Carmelo Saccà

Entrance channel effect on the formation of heavy and superheavy nuclei

We study the effect of the entrance channel and the shell structure of reacting massive nuclei on the fusion mechanism and the formation of evaporation residues of heavy and superheavy nuclei. In the framework of the combined dinuclear system concept and advanced statistical model, we analyze the 40 Ar + 176 Hf, 86 Kr + 130 Xe and 124 Sn + 92 Zr reactions leading to 216 Th * ; the 32 S + 182 W, 48 Ti + 166 Er, and 60 Ni + 154 Sm reactions leading to 214 Th * ; the 40 Ar + 181 Ta reaction leading to 221 Pa * ; the 48 Ca + 248 Cm reaction leading to the 296 116 compound nucleus. In our calculations of the excitation functions for capture, fusion and evaporation residues we use the relevant variables such as mass-asymmetry of nuclei in the entrance channel, relative distance between nuclear centers, shell effect and shape of colliding nuclei and such characteristics of the reaction mechanism as potential energy surface, driving potential, the dependence of capture, fusion cross sections and survival probabil...

Role of the Target Orientation Angle and Orbital Angular Momentum in the Evaporation Residue Production

The influence of the orientation angles of the target nucleus symmetry axis, relative to the beam direction, on the production of the evaporation residues is investigated for the 48 Ca+ 154 Sm reaction as a function of beam energy. At low energies ( E c.m. 180 MeV, σ ER ranges approximately 0.1–10 mb because the fission barrier for a compound nucleus decreases with increasing excitation energy and angular momentum.

BREMSSTRAHLUNG EMISSION DURING α-DECAY OF 226Ra

We obtained the spectrum of probability of the bremsstrahlung emission accompanying the α-decay of 226Ra(Eα = 4.8 MeV) by measuring the α-γ coincidences and using the model presented in our previous study on the α-decay of 214Po(Eα = 7.7 MeV). We compare the experimental data with the quantum mechanical calculation and find a good agreement between theory and experiment. We discuss the differences between the photon spectra connected with the α-decay of the 226Ra and 214Po nuclei. For the two mentioned nuclei, we analyze the bremsstrahlung emission contributions from the tunneling and external regions of the nucleus barrier into the total spectrum, and we find the destructive interference between these contributions. We also find that the emission of photons during tunneling of the α-particle gives an important contribution to the bremsstrahlung spectrum in the whole Eγ energy range of the studied 226Ra nucleus.

Investigation of the role of the projectile-target orientation angles on the evaporation residue production

The measured yield of evaporation residues in reactions with massive nuclei have been well reproduced by using the partial fusion and quasifission cross sections obtained in the dinuclear-system model. The influence of the orientation angles of the projectile- and target-nucleus symmetry axes relative to the beam direction on the production of the evaporation residues is investigated for the 48Ca + 154Sm reaction as a function of the beam energy. At the low beam energies only the orientation angles close to αP = 30° (projectile) and αP = 0°–15° (target) can contribute to the formation of evaporation residues. At large beam energies (about Ec.m. = 140–180 MeV) the collisions at all values of orientation angles αP and αT of reactants can contribute to the evaporation residue cross section which ranges between 10–100 mb, while at Ec.m. > 185 MeV the evaporation residue cross section ranges between 0.1–1 mb because the fission barrier for the compound nucleus decreases by increasing its excitation energy and angular momentum.

Bremsstrahlung emission of photons accompanying ternary fission of 252Cf

We present the first results on the bremsstrahlung emission of photons accompanying ternary spontaneous fission of the 252Cf nucleus. We also compare our calculations on the basis of quantum model with preliminary experimental data and find a good agreement between theory and experiment for photon energies up to 500 keV, when the α-particle emission is in presence of the field of two fission fragments of the daughter nucleus.

Associazioni a Foraminiferi nel sistema di stagni costieri di Oliveri-Tindari (Sicilia nordorientale)

Foraminiferal assemblages in the coastal pools system from Oliveri-Tindari (North-eastern Sicily).Benthic foraminiferal assemblages from the Oliveri-Tindari lagoon (Messina, Italy), located on the Tyrrhenian coast of Sicily, have been studied.Results of grain size analyses showed that the silt fraction is predominant in almost all pools, except for the Marinello and Mergolo pools, whose sediment can be classified as silty clays.Optical microscopy examination revealed that size fractions higher than 63µm include both terrigenous and biogenic components (mostly Foraminifera).Based on micropaleontological study, the fauna consisted of 55 foraminiferal species belonging to 26 genera. The benthic foraminiferal assemblages included eurytherme and euryhaline taxa (Miliolids, Peneroplids and Ammonias), that are characteristic of sandy substratum and warm shallow waters or brackish environments. The foraminiferal assemblages also seemed to be diversified in relation to the grain-size.An estimation of the species diversity was performed using different parameters.Statistic diversity indexes showed that the two most ancient pools (Marinello and Mergolo) are considerably less rich in species than the other ones (Nuovo, Porto Vecchio, Fondo Porto, Verde). The observed stability of the foraminiferal assemblages confirmed they are reliable indicators of average environmental conditions of coastal ponds as highly dynamic environments, at least in the short-middle temporal scale.

