From the stable to the exotic: clustering in light nuclei

A great deal of research work has been undertaken in alpha-clustering study since the pioneering discovery of 12C+12C molecular resonances half a century ago. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of the superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Evolution of clustering from stability to the drip-lines is examined: clustering aspects are, in particular, discussed for light exotic nuclei with large neutron excess such as neutron-rich Oxygen isotopes with their complete spectroscopy.Comment: 15 pages, 5 figures, Presented at the International Symposium on "New Horizons in Fundamental Physics - From Neutrons Nuclei via Superheavy Elements and Supercritical Fields to Neutron Stars and Cosmic Rays" held at Makutsi Safari Farm, South Africa, December 23-29, 2015. arXiv admin note: substantial text overlap with arXiv:1402.6590, arXiv:1303.0960, arXiv:1408.0684, arXiv:1011.342

Beta-delayed proton emission from 20Mg

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 27 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 15O( $\alpha$ , $\gamma$ )19Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 91.4(1.0)ms

Three-body effects in the Hoyle-state decay

We use a sequential R-matrix model to describe the breakup of the Hoyle state into three α particles via the ground state of Be8. It is shown that even in a sequential picture, features resembling a direct breakup branch appear in the phase-space distribution of the α particles. We construct a toy model to describe the Coulomb interaction in the three-body final state and its effects on the decay spectrum are investigated. The framework is also used to predict the phase-space distribution of the α particles emitted in a direct breakup of the Hoyle state and the possibility of interference between a direct and sequential branch is discussed. Our numerical results are compared to the current upper limit on the direct decay branch determined in recent experiments.status: publishe

Analysis of the response of silicon detectors to α particles and 16O ions

We clarify basic concepts concerning the response of silicon detectors to ionizing radiation, focusing on light ions with energies ranging from a few hundred keV to a few MeV. Through reanalysis of existing experimental data, we quantify the difference in the response of silicon detectors to α particles and 16O ions, and we determine the correction that must be made before an energy calibration obtained with α particles can be applied to the measurement of 16O ions. Finally, we show that an apparent disagreement among three recent measurements of the decay spectrum of 8B can be explained by a failure to correctly take into account the different response of silicon detectors to α particles and 16O ions.status: publishe

Inverse Kinematic Study of the Al26g(d,p)Al27 Reaction and Implications for Destruction of Al26 in Wolf-Rayet and Asymptotic Giant Branch Stars

In Wolf-Rayet and asymptotic giant branch (AGB) stars, the Al26g(p,γ)Si27 reaction is expected to govern the destruction of the cosmic γ-ray emitting nucleus Al26. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the Al26g(d,p)Al27 reaction as a method for constraining the strengths of key astrophysical resonances in the Al26g(p,γ)Si27 reaction. In particular, the results indicate that the resonance at Er=127  keV in Si27 determines the entire Al26g(p,γ)Si27 reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars

Inverse Kinematic Study of the Al26g(d,p)Al27 Reaction and Implications for Destruction of Al26 in Wolf-Rayet and Asymptotic Giant Branch Stars

In Wolf-Rayet and asymptotic giant branch (AGB) stars, the Al26g(p,γ)Si27 reaction is expected to govern the destruction of the cosmic γ-ray emitting nucleus Al26. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the Al26g(d,p)Al27 reaction as a method for constraining the strengths of key astrophysical resonances in the Al26g(p,γ)Si27 reaction. In particular, the results indicate that the resonance at Er=127  keV in Si27 determines the entire Al26g(p,γ)Si27 reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars

Fusion Cross Sections of Astrophysics Interest Within the STELLA Project

Low energy fusion between light heavy-ions is a key feature of the evolution of massive stars. In systems of astrophysical interest, the process may be strongly affected by molecular configurations of the compound nucleus, leading to resonant S factors. In particular, the 12C+12C fusion reaction has been the object of numerous experimental investigations. The STELLA project has been developed to extend these investigations to lower energies towards the Gamow window

Detailed study of the decay of 21^{21}Mg

Beta-delayed proton and gamma emission in the decay of $^{21}$Mg has been measured at ISOLDE, CERN with the ISOLDE Decay Station (IDS) set-up. The existing decay scheme is updated, in particular what concerns proton transitions to excited states in $^{20}$Ne. Signatures of interference in several parts of the spectrum are used to settle spin and parity assignments to highly excited states in $^{21}$Na. The previously reported $\beta$p$\alpha$ branch is confirmed. A half-life of 120.5(4) ms is extracted for $^{21}$Mg. The revised decay scheme is employed to test mirror symmetry in the decay and to extract the beta strength distribution of $^{21}$Mg that is compared with theory