EPJ D Topical review - Electron-scattering on molecular hydrogen: convergent close-coupling approach
- Published on 24 March 2020
Molecular hydrogen is the simplest neutral molecule, the most abundant molecule in the universe and an important constituent of plasmas with applications in astrophysics, fusion, atmospheric physics, and various industries. Elemental collision processes play an important role in modelling these plasmas, and collisions with electrons have attracted significant interest from both experiment and theory. A number of compilations of cross sections for electron collisions with molecular hydrogen have been produced. In all cases these cross section data sets have been produced from an analysis of experimental data, even though there were significant discrepancies between different experiments for many transitions. Theoretical calculations have been largely excluded from critical evaluations of the data due to large uncertainties. This changed with the application of the convergent close-coupling (CCC) method to electron collisions with molecules.
- Published on 18 March 2020
In an elegant study published in EPJ D, physicists from Serbia and Russia have mapped the energy levels and estimated the stability of a ‘frozen planet’ configuration of anti-protonic helium.
Exotic subatomic particles that are like ‘normal’ particles apart from one, opposite, property - such as the positron, which is like an electron but positively rather than negatively charged - are collectively known as antimatter. Direct studies of collisions between particles of matter and those of antimatter using giant facilities such as those at CERN can advance our understanding of the nature of matter. A new study by Tasko Grozdanov from the University of Belgrade in Serbia and Evgeni Solov’ev from the Institute of Nuclear Research near Moscow in Russia has mapped the energy levels of an exotic form of helium produced in this way. This work, which is published in EPJ D, has been described by one commentator as ”... a new jewel in the treasure of scientific achievements in atomic physics theory”.
- Published on 25 February 2020
Updated mathematical techniques which can distinguish between two types of ‘non-Gaussian curve’ could make it easier for researchers to study the nature of quantum entanglement.
Quantum entanglement is perhaps one of the most intriguing phenomena known to physics. It describes how the fates of multiple particles can become entwined, even when separated by vast distances. Importantly, the probability distributions needed to define the quantum states of these particles deviate from the bell-shaped, or ‘Gaussian’ curves which underly many natural processes. Non-Gaussian curves don’t apply to quantum systems alone, however. They can also be composed of mixtures of regular Gaussian curves, producing difficulties for physicists studying quantum entanglement. In new research published in EPJ D, Shao-Hua Xiang and colleagues at Huaihua University in China propose a solution to this problem. They suggest an updated set of equations which allows physicists to easily check whether or not a non-Gaussian state is genuinely quantum.
- Published on 14 February 2020
The French theoretical physicist Franck Laloë presents a modification of Schrödinger’s famous equation that ensures that all measured states are unique, helping to solve the problem that is neatly encompassed in the Schördinger’s cat paradox.
The paradox of Schrödinger’s cat – the feline that is, famously, both alive and dead until its box is opened – is the most widely known example of a recurrent problem in quantum mechanics: its dynamics seems to predict that macroscopic objects (like cats) can, sometimes, exist simultaneously in more than one completely distinct state. Many physicists have tried to solve this paradox over the years, but no approach has been universally accepted. Now, however, theoretical physicist Franck Laloë from Laboratoire Kastler Brossel (ENS-Université PSL) in Paris has proposed a new interpretation that could explain many features of the paradox. He sets out a model of this possible theory in a new paper in EPJ D.
- Published on 04 February 2020
A new study describes how the amino acid, glutamine, is broken up when bombarded with different doses of electrons. This has implications for cancer radiotherapy and understanding the origin of life.
Small organic molecules, including the amino acids that form the ‘building blocks’ of proteins in living cells, fragment to form ions under the impact of high-energy radiation such as electron beams. A new study published in EPJ D has now shown what happens when electrons collide with one amino acid, glutamine. The extent of the damage and the nature of the ions formed are both affected by the energy of the colliding electrons. This work arises from a collaboration between experimental physicists led by Alexander Snegursky at the Institute of Electron Physics, Uzhgorod, Ukraine and theoreticians led by Jelena Tamuliene at Vilnius University, Vilnius, Lithuania.
- Published on 23 December 2019
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.
- Published on 18 December 2019
EPJ is pleased to announce that Prof Sylwia Ptasinska of the University of Notre Dame, USA has been appointed as an Editor-in-Chief for EPJ D, effective January 2020. She will be responsible for the plasmas section of the journal, and succeeds Prof Holger Kersten, who steps down after five years in the role. A faculty member at Notre Dame since 2010, her research focuses on understanding the variety of processes occurring in heterogeneous systems, including plasmas and interfaces. Though experimental investigations in her laboratory address fundamental questions, the goal of her team is to apply this research in areas such as energy, medicine, and industry. Sylwia Ptasinska is a member of the Executive Committee for the Gaseous Electronics Conference (GEC) and is also the local chair of the next POSMOL meeting. She has been a member of the Editorial Board for EPJD since 2015.
- Published on 16 December 2019
A new prototype design doubles the frequencies of widely used telecommunications lasers to study the dynamics of cold atoms while in space.
By tracking the motions of cold atom clouds, astronomers can learn much about the physical processes which play out in the depths of space. To make these measurements, researchers currently use instruments named ‘cold atom inertial sensors’ which, so far, have largely been operated inside the lab. In new work published in EPJ D, a team of physicists at Muquans and LNE-SYRTE (the French national metrology laboratory for time, frequency and gravimetry) present an innovative prototype for a new industrial laser system. Their design paves the way for the development of cold atom inertial sensors in space.
- Published on 13 December 2019
A new theoretical study of the interaction between positrons and simple tetrahedral and octahedral molecules agrees with experimental work and could have useful implications for PET scanning techniques.
Antiparticles - subatomic particles that have exactly opposite properties to those that make up everyday matter - may seem like a concept out of science fiction, but they are real, and the study of matter-antimatter interactions has important medical and technological applications. Marcos Barp and Felipe Arretche from the Universidade Federal de Santa Catarina, Brazil have modelled the interaction between simple molecules and antiparticles known as positrons and found that this model agreed well with experimental observations. This study has been published in EPJ D.
- Published on 02 December 2019
A new theoretical model predicts how protons will collide with hydrogen atoms which have been excited to higher energy levels, over a wide range of impact energies
The motions of plasmas may be notoriously difficult to model, but they can be better understood by analysing what happens when protons are scattered by atoms of hydrogen. In itself, this property is characterised by the size of a particular area surrounding the atom, known as its ‘cross section’. In new research published in EPJ D, Anthony Leung and Tom Kirchner at York University in Canada used new techniques to calculate the cross sections of atoms which have been excited to higher energy levels. They analysed the behaviour over a wide range of impact energies.