492 research outputs found
Elastic -transfer in the elastic scattering of OC
The elastic scattering OC angular distributions at O
bombarding energies of 100.0, 115.9 and 124.0 MeV and their optical model
description including the -particle exchange contribution calculated in
the Coupled Reaction Channel approach are presented. The angular distributions
show not only the usual diffraction pattern but also, at larger angles,
intermediate structure of refractive origin on which finer oscillations are
superimposed. The large angle features can be consistently described including
explicitly the elastic -transfer process and using a refractive optical
potential with a deep real part and a weakly absorptive imaginary part.Comment: 3 pages, 2 figures, accepted in Eur.Phys.J A (Short note
Refractive elastic scattering of carbon and oxygen nuclei: The mean field analysis and Airy structures
The experimental data on the OC and OC elastic
scatterings and their optical model analysis are presented. Detailed and
complete elastic angular distributions have been measured at the Strasbourg
Vivitron accelerator at several energies covering the energy range between 5
and 10 MeV per nucleon. The elastic scattering angular distributions show the
usual diffraction pattern and also, at larger angles, refractive effects in the
form of nuclear rainbow and associated Airy structures. The optical model
analysis unambiguously shows the evolution of the refractive scattering
pattern. The observed structure, namely the Airy minima, can be consistently
described by a nucleus-nucleus potential with a deep real part and a weakly
absorptive imaginary part. The difference in absorption in the two systems is
explained by an increased imaginary (mostly surface) part of the potential in
the OC system. The relation between the obtained potentials and
those reported for the symmetrical OO and CC
systems is drawn.Comment: 10 pages, 9 figures, Phys. rev. C in pres
Octupole correlations near 110Te
The lifetime of the 2+ and 9-, 11-, 13-, 15- states in the neutron-deficient 110Te was measured for the first time using the recoil distance Doppler shift technique. The reported value of the reduced transition probability B(E2;0+g.s?2+)=4.3(8)×103e2fm4 supports the systematic for even-mass Te isotopes and was interpreted in the framework of the large-scale shell model and cranked shell model calculations. The measured reduced transition probabilities in the negative-parity yrast band revealed the upward trend towards the high spins. The enhanced collectivity is discussed in terms of the tilted axis cranking approach and the symmetry configuration mixing method with the Gogny D1S interaction.The authors would like to thank the technical staff of the LNL Legnaro facility for their assistance in providing excellent operation of the XTU-tandem accelerator. The authors wish to acknowledge the support of local engineers P. Cocconi and R. Isocrate. The work was partially supported by the DoE Grant No. DE-FG02-95ER4093 and Spanish MICINN Grant No. PGC2018-094583-B-I00
Search for emission of unstable Be clusters from hot Ca and Ni nuclei
The possible occurence of highly deformed configurations is investigated in
the Ca and Ni di-nuclear systems as formed in the Si +
C and Si + Si reactions, respectively, by using the
properties of emitted light charged particles. Inclusive as well as exclusive
data of the heavy fragments (A 6) and their associated light charged
particles (p, d, t, and -particles) have been collected at the IReS
Strasbourg VIVITRON Tandem facility with two bombarding energies
Si) = 112 and 180 MeV by using the ICARE charged particle
multidetector array, which consists of nearly 40 telescopes. The measured
energy spectra, velocity distributions, in-plane and out-of-plane angular
correlations are analysed by Monte Carlo CASCADE statistical-model calculations
using a consistent set of parameters with spin-dependent level densities.
