Systematic trends in beta-delayed particle emitting nuclei: The case of beta-p-alpha emission from 21Mg

We have observed beta+-delayed alpha and p-alpha emission from the proton-rich nucleus 21Mg produced at the ISOLDE facility at CERN. The assignments were cross-checked with a time distribution analysis. This is the third identified case of beta-p-alpha 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.Comment: 6 pages, 5 figure

Thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC)

The thermal neutron background at Laboratorio Subterráneo de Canfranc (LSC) has been determined using several He proportional counter detectors. Bare and Cd shielded counters were used in a series of long measurements. Pulse shape discrimination techniques were applied to discriminate between neutron and gamma signals as well as other intrinsic contributions. Montecarlo simulations allowed us to estimate the sensitivity of the detectors and calculate values for the background flux of thermal neutrons inside Hall-A of LSC. The obtained value is (3.5±0.8)×10 n/cms, and is within an order of magnitude compared to similar facilities.This work was supported partially by the Spanish Ministerio de Ciencia e Innovación and its Plan Nacional de I+D+i de Física de Partículas projects: FPA2016-76765-P and FPA2018-096717-B-C21. The authors want to acknowledge the help provided by the staff at LSC in the preparation and support for this work

Second T = 3/2 state in 9^9B and the isobaric multiplet mass equation

Recent high-precision mass measurements and shell model calculations~[Phys. Rev. Lett. {\bf 108}, 212501 (2012)] have challenged a longstanding explanation for the requirement of a cubic isobaric multiplet mass equation for the lowest $A = 9$ isospin quartet. The conclusions relied upon the choice of the excitation energy for the second $T = 3/2$ state in $^9$B, which had two conflicting measurements prior to this work. We remeasured the energy of the state using the $^9{\rm Be}(^3{\rm He},t)$ reaction and significantly disagree with the most recent measurement. Our result supports the contention that continuum coupling in the most proton-rich member of the quartet is not the predominant reason for the large cubic term required for $A = 9$ nuclei

Beta-delayed proton emission from ²¹Mg

16 pags.; 9 figs.; 6 tabs.© 2015, SIF, Springer-Verlag Berlin Heidelberg. Beta-delayed proton emission from 21Mg has been measured at ISOLDE, CERN, with a detection setup consisting of two charged-particle telescopes surrounding the decay point. Altogether 27 βp branches were measured with center-of-mass energies between 0.4–7.2 MeV. Seven new βp branches were observed. Beta-delayed protons were used to determine the half-life of 21Mg as 118.6 ± 0.5 ms. From a line shape fit of the βp branches we extract the widths, spins, and parities of the resonances of 21Na. An improved interpretation of the decay scheme in accordance with the results obtained in reaction studies is presented.This work has been supported by the European Commision within the Seventh Framework Programme “European Nuclear Science and Applications Research”, contract no. 262010 (ENSAR), and by the Spanish research agency under number FPA2012-32443.Peer Reviewe

Study of bound states in 12Be through low-energy 11Be(d,p)-transfer reactions

The bound states of 12Be have been studied through a 11Be(d,p)12Be transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of 11Be was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in 12Be. The gamma-ray detection enabled a clear identification of the four known bound states in 12Be, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from DWBA calculations and have been compared to previous experimental and theoretical results

Reaction of the halo nucleus be on heavy targets at energies around the coulomb barrier

Presented at the XXXIII Mazurian Lakes Conference on Physics, Piaski, Poland, September 1–7, 2013.-- et al.New data for the reaction 11Be on 197Au at E lab = 31:9 MeV are presented. The angular distributions of the inelastically scattered 11Be and the 10Be fragments coming from the 11Be dissociation have been extracted and compared with semiclassical and coupled-channels calculations in an angular range θlab = 13deg;-46deg; for the detected Be fragment.This work was supported by the Spanish Government under the projects FPA2009-07387, FPA2009-07653, FPA2009-08848, FPA2012-32443 and Consolider CPAN CSD2007-00042; the Helmholtz Association (HGT) through the Nuclear Astrophysics Virtual Institute (VH-VI-417); ATI Sistemas; a Natural Sciences and Engineering Research Council of Canada grant. TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada.Peer Reviewe

Scattering of the Halo Nucleus 11Be on 197Au at Energies around the Coulomb Barrier

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus 11Be on197 Au were measured at energies below (Elab =31.9 MeV) and around (39.6 MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of 11Be on a high-Z target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the β (E1) distribution in 11Be, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in 11Be.Ministerio de Economía y Competitividad FPA2015-64969-P, FIS2014-53448-C2-1-P, FPA2013-47327-c02-01-R, FPA2012-32443, FIS2013-41994-PCentro Nacional de Física de Partículas, Astropartículas y Nuclear CSD2007- 00042European Collaborative Research EUI-2009-04162European Unions 654002Nuclear Astrophysics Virtual Institute VH-VI-417European Commission, Seventh Framework Program 60037

Study of proton-unbound states in 24Al^{24}{\rm Al} relevant for the 23Mg(p,γ)^{23}{\rm Mg}(p,\gamma) reaction in novae

Background: The nucleosynthesis of several proton-rich nuclei is determined by radiative proton-capture reactions on unstable nuclei in nova explosions. One such reaction is $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$, which links the NeNa and MgAl cycles in oxygen-neon (ONe) novae. Purpose: To extract $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonance strengths from a study of proton-unbound states in $^{24}{\rm Al}$, produced via the $^{24}$Mg($^{3}$He,$t$) reaction. Methods: A beam of $^3 {\rm He}^{2+}$ ions at 50.7 MeV was used to produce the states of interest in $^{24}$Al. Proton-triton angular correlations were measured with a $K=600$ QDD magnetic spectrometer and a silicon detector array, located at iThemba LABS, South Africa. Results: We measured the excitation energies of the four lowest proton-unbound states in $^{24}$Al and place lower-limits on $\Gamma_p/\Gamma$ values for these four states. Together with USD-C shell-model calculations of partial gamma widths, the experimental data are also used to determine resonance strengths for the three lowest $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonances. Conclusions: The energy of the dominant first $^{23}{\rm Mg}(p,\gamma)$ resonance is determined to be $E_{r} = 481.4 \pm 1.1$ keV, with a resonance strength $\omega \gamma = 18 \pm 6$ meV

Scattering of light halo nuclei on heavy target at energies around the Coulomb barrier

This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0.-- et al. and the E1104 S1202 collaborations at TRIUMF.-- Trabajo presentado a la: "25th International Nuclear Physics Conference" (INPC), celebrada en Firenze (Italia) del 2 al 7 de junio de 2013.We report here on experiments performed at TRIUMF to study the scattering of the light halo nuclei 11Li on lead at energies below and around the Coulomb barrier. The the elastic and break-up differential cross section are interpreted in the framework of Continuum-Discretized Coupled-Channel calculations. The departure from Rutherford scattering at energies below the barrier is well beyond the behavior of normal nuclei.This work was supported by the Spanish CICYT under the project numbers FPA2009-07387, FPA2012-32443, FPA2009-08848, FPA2009-07653, and FPA2010-22131-C02-01 and by the Consolider Ingenio 2010 Program CPAN (CSD2007- 00042).Peer Reviewe