D. Jelavić Malenica,1,* M. Milin,2,† S. Blagus,1 A. Di Pietro,3 P. Figuera,3 M. Lattuada,3 Đ. Miljanić,1 A. Musumarra,3 M. G. Pellegriti,3 L. Prepolec,1 V. Scuderi,3 N. Skukan,1 N. Soić,1 S. Szilner,1 D. Torresi,3 and M. Uroić1 1Division of Experimental Physics, Ruđer Bošković Institute, HR-10000 Zagreb, Croatia 2Physics Department, Faculty of Science, University of Zagreb, HR-10000 Zagreb, Croatia 3INFN Laboratori Nazionali del Sud and Sezione di Catania, I-95123 Catania, Italy

B-10 + B-10 reactions are measured with 50 and 72 MeV beams. The large spin of both beam and target nuclei (J(pi) = 3(+)) is particularly suitable for the population of high spin states in the exit channels. Population and decay of different states in C-12 are studied through sequential decay reactions. The C-12 excitation energy spectrum obtained from the B-10(B-10, Be-8) reaction shows a number of both known and new states. In particular, a new state at E-x = 24.4 MeV is observed to be strongly populated in the triple alpha-particle coincidences. The rarely seen state at E-x = 30.3 MeV is found to be strong in the d + B-10 decay channel, reinforcing the previous suggestions that it has the exotic 2 alpha + 2d molecular structure.

The main source of F-19 in the universe has not yet been clearly identified and this issue represents one of the unanswered questions of stellar modeling. This lack of knowledge can be due to the F-19(alpha, p)Ne-22 reaction cross-section that has proven to be difficult at low energies: direct measurements stop only at about similar to 660 keV, leaving roughly half of the astrophysical relevant energy region (from 200 keV to 1.1 MeV) explored only by R-matrix calculations. In this work, we applied the Trojan Horse Method to the quasi-free three-body Li-6(F-19, p(22)Ne)d reaction performed at E-beam = 6 MeV in order to indirectly study the F-19(alpha, p)Ne-22 reaction in the sub-Coulomb energy region. In this way, we obtained the cross-section and the reaction rate in the temperature region of interest for astrophysics and free from electron screening effects. A brief analysis of the impact of the new measured reaction rate in AGB star nucleosynthesis is also presented.

V. Tokića, N. Soića, S. Blagusa, S. Fazinića D. Jelavić-Malenicaa, T. Mijatovića, Ð. Miljanića L. Prepoleca, N. Skukana, S. Szilnera, M. Uroića M. Milinb A. Di Pietroc, P. Figuerac, J.P. Fernández-Garcíac M. Fisichellac, M. Lattuadac, V. Scuderic, E. Stranoc D. Torresic, S. Baileyd, N. Curtisd, M. Freerd, R. Smithd J. Walshed, V. Zimand, L. Acostae, I. Martele G. Marquinez-Duráne, A.M. Sánchez-Beníteze, E. Fiorettof

The abundance of 19F in the universe is strictly related to standard and extramixing processes taking place inside AGB-stars, that are considered to be the most important sites for its production. Nevertheless the way in which it is destroyed is far from being well understood. For this reason we studied the 19F(α,p)22Ne reaction, that is supposed to be the main destruction channel in the Helium-rich part of the star. In this experiment, the reaction has been studied in the energy range of relevance for astrophysics (0÷1 MeV) via the Trojan Horse Method (THM), using the three-body reaction 6Li(19F,p22Ne)d.

The observational F-19 abundance in stellar environments systematically exceeds the predicted one, thus representing one of the unsolved challenges for stellar modeling. It is therefore clear that further investigation is needed in this field. In this work, we focus our attention on the measurement of the F-19(alpha, p)Ne-22 reaction in the astrophysical energy range, between 0.2 and 0.8. MeV (far below the Coulomb barrier, 3.8MeV), as it represents the main destruction channel in He-rich environments. The lowest energy at which this reaction has been studied with direct measurements is similar to 0.66. MeV, covering only the upper tail of the Gamow window, causing the reactionrate evaluation to be based on extrapolation. To investigate lower energies, the F-19(alpha, p) Ne-22 reaction has been studied by means of the Trojan horse method, applied to the quasi-free Li-6(F-19, p(22)Ne) H-2 reaction at E-beam = 6 MeV. The indirect cross section of the F-19(alpha, p)Ne-22 reaction at energies. less than or similar to 1 MeV was extracted, fully covering the astrophysical region of interest and overlapping. existing direct data for normalization. Several resonances have been detected for the first time inside the Gamow window. The reaction rate has been calculated, showing an increase up to a factor of 4 with respect to the literature at astrophysical temperatures. This might lead to potential major astrophysical implications.

