119 research outputs found
Fission decay of N = Z nuclei at high angular momentum: Zn
Using a unique two-arm detector system for heavy ions (the BRS, binary
reaction spectrometer) coincident fission events have been measured from the
decay of Zn compound nuclei formed at 88MeV excitation energy in the
reactions with Ar beams on a Mg target at Ar) =
195 MeV. The detectors consisted of two large area position sensitive (x,y) gas
telescopes with Bragg-ionization chambers. From the binary coincidences in the
two detectors inclusive and exclusive cross sections for fission channels with
differing losses of charge were obtained. Narrow out-of-plane correlations
corresponding to coplanar decay are observed for two fragments emitted in
binary events, and in the data for ternary decay with missing charges from 4 up
to 8. After subtraction of broad components these narrow correlations are
interpreted as a ternary fission process at high angular momentum through an
elongated shape. The lighter mass in the neck region consists dominantly of two
or three-particles. Differential cross sections for the different mass splits
for binary and ternary fission are presented. The relative yields of the binary
and ternary events are explained using the statistical model based on the
extended Hauser-Feshbach formalism for compound nucleus decay. The ternary
fission process can be described by the decay of hyper-deformed states with
angular momentum around 45-52 .Comment: 23 pages, 25 figure
The population of deformed bands in Cr by emission of Be from the S + Mg reaction
Using particle- coincidences we have studied the population of final
states after the emission of 2 -particles and of Be in nuclei
formed in S+Mg reactions at an energy of . The data were obtained in a setup
consisting of the GASP -ray detection array and the multidetector array
ISIS. Particle identification is obtained from the E and E signals of
the ISIS silicon detector telescopes, the Be being identified by the
instantaneous pile up of the E and E pulses. -ray decays of the
Cr nucleus are identified with coincidences set on 2 -particles
and on Be. Some transitions of the side-band with show
stronger population for Be emission relative to that of 2
-particles (by a factor ). This observation is interpreted as
due to an enhanced emission of Be into a more deformed nucleus.
Calculations based on the extended Hauser-Feshbach compound decay formalism
confirm this observation quantitatively.Comment: 17 pages, 9 figures accepted for publication in J. Phys.
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
Alpha-cluster Condensations in Nuclei and Experimental Approaches for their Studies
The formation of alpha-clusters in nuclei close to the decay thresholds is
discussed. These states can be considered to be boson-condensates, which are
formed in a second order phase transition in a mixture of nucleons and
alpha-particles. The de Broglie wavelength of the alpha-particles is larger
than the nuclear diameter, therefore the coherent properties of the
alpha-particles give particular effects for the study of such states. The
states are above the thresholds thus the enhanced emission of multiple-alphas
into the same direction is observed. The probability for the emission of
multiple-alphas is not described by Hauser-Feshbach theory for compound nucleus
decay.Comment: 21 pages, 12 figures
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
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
Particle-gamma coincidences and coplanarity in the binary reaction
The reaction 32S (165.4 MeV) + 24Mg is studied using the binary reaction spec- trometer (BRS) coupled to the Euroball germanium array. Particle-particle-gamma and particle-gamma-gamma coincidences have been examined. The Z-identification, position and energy information for binary reaction products are shown together with the Doppler-shift corrected gamma-rays emitted from the fragments. Recent reports of evi- dence for hyper-deformation from angular correlations in similar data are also in- vestigated. Analogous out-of-plane angular correlations are observed but attributed to reactions with the target contaminants 16O and 12C
Reaction mechanisms in 24Mg+12C and 32S+24Mg
The occurence of "exotic" shapes in light N=Z alpha-like nuclei is
investigated for 24Mg+12C and 32S+24Mg. Various approaches of superdeformed and
hyperdeformed bands associated with quasimolecular resonant structures with low
spin are presented. For both reactions, exclusive data were collected with the
Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the
VIVITRON Tandem facility of Strasbourg. Specific structures with large
deformation were selectively populated in binary reactions and their associated
-decays studied. The analysis of the binary and ternary reaction
channels is discussed.Comment: 7 pages, 4 figures, Paper presented at the Fusion08 International
Conference on New Aspects of Heavy Ion Collisions Near the Coulomb Barrier,
Chicago. Proceedings to be published by AIP Conference Proceedings Illinois,
USA, September 22-26, 200
High-spin states and band terminations in v 49
High-spin states in 49 V have been studied through the 28 Si(28 Si, α3p) reaction using the EUROBALL γ-ray detector array. The 49 V level scheme has been extended up to 13.1 MeV including 21 new states. Both negative and positive parity states have been interpreted in the framework of theShell Model. The 27/2− and the 31/2+ band termination states have been observed in agreement with theoretical predictions.Fil: Rodrigues Ferreira Maltez, Dario Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Hojman, Daniel Leonardo. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lenzi, Silvia M.. Istituto Nazionale Di Fisica Nucleare.; Italia. Università di Padova; ItaliaFil: Cardona, Maria Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Fernea, Enrico. Università di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Axiotis, M.. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Beck, C.. Université de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Bednarczyk, P.. Polish Academy of Sciences; ArgentinaFil: Bizzetti, P. G.. Università di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Bizzetti Sona, A. M.. Università di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Della Vedova, F.. Università di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Grebosz, J.. Polish Academy of Sciences; ArgentinaFil: Haas, F.. Université de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Kmiecik, M.. Polish Academy of Sciences; ArgentinaFil: Maj, A.. Polish Academy of Sciences; ArgentinaFil: Męczyński, W.. Polish Academy of Sciences; ArgentinaFil: Napoli, D. R.. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Nespolo, M.. Università di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Papka, P.. Université de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Sánchez i Zafra, A.. Université de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Styczen, J.. Polish Academy of Sciences; ArgentinaFil: Thummerer, S.. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung; AlemaniaFil: Ziębliński, M.. Polish Academy of Sciences; Argentin
Clusters in Light Nuclei
A great deal of research work has been undertaken in the alpha-clustering
study since the pioneering discovery, half a century ago, of 12C+12C molecular
resonances. Our knowledge of the field of the physics of nuclear molecules has
increased considerably and nuclear clustering remains one of the most fruitful
domains of nuclear physics, facing some of the greatest challenges and
opportunities in the years ahead. In this work, the occurence of "exotic"
shapes in light N=Z alpha-like nuclei is investigated. Various approaches of
superdeformed and hyperdeformed bands associated with quasimolecular resonant
structures are presented. Results on clustering aspects are also discussed for
light neutron-rich Oxygen isotopes.Comment: 12 pages, 5 figures. Invited Talk presented by C. Beck at the
Zakopane Conference on Nuclear Physics "Extremes of the Nuclear Landscape"
XLV in the series of Zakopane Schools of Physics - International Symposium -
Zakopane, Poland, August 30 - September 5, 2010.To be publihed in Acta
Physica Polonica B42 no 3, March 201
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