Study of 12C(α,γ)16O reaction via the transfer reaction 12C(7Li,t)16O

International audienceThe 12C(a,g )16O reaction plays an important role in helium burning in massive stars and their evolution. However, despite many experimental studies, the low-energy cross section of 12C(a,g )16O remains highly uncertain. The extrapolation of the measured cross sections to stellar energies (E=300 keV) is made difficult by the presence of the two sub-threshold states at 6.92 (2+) and 7.12 (1−) MeV of 16O. In order to further investigate the contribution of these twosubthreshold resonances to the 12C(a,g )16O cross section, we performed a new determination of the a-reduced widths of the 6.92 and 7.12 MeV of 16O via a measurement of the transfer reaction 12C(7Li,t)16O at two incident energies, 34 and 28 MeV. The measured and calculated differential cross sections are presented as well as the obtained spectroscopic factors and the a-reduced widths for the 2+ and 1− sub-threshold states and their effect on the R-matrix calculations of 12C(a,g )16O

Interesting states in A = 10 mass region, populated in 10B + 10B nuclear reactions

The 10B+10B reactions are measured at beam energies of 50 and 72.2 MeV. The large spin of 10B nucleus (J= 3+) makes this reaction particularly suitable to populate high spin states in the exit channels. Population and decay of different states in A≈10 mass region is studied, and the results are discussed from the structure point of view. In particular, a new state in 12C at Ex= 24.4 MeV is observed to be strongly populated in the triple α-particle coincidences

Thick-target inverse kinematic method in order to investigate alpha-clustering in212Po

The inverse-kinematic thick-target method has been used in order to investigate 212Po alpha-structure by the elastic scattering of 208Pb on 4He target. A 208Pb beam, accelerated by the Superconducting Cyclotron (CS) of Laboratori Nazionali del Sud - INFN, at the incident energy of 10.1 A MeV was impinging onto a specifically designed 4He gas cell, two meter long. The gas cell wasacting both as target and as beam degrader, stopping the beam before reaching the alpha-particle detection system placed at 0° with respect to the beam axis. In order to disentangle the elastic contribution from other reaction channels (e.g. inelastic scattering) a microchannel plate was used to measure the Time of Flight(ToF) of both the 208Pb beam particles and the ejectiles along the gas cell. The 208Pbstopping power in the 4He gas target was also measured, as a key ingredient in order to establish theinteraction point inside the gas cell, in turn determining the solid angle covered by the detector. In the following, the experimental technique will be described, and the results of a preliminary data analysis will be shown

An above-barrier narrow resonance in F-15

Intense and purified radioactive beam of post-accelerated O-14 was used to study the low-lying states in the unbound F-15 nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at E-R = 4.757(6)(10) MeV with a width of Gamma = 36(5)(14) keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a C-12 core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the 2s(1/2) shell. (C) 2016 The Authors. Published by Elsevier B.V

XRF analysis searching for fingerprint elemental profile in south-eastern Sicily tomatoes

Abstract The implementation of analytical techniques able to certify food quality and origin in a fast and non-destructive way is becoming a widespread need in the agri-food sector. Among the physical non-destructive techniques, X-ray fluorescence (XRF) spectrometry is often used to analyze the elemental composition of biological samples. In this study, X-ray fluorescence (XRF) elemental profiles were measured on tomato samples belonging to different geographical areas in Sicily (Italy). The purpose of this investigation was aiming to establish a protocol for in-situ measurement and analysis able to provide quality assessment and traceability of PGI agri-food products, specifically sustaining health safety and self qualifying bio-chemical signature. In detail, sampling was performed in one of the most tomato productive area of south-eastern Sicily (Pachino district), characterised by a relative higher amount of Organic Carbon and Cation Exchange Capacity, and compared with samples from other growing areas of Sicily, falling in Ragusa province and Mt. Etna region. Experimental data were analyzed in the framework of multivariate analysis by using principal component analysis and further validated by discriminant analysis. The results show the presence of specific elemental signatures associated to several characterizing elements. This methodology establishes the possibility to disentangle a clear fingerprint pattern associated to the geographical origin of an agri-food product

Thick-target inverse kinematic method in order to investigate alpha-clustering in

The inverse-kinematic thick-target method has been used in order to investigate 212Po alpha-structure by the elastic scattering of 208Pb on 4He target. A 208Pb beam, accelerated by the Superconducting Cyclotron (CS) of Laboratori Nazionali del Sud - INFN, at the incident energy of 10.1 A MeV was impinging onto a specifically designed 4He gas cell, two meter long. The gas cell wasacting both as target and as beam degrader, stopping the beam before reaching the alpha-particle detection system placed at 0° with respect to the beam axis. In order to disentangle the elastic contribution from other reaction channels (e.g. inelastic scattering) a microchannel plate was used to measure the Time of Flight(ToF) of both the 208Pb beam particles and the ejectiles along the gas cell. The 208Pbstopping power in the 4He gas target was also measured, as a key ingredient in order to establish theinteraction point inside the gas cell, in turn determining the solid angle covered by the detector. In the following, the experimental technique will be described, and the results of a preliminary data analysis will be shown

Indirect study of 13C(α,n)16O

The reaction 13C(α,n)16O is considered as the main neutron source for s-process in low-mass asymptotic giant branch stars. At low energies of astrophysical interest, the contribution of the subthreshold state 6.356 MeV of 17O to the 13C(α,n)16O cross section should be taken into account. However, the results of previous studies of this contribution lead to different conclusions. Hence, we investigated the effect of this resonance on the astrophysical S-factor through a new precise measurement of the alpha spectroscopic factor, S α, of the 6.356 MeV state using the transfer reaction 13C(7Li,t)17O at two different incident energies. The measured angular distributions and the obtained spectroscopic factors will be presented as well as their impact on C(α,n)16O cross section and reaction rate. © 2008 American Institute of Physics.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Transfer reactions as tool for nuclear astrophysics: the 13 C(α,n) 16 O case

The cross section of the nuclear reactions involved in stellar nucleosynthesis (e.g. AGB stars) are often very difficult to measure directly at stellar energies because of their very small value. Moreover, this situation can be complicated by the existence of very low energy resonances and/or subthreshold resonances. Indirect methods such as transfer reactions and the ANC method offer the possibility to overcome these difficulties. In this context, recent indirect measurement of the reaction 13 C(α,n) 16 O is presented. The 13 C(α,n) 16 O reaction is considered as the main neutron source for s-process in low-mass asymptotic giant branch stars. At low energies of astrophysical interest, the contribution of the subthreshold state 6.356 MeV of 17 O to the 13 C(α,n) 16 O cross section should be taken into account. However, the results of previous studies of this contribution lead to different conclusions. Hence, we investigated the effect of this resonance on the astrophysical S-factor through a new precise measurement of the alpha spectroscopic factor, Sα, and the corresponding ANC of the 6.356 MeV state using the transfer reaction 13 C ( 7 Li,t) 17 O at two different incident energies. The measured angular distributions and the obtained spectroscopic factor and the asymptotic normalization constant (ANC) are presented as well as their impact on 13 C(α,n) 16 O cross section an

Indirect study of the 13C(alpha,n)16O reaction via the 13C(7Li,t)17O transfer reaction

info:eu-repo/semantics/publishe