What is it about?

We have shown how to make a beam of excited state (2S) positronium atoms that we hope to use for microwave spectroscopy experiments. Positronium is an atomic system made of a positron and an electron, bound together in the same way as a hydrogen atom. Because positrons and electrons tend to destroy each other in a process called annihilation, these atoms don't live for a very long time. However, if they are in excited states they can live for longer, and can be used for different kinds of experiments. We have made a beam of atoms that are in the 2S excited state by passing a positron beam through a gas cell filled with Xe.

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Why is it important?

This beam will be useful for spectroscopy of the excited positronium states because we can control the speed of the positronium beam by controlling the speed of the positron beam. It will allow us to do experiments in a different way compared to what has been done before, and we are hoping to use some well-known interference methods (known as the Ramsey method of seperated oscillatory fields) to get to high precision using this new approach.


This beam will transform the way we do microwave spectroscopy because it will (we hope) make it possible to use more advanced methods than have previously been employed. The fast beam of positronium is markedly different to the usual slow positronium atoms generated from solid state materials, and opens the door to using seperated fields for interferometry measurements. These methods have been shown to be capable of more precise measurements, and the prospect of using them for positronium experiments is very exciting!

David Cassidy
University College London

Read the Original

This page is a summary of: An energy tunable continuous 23S1 positronium beam, Review of Scientific Instruments, August 2023, American Institute of Physics, DOI: 10.1063/5.0167125.
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