Although significant deformation effects at high spin are needed, the remaining
disagreement observed in the Si + C reaction for the S
evaporation residue suggests an unexpected large unstable Be cluster
emission of a binary nature.Comment: 13 pages latex, 9 eps figures. Paper presented at the XXXIX
International Winter Meeting on Nuclear Physics, Bormio(Italy) January 22-27,
2001 (to be published at Ricerca Scientifica ed Educazione Permanente
8Be cluster emission versus alpha evaporation in 28Si + 12C
The possible occurence of highly deformed configurations in the Ca
di-nuclear system formed in the Si + C reaction is investigated
by analyzing the spectra of emitted light charged particles. Both inclusive and
exclusive measurements of the heavy fragments (A 10) and their
associated light charged particles (protons and particles) have been
made at the IReS Strasbourg {\sc VIVITRON} Tandem facility at bombarding
energies of (Si) = 112 MeV and 180 MeV by using the {\sc
ICARE} charged particle multidetector array. The energy spectra, velocity
distributions, in-plane and out-of-plane angular correlations of light charged
particles are compared to statistical-model calculations using a consistent set
of parameters with spin-dependent level densities. This spin dependence
approach suggests the onset of large nuclear deformation in Ca at high
spin. This conclusion might be connected with the recent observation of
superdeformed bands in the Ca nucleus. The analysis of
particles in coincidence with S fragments suggests a surprisingly strong
Be cluster emission of a binary nature.Comment: 39 pages 15 figure
Light and heavy fragments mass correlation in the 197Au + 130Te transfer reaction
We studied multinucleon transfer (MNT) processes in the 197Au + 130Te at Elab=1.07 GeV system coupling the PRISMA magnetic spectrometer to NOSE, an ancillary particle detector. We constructed a mass correlation matrix
associating to each light fragment identified in PRISMA the corresponding mass distribution of the heavy partner detected in NOSE and, through the comparison with Monte Carlo simulations, we could infer about the role of neutron evaporation in multinucleon transfer reactions for the population of neutron-rich heavy nuclei
Probing nucleon-nucleon correlations in heavy-ion transfer reactions
Pair correlations have been investigated in heavy-ion collisions via studies of the transfers of different nucleon pairs. In particular, excitation functions of one- and two-neutron transfer channels have been measured for the closed shell 40Ca + 96Zr and superfluid 60Ni + 116Sn systems from the Coulomb barrier energy to energies far below. By using the unique performance of the magnetic spectrometer PRISMA, in terms of resolution and efficiency, measurements at very low bombarding energies have been performed. The experimental transfer probabilities have been compared with semiclassical microscopic calculations that incorporate nucleonnucleon correlations, together with known structure information of entrance and exit channels nuclei and reaction dynamics. These calculations well reproduce, in the whole energy range, one- and two-neutron transfer channels in shape and magnitude
First in-beam γ -ray study of the level structure of neutron-rich S 39
R. Chapman et al. ; 8 págs.; 6 figs.; 1 tab.The neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2-). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ω shell-model calculations presented here. ©2016 American Physical SocietyThis work was supported in part by the EPSRC (UK)
and by the European Union under Contract No. RII3-CT-
2004-506065. Five of us (D.O., M.B., A.H., K.K., and A.P.)
acknowledge financial support from the EPSRC. Z.M.W.
acknowledges support from ORSAS and from the University
of the West of Scotland. A.N.D. acknowledges support from
the STFC. A.J. acknowledges financial support from the
Spanish Ministerio de Ciencia e Innovación under Contracts
No. FPA2007-66069 and No. FPA2009-13377-C02-02. Zs.D.
acknowledges financial support from OTKA under Project
No. K100835. S.S. acknowledges support from the Croatian
Science Foundation under Project No. 7194. The contribution
of the accelerator and target-fabrication staff at the INFN
Legnaro National Laboratory is gratefully acknowledged.Peer Reviewe
How does fusion hindrance show up in medium-light systems? The case of 48Ca + 48Ca
The fusion excitation function of 48Ca + 48Ca has been measured above and well below the Coulomb barrier, thereby largely extending the energy range of a previous experiment down to very low cross sections. This system has a negative Q-value for compound nucleus formation. The fusion cross section decreases steadily below the barrier with no conspicuous change of slope below 300 μb. Coupled-channels calculations using a Woods–Saxon potential indicate that a large diffuseness parameter is needed to reproduce the sub-barrier cross sections. A close analogy with the case of 36S + 48Ca, with Q>0, is pointed out. The sign of the Q-value does not influence fusion cross sections down to the 300–600 nb leve
Binary reaction decays from 24Mg+12C
Charged particle and gamma decays in 24Mg* are investigated for excitation
energies where quasimolecular resonances appear in 12C+12C collisions. Various
theoretical predictions for the occurence of superdeformed and hyperdeformed
bands associated with resonance structures with low spin are discussed within
the measured 24Mg* excitation energy region. The inverse kinematics reaction
24Mg+12C is studied at E_lab(24Mg) = 130 MeV, an energy which enables the
population of 24Mg states decaying into 12C+12C resonant break-up states.
Exclusive data were collected with the Binary Reaction Spectrometer in
coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at
Strasbourg. Specific structures with large deformation were selectively
populated in binary reactions and their associated gamma decays studied.
Coincident events associated with inelastic and alpha-transfer channels have
been selected by choosing the excitation energy or the entry point via the
two-body Q-values. The analysis of the binary reaction channels is presented
with a particular emphasis on 24Mg-gamma, 20Ne-gamma and 16O-gamma
coincidences. New information (spin and branching ratios) is deduced on
high-energy states in 24Mg and 16O, respectively.Comment: 27 pages, 8 figures, 1 tabl
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