The Giant Dipole Resonance in hot Sn nuclei

Pierroutsakou, D.; Auger, F.; Alamanos, N.; Gomes, P. R. S.; Sida, J. L.; Gillibert, A.; Frascaria, N.; Lhenry, I.; Roynette, J.C.; Suomijärvi, T.

doi:10.1016/0375-9474(95)00470-x

Cited by 29 publications

(22 citation statements)

References 46 publications

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“…The data can be reproduced well in the whole energy region of interest by using the following parameters in the calculation (solid line in the figure): a compound nucleus mass A = 126, E * = 284 MeV, as obtained by the charged particle spectra analysis, and a level density parameter varying with nuclear temperature as described in Ref. [44] and in Ref. [26] therein.…”

Section: Gdr In the Charge Symmetric Reactionmentioning

confidence: 99%

Dynamical dipole mode in fusion reactions at 16 MeV/nucleon and beam energy dependence

Pierroutsakou¹,

Martin²,

Agodi³

et al. 2009

Phys. Rev. C

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High-energy γ rays and light charged particles from the 36Ar + 96Zr and 40Ar + 92Zr reactions at Elab = 16\ud and 15.1 MeV/nucleon, respectively, were measured in coincidence with evaporation residues by means of the\ud MEDEA multidetector array coupled to four parallel plate avalanche counters. The aim of this experiment was to\ud investigate the prompt γ radiation, emitted in the decay of the dynamical dipole mode, in the about 16 MeV/nucleon\ud energy range and to map its beam energy dependence, comparing the present results with our previous ones\ud obtained at lower energies. The studied reactions populate, through entrance channels having different charge\ud asymmetries, a compound nucleus in the region of Ce under the same conditions of excitation energy and spin.\ud Light charged particle energy spectra were used to pin down the average excitation energy and the average mass\ud of the system. By studying the γ -ray spectra of the charge symmetric reaction 40Ar + 92Zr, the statistical giant\ud dipole resonance (GDR) parameters and angular distribution were extracted, and a comparison of the linearized\ud 90◦γ -ray spectra of the two reactions revealed a 12% extra yield in the GDR energy region for the more charge\ud asymmetric system. The center-of-mass angular distribution data of this extra γ yield, compatible with a dipole\ud oscillating along the symmetry axis of the dinuclear system, support its dynamical nature. The experimental\ud findings are compared with theoretical predictions performed within a Boltzmann-Nordheim-Vlasov transport\ud model and based on a collective bremsstrahlung analysis of the entrance channel reaction dynamics.An interesting\ud sensitivity to the symmetry term of the equation of state and to in-medium effects on nucleon-nucleon (nn) cross\ud sections is finally discussed

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Section: Gdr In the Charge Symmetric Reactionmentioning

confidence: 99%

Dynamical dipole mode in fusion reactions at 16 MeV/nucleon and beam energy dependence

Pierroutsakou¹,

Martin²,

Agodi³

et al. 2009

Phys. Rev. C

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“…PACS numbers: 24.30.Cz, 21.60.Ev, 21.65.+f In recent years the GDR built on highly excited states is in the center of many experimental and theoretical studies (c.f. [1] and references therein). In this context, one of the most important open problems is the behaviour of the GDR width in nonrotating nuclei as a function of temperature.…”

