Berlin 2005 – wissenschaftliches Programm
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A: Atomphysik
A 11: Ion-Atom/Molecule Collisions, Exotic Atoms
A 11.5: Fachvortrag
Montag, 7. März 2005, 17:30–17:45, HU 3075
A new Measurement of the Decay Rate of the Positronium Negative Ion — •F. Fleischer1, G. Gwinner1, K. Degreif1, M. Lestinsky1, V. Liechtenstein2, F. Plenge1, and D. Schwalm1 — 1MPI für Kernphysik, 69029 Heidelberg — 2Kurchatov Institute, Moscow
Consisting of two electrons and a positron, the
positronium negative ion (Ps−) represents the simplest
three-body-system with a bound state. As no perturbations due to
strong interactions have to be considered and because of its unique
mass ratio the system provides interesting opportunities to test our
understanding of the three-body problem and quantum electrodynamics.
Previous experiments have so far only proved the existence of Ps−
[1] and determined the decay rate with 4% accuracy [2]. To allow for
a test of radiative corrections and bound-state contributions to the
decay rate an increase in precision is necessary. Other parameters of
particular interest are the photodetachment cross section with its
narrow resonances predicted around the Ps(n=2,3,4…) threshold
and the 3γ/2γ-branching ratio. An experiment has been
built up at the MPI für Kernphysik to investigate the decay rate and
other properties of Ps− in more detail. The results of a new
measurement of the decay rate as well as possibilities for further
experiments concerning the properties of Ps− — using the
new high-flux positron source NEPOMUC at the FRM II research reactor
in Munich — will be discussed.
[1] A.P. Mills, Jr., Phys. Rev. Lett. 46, 717(1981)
[2] A.P. Mills, Jr., Phys. Rev. Lett. 50, 671(1983)