M. Trotta

Search for pairing-vibration states of even Ca isotopes in 40Ca + 208Pb transfer reactions

Abstract.Multi-nucleon transfer reactions in 40Ca + 208Pb have been studied at several bombarding energies close to the Coulomb barrier. Light reaction products have been identified in mass and charge with a time-of-flight spectrometer. The energy spectra of the inclusive two-neutron pick-up channel show a population in a narrow region of excitation energies which corresponds to the predicted energy of pairing-vibration states in 42Ca.

Statistics vs. dynamics in fission: light and shade from systems of intermediate fissility

Systems of intermediate fissility are characterized by an evaporation residues cross section comparable or larger than the fission cross section, and by a relatively higher probability for charged particle emission in the pre‐scission channel. In a theoretical framework in which time scale estimates of the fission process rely on statistical model calculations, the analysis of particle emission in the evaporation residues channel is the source of additional constraints on the statistical and dynamical models. This contribution will focus on our statistical and dynamical analysis of a more complete set of data from the system 32S+100Mo at ELab = 200 MeV. Statistical model fails in reproducing the whole set of data and no convincing estimate is possible of the fission time scale. In particular, while pre‐scission multiplicities can be reproduced without delay, the model strongly overestimates proton and alpha particle multiplicities in the evaporation residues channel irrespective of the statistical model i...

Yrast structure of the neutron-rich N=31 isotones Ca51 and Sc52

The low-lying yrast states in the 51 Ca and 52 Sc nuclei were investigated to obtain information on the evolution of the P1/2 and f 5 / 2 neutron single-particle orbitals in neutron-rich nuclei near proton number Z = 20. Level structures associated with neutron excitations into these two orbitals and with proton excitations across the Z = 20 shell gap were identified. Shell-model calculations with the recently proposed GXPF1A interaction account reasonably well for the fp-shell states. The energy separation between the vp1/2 and vf5/2 orbitals in the Ca isotopes appears to be overestimated by the GXPF1A Hamiltonian.

γ‐ray Spectroscopy of Proton Drip‐Line Nuclei in the A∼130 Region using SPIRAL beams

A fusion‐evaporation experiment has been performed with a SPIRAL 76Kr radioactive beam in order to study the deformation of rare‐earth nuclei near the proton drip‐line. The experimental setup consisted in the EXOGAM γ‐array, coupled to the light‐charged particles (LCP) DIAMANT detector and to the VAMOS heavy‐ion spectrometer. The difficulties inherent to such measurements are enlightened. The coupling between EXOGAM and DIAMANT has been used to decrease the huge background caused by the radioactivity of the beam. It further permits assigning new γ‐ray transitions to specific residual nuclei. A γ‐ray belonging to the 130Pm level scheme has thus been observed for the first time.

Probing the maximally deformed light rare-earth region around the drip-line nucleus 130Sm

The neutron deficient rare-earth nuclei of the A~130 region are of particular interest since highly deformed prolate ground states are expected. Indeed these nuclei are predicted to show maximal ground-state deformations of β2 ~ 0.40 (axis ratio of 3:2), comparable to the deformation deduced for superdeformed cerium isotopes at high spin. A fusion–evaporation experiment was performed with radioactive ion beams at GANIL in October 2004 which had the goal to reach very proton-rich exotic nuclei located near the proton drip-line. A radioactive 76Kr beam, delivered by the SPIRAL facility, was used to bombard a thin 58Ni target. Emitted γ-rays were detected by the EXOGAM γ-ray spectrometer which was, for the first time, coupled with both the DIAMANT charged-particle array and the VAMOS spectrometer.

{gamma}-Spectroscopy and Radioactive Beams: How To Perform Channel Selection ?

An experiment has been performed using a SPIRAL 76Kr radioactive beam at GANIL to investigate rare‐earth nuclei near the proton drip‐line. The EXOGAM gamma array was coupled with the DIAMANT light charged‐particle detector and the VAMOS spectrometer. We report here on the powerful of this setup to extract fusion‐evaporation γ‐rays from a large beam contamination.

Search for fusion suppression in reactions having entrance-channel mass-asymmetry values around the Businaro-Gallone point *

Available data on evaporation residue (ER) production and fission in a wide region of compound nucleus (CN) masses and entrance‐channel mass‐asymmetry values have been analyzed in search for the “starting point”, where the fusion suppression due to the quasi‐fission (QF) effect starts to show up. Comparing cross sections for the ER production and fission in reactions leading to the same CN, but having different values of entrance‐channel mass‐asymmetry, one can extract the fusion probability for a more symmetric combination with respect to quite an asymmetric one, where no limitation seems to occur. An attempt to find correlations between the fusion probabilities derived for the considered combinations and some entrance‐channel characteristics is undertaken.

γ-ray spectroscopy of 1738Cl using grazing reactions

Excited states of

γ-ray spectroscopy of1738Clusing grazing reactions

^{38}_{17}

Yrast structure of the neutron-rich N = 31 isotones 51Ca and 52Sc

Cl