Lifetime measurements in 63^{63}Co and 65^{65}Co

Lifetimes of the $9/2^-_1$ and $3/2^-_1$ states in $^{63}$Co and the $9/2^-_1$ state in $^{65}$Co were measured using the recoil distance Doppler shift and the differential decay curve methods. The nuclei were populated by multi-nucleon transfer reactions in inverse kinematics. Gamma rays were measured with the EXOGAM Ge array and the recoiling fragments were fully identified using the large-acceptance VAMOS spectrometer. The E2 transition probabilities from the $3/2^-_1$ and $9/2^-_1$ states to the $7/2^-$ ground state could be extracted in $^{63}$Co as well as an upper limit for the $9/2^-_1\rightarrow7/2^-_1$ $B$(E2) value in $^{65}$Co. The experimental results were compared to large-scale shell-model calculations in the $pf$ and $pfg_{9/2}$ model spaces, allowing to draw conclusions on the single-particle or collective nature of the various states.Comment: 8 pages, 8 figures, 1 table, accepted for publication in Physical Review

Counting rate measurements for lifetime experiments using the RDDS method with the new generation \u3b3-ray array AGATA

The differential Recoil Distance Doppler Shift (RDDS) method after multinucleon transfer (MNT) reactions to measure lifetimes of excited states in neutron-rich nuclei requires the use of a thick energy degrader for the recoiling ejectiles that are then detected in a spectrometer. This type of measurements greatly benefits from the use of the new generation segmented \u3b3-ray detectors, such as the AGATA demonstrator which offers unprecedented energy and angular resolutions. In order to make an optimized choice of the material and the thickness of the degrader for lifetime measurements using the RDDS method after MNT, an experiment has been performed with the AGATA demonstrator. Counting rate measurements for different degraders are presented. \ua9 2014 Elsevier B.V

Multinucleon transfer reactions: Present status and perspectives

Significant advances have been achieved in the last years in the field of multinucleon transfer reactions. The advent of the last generation large solid angle magnetic spectrometers pushed the detection efficiency more than an order of magnitude above previous limits, with a significant gain in mass resolution for very heavy ions. Further, the coupling of these spectrometers to large gamma arrays allowed to perform gamma-particle coincidences. One can thus detect the transfer strength to the lowest excited levels of binary products and perform gamma spectroscopy for nuclei moderately far from stability, especially in the neutron-rich region. Via transfer of multiple pairs valuable information on nucleon-nucleon correlations can also be derived, especially from measurements performed below the Coulomb barrier. There is growing interest in the study of the properties of the heavy binary partner, since the transfer mechanism may allow the production of (moderately) neutron rich nuclei in the Pb and in the actinides regions, crucial also for astrophysics. Present studies are relevant for future studies with radioactive beams. (C) 2013 Elsevier B.V. All rights reserved

Multinucleon transfer reactions: an overview of recent results

Large acceptance magnetic spectrometers, such as PRISMA installed at Laboratori Nazionali di Legnaro, gave a further boost to the renewed interest for multinucleon transfer reactions in the last decade. The large solid angles of these devices and the high resolving powers of their detection systems allowed to investigate the transfer process around and well below the Coulomb barrier and to perform nuclear structure studies in several mass regions of the nuclide chart when coupled with large gamma-ray arrays such as CLARA. Selected results obtained with the PRISMA-CLARA set-up in odd argon isotopes populated by using the multinucleon transfer process and in sub-barrier transfer measurements are presented in this contribution. The status of an ancillary detector which is being developed for PRISMA in order to perform kinematical coincidence measurements is also reported

The 4 \u3c0 highly-efficient light-charged-particle detector EUCLIDES, installed at the GALILEO array for in-beam \u3b3 -ray spectroscopy