mentioning

confidence: 99%

Isovector vibrations in nuclear matter at finite temperature

1999

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We consider the propagation and damping of isovector excitations in heated nuclear matter within the Landau Fermi-liquid theory. Results obtained for nuclear matter are applied to calculate the Giant Dipole Resonance (GDR) at finite temperature in heavy spherical nuclei within Steinwedel and Jensen model. The centroid energy of the GDR slightly decreases with increasing temperature and the width increases as T 2 for temperatures T < 5 MeV in agreement with recent experimental data for GDR in 208 Pb and 120 Sn.The validity of the method for other Fermi fluids is finally suggested.PACS numbers: 24.30. Cz, 21.60.Ev, 21.65.+f In recent years the GDR built on highly excited states is in the center of many experimental and theoretical studies (c.f. [1] and references therein). In this context, one of the most important open problems is the behaviour of the GDR width in nonrotating nuclei as a function of temperature. There are two essentially different theoretical approaches to this problem. The first one [2] explains the temperature increasing of the width as an effect of the adiabatic coupling of the GDR to thermal shape deformations. In the second approach [3,4,5] the thermal contribution to the damping width arises from 1 an increasing nucleon-nucleon collision rate (2p2h excitations) plus a Landau spreading due to thermally allowed ph transitions [6,7,8,9].In the present work, following the ideology of the second approach, we consider isovector volume vibrations in spin-isospin symmetrical nuclear matter at finite temperature. A similar problem was considered in Refs. [7,8] within the RPA method. However the Landau damping mechanism of the dissipation of a propagating mode due to thermal smearing of Fermi distribution is too weak to be responsible for the fast increase of the observed GDR width with temperature [7,8,11]. This problem can be solved by taking into account the two-body dissipation through the collision integral of the Landau-Vlasov equation [3]. The use of a quantum kinetic equation leads to memory effects in the collision term in order to include off energy-shell contributions [12]. Moreover it was shown in Refs. [13,14], that memory effects are essentially increasing the widths of multipole resonances at small temperatures. In this Rapid Communication we calculate the isovector strength function of nuclear matter taking into account both thermal Landau damping and two-body collisional dissipation, including the quantum memory contribution.The isovector response of uniform nuclear matter is described by the linearized Landau-Vlasov equation with a collision term treated in the relaxation time approximation [4,9,14] where δf ≡ δf n −δf p and δU ≡ δU n −δU p are differences between neutron and proton distribution functions (d.f.) and mean fields respectively, δV ≡ δV n − δV p is external field (δV q = τ q δV, τ n = +1,) is the equilibrium finite temperature Fermi distribution, and the notation l ≥ 1 means that the perturbation of the d.f. δf | l≥1 in collision integral includes only Fermi ...

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“…Till now most of the measurements of GDR cross-section built on excited states have been made with Sn and near-Sn nuclei formed by heavy ion fusion reactions. Previous measurements [1,7,8,9,10] suggest the continuous growth of GDR width with excitation energy (E * ) up to 120-130 MeV (T ≤ 2 MeV) and attribute the same to rapid increase of spin-induced deformations and thermal shape fluctuations. As per the experimental observations, beyond the bombarding energy at which angular momentum saturates, the increase in GDR width is very small.…”

Section: Introductionmentioning

confidence: 91%

Giant dipole resonance width in nuclei near Sn at low temperature and high angular momentum

Bhattacharya¹,

Mukhopadhyay

Pandit

et al. 2008

Phys. Rev. C

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High energy γ-rays in coincidence with low energy yrast γ-rays have been measured from 113 Sb, at excitation energies of 109 and 122 MeV, formed by bombarding 20 Ne on 93 Nb at projectile energies of 145 and 160 MeV respectively to study the role of angular momentum (J) and temperature (T) over Giant Dipole Resonance (GDR) width (Γ). The maximum populated angular momenta for fusion were 67h and 73h respectively for the above-mentioned beam energies. The high energy photons were detected using a Large Area Modular BaF 2 Detector Array (LAMBDA) along with a 24-element multiplicity filter. After pre-equilibrium corrections, the excitation energy E * was averaged over the decay steps of the compound nucleus (CN). The average values of temperature, angular momentum, CN mass etc. have been calculated by the statistical model code CASCADE.Using those average values, results show the systematic increase of GDR width with T which is consistent with Kusnezov parametrization and the Thermal Shape Fluctuation Model. The rise of GDR width with temperature also supports the assumptions of adiabatic coupling in the Thermal Shape Fluctuation Model. But the GDR widths and corresponding reduced plots with J are not consistent with the theoretical model at high spins.

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The Giant Dipole Resonance in hot Sn nuclei

Cited by 29 publications

References 46 publications

Dynamical dipole mode in fusion reactions at 16 MeV/nucleon and beam energy dependence

Dynamical dipole mode in fusion reactions at 16 MeV/nucleon and beam energy dependence

Isovector vibrations in nuclear matter at finite temperature

Giant dipole resonance width in nuclei near Sn at low temperature and high angular momentum

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