Observation of the β-delayed protons from 25Si by means of a recoil mass separator and β-proton coincidence method

Nuclear spectroscopy based on the decay of unstable nuclei away from the stable β-rays towards the proton-rich side has been used widely since the 1960s, when the β-delayed proton decay phenomenon was found in 25Si. The nuclei of Tz=-3/2 and A=4n+1 were examined extensively in the 1960s and 1970s. However, the β transition intensity has been determined only for 17Ne and 41Ti. Here, a recoil nucleus mass analyzer is used for mass separation of unstable nuclei, and the decay process is observed by the beta-proton coincidence method. Mass analysis serves to eliminate the effects of other proton-releasing nuclei. β-proton coincidence measurement serves to determine the β branching ratio, identify the excitation level, and reduce the background. Investigations demonstrate that the β-delayed proton decay of 25Si can be successfully measured by this approach, and the branching ratio of the β-decay and the value of <στ>2 are determined experimentally. In addition, a proton peak that corresponds to the β-transition to the Ex(25Al*)=2.763MeV is identified at Ep=367keV. (N.K.)