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The space and time configurations of the dissociation of 8 He into 6 He+n+n, on C and Pb targets, have been explored simultaneously for the first time. The final-state interactions in the n-n and 6 He-n channels are successfully described within a model that considers independent emission of neutrons from a Gaussian volume with a given lifetime. The dissociation on C target exhibits a dominant sequential decay through the ground state of 7 He, consistent with neutrons being emitted from a Gaussian volume of fm with a n-n delay in the sequential channel of 1400 400 fm/c, in agreement with the lifetime of 7 He. The lower-statistics data on Pb target correspond mainly to direct breakup, and are well described using the n-n volume measured, without any n -n delay. The validity of the phenomenological model used is discussed., SCOPUS: ar.j, DecretOANoAutActif, info:eu-repo/semantics/published

Direct observation of the survival of199Au residues after 2n transfer in the He8+Au197 system and the absence of the corresponding67Cu in the He8+Cu65 system at various energies are reported. The measurements of the surprisingly large cross sections for199Au, coupled with the integral cross sections for the various Au residues, is used to obtain the first model-independent lower limits on the ratio of 2n to 1n transfer cross sections from8He to a heavy target. A comparison of the transfer cross sections for6,8He on these targets highlights the differences in the interactions of these Borromean nuclei. These measurements for the most neutron-rich nuclei on different targets highlight the need to probe the reaction mechanism with various targets and represent an experimental advance towards understanding specific features of pairing in the dynamics of dilute nuclear systems.

Differential cross sections for elastic-scattering and neutron-transfer reactions along with cross sections for fusion in the 8He+65Cu system are reported at energies above the Coulomb barrier (Elab = 19.9 and 30.6 MeV). The present work demonstrates the

The B (E 1 ;1 / 2+ → 1 / 2-) strength for 11Be has been extracted from intermediate energy Coulomb excitation measurements, over a range of beam energies using a new reaction model, the extended continuum discretized coupled channels (XCDCC) method. In addition, a measurement of the excitation cross section for 11Be + 208Pb at 38.6 MeV/nucleon is reported. The B (E 1) strength of 0.105(12) e2 fm2 derived from this measurement is consistent with those made previously at 60 and 64 MeV/nucleon, in contrast to an anomalously low result obtained at 43 MeV/nucleon. By coupling a multi-configuration description of the projectile structure with realistic reaction theory, the XCDCC model provides for the first time a fully quantum mechanical description of Coulomb excitation. The XCDCC calculations reveal that the excitation process involves significant contributions from nuclear, continuum, and higher-order effects. An analysis of the present and two earlier intermediate energy measurements yields a combined B(E1) strength of 0.105(7) e2 fm2. This value is in good agreement with the value deduced independently from the lifetime of the 1 / 2- state in 11Be, and has a comparable precision. © 2007 Elsevier B.V. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published

The breaking of the N=8 shell-model magic number in the Be12 ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than Be12. The occupancies of the 0ω νp1/2 orbital and the 1 ω, νd5/2 intruder orbital were deduced from a measurement of neutron removal from a high-energy Be12 beam leading to bound and unbound states in Be11. © 2006 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the 0 hbar omega neutron p1/2-orbital and the 1 hbar omega, neutron d5/2 intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be. Comment: 5 pages, 2 figures

Data have been obtained on exclusive single neutron knockout cross sections from 12Be to study its ground state structure. The cross sections for the production of 11Be in its ground state (1/2 +) and first excited state (0.32 MeV, 1/2 -) have previously been measured, indicating a strong (2s 1 2) 2 component to the 12Be ground state. In the present experiment, performed at the GANIL laboratory, cross sections for the first (0.32 MeV, 1/2 -) and second (1.78 MeV, 5/2 +, unbound) excited states in 11Be were measured, which gives information on the admixture of (1p 1 2) 2 and (1d 5 2) 2 components in the ground state of 12Be. A fragmentation beam of 12Be of ∼10000 pps (95% pure) was incident on a carbon target at 41 MeV/u. The beam particles were tracked onto the target, and their energies were measured event-by-event. The beam-like residues were measured in a position sensitive telescope mounted at zero degrees, and neutrons were measured in the DéMoN array. The 1/2 - state of 11Be was identified by measuring coincident 320 keV γ-rays, using four NaI detectors. Full kinematic reconstruction of unbound states in 11Be was performed using coincident neutrons and 10Be ions. Detailed simulations were performed in order to interpret the data, and spectroscopic factors were calculated, using preliminary single particle removal cross sections calculated using a Glauber model. © 2005 American Institute of Physics., SCOPUS: cp.p, info:eu-repo/semantics/published

Data have been obtained on exclusive single neutron knockout cross sections from 12Be to study its ground state structure. Preliminary cross sections for the first (0.32 MeV, 1/2-) and second (1.78 MeV, 5/2+, unbound) excited states in 11Be have been obtained, giving evidence of significant admixtures of both ν(1p1/2) 2 and ν(1d5/2)2 configurations in the ground state of 12Be. © Società Italiana di Fisica / Springer-Verlag 2005., SCOPUS: cp.j, info:eu-repo/semantics/published

