Quantum mechanics makes it easy to describe hydrogen, the simplest atom, but bigger atoms are more complicated owing to interactions between their electrons. It is especially difficult to predict the dynamics of atomic reactions during a collision. Now a team including RIKEN researchers has shed more light on this problem by performing collision experiments with slow beams of particles called antiprotons (1).
The researchers, based at the CERN particle accelerator complex in Switzerland, bombarded helium atoms with antiprotons. There is particular demand to do this with very slow antiproton beams, because current theories may not be accurate for low-energy collisions.
“Ionization by an antiproton, a unique heavy negative particle, is in itself quite exotic,” explains RIKEN scientist Yasunori Yamazaki. “In addition to this, helium is one of the most important targets to study collision dynamics because it has two electrons with a strong correlation between them.”
At CERN, antiprotons are produced in a nuclear reaction which gives them very high energies measured in billions of electron volts. They are then collected in an AD (antiproton decelerator), cooled and decelerated, so that their energies are reduced to a few million electron volts.
Yamazaki and co-workers constructed a new ‘radio frequency quadrupole decelerator’ and a ‘multi-ring trap’ to reduce the antiproton energy further down to a fraction of an electron volt, before re-accelerating them to 3,000–25,000 electron volts. This corresponds to speeds around 6,000 meters per second—very slow in particle accelerator terms.
The researchers directed their beam of slow antiprotons onto a jet of helium and argon, and monitored the energies of ions created. Their results show that the new theoretical models of low energy reactions are working, as Yamazaki explains.
“The previous experimental data did not agree with any reasonable theories, so there were big discussions on whether we forgot to include some important effects,” he says. “The good news is that it looks like our understanding on the collision dynamics of a slow antiproton and helium atom is now within satisfactory levels.”
Yamazaki and co-workers plan to develop more sophisticated equipment in order to achieve even lower antiproton energies, and observe not only the ions created during collisions, but also the electrons ‘knocked off’ the atoms. At lower energies the antiproton may get trapped in an orbit of the target atom, creating an interesting ‘molecule’ called an antiprotonic atom. The data could even help scientists investigating the use of antiprotons in treating cancer.
1. Knudsen, H., Kristiansen, H.-P.E., Thomsen, H.D., Uggerhøj, U.I., Ichioka, T., Møller, S.P., Hunniford, C.A., McCullough, R.W., Charlton, M., Kuroda, Y., et al. Ionization of helium and argon by very slow antiproton impact. Physical Review Letters 101, 043201 (2008).
The corresponding author for this highlight is based at the RIKEN Atomic Physics Laboratory
New quantum phenomena in graphene superlattices
19.09.2017 | Graphene Flagship
Solar wind impacts on giant 'space hurricanes' may affect satellite safety
19.09.2017 | Embry-Riddle Aeronautical University
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...
Scientists from the MPI for Chemical Energy Conversion report in the first issue of the new journal JOULE.
Cell Press has just released the first issue of Joule, a new journal dedicated to sustainable energy research. In this issue James Birrell, Olaf Rüdiger,...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
19.09.2017 | Event News
19.09.2017 | Physics and Astronomy
19.09.2017 | Power and Electrical Engineering