Mass measurements of 99-101In challenge ab initio nuclear theory of the nuclide 100Sn
Summary: Scientists at the ISOLDE/CERN facility managed to measure the nuclear mass of the rarest indium isotopes with the ISOLTRAP mass spectrometer. Since 100In is the beta-decay daughter of 100Sn, the mass of the latter could be deduced indirectly by combining the new measurement with previous beta-decay measurements of 100Sn. The results are compared to predictions of advanced nuclear theory calculations; ab initio many-body calculations. From the trends of various mass derivatives in this region, the authors reveal the discrepancy between the two previously measured 100Sn Q-values.
Why should we care?
100Sn is the heaviest doubly magic nucleus with the same neutron and proton numbers N=Z=50 that we know is stable against proton emission. The question about the doubly magic nature of this nucleus is still not fully settled, which has serious implications in nuclear physics and astrophysics. The magicity of 100Sn at the proton dripline is decisive for the end of the astrophysical rapid-proton (rp) process. In addition, 100Sn has unique nuclear structure features such as high-spin isomerism, a seniority system that introduces additional symmetries, and a super-allowed Gamow-Teller decay.
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Direct Q-Value Determination of the beta- Decay of 187Re
Summary: Researchers measured with the highest precision the smallest decay energy (Q value) of 187Re. To perform such a remarkable measurement, they used a cryogenic 5 Penning traps system named PENTATRAP, where a single highly charged ion could be trapped in each trap. Due to the high precision they reached, the small binding energy of the 29 electrons in Re and Os had to be taken into account. This involved the use of advanced relativistic multi-configuration methods calculations.
Why should we care?
The beta decay energy of 187Re to 187Os is about 2.5-keV, the smallest transition between ground states. Since beta decay involves emission of neutrinos, this transition is particularly important for the determination of the neutrino rest mass as well as for related neutrino physics.
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4D-imaging of drip-line radioactivity by detecting proton emission from 54mNi picture with ACTAR TPC
Summary: Researchers developed a remarkable new 4D-imaging technique to visualize proton radioactivity in real time. They were particularly interested in proton decay of high spin (10+) isomeric state in one of radioactive isotope of nickel with mass number A=54. The nuclear shell model describes very well the 10+ isomeric state decay in 54Fe but fails to describe its mirror decay in 54Ni. The researcher found that the reason is due to the existence of a second branch of proton decay of 10+ that previous experiment was not sensitive to.
Why should we care?
Studying differences between mirror nuclei* such as 54Ni and 54Fe is very important to understand the isospin symmetry** breaking. In fact the observation of the proton decay from 10+ isomeric state in 54Ni is the first proof of non-Coulomb origin of isospin symmetry breaking since the 10+ isomeric state in 54Fe decays only by emitting gamma rays. In addition, proton radioactivity can reveal fundamental aspects in quantum mechanics such as quantum tunneling and coupling of (quasi) bound quantum states with the continuum. Proton radioactivity is also the time-reversed process of radiative proton capture, which is important for the synthesis of elements in certain stellar scenarios such as accreting neutron stars in binary stars systems. In such astrophysical environment, rapid proton capture process takes place starting with the doubly magic 56Ni as a seed nucleus.
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* Mirror nuclei have the same mass number A, but with reversed proton (Z) and neutron (N) numbers (nucleus A1=Z1+N1, its mirror nucleus A2=Z2+N2, with A1=A2, Z1=N2 and Z2=N1).
**Isospin symmetry suggests that the nuclear force acts similarly on protons and neutrons.