Synopsis: Decrypting krypton

Improved data from positron scattering off krypton may lead to advances in certain techniques in tomography and spectroscopy.

An electron and its antimatter counterpart—a positron—can annihilate each other to leave behind a distinct signature of gamma rays. At certain incident energies, however, the particles combine to form positronium. It too decays into gamma rays, but after a lifetime of tens of nanoseconds, enough time for it to wander away from the nuclear core to interstitial regions of materials such as nanostructures and biological matter. Gamma-ray emissions from nuclear and interstitial sites produce a comprehensive image of a material, forming the basis of positron emission tomography (PET) and positron annihilation lifetime spectroscopy.

In a paper in Physical Review A, Casten Makochekanwa at the ARC Centre for Antimatter-Matter Studies in Australia and his coauthors present cross-section measurements of positron scattering off an atomic target (krypton). The measurements are compared with earlier results in the literature, providing a history of the progress in this field. While current experimental and theoretical techniques produce generally good agreement, some energy regimes, for example that for positronium formation, still exhibit disagreements at the 20% level. While this work demonstrates progress, more sophisticated calculations and measurements are planned that should narrow these differences and provide guidance for extension to more complex systems at the nanoscale. – Lee Collins and Jihane Mimih


Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Interdisciplinary Physics

Control of rare events

Read More »

Next Synopsis

Graphene

Imaging puddles

Read More »

Related Articles

Viewpoint: Ionization Delays That Stand Out
Optics

Viewpoint: Ionization Delays That Stand Out

Attosecond-resolution experiments have determined the delay in an electron’s emission from a molecule after being ionized with light. Read More »

Focus: Giant Molecule Made from Two Atoms
Atomic and Molecular Physics

Focus: Giant Molecule Made from Two Atoms

Experiments confirm the existence of 1-micrometer-sized molecules made of two cesium atoms by showing that their binding energies agree with predictions.   Read More »

Focus: Choose the Number of Atoms in Your Cloud
Atomic and Molecular Physics

Focus: Choose the Number of Atoms in Your Cloud

A new technique allows researchers to specify the number of atoms in an ultracold cloud (in the millions) and then to reproduce that same number in repeated experiments. Read More »

More Articles