Compilation of Giant Electric Dipole Resonances Built on Excited States

Giant Electric Dipole Resonance (GDR) parameters for gamma decay to excited states with finite spin and temperature are compiled. Over 100 original works have been reviewed and from some 70 of which more than 300 parameter sets of hot GDR parameters for different isotopes, excitation energies, and spin regions have been extracted. All parameter sets have been brought onto a common footing by calculating the equivalent Lorentzian parameters. The current compilation is complementary to an earlier compilation by Samuel S. Dietrich and Barry L. Berman (At. Data Nucl. Data Tables 38(1988)199-338) on ground-state photo-neutron and photo-absorption cross sections and their Lorentzian parameters. A comparison of the two may help shed light on the evolution of GDR parameters with temperature and spin. The present compilation is current as of January 2006.Comment: 31 pages including 1 tabl

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.

Quadrupole collectivity in Ca 42 from low-energy Coulomb excitation with AGATA

A Coulomb-excitation experiment to study electromagnetic properties of Ca42 was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in Ca42 were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2 matrix elements coupling six low-lying states in Ca42, including the diagonal E2 matrix elements of 21+ and 22+ states, were determined using the least-squares code gosia. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 01,2+ and 21,2+ states, as well as triaxiality for 01,2+ states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in Ca42. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in Ca42

Superdeformed and Triaxial States in Ca 42

Shape parameters of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in ^{42}Ca were determined from E2 matrix elements measured in the first low-energy Coulomb excitation experiment performed with AGATA. The picture of two coexisting structures is well reproduced by new state-of-the-art large-scale shell model and beyond-mean-field calculations. Experimental evidence for superdeformation of the band built on 0_{2}^{+} has been obtained and the role of triaxiality in the A∼40 mass region is discussed. Furthermore, the potential of Coulomb excitation as a tool to study superdeformation has been demonstrated for the first time

Thermonuclear rates of the 28Si(p, y) reaction

The 28Si(p, y) reaction data have been analysed in terms of two alternative versions of the directsemidirect model. The extrapolation of the theoretical excitation functions has been made and the astrophysical S-factor has been extracted with no significant differences between the predictions of the models. The analysis reveals the dominant role of the nonresonant process at temperatures less than T9 = 0.10.Nous avons analysé les données de la réaction 28Si(p, y) suivant deux versions du modèle directsemidirect. L'extrapolation des fonctions d'excitation théoriques et le coefficient astrophysique S sont obtenus sans différences significatives entre les deux modèles. L'analyse révèle le rôle dominant du processus non résonnant pour des températures inférieures à T9 = 0,10

Measurement of the γ\gamma Decay from the Energy Region of the Pygmy Dipole States Excited in the 208^{208}Pb(p,p′γ)(p,p'\gamma ) Reaction at CCB

International audienceFor a few years, the medical cyclotron Proteus C-235 at the Cyclotron Centre Bronowice in Kraków, Poland has been regularly used for nuclear structure experiments. One of the ongoing studies is focused on the γ decay of collective states populated in (p, p0γ) reactions. In a recent experiment, γ decays of excited states in the energy region of the Pygmy Dipole States in 208Pb have been observed. Good efficiency and energy resolution provided by the PARIS clusters and LaBr3:Ce scintillators facilitate a comparison of the obtained energy spectra with previous measurements of pygmy states in this nucleus