Study of internal structures of 9,10Be and 10B in scattering of 4He from 9Be

A study of inelastic scattering and single-particle transfer reactions was performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and 9Be(4He,t)10B reactions were measured. Experimental angular distributions of the differential cross sections for the ground state and a few low-lying states were analyzed in the framework of the optical model, coupled channels and distorted-wave Born approximation. An analysis of the obtained spectroscopic factors was performed.Comment: 16 pages, 7 figures, 3 tables, regular paper, mispritns are corrected in new versio

Collapse of the N=28 shell closure in 42^{42}Si

The energies of the excited states in very neutron-rich $^{42}$Si and $^{41,43}$P have been measured using in-beam $\gamma$-ray spectroscopy from the fragmentation of secondary beams of $^{42,44}$S at 39 A.MeV. The low 2$^+$ energy of $^{42}$Si, 770(19) keV, together with the level schemes of $^{41,43}$P provide evidence for the disappearance of the Z=14 and N=28 spherical shell closures, which is ascribed mainly to the action of proton-neutron tensor forces. New shell model calculations indicate that $^{42}$Si is best described as a well deformed oblate rotor.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. let

Structure of the N=27 isotones derived from the 44^{44}Ar(d,p)45^{45}Ar

Expérience GANIL/SPIRAL, détecteur CATS, détecteur MUST, 7 figures,International audienceThe $^{44}$Ar(d,p)$^{45}$Ar neutron transfer reaction was performed at 10~A.MeV. Measured excitation energies, deduced angular momenta and spectroscopic factors of the states populated in $^{45}$Ar are reported. A satisfactory description of these properties is achieved in the shell model framework using a new $sdpf$ interaction. The model analysis is extended to more exotic even-Z nuclei down to $^{41}_{14}$Si$_{27}$ to study how collectivity impacts the low lying structure of N~=~27 neutron-rich nuclei

Properties of odd nuclei and the impact of time-odd mean fields: A systematic Skyrme-Hartree-Fock analysis

We present a systematic analysis of the description of odd nuclei by the Skyrme-Hartree-Fock approach augmented with pairing in BCS approximation and blocking of the odd nucleon. Current and spin densities in the Skyrme functional produce time-odd mean fields (TOMF) for odd nuclei. Their effect on basic properties (binding energies, odd-even staggering, separation energies and spectra) is investigated for the three Skyrme parameterizations SkI3, SLy6, and SV-bas. About 1300 spherical and axially-deformed odd nuclei with 16 < Z < 92 are considered. The calculations demonstrate that the TOMF effect is generally small, although not fully negligible. The influence of the Skyrme parameterization and the consistency of the calculations are much more important. With a proper choice of the parameterization, a good description of binding energies and their differences is obtained, comparable to that for even nuclei. The description of low-energy excitation spectra of odd nuclei is of varying quality depending on the nucleus

In-beam spectroscopic studies of 44^{44}S nucleus

The structure of the $^{44}$S nucleus has been studied at GANIL through the one proton knock-out reaction from a $^{45}$Cl secondary beam at 42 A$\cdot$MeV. The $\gamma$ rays following the de-excitation of $^{44}$S were detected in flight using the 70 BaF${_2}$ detectors of the Ch\^{a}teau de Cristal array. An exhaustive $\gamma\gamma$-coincidence analysis allowed an unambiguous construction of the level scheme up to an excitation energy of 3301 keV. The existence of the spherical 2$^+_2$ state is confirmed and three new $\gamma$-ray transitions connecting the prolate deformed 2$^+_1$ level were observed. Comparison of the experimental results to shell model calculations further supports a prolate and spherical shape coexistence with a large mixing of states built on the ground state band in $^{44}$S.Comment: 6 pages, 5 figures, accepted for publication in Physical Review