Opažanje α-raspada 10B i 12B u 9Be +7Li reakcijama

The 10B and 12B excitation energy spectra have been obtained from the inclusive and coincident measurements of the 9Be +7Li reactions at Ebeam=52 MeV. Contributions of the 10B states below 10 MeV and of the 12B states below 16 MeV excitation have been resolved. 10B states at 4.77 and 6.56 MeV as well as groups of states around 5.1 and 6 MeV decaying into α +6Li, and of the state at 7.0 MeV decaying into α +6Li∗ have been found. These measurements give the first evidence for α +8Li decay of the 12B states. In our data, there is no evidence for the α +8Li∗ (0.98 MeV) and α +8Li∗ (2.26 MeV) decays of 12B. The influence of α-decaying 12B states on the cross section of the astrophysically important 8Li(α,n)11B reaction is discussed.Odredili smo uzbudne energijske spektre 10B i 12B uključivim i sudesnim mjerenjima reakcije 9Be+7Li na Esnop=52 MeV. Razdvojili smo doprinose stanja 10B ispod 10 MeV i stanja 12B ispod 16 MeV. Našli smo raspade stanja 10B na 4.77 i 6.56 MeV i grupa stanja oko 5.1 i oko 6 MeV u α +6Li, i stanja na 7.0 MeV u α +6Li∗ . Ovo su prva mjerenja u kojima se nalazi α +8Li raspad viših stanja 12B. Naši podaci ne ukazuju prisutnost α +8Li∗ (0.98 MeV) i α +8Li∗ (2.26 MeV) raspada 12B. Raspravljamo utjecaj stanja 12B koja podliježu α-raspadu na udarne presjeke astrofizički važne reakcije 8Li(α,n)11B

Reakcija 11B(p,αα) 4He u uvjetima kolinearnosti

The 11B(p,αα) 4He reaction was measured at eight incident proton energies, from 2 to 5.5 MeV, for the collinearity configurations (an α-particle at rest in the c.m. system). The results are compared with predictions of the Sch¨afer model. Involvement of the 12C states with excitation energy between 17.8 and 21 MeV is discussed.Mjerena je reakcija 11B(p,αα) 4He za osam upadnih energija protona, od 2 do 5.5 MeV, u uvjetima kolinearnosti (jedna α-čestica miruje u sustavu centra masa). Rezultati su uspoređeni s predviđanjima Schaferovog modela. Diskutirana je uloga stanja jezgre 12C s energijama pobuđenja između 17.8 i 21 MeV

Reaction studies with low-energy weakly-bound beams at INFN-LNS

The reaction dynamics of collisions involving halo or weakly bound nuclei, at energies around the Coulomb barrier, can be strongly affected by the structure of such nuclei. Very strong entrance channel effects have been observed on various reaction pocess such as, elastic scattering, fusion and direct reactions when comparing collision induced by the 6He and 11Be halo nuclei with the ones induced by their cores 4He and 10Be. Collisions induced by the stable weakly bound nuclei 6Li, 7Li show also some peculiarities in comparison to the ones induced by well bound nuclei; coupling with the break-up channel is in fact very important in reproducing low energy data. In this contribution an overview of our present understanding of the discussed topic will be given along with the discussion of some new preliminary results

15O+α resonant elastic scattering to study cluster states in19Ne

Clustering phenomena are well known in nuclear physics for stable nuclei, both α-conjugate (N=Z, A=2N), like8Be,16O,20Ne, and non-α-conjugate, like6Li and7Li. In general, it is expected that light exotic nuclei may also exhibit cluster behavior. Moving out of the valley of stability configurations can be found where at least one of the clusters is unbound or weakly bound, thus not satisfying the strong internal correlation requirement of classical clusters. This is so-called exotic clustering. The study of such systems presents many difficulties, due, mainly, to the low intensities typical of radioactive ion beams. Therefore, few significant experimental studies have been performed so far. In this work we searched for α-cluster states in19Ne above its α-decay threshold measuring, for the first time, the15O(4He,4He) elastic scattering excitation function. Moreover, this study classified low-energy states in Ne in the astrophysically important region in this HCNO-break-out nucleus.European Unions Horizon 2020 65974

Comparison of the effects of couplings to breakup channels in reactions induced by 6Li and 6He on the same 64Zn target

The experimental elastic scattering angular distributions for the weakly bound nuclei 6,7Li and for the halo nucleus 6He on the same 64Zn target at several energies around the Coulomb barrier were measured at the Laboratori Nazionali del Sud (LNS, Italy) and at the Cyclotron Research Center, Louvain La Neuve (Belgium), respectively. The measured elastic scattering angular distributions of these three systems at the same center of mass energy have been compared. The experimental data of the 6,7Li+ 64Zn systems have been analyzed within the CDCC method, while the 6He+64Zn data have been compared with both both CDCC and CRC calculations

A new analysis technique to measure fusion excitation functions with large beam energy dispersions

Peculiar nuclear structures of two colliding nuclei such has clustering, neutron halo/skin or very low breakup thresholds can affect the reaction dynamics below the Coulomb barrier and this may also have astrophysical consequences. In order to have a better understanding of this topic, in the last decade, several experiments were performed. A typical experimental challenge of such studies is the need to measure excitation functions below the Coulomb barrier, having a strong energy dependence, with rather large beam energy dispersions inside the target. This may easily lead to ambiguities in associating the measured cross section with a proper beam energy. In this paper a discussion on this topic is reported and a new technique to deal with the above problem will be proposed

Experimental investigation of exotic clustering in 13B and 14C using the resonance scattering method

In order to investigate the existence of molecular and/or exotic cluster configurations in Boron and Carbon n-rich isotopes we undertook two experiments: the first experimental study of exotic 9Li+α cluster states in 13B using the resonance scattering method at TRIUMF (Canada), and, with the same technique, the measurement of 10Be+α scattering at LNS in Catania, where a 10Be radioactive beam was produced for the first time. In order to measure the excitation function in a wide energy range, the beams were stopped in a Helium-flooded chamber. In the case of 13B, the elastic excitation function shows the presence of various peaks in an excitation energy region never explored before. In the case of 14C, our exclusive measurement of elastic scattering data with a high intensity beam, sheds some light on the contradictory previously published results [1, 2]

Stopping power of helium gas for ^9Be ions from 2 to 31 MeV

Abstract The stopping power of helium gas for 9Be ions from 2 to 31 MeV is experimentally determined using an indirect method. The residual energy of the 9Be beam as a function of the gas thickness is measured and the stopping power determined by differentiating the thickness–energy curve. The results are compared with predictions of the semi-empirical codes SRIM-2003 and MSTAR. Our data are in better agreement with the MSTAR calculations. The elastic scattering excitation function for the system 9Be + α, extracted using the thick target technique and our stopping power data, is in excellent agreement with the ones measured directly confirming the quality of our data