Ps- photodetachment spectroscopy and its application

203 (RIBF)



The 23rd Nuclear Spectroscopy Laboratory Seminar
第23回 核分光研セミナー
Lecturer: 長嶋 泰之 (東京理科大学 理学部第二部物理学科)

Title: Ps- photodetachment spectroscopy and its application

Language: Japanese (slides in English)

Date: Oct. 18 (Wed.), 2016, 13:30-

Place: RIBF #203

Abstract: One electron can bind to a positron to form a positronium (Ps) atom. Another electron can further weakly bind to Ps to form a positronium negative ion (Ps-). Ps- is a bound state through Coulomb interaction composed of three leptons with equal rest masses. Thus Ps- provides an ideal testing ground for quantum three-body problems and many theoretical investigations have been performed since its prediction by Wheeler in 1946. Its decay rate, ground state energy and magnetic moment have been precisely calculated. Although there are no excited states of Ps-, its resonance states have been predicted and the resonance energies have been calculated.
In spite of active theoretical investigations, only a few experimental studies on Ps- have been performed because of the low production efficiency of Ps- (< 0.03%) until a decade ago. In 2008, a dramatic increase in the efficiency up to 1.9 % was accomplished using alkali-metal coated surfaces. This has opened a new era for the experimental investigations of Ps- [1]. The first observation of its photodetachment has been performed. Its shape resonance has also been observed and the resonance energy has been recently determined [2]. Moreover, a high-brightness and collimated energy-variable Ps beam has been developed using the photodetachment technique and applied for the studies of Ps scattering from surfaces.
[1] Y. Nagashima, Phys. Rep. 545, 95 (2014) and references therein.
[2] K. Michishio et al., Nat. Commun. 7, 11060 (2016).

Host laboratory: Nuclear spectroscopy laboratory

Contact person: Aiko Takamine
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