200 research outputs found
Z=50 shell gap near Sn from intermediate-energy Coulomb excitations in even-mass Sn isotopes
Rare isotope beams of neutron-deficient Sn nuclei from the
fragmentation of Xe were employed in an intermediate-energy Coulomb
excitation experiment yielding transition strengths.
The results indicate that these values are much larger
than predicted by current state-of-the-art shell model calculations. This
discrepancy can be explained if protons from within the Z = 50 shell are
contributing to the structure of low-energy excited states in this region. Such
contributions imply a breaking of the doubly-magic Sn core in the light
Sn isotopes.Comment: 4 pages, 4 figure
Study of elastic and inelastic scattering of Be + C at 35 MeV
The elastic and inelastic scattering of Be from C have been
measured at an incident energy of 35 MeV. The inelastic scattering leading to
the 4.439 MeV excited state of C has been measured for the first time.
The experimental data cover an angular range of =
15-120. Optical model analyses were carried out with
Woods-Saxon and double-folding potential using the density dependent M3Y
(DDM3Y) effective interaction. The microscopic analysis of the elastic data
indicates breakup channel coupling effect. A coupled-channel analysis of the
inelastic scattering, based on collective form factors, show that mutual
excitation of both Be and C is significantly smaller than the single
excitation of C. The larger deformation length obtained from the DWBA
analysis could be explained by including the excitation of Be in a
coupled-channel analysis. The breakup cross section of Be is estimated to
be less than 10 of the reaction cross section. The intrinsic deformation
length obtained for the C (4.439 MeV) state is = 1.37
fm. The total reaction cross section deduced from the analysis agrees very well
with Wong's calculations for similar weakly bound light nuclei on C
target.Comment: 8 pages, 5 figure
First Results on In-Beam gamma Spectroscopy of Neutron-Rich Na and Mg Isotopes at REX-ISOLDE
After the successful commissioning of the radioactive beam experiment at
ISOLDE (REX-ISOLDE) - an accelerator for exotic nuclei produced by ISOLDE -
first physics experiments using these beams were performed. Initial experiments
focused on the region of deformation in the vicinity of the neutron-rich Na and
Mg isotopes. Preliminary results show the high potential and physics
opportunities offered by the exotic isotope accelerator REX in conjunction with
the modern Germanium gamma spectrometer MINIBALL.Comment: 7 pages, RNB6 conference contributio
Probing proton halo effects in the 8B+64Zn collision around the Coulomb barrier
Proton halo effects in the 8B+64Zn reaction at an energy around 1.5 times the Coulomb barrier have been studied at HIE-ISOLDE CERN using, for the first time, the only existing postaccelerated 8B beam. This, together with the use of a high granularity and large solid angle detection system, allowed for a careful mapping of the elastic angular distribution, especially in the Coulomb-nuclear interference region. Contrary to what is observed for the one-neutron halo nucleus 11Be on the same target in a similar energy range, the analysis of the elastic scattering angular distribution shows only a modest suppression of the Coulomb-nuclear interference peak, with no remarkable enhancement of the total reaction cross-section. Inclusive angular and energy distributions of 7Be produced in direct reaction processes have also been measured. The comparison of these data with the results of theoretical calculations for the elastic and non-elastic breakup contributions indicate that both processes are important. Overall, the experimental data suggest a 8B collision dynamics at the barrier very different from the one of neutron halo nuclei, showing only modest effects of coupling to continuum. This behaviour can be interpreted as due to the presence of the additional Coulomb interactions halo-core and halo-target together with the presence of the centrifugal barrier felt by the valence proton of 8B
Commissioning of the CALIFA Barrel Calorimeter of the RB Experiment at FAIR
CALIFA is the high efficiency and energy resolution calorimeter for the
RB experiment at FAIR, intended for detecting high energy charged
particles and -rays in inverse kinematics direct reactions. It
surrounds the reaction target in a segmented configuration of Barrel and
Forward End-Cap pieces. The CALIFA Barrel consists of 1952 detection units made
of CsI(Tl) long-shaped scintillator crystals, and it is being commissioned
during the Phase0 experiments at FAIR. The first setup for the CALIFA Barrel
commissioning is presented here. Results of detector performance with
-rays are obtained, and show that the system fulfills the design
requirements
Restoring the valence-shell stabilization in Nd-140
A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE at CERN to obtain E2 and M1 transition matrix elements of Nd-140 using the multistep Coulomb-excitation code GOSIA. The absolute M1 strengths, B(M1; 2(2)(-) -> 2(1)(+)) = 0.033(8)mu(2)(N), B(M1 ; 2(3)(+) -> 2(1)(+)) = 0.26(-0.10)(+0.11)mu(2)(N), and B(M1; 2(4)+ -> 2(1)(+)) <0.04 mu(2)(N) identify the 2(3)(+) state as the main fragment of the one-quadrupole-phonon proton-neutron mixed-symmetry state of Nd-140. The degree of F-spin mixing in Nd-140 was quantified with the determination of the mixing matrix element VF-mix <7(-7)(-13) keV.Peer reviewe
Collective and broken pair states of 65,67Ga
Excited states of 65Ga and 67Ga nuclei were populated through the 12C(58Ni,αp) and 12C(58Ni,3p) reactions, respectively, and investigated by in-beam Îł-ray spectroscopic methods. The NORDBALL array equipped with a charged particle ball and 11 neutron detectors was used to detect the evaporated particles and Îł rays. The level schemes of 65,67Ga were constructed on the basis of γγ-coincidence relations up to 8.6 and 10 MeV excitation energy, and IÏ=27/2 and 33/2+ spin and parity, respectively. The structure of 65,67Ga nuclei was described in the interacting boson-fermion plus broken pair model, including quasiproton, quasiproton-two-quasineutron, and three-quasiproton fermion configurations in the boson-fermion basis states. Most of the states were assigned to quasiparticle + phonon and three quasiparticle configurations on the basis of their electromagnetic decay properties
Design of an optimized nested-mirror neutron reflector for a NNBAR experiment
The NNBAR experiment for the European Spallation Source will search for free neutrons converting to antineutrons with an expected sensitivity improvement of three orders of magnitude compared to the last such search. This paper describes both the simulations of a key component for the experiment, the neutron optical reflector and the expected gains in sensitivity
Coulomb excitation of 222Rn
The nature of quadrupole and octupole collectivity in 222Rn was investigated by determining the electricquadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive 222Rn beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball gamma -ray spectrometer following the bombardment of two targets, 120Sn and 60Ni. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10 h over bar and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) e fm2. The values of the intrinsic electric-octupole moment for the 0+ -> 3- and 2+ -> 5- transitions were found to be respectively -210 e fm3 and 2300+300-500 e fm3 while a smaller value, 1200+500-900 e fm3, was found for the 2+ -> 1- transition. In addition, four excited non-yrast states were identified in this work via gamma -gamma coincidences.Peer reviewe
Beta-delayed proton emission from 20Mg
Beta-delayed proton emission from 20 Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in 20 Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in 20 Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in 19 Ne through the beta decay of 20 Mg, which is important for the astrophysically relevant reaction 15O( , )19Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 91.4(1.0)ms
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