A kinetically complete measurement of the C12(Be10, α+α+n) and (Be10, α+α) reactions has been performed at a beam energy of 30 MeV/nucleon. The charged beam velocity particles were detected in an array of Si-CsI detectors placed at zero degrees, and the neutrons in an 81-element neutron array. The coincident detection of the final-state particles, produced in the breakup of Be10, allowed the reconstruction of the excitation energy in the Be8 and Be9 systems. States in Be8 were identified, in particular the ground and first-excited states; and in Be9, states at 1.68, 2.43, and (2.78, 3.05) MeV were observed. The population of these levels, in particular the 2.43 MeV 5/2- level, suggests that collective excitations play an important role in the neutron removal process. Distorted wave Born approximation and Glauber-type calculations have been used to model the direct neutron removal from the Be10 ground state and the two-step removal via inelastic excitations of the Be10(2+) and Be9(5/2-) excited states. © 2005 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published

The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the 0 hbar omega neutron p1/2-orbital and the 1 hbar omega, neutron d5/2 intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be. Comment: 5 pages, 2 figures

Measurements of the helium-cluster breakup and neutron removal cross-sections for neutron-rich Be isotopes 10-12,14Be are presented. These have been studied in the 30 to 42 MeV/nucleon energy range where reaction measurements are proposed to be sensitive to the cluster content of the ground-state wave-function. These measurements provide a comprehensive survey of the decay processes of the Be isotopes by which the valence neutrons are removed revealing the underlying α-α core-cluster structure. The measurements indicate that clustering in the Be isotopes remains important up to the drip-line nucleus 14Be and that the dominant helium-cluster structure in the neutron-rich Be isotopes corresponds to α-Xn-α. © 2003 Published by Elsevier B.V., SCOPUS: ar.j, info:eu-repo/semantics/published

Measurements of the neutron removal and cluster breakup cross sections for the neutron-rich nuclei 14Be and 14B have been performed at 34.4 and 40.8 MeV/nucleon, respectively. Enhancement of the first chance cluster breakup cross section for 14Be compared to that of 14B provides evidence for a well-developed He cluster structure of the ground state of 14Be. Measurements of both the cross sections and decay-particle velocities suggest that multistep processes play an important role in the excitation and decay of both 14B and 14Be., SCOPUS: ar.j, info:eu-repo/semantics/published

The structure of 10Be has been investigated by inelastic scattering to states above the breakup threshold using the reaction 12C(10Be,10Be* → 6He+4/He)12C at Ebeam=302 MeV. Excited states in 10Be were observed at 9.6±0.1 and 10.2±0.1 MeV. No evidence was observed for the population of the 4 + member of the ground-state band of 10Be indicating the shell-model-like structure of the ground state. In addition, the decay of 8Be, 10B, and 11B, populated in the two-neutron, proton pickup, breakup and 1p pickup reactions, was reconstructed through the detection of coincident 4He+4He, 4He+6Li, and 4He+7Li particles. Cross sections for the formation of the 8Be, 9Be, 10B, and 11B were also deduced. Contrary to expectations, the two-neutron removal results in the production of 8Be predominantly (80%) in the first excited (2+) state. This suggests that dynamical excitations play an important role in the neutron removal process., SCOPUS: ar.j, info:eu-repo/semantics/published

Measurements of the breakup and the neutron removal reactions of 16C have been made at 46 MeV/A and the decay cross sections measured. A correlation between the cluster breakup channels and the reaction Q value suggests that the reaction mechanism is strongly linked to quasielastic processes. No enhancement of the two-body cluster breakup cross section is seen for 16C. This result would indicate that 16C does not have a well developed cluster structure in the ground state, in agreement with recent calculations., SCOPUS: ar.j, SCOPUS: ar.j, info:eu-repo/semantics/published

The structure of [Formula Presented] has been investigated by inelastic scattering to states above the breakup threshold using the reaction [Formula Presented] at [Formula Presented]. Excited states in [Formula Presented] were observed at [Formula Presented] and [Formula Presented]. No evidence was observed for the population of the [Formula Presented] member of the ground-state band of [Formula Presented] indicating the shell-model-like structure of the ground state. In addition, the decay of [Formula Presented], [Formula Presented], and [Formula Presented], populated in the two-neutron, proton pickup, breakup and [Formula Presented] pickup reactions, was reconstructed through the detection of coincident [Formula Presented], [Formula Presented], and [Formula Presented] particles. Cross sections for the formation of the [Formula Presented], [Formula Presented], [Formula Presented], and [Formula Presented] were also deduced. Contrary to expectations, the two-neutron removal results in the production of [Formula Presented] predominantly [Formula Presented] in the first excited [Formula Presented] state. This suggests that dynamical excitations play an important role in the neutron removal process. © 2004 The American Physical Society., SCOPUS: ar.j, info:eu-repo/semantics/published