electronic Edition)

© EDP Sciences