6533b7d4fe1ef96bd1262790

RESEARCH PRODUCT

Spectroscopy of excited state positronium

subject

description

Electric dipole transitions in the microwave range have been induced between the fine-structure levels of positronium in the excited staten=2. As an indication of the transitions, we used the increase in Lyman-α radiation when the metastable 23S1-level is depopulated. The results for the transitions 23S1→23P0,1,2 areΝ 0=18499.65±1.20±4.00 MHz,Ν 1=13012.42 ±0.65±1.54 MHz andΝ 2=8624.38±0.54±1.40 MHz. The first error is statistical and the second systematic. The precision of the present measurement has improved by a factor of 3, compared to previous data. Recent bound state QED-calculations have been extended to the orderR t8 α 4lnα −1. The not yet completely calculated orderR t8 α 4 is estimated to contribute less than 1 MHz. Our experimental results are in good agreement with theory. By applying a weak magnetic field, we were able to observe the transition 23S1→21P1 which is strictly forbidden byC-invariance in zero field. Our result, corrected for Zeeman- and motional Starkeffect, isΝ 3=11180.0±5.0±4.0 MHz. An upper limit for theC-violating matrix element of $$|\langle 2^1 P_1 |H_ \not\subset |2^3 P_1 \rangle |< 76$$ MHz could be deduced. Our experiment used moderated slow positrons from the bremsstrahlung and pair production of a pulsed electron linear accelerator (TEPOS facility at the university of Giessen).