A positron trap for observing molecules containing positronium

May 22, 2023, 5:30 PM
2h 30m
Poster presentation spectroscopy of exotic atoms Poster Session 1


Alina Weiser (Austrian Academy of Sciences (AT))


A positron trap is a powerful and adaptable tool for performing experiments with positrons and positronium. These devices use a strong magnetic field, a stepped potential well and Nitrogen and CF$_4$ buffer gas. Positrons are initially trapped via the electronic excitation of N$_2$, CF$_4$ is added for efficient cooling via vibrational and rotational excitations. This type of positron trap can typically produce ~105 e+/s in bunches with a diameter of 1-2 mm and an energy spread of approximately 50 meV [e.g. 1,2].

We aim to use the positron pulses from such a trap to observe molecules containing positronium, such as PsH [3] and PsO [4] via collisions in gases such as methane and carbon dioxide. By using a high mass resolution ion spectrometer to detect fragments from dissociation, precise measurement of their binding energy will be performed.

This poster will describe the positron beam, trap, and ion spectrometer from the newly constructed positron beamline in Vienna.

[1] J. P. Sullivan, A. Jones, P. Caradonna, C. Makochekanwa, and S. J. Buckman , "A positron trap and beam apparatus for atomic and molecular scattering experiments", Review of Scientific Instruments 79, 113105 (2008).
[2] J. Clarke, D.P. van der Werf, B. Griffiths, D.C.S. Beddows, M. Charlton, H.H. Telle, P.R. Watkeys, Design and operation of a two-stage positron accumulator, Review of Scientific Instruments. 77 (2006) 063302.
[3] D.M. Schrader, F.M. Jacobsen, N.-P. Frandsen, U. Mikkelsen, Formation of positronium hydride, Phys. Rev. Lett. 69 (1992) 57–60.
[4] X. Cheng, D. Babikov, D.M. Schrader, Binding-energy predictions of positronium-atom systems, Phys. Rev. A. 85 (2012) 012503.

Primary author

Alina Weiser (Austrian Academy of Sciences (AT))

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