Pionic nitrogen

A first version of the experimental set-up was successfully used at CERN on LEAR (Low Energy Antiproton Ring), to study 3d -> 2p transitions in antiprotonic hydrogen and deuterium [4], to obtain information on the antiproton-nucleon interaction. It was also used to measure the mass of the charged pion for the first time in a low density gas, using transitions between circular levels of pionic nitrogen [5], using copper Ka transitions as X-ray standards. 

FIGURE 11.9 Spectrum of the 5 4 transitions in pionic nitrogen and muonic oxygen. 

Previous tests of the Klein-Gordon equation has been obtained from the observation of pionic titanium transitions [29] with an accuracy of 2%, and from the observation of pionic nitrogen transitions [5]. 

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