Towards the lowest-energy limit for light ions identification with silicon pixel-type detectors

An in-beam test of two pixel-type silicon detectors of the TRACE detector project has been performed at Laboratori Nazionali di Legnaro (Italy). The aim was to investigate the lowest kinetic energy values at which isotopic identification of heavy-ion reactions products with mass A 3c 10 is possible, by using a single-layer silicon detector. Two separate read-out chains, analog and digital, were used, and the Pulse Shape Analysis technique was employed to obtain the particle identification matrices for the digitally processed data. The results confirmed the high capability of the Pulse Shape Analysis method which can be used for light ion identification, with performances similar to the analog approach. Separation in both charge and mass was obtained for Li and Be isotopes, however, the presence of a significant background from alpha particles severely limited the data analysis in the lower energy region. Due to this effect, the identification of the light products ( 7,6 Li isotopes) could be possible down to 3c 24.5 MeV only, while the 9,7 Be isotopes were separable down to 3c 29 MeV. This gives the value of < 4 MeV/nucleon as the lowest kinetic energy for light products identification by using the pixel-type detectors of the TRACE project, in the present experimental conditions

Evolution of collectivity in the 78Ni region: Coulomb excitation of 74Ni at intermediate energies.

The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic ob- servables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the ef- fective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently per- formed an experiment with the goal to extract the B(E2; 0 + ! 2 + ) value for the 74 Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed

Observation of an isomeric state in 197Au

A medium spin isomer in 197Au is identified with t1 2 150 5 ns following a multinucleon transfer reaction between an 850 MeV 136Xe beam and a 198Pt target. The transitions identified here are considered and possible configurations for the associated levels discussed. In addition, a newly observed out of beam transition in 195Au is briefly reporte

Population of neutron-rich nuclei around Ca-48 with deep inelastic collisions

The deep inelastic reaction 48Ca+64Ni at 6 MeV/A has been studied using the CLARA-PRISMA setup. Angular distributions for pure elastic scattering and total cross-sections of the most relevant transfer channels have been measured. The experimental results are compared with predictions from a semiclassical model, showing good agreement for the presently analyzed few neutrons transfer channels. The \u3b3-decay of the most intense reaction products has also been studied, giving indications of the population of states with very short lifetimes

Toward the N = 40 sub-shell closure in Co isotopes and the new island of inversion

Neutron-rich Co isotopes from N = 34 to 40 were studied through multinucleon transfer by bombarding a 238U target with a 460 MeV 70Zn beam at the Legnaro National Laboratories. Gamma-recoil coincidences were recorded identifying the ions by using a high-acceptance magnetic spectrometer (PRISMA) and detecting the gamma radiation by using an array of HPGe clover detectors (CLARA). The results are discussed in comparison with the predictions of large-scale shell-model calculations

Spectroscopy of neutron-rich Co nuclei populated in the 70Zn+ 238U reaction

Neutron-rich Co isotopes from N = 34 to 40 were studied through multinucleon transfer by bombarding a 238U target with a 460 MeV 70Zn beam at LNL. Gamma-recoil coincidences were recorded identifying the ions by a high-acceptance magnetic spectrometer (PRISMA) and detecting the gamma radiation by an array of HPGe clover detectors (CLARA). The results are discussed in comparison with the predictions of large-scale shell-model calculations. \ua9 Published under licence by IOP Publishing Ltd