The main idea of the two presented experiments is to study the decay of resonances in 24Mg at excitation energies above the 12C+12C decay threshold, in the astrophysical energy region of interest. The measurement of the 12C(16O, gamma)24Mg* reaction was performed at INFN-LNS in Catania. Only the alpha+20Ne decay channel of 24Mg is presented here, because it was a motivation for conducting a new experiment, a study of the4He(20Ne, 4He)20Ne reaction, performed at INFN-LNL in Legnaro. Some preliminary results of this measurement are also presented.

Learning how F-19 is produced and destructed in AGB-stars is crucial. Fluorine abundance is in fact important, given that it is strongly tied to standard and extra-mixing processes taking place in AGB-stars. This kind of objects are considered to be the main sources of fluorine in galactic environment, in which experimental abundances are far overestimated. For this reason the reaction F-19(alpha,p)Ne-22, that represents the main destruction channel in He-rich environment, was studied at energies corresponding to T similar to 2.10(8) K. Such reaction has been studied with direct method at E-beam = 1100 keV for alpha particles impinging on a fluorine target, corresponding to E-C.M. similar to 900 keV, still far from the Gamow window, placed at 390 divided by 800 keV, below the Coulomb barrier (3.81 MeV). An experiment was performed at Rujer Boskovic Institut (Zagreb), applying the Trojan Horse Method. With this experimental procedure we were able to select the quasi-free contribution coming from 6Li(F-19,p Ne-22)H-2 at E-beam = 6 MeV at kinematically useful angles. We measured the F-19(alpha,p)Ne-22 at 0 MeV <= E-C.M <= 0.9 MeV, extracting the two body cross-section in absolute units at energies of astrophysical interest.

Learning how 19F is produced and destructed in AGB-stars is crucial. Fluorine abundance is in fact important, given that it is strongly tied to standard and extra-mixing processes taking place in AGB-stars. This kind of objects are considered to be the main sources of fluorine in galactic environment, in which experimental abundances are far overestimated. For this reason the reaction 19F(α, p)22Ne, that represents the main destruction channel in He-rich environment, was studied at energies corresponding to T∼2·108 K. Such reaction has been studied with direct method at Ebeam = 1100 keV for alpha particles impinging on a fluorine target, corresponding to EC.M. ∼ 900 keV, still far from the Gamow window, placed at 390÷800 keV, below the Coulomb barrier (3.81 MeV). An experiment was performed at Rujer Boskovic Institut (Zagreb), applying the Trojan Horse Method. With this experimental procedure we were able to select the quasi-free contribution coming from 6Li(19F,p 22Ne)2H at Ebeam = 6 MeV at kinematically useful angles. We measured the 19F(α, p)22Ne at 0 MeV ≤ EC.M ≤ 0.9 MeV, extracting the two body cross-section in absolute units at energies of astrophysical interest.

19F experimental abundances is overestimated in respect to the theoretical one: it is therefore clear that further investigations are needed. We focused on the 19F(α, p)22 Ne reaction, representing the main destruction channel in He-rich environments. The lowest energy at which this reaction has been studied with direct methods is EC.M. ≈ 0.91 MeV, while the Gamow region is between 0.39 ÷ 0.8 MeV, far below the Coulomb barrier (3.8 MeV). For this reason, an experiment at Rudjer Boskovic Institute (Zagreb) was performed, applying the Trojan Horse Method. Following this method we selected the quasi-free contribution coming from 6Li(19F,p22 Ne)2 H at Ebeam=6 MeV at kinematically favourable angles, and the cross section at energies 0 < EC.M. < 1.4 MeV was extracted in arbitrary units, covering the astrophysical region of interest.

F-19 experimental abundances is overestimated in respect to the theoretical one: it is therefore clear that further investigations are needed. We focused on the F-19(alpha, p)Ne-22 reaction, representing the main destruction channel in He-rich environments. The lowest energy at which this reaction has been studied with direct methods is E-C.M. approximate to 0.91 MeV, while the Gamow region is between 0.39 divided by 0.8 MeV, far below the Coulomb barrier (3.8 MeV). For this reason, an experiment at Rudjer Boskovic Institut (Zagreb) was performed, applying the Trojan Horse Method. Following this method we selected the quasi-free contribution coming from Li-6(F-19,p(22)Ne)H-2 at E-beam=6 MeV at kinematically favourable angles, and the cross section at energies 0 < E-C.M. < 1.4 MeV was extracted in arbitrary units, covering the astrophysical region of interest.

