In-beam studies of proton emitters using the Recoil-Decay Tagging method

The last five years have witnessed a rapid increase in the volume of data on proton decaying nuclei. The path was led by decay studies with recoil mass separators equipped with double-sided Si strip detectors. The properties of many proton-decaying states were deduced, which triggered renewed theoretical interest in the process of proton decay. The decay experiments were closely followed by in-beam γ-ray studies which extended one's knowledge of high-spin states of proton emitters. The unparalleled selectivity of the Recoil-Decay Tagging method combined with the high efficiency of large arrays of Ge detectors allowed, despite small cross sections and overwhelming background from strong reaction channels, the observation of excited states in several proton emitters. Recently, in-beam studies of the deformed proton emitters 141Ho and 131Eu have been performed with the GAMMASPHERE array of Ge detectors and the Fragment Mass Analyzer at ATLAS. Evidence was found for rotational bands in 141Ho and 131Eu. The deformations and the single-particle configurations proposed for the proton emitting states from the earlier proton-decay studies were confronted with the assignments deduced based on the in-beam data. It should be noted that the cross section for populating 131Eu is only about 50 nb, and it represents the weakest channel ever studied in an in-beam experiment