In a fusion-evaporation reaction, nuclei are produced by evaporating light-charged particles and neutrons from the compound nucleus. Typically, a nucleus of interest is produced as a result of a part of the total cross-section and, in order to guarantee a good channel discrimination, a particle detector, like the EUCLIDES $4\pi$ Si-ball array, is necessary. EUCLIDES has been quoted in more than a hundred publications resulting from many experiments performed in combination with the EUROBALL and GASP $\gamma$-ray spectrometers. The present paper reports on the upgraded version of EUCLIDES, that is presently coupled to the new GALILEO $\gamma$-ray spectrometer, installed at the Laboratori Nazionali di Legnaro, INFN. The design, characteristics and performance of the EUCLIDES array are presented and discussed

Lifetime measurements in neutron-rich Fe and Co isotopes

Lifetimes of yrast states in neutron-rich Fe and Co isotopes were measured using the differential Recoil Distance Doppler Shift (RDDS) and the differential decay curves methods. The nuclei of interest were populated in multi-nucleon transfer in inverse kinematics. The deduced B(E2) values are compared with large-scale shell-model calculations, leading to a better understanding of the mechanisms at the origin of the onset of collectivity in the region just below 68Ni

Transfer reaction studies with spectrometers

The revival of transfer reaction studies benefited from the construction of the new generation large solid angle spectrometers, coupled to large \u3b3arrays. The recent results of \u3b3-particle coincident measurements in 40Ca+96Zr and 40Ar+208Pb reactions demonstrate a strong interplay between single-particle and collective degrees of freedom that is pertinent to the reaction dynamics. The development of collectivity has been followed in odd Ar isotopes populated in the 40Ar+208Pb reaction through the excitation of the 11=2 states, understood as the coupling of single particle degrees of freedom to nuclear vibration quanta. Pair transfer modes is another important degree of freedom which is presently being studied with Prisma in inverse kinematics at energies far below the Coulomb barrier. First results from the 96Zr+40Ca reaction elucidate the role played by nucleon-nucleon correlation

A powerful combination measurement for exploring the fusion reaction mechanisms induced by weakly bound nuclei

The GALILEO array is a high-efficiency gamma-ray spectrometer, resident at the Legnaro National Laboratory (LNL) in Italy, and it is currently used in combination with the Si-ball EUCLIDES for the detection of charged-particles. The combined setup was used in the Li-6+Y-89 experiment with incident energies of 22 MeV and 34 MeV to investigate the influence of breakup and transfer of weakly bound projectile on the fusion process. Using the coincidence by the charged particles and gamma-rays, the different reaction channels can be clearly identified and the different reaction mechanisms can be clearly studied. It is shown that this facility can be used well to explore the fusion reaction mechanisms induced by weakly bound nuclei

Spectroscopic studies with the PRISMA-CLARA set-up

The large solid angle magnetic spectrometer for heavy ions PRISMA, installed at Laboratori Nazionali di Legnaro (LNL), was operated up to the end of March 2008 in conjunction with the highly efficient CLARA set-up. It allowed to carry out nuclear structure and reaction mechanism studies in several mass regions of the nuclide chart. Results obtained in the vicinity of the island of inversion and for the heavy iron and chromium isotopes are presented in this contribution. The status of the new focal plane detectors specifically designed for light ions and slow moving heavy ions is also reported

High-spin structure and intruder excitations in ^{36}Cl

Excited states up to J\u3c0=11 12 at 10 296 keV and J\u3c0=10+ at 10 707 keV have been populated in the odd-odd 36Cl nucleus using the 24Mg(14N, 2p) fusion-evaporation reaction at Elab=31 MeV. Twenty new states and 62 new \u3b3 transitions have been identified by employing \u3b3-\u3b3 and \u3b3-\u3b3-\u3b3 coincidences. Lifetimes have been investigated by the Doppler shift attenuation method. The experimental data have been compared with the results of large-scale shell-model calculations performed using different effective interactions and model spaces allowing particle-hole excitations across the N=Z=20 shell gap