The Li-6 + Li-6 -> 3 alpha reaction was measured in a kinematically complete experiment at 3.1 and 2.5 MeV to investigate the presence of quasifree processes at sub-Coulomb energies. Results from the present experiment show a very clear evidence of quasifree mechanisms with an alpha-particle spectator either in the target or in the projectile. To check the occurrence of quasifree processes, "energy sharing" and "angular correlation" analyses have been performed in the framework of the plane wave impulse approximation, both leading to consistent results. The huge peak in the angular correlation spectra, previously ascribed to the "anomalous quasifree" process, corresponds instead to the population of the 22.2-MeV (2(+), Gamma = 800 keV) state of Be-8.

C. Spitaleri,1,2,* A. Tumino,1,3 M. Lattuada,1,2 R. G. Pizzone,1 S. Tudisco,1 Đ. Miljanić,4 S. Blagus,4 M. Milin,5 N. Skukan,4 and N. Soić4 1INFN, Laboratori Nazionali del Sud, I-Catania, Italy 2Dipartimento di Fisica e Astronomia, Universitá di Catania, I-Catania, Italy 3Facoltá di Ingegneria e Architettura, Universitá degli Studi di Enna “Kore”, I-Enna, Italy 4Ruđer Bošković Institute, Zagreb, Croatia 5Faculty of Science, University of Zagreb, Zagreb, Croatia (Received 4 December 2014; published 18 February 2015)

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation V. Tokić, N. Soić, S. Blagus, S. Fazinić, D. Jelavić-Malenica, ð. Miljanić, L. Prepolec, N. Skukan, S. Szilner, M. Uroić, M. Milin, A. Di Pietro, P. Figuera, M. Fisichella, M. Lattuada, V. Scuderi, E. Strano, D. Torresi, M. Freer, V. Ziman, I. Martel, A. M. Sánchez-Benítez, L. Acosta; Study of 24Mg resonances relevant for carbon burning nucleosynthesis. AIP Conference Proceedings 9 May 2014; 1595 (1): 248–250. https://doi.org/10.1063/1.4875324 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

We have studied the decays of the resonances of 24Mg at excitation energies 1–6 MeV above the 12C+12C decay threshold, using the 12C(16O,α)24Mg* reaction at E(16O) = 94 MeV. Some preliminary results are presented and further analysis is in progress.

Phototransfered thermoluminescence (PTTL) found its use in radiation dosimetry for dose reassessment primarily in photon radiation fields. After the dose has first been evaluated by a “normal” thermoluminescence (TL) measurement, the same detector is subjected to the PTTL dose reassessment procedure providing a new estimation by an independent measurement procedure. PTTL also gives a new possibility for a dose reassessment and for separate dose determination in the mixed fields. It was shown in our previous papers that it is possible to determine separately gamma and neutron dose components with a single detector due to different sensitivities of TL and subsequent PTTL to neutrons in comparison to gamma rays. The main disadvantage, the low sensitivity of both, TL and PTTL, to neutrons restricts the use only for the case of radiation accident. In this work we have investigated the possibilities of improvement the sensitivities of PTTL by heating the samples during UV irradiation and by using the sensitization technique involving a “pre-dose” followed by annealing. Two types of LiF:Mg,Ti detectors, TLD-100 and TLD-700, were examined by irradiation in 137Cs gamma ray field and with neutrons of 14.5 MeV. After UV irradiation at different temperatures, PTTL increases reaching the values 2.1 and 2.5 times higher at 90 °C than that at 25 °C for TLD-100 and TLD-700 respectively. Increasing level is approximately the same for gamma rays and neutrons. After sensitization, TL signal is one half of that before sensitization. PTTL signal has increased 11 times for gamma rays and 5 times for neutrons at 25 °C with significant increase with increasing temperature during UV irradiation.

Differential cross sections of Li-6,Li-7+Li-7 nuclear reactions have been measured at forward angles (10 degrees and 20 degrees), using particle identification detector telescopes, over the energy range 2.75-10.00 MeV. Excitation functions have been obtained for low-lying residual-nucleus states. The well pronounced peak in the excitation function of Li-7(Li-7,He-4)Be-10(3.37 MeV, 2(+)) at beam energy about 8 MeV, first observed by Wyborny and Carlson in 1971 at 0 degrees, has been observed at 10 degrees, but is less evident at 20 degrees. The cross section obtained for the Li-7(Li-7,He-4)Be-10(g.s, 0(+)) reaction is about ten times smaller. The well pronounced peak in the excitation function of Li-7(Li-7,He-4)Be-10(3.37 MeV, 2+) reaction could correspond to excited states in C-14, at excitation energies around 30 MeV.

Current status of the search for T=1 cluster states in Be-10, B-10 and C-10 is presented. The best known of the three, Be-10, has an established rotational band (6.18, 7.54 and 10.15 MeV) with unusually large moment of inertia. Search of their isobaric analogue in B-10 is presented, with emphasis on He-3+B-11 reaction.