Bonn 2010 – wissenschaftliches Programm
HK 54.8: Vortrag
Donnerstag, 18. März 2010, 18:45–19:00, HG V
A New Decay Rate Measurement of the Negative Positronium Ion† — •Stefan Alexander Gärtner1, Hubert Ceeh2, Frank Fleischer3, Christoph Hugenschmidt2, Klaus Schreckenbach2, Dirk Schwalm4, and Peter Thirolf1 — 1Ludwig-Maximilians-Universität München, Garching, Germany — 2Technische Universität München and FRM II, Garching, Germany — 3University of Washington, Seattle, USA — 4Max-Planck-Institut für Kernphysik, Heidelberg, Germany
The results of a new decay rate measurement of the Ps− ion (e+e−e−) at the NEPOMUC high flux positron source (≈ 4·107 remoderated positrons per second) at the FRM II reactor in Garching are shown. The setup utilizes ≈ 5 nm thin Diamond Like Carbon (DLC) foils for the Ps− production as well as for stripping off the electrons, which takes place immediately after the acceleration across a variable length gap. This technique has been employed by a previous experiment  in Heidelberg using a 22Na source resulting in the most recent decay rate value of Γ = 2.089(15) ns−1. Higher statistics led to new insight into systematic errors, which could be improved by an electrically field-free decay gap, thus yielding an error of ≈ 0.2 %, which allows to test QED  for this fundamental three-body system. In a further step the photodetachment cross section of Ps− will be measured at the two energies provided by the fundamental and second harmonic mode of a high power Nd:YAG laser for the first time.  F. Fleischer et al., Phys. Rev. Lett. 96, 063401 (2006).  M. Puchalski et al., Phys. Rev. Lett. 99, 203401 (2007). †Supported by DFG under contract HA1101/13-1.