Radiation of bremsstrahlung accompanying the α-decay of heavy nuclei

This paper presents the spectrum of the bremsstrahlung emission accompanying the α-decay of 226Ra (E α=4.8 MeV) by measuring the α−γ coincidences. We analyze the spectrum by using the model presented in our previous study on the α-decay of 214Po (E α=7.7 MeV). We compare the experimental data with the quantum mechanical calculation and find a good agreement between theory and experiment. We analyze the bremsstrahlung emission contributions from the tunneling and external regions of the nucleus barrier into the total spectrum, and find destructive interference between these contributions.

Role of the orientation angles of reacting nuclei in evaporation residue production

The influence of the orientation angles of the projectile- and target-nucleus symmetry axes relative to the beam direction on the production of the evaporation residues (ERs) is investigated for the 48Ca+154Sm reaction as a function of the beam energy. The measured yields of ERs by massive nuclei reactions have been well reproduced by using the partial fusion and quasi-fission cross-sections obtained in the dinuclear system model. At lower beam energies, only the orientation angles close to αP=30° (projectile) to αP=0°–15°(target) can contribute to the ER formation. At large beam energies (about E c.m.=140–180 MeV), all αP−αT configurations of reactants can contribute to the ER cross-section, which ranges between 10 and 100 mb, while at E c.m.>185 MeV, the ER cross-section ranges between 1 and 0.1 mb because the fission barrier for the compound nucleus decreases by increasing its excitation energy and angular momentum.

The main lithoid material origin of the Temple of Hercules in San Marco d'Alunzio (Sicily, Italy)

This study compares four samples of travertine collected in the lithoid material of the Temple of Hercules (III-IV century B.C.) in San Marco d’Alunzio (Messina) and other four samples of the same lithotype collected in an outcrop found in the surroundings of Alcara Li Fusi (Messina). Analyses on sedimentary petrology, paleontology, XRay diffraction and infrared spectroscopy have been carried out on both series of samples. Chemical analyses, for the determination of the major and trace elements, were carried out too. Sedimentary petrology and paleontological studies have indicated that all samples consist of Quaternary soft and porous organic limestones with plant remains, formed in wet and warm zones. X-ray diffraction analyses have shown that studied travertines are prevalently made up of calcite. Infrared spectroscopy studies also showed small quantities of kaolinite and dolomite. Chemical analyses have confirmed the compositional homogeneity among the different samples. Data, as a whole, allow us to hypothesize that the travertines used to build the Temple of Hercules were extracted in the surroundings areas of Alcara Li Fusi, in ancient open quarries set up in Quaternary travertines.

Geochemical and mineralogical features of the polymetallic deposit from Alì (NE Sicily, Italy)

The mineralization processes in the Peloritani Belt (Southern Sector of the Calabria- Peloritani Arc), related to Pre-Variscan intracontinental rifting, produced sedextype Pb, Zn, F (Ag), Cu, W (As, Sb) ores. This paper focuses on the metalliferous stratabound mineralization outcropping in the Al`? area (Tripi locality). It is part of sulphide ores, concordant with the regional foliation of the hosting unit (Fv2), very widespread in the Mandanici Unit (MaU). This unit is characterized by a Variscan low-P, polyphasic and plurifacial metamorphic overprint involving the basement. This metamorphic overprint exhibits a prograde zoning, from a chlorite zone of greenschist facies to an oligoclasealmandine zone of amphibolite facies. The metalliferous mineral association is formed by galena, sphalerite, pyrite, chalcopyrite, arsenopyrite and covellite. Quartz and fluorite among non-metalliferous minerals are predominant. Some minerals like quartz, fluorite, galena, sphalerite and pyrite are present in two generations, the second of which can be related to intense hydrothermal activity involving the whole Peloritani Belt. Trace-element contents of sulphide ores detected by Atomic Absorption and Inductively Coupled Plasma-Mass Spectrometry on powdered and selected samples of minerals have been determined. Major elements have been analyzed by Scanning Electron Microscopy. The Ag content is quite high in galena, relative to the same mineral of other Peloritani deposits in which this content is around 1000 ppm. Galena shows a high content of Sb (¯x= 621) and lower values of Cd (¯x=132) and Cu (¯x=108) whereas in sphalerite the Sb content (¯x= 134) is lower than Cd (¯x= 1118) and Cu (¯x= 1127). Mn is scarcely present in sphalerite, while galena shows higher contents. Fe content in sphalerite is about 6%, in agreement with Pressure-Temperature conditions of the Unit.