The measurement of positronium atom n = 2 states

With Delay-Coincide technique, the n = 2 states of the Ps atom can be confirmed by measuring the lifetime of the Ps 13S1 state, in which the Ps de-exciting signal is used as start signal and the annihilating γ photon of the de-excited Ps ground state, stop one. According to the detector efficiency of this experiment measurement system and the absolute intensity of the Ps atom, the experiment tells, after considering the e+-beam transfer magmatic field correction of the detector efficiency, that only about 1% Ps atoms are on their n = 2 states, which agrees with that of the previous reports