On the alpha decay of 109I and its implications for the proton decay of 105Sb

In an experiment at the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility, the very small α‐decay branch of 109I, bα = (1.4±0.4)⋅10−4, has been measured. The Qα‐value for this transition allowed for the determination of Qp(105Sb) = 356±22 keV, about 130 keV lower than previously claimed. This difference increases the partial half‐life for proton decay by several orders of magnitude, making the probability of observing direct proton decay of 105Sb very small, much below any previous experimental limit. The results and consequences for the astrophysical rp‐process are discussed.