317 research outputs found
Nuclear alpha-clustering, superdeformation, and molecular resonances
Nuclear alpha-clustering has been the subject of intense study since the
advent of heavy-ion accelerators. Looking back for more than 40 years we are
able today to see the connection between quasimolecular resonances in heavy-ion
collisions and extremely deformed states in light nuclei. For example
superdeformed bands have been recently discovered in light N=Z nuclei such as
Ar, Ca, Cr, and Ni by -ray spectroscopy.
The search for strongly deformed shapes in N=Z nuclei is also the domain of
charged-particle spectroscopy, and our experimental group at IReS Strasbourg
has studied a number of these nuclei with the charged particle multidetector
array {\sc Icare} at the {\sc Vivitron} Tandem facility in a systematical
manner. Recently the search for -decays in Mg has been
undertaken in a range of excitation energies where previously nuclear molecular
resonances were found in C+C collisions. The breakup reaction
MgC has been investigated at E(Mg) = 130 MeV, an
energy which corresponds to the appropriate excitation energy in Mg for
which the C+C resonance could be related to the breakup
resonance. Very exclusive data were collected with the Binary Reaction
Spectrometer in coincidence with {\sc Euroball IV} installed at the {\sc
Vivitron}.Comment: 10 pages, 4 eps figures included. Invited Talk 10th Nuclear Physics
Workshop Marie and Pierre Curie, Kazimierz Dolny Poland, Sep. 24-28, 2003; To
be published in International Journal of Modern Physics
Dissipation of angular momentum in light heavy ion collision
The inclusive energy distributions of fragments (4Z7) emitted in
the reactions O (116 MeV) + Al, Si, Ne (145 MeV) +
Al, Co have been measured in the angular range =
10 - 65. Fusion-fission and deep inelastic components of the
fragment emission have been extracted from the experimental data. The angular
mometum dissipations in fully damped deep inelastic collisions have been
estimated assming exit channel configuration similar to those for
fusion-fission process. It has been found that, the angular momentum
dissipations are more than those predicted by the empirical sticking limit in
all cases. The deviation is found to increase with increasing charge transfer
(lighter fragments). Qualitatively, this may be due to stronger friction in the
exit channel. Moreover, for the heavier system Ne + Co, the
overall magnitude of deviation is less as compared to those for the lighter
systems, {\it i.e.}, O + Al, Si, Ne + Al.
This may be due to lesser overlap in time scales of fusion and deep inelastic
time scales for heavier systems.Comment: 15 pages, 9 figures, accepted for publication in Phys. Rev.
Study of Deformation Effects in the Charged Particle Emission from 46Ti
The 46Ti compound nucleus, as populated by the fusion-evaporation reaction
27Al + 19F at the bombarding energy of 144 MeV, has been investigated by
charged particle spectroscopy using the multidetector array ICARE at the
VIVITRON tandem facility of the IReS (Strasbourg). The light charged particles
have been measured in coincidence with evaporation residues. The CACARIZO code,
a Monte Carlo implementation of the statistical-model code CASCADE, has been
used to calculate the spectral shapes of evaporated alpha-particles which are
compared with the experimental spectra. This comparison indicates the possible
signature of large deformations of the compound nucleus.Comment: 6 pages, 4 figures, Proceedings od the Zakopane 20004 Symposium, to
be published in Acta Phys. Pol. B36 (2005
Large Deformation Effects in the N = Z 44Ti Compound Nucleus
The N = Z 44Ti* nucleus has been populated in Fusion Evaporation process at
very high excitation energies and angular momenta using two entrance channels
with different mass-asymmetry. The deformation effects in the rapidly rotating
nuclei have been investigated through the energy distribution of the
alpha-particle combined to statistical-model calculations. In the case of
low-multiplicity events, the ratio between first particle emitted has been
measured and shows significant disagreement with the predictions of the
statistical-model. This may explain The large discrepancies observed in proton
energy spectra measured in previous experiments performed in the same mass
region.Comment: Proceeding of the 10th International Conference on Nuclear Reaction
Mechanisms, Varenna Italy, June 9-13 2003. 10 pages, 6 figures, 1 tabl
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
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
Second T = 3/2 state in B and the isobaric multiplet mass equation
Recent high-precision mass measurements and shell model calculations~[Phys.
Rev. Lett. {\bf 108}, 212501 (2012)] have challenged a longstanding explanation
for the requirement of a cubic isobaric multiplet mass equation for the lowest
isospin quartet. The conclusions relied upon the choice of the
excitation energy for the second state in B, which had two
conflicting measurements prior to this work. We remeasured the energy of the
state using the reaction and significantly disagree
with the most recent measurement. Our result supports the contention that
continuum coupling in the most proton-rich member of the quartet is not the
predominant reason for the large cubic term required for nuclei
Deformation Effects in Hot Rotating 46Ti Probed by the Charged Particle Emission and GDR gamma-Decay
The 46Ti* compound nucleus, as populated by the fusion-evaporation reaction
27Al+19F at the bombarding energy of E_lab=144 MeV, has been investigated by
charged particle spectroscopy using the multidetector array ICARE at the
VIVITRON tandem facility of the IReS (Strasbourg). The light charged particles
and high-energy gamma-rays from the GDR decay have been measured in coincidence
with selected evaporation residues. The CACARIZO code, a Monte Carlo
implementation of the statistical-model code CASCADE, has been used to
calculate the spectral shapes of evaporated alpha-particles which are compared
with the experimental coincident spectra. This comparison indicates the
signature of large deformations (possibly superdeformed and hyperdeformed
shapes) present in the compound nucleus decay. The occurrence of the Jacobi
shape transition is also discussed in the framework of a newly developed
rotating liquid drop model.Comment: contribution to the COMEX2 conference proceedings, to be published in
Nucl. Phys.
Strong Deformation Effects in Hot Rotating 46Ti
Exotic-deformation effects in 46Ti nucleus were investigated by analysing the
high-energy gamma-ray and the alpha-particle energy spectra. One of the
experiments was performed using the charged-particle multi-detector array ICARE
together with a large volume (4"x4") BGO detector. The study focused on
simultaneous measurement of light charged particles and gamma-rays in
coincidence with the evaporation residues. The experimental data show a
signature of very large deformations of the compound nucleus in the Jacobi
transition region at the highest spins. These results are compared to data from
previous experiments performed with the HECTOR array coupled to the EUROBALL
array, where it was found that the GDR strength function is highly fragmented,
strongly indicating a presence of nuclei with very large deformation.Comment: 10 pages, 6 figures, Proceedings of the Zakopane Conference on
Nuclear Physics, to be published in Acta Phys. Pol. B (2007
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