Spectroscopy of the fundamental few-lepton systems Ps and Ps-

将对纯轻子少数几体系统Ps-(e+e-e-)和Ps(e+e-)的性质进行精确实验，利用Garching FRM II上前所未有的正电子源强度。Ps-的衰减率将被测量到大约0.1%的精度，从而允许在这个基本的三体系统中对QED预测进行灵敏的测试。首次测量了Ps-的光剥离截面以及自电离双激发Ps-共振态，从而首次确定了Ps-的结合能，并与精确的理论预测进行了比较。Ps的光致电离将允许产生一束纯的、能量可变的3S1ps光束。使用不同的ps产生方法和与ps激发相同的激光系统，设想对3s1ps的1s-2s跃迁频率进行基础精度研究，目的是基于前所未有的正电子源强度和利用频率梳技术进行超精密频率测量，将目前的最佳实验值提高一个数量级。

Precision experiments will be performed on the properties of the purely leptonic fewbody systems Ps- (e+e-e-) and Ps (e+e-), exploiting the unprecedented intensity of the positron source at the FRM II in Garching. The decay rate of Ps- will be measured to an accuracy of about 0.1%, thus allowing for sensitive tests of QED predictions in this fundamental 3-body system. For the first time the photodetachment cross section of Ps- will be measured as well as autoionizing doubly-excited Ps- resonance states, allowing for the first determination of the binding energy of Ps- and a comparison with precise theoretical predictions. Photo-ionization of Ps- will allow to produce a pure, energy-variable 3S1 Ps beam. Using a different Ps production method and the same laser system as for the Ps- excitation, fundamental precision studies on the 1S-2S transition frequency in 3S1 Ps are envisaged, aiming at an improvement of the present best experimental value by an order of magnitude based on the unprecedented intensity of the positron source and the ultra-precise frequency measurement using the frequency comb technology.