Abstract. Beta-delayed proton emission from 21 Mg has been measured at ISOLDE, CERN, with a detection setup including particle identification capabilities. β-delayed protons with center of mass energies between 0.39 MeV and 7.2 MeV were measured and used to determine the half life of 21 Mg as 118.6±0.5 ms. From a line shape fit of the βp branches we extract spectroscopic information about the resonances of 21 Na. Finally an improved interpretation of the decay scheme in accordance with the results obtained in reaction studies is presented.PACS. 23.40.Hc Relation with nuclear matrix elements and nuclear structure -27.30.+t 20 ≤ A ≤ 38 -29.30.Ep Charged-particle spectroscopy

Beta-delayed proton emission from 20 Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 26 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in 20 Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in 20 Na is observed. This may allow studies of the 4032.9(2.4) keV resonance in 19 Ne through the beta decay of 20 Mg, which is important for the astrophysically relevant reaction 15 O(α, γ) 19 Ne. Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 90.9(1.2) ms. PACS. 23.20.Lv γ transitions and level energies-26.30.Ca Explosive burning in accreting binary systems (novae, x-ray bursts)-27.30.+t 20 ≤ A ≤ 38-29.30.Ep Charged-particle spectroscopy

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We report on an attempt to reproduce the observation of β −-delayed proton emission from 11 Be through detection of the final state nucleus 10 Be with accelerator mass spectrometry. Twelve samples were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination to be carried out. The observed amounts of 10 Be per collected 11 Be rule out several contamination sources, but do not agree internally. Formation of BeH molecular ions in the ion source may explain our data, in which case an upper limit of the βp branching ratio of 2.2 • 10 −6 can be derived.

We have observed β + -delayed α and pα emission from the proton-rich nucleus 21 Mg produced at the ISOLDE facility at CERN. The assignments were cross-checked with a time distribution analysis. This is the third identified case of βpα emission. We discuss the systematic of beta-delayed particle emission decays, show that our observed decays fit naturally into the existing pattern, and argue that the patterns are to a large extent caused by odd-even effects.

The 12 C(α, γ) 16 O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced α width, γ11, of the bound 1 − level in 16 O is particularly important to determine the cross section. The magnitude of γ11 is determined via sub-Coulomb α-transfer reactions or the β-delayed α decay of 16 N, but the latter approach is presently hampered by the lack of sufficiently precise data on the β-decay branching ratios. Here we report improved branching ratios for the bound 1 − level [b β,11 = (5.02 ± 0.10) × 10 −2 ] and for β-delayed α emission [b βα = (1.59 ± 0.06) × 10 −5 ]. Our value for b βα is 33% larger than previously held, leading to a substantial increase in γ11. Our revised value for γ11 is in good agreement with the value obtained in α-transfer studies and the weighted average of the two gives a robust and precise determination of γ11, which provides significantly improved constraints on the 12 C(α, γ) cross section in the energy range relevant to hydrostatic He burning.

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The rare β-decay channel of 6 He into the α + d continuum was investigated at the REX-ISOLDE facility. Bunches of postaccelerated 6 He ions were implanted into the optical time projection chamber (OTPC), where the decays with emission of charged particles were recorded. This novel technique allowed us to extend the low-energy end of the spectrum down to 150 keV in α + d center of mass, corresponding to a deuteron energy of 100 keV. The branching ratio for this process amounts to [2.78 ± 0.07(stat) ± 0.17(sys)] × 10 −6. The shape of the spectrum is found to be in a good agreement with a three-body model, while the total intensity is about 20% larger than the predicted one.