Search

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Detailed spectroscopy of the neutron-deficient nucleus Ca36 was obtained up to 9 MeV using the Ca37(p,d)Ca36 and the Ca38(p,t)Ca36 transfer reactions. The radioactive nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce light ejectiles (the deuteron d or triton t) that were detected in the MUST2 detector array, in coincidence with the heavy residues identified by a zero-degree detection system. Our main findings are (i) a similar shift in energy for the 11+ and 21+ states by about -250 keV, as compared with the mirror nucleus S36; (ii) the discovery of an intruder 02+ state at 2.83(13) MeV, which appears below the first 2+ state, in contradiction with the situation in S36; and (iii) a tentative 03+ state at 4.83(17) MeV, proposed to exhibit a bubble structure with two neutron vacancies in the 2s1/2 orbit. The inversion between the 02+ and 21+ states is due to the large mirror energy difference (MED) of -516(130) keV for the former. This feature is reproduced by shell model calculations, using the sd-pf valence space, predicting an almost pure intruder nature for the 02+ state, with two protons (neutrons) being excited across the Z=20 magic closure in Ca36 (S36). This mirror system has the largest MEDs ever observed, if one excludes the few cases induced by the effect of the continuum

The B(E2, 2+ → 0+) transition strengths of the T = 1 isobaric triplet 70Kr, 70Br, 70Se, recently measured at the RIKEN Radioactive Isotope Beam Factory (RIBF), are discussed in terms of state-of-the-art large scale shell model calculations using the JUN45 and JUN45+LNPS plus Coulomb interactions. In this Letter we argue that, depending on the effective charges used, the calculations are either in line with the experimental data within statistical uncertainties, or the anomaly happens in 70Br, rather than 70Kr. In the latter case, we suggest that it can be due to the presence of a hitherto undetected 1+ T = 0 state below the yrast 2+ T = 1 state. Our results do not support a shape change of 70Kr with respect to the other members of the isobaric multiplet

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Background: The evolution of shell structure around doubly magic exotic nuclei is of great interest in nuclear physics and astrophysics. In the 'southwest' region of Ni78, the development of deformation might trigger a major shift in our understanding of explosive nucleosynthesis. To this end, new spectroscopic information on key close-lying nuclei is very valuable. Purpose: We intend to measure the isomeric and β decay of Co75, with one-proton and two-neutron holes relative to Ni78, to access new nuclear structure information in Co75 and its β-decay daughters Ni75 and Ni74. Methods: The nucleus Co75 is produced in relativistic in-flight fission reactions of U238 at the Radioactive Ion Beam Factory in the RIKEN Nishina Center. Its isomeric and β decay are studied exploiting the BigRIPS and EURICA setups. Results: We obtain partial β-decay spectra for Ni75 and Ni74, and report a new isomeric transition in Co75. The energy [Eγ = 1914(2)keV] and half-life [t1/2 = 13(6)μs] of the delayed γ ray lend support for the existence of a Jπ = (1/2-) isomeric state at 1914(2) keV. A comparison with PFSDG-U shell-model calculations provides a good account for the observed states in Ni75, but the first calculated 1/2- level in Co75, a prolate K = 1/2 state, is predicted about 1 MeV below the observed (1/2-) level. Conclusions: The spherical-like structure of the lowest-lying excited states in Ni75 is proved. In the case of Co75, the results suggest that the dominance of the spherical configurations over the deformed ones might be stronger than expected below Ni78. Further experimental efforts to discern the nature of the Jπ = (1/2-) isomer are necessary

The region of neutron-rich Cr isotopes has garnered much attention in recent years due to a rapid onset of collectivity near neutron number N=40. We report here on the first γ-ray spectroscopy beyond the (41+) state in Cr62,64, using nucleon removal reactions from several projectiles within a rare-isotope beam cocktail. A candidate for the 6+ state in Cr64 is presented as well as one for, possibly, the second excited 0+ state in Cr62. The results are discussed in comparison to the LNPS shell-model predictions that allow for neutron excitations across the N=40 harmonic oscillator gap into the g9/2 and d5/2 orbitals. The calculated level schemes for Cr62,64 reveal intriguing collective structures. From the predicted neutron particle-hole character of the low-lying states in these Cr isotopes, Cr62 emerges as a transitional system on the path to the center of the N=40 island of inversion.

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM