M. L. Sergi
University of Catania
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Featured researches published by M. L. Sergi.
The Astrophysical Journal | 2013
L. Lamia; C. Spitaleri; R. G. Pizzone; E. Tognelli; A. Tumino; S. Degl'Innocenti; P. G. Prada Moroni; M. La Cognata; L. Pappalardo; M. L. Sergi
The lithium problem influencing primordial and stellar nucleosynthesis is one of the most interesting unsolved issues in astrophysics. 6Li is the most fragile of lithiums stable isotopes and is largely destroyed in most stars during the pre-main-sequence (PMS) phase. For these stars, the convective envelope easily reaches, at least at its bottom, the relatively low 6Li ignition temperature. Thus, gaining an understanding of 6Li depletion also gives hints about the extent of convective regions. For this reason, charged-particle-induced reactions in lithium have been the subject of several studies. Low-energy extrapolations of these studies provide information about both the zero-energy astrophysical S(E) factor and the electron screening potential, Ue . Thanks to recent direct measurements, new estimates of the 6Li(p, ?)3He bare-nucleus S(E) factor and the corresponding Ue value have been obtained by applying the Trojan Horse method to the 2H(6Li, ? 3He)n reaction in quasi-free kinematics. The calculated reaction rate covers the temperature window 0.01 to 2T 9 and its impact on the surface lithium depletion in PMS models with different masses and metallicities has been evaluated in detail by adopting an updated version of the FRANEC evolutionary code.
The Astrophysical Journal | 2010
M. La Cognata; C. Spitaleri; A. M. Mukhamedzhanov; A. Banu; S. Cherubini; A. Coc; V. Crucillà; V. Z. Goldberg; M. Gulino; B. F. Irgaziev; G. G. Kiss; L. Lamia; J. Mrazek; R. G. Pizzone; S. M. R. Puglia; G. G. Rapisarda; S. Romano; M. L. Sergi; G. Tabacaru; L. Trache; R. E. Tribble; W. H. Trzaska; A. Tumino
The 18O(p, ?)15N reaction is of primary importance to pin down the uncertainties, due to nuclear physics input, affecting present-day models of asymptotic giant branch stars. Its reaction rate can modify both fluorine nucleosynthesis inside such stars and oxygen and nitrogen isotopic ratios, which allow one to constrain the proposed astrophysical scenarios. Thus, an indirect measurement of the low-energy region of the 18O(p, ?)15N reaction has been performed to access, for the first time, the range of relevance for astrophysical application. In particular, a full, high-accuracy spectroscopic study of the 20 and 90 keV resonances has been performed and the strengths deduced to evaluate the reaction rate and the consequences for astrophysics.
The Astrophysical Journal | 2014
A. Tumino; R. Spartá; C. Spitaleri; A. M. Mukhamedzhanov; S. Typel; R. G. Pizzone; E. Tognelli; S. Degl'Innocenti; V. Burjan; V. Kroha; Z. Hons; M. La Cognata; L. Lamia; J. Mrazek; S. Piskor; P. G. Prada Moroni; G. G. Rapisarda; S. Romano; M. L. Sergi
The cross sections of the 2H(d,p)3H and 2H(d,n)3He reactions have been measured via the Trojan Horse method applied to the quasi-free 2H(3He,p 3H)1H and 2H(3He,n 3He)1H processes at 18 MeV off the proton in 3He. For the first time, the bare nucleus S(E) factors have been determined from 1.5 MeV, across the relevant region for standard Big Bang nucleosynthesis, down to the thermal energies of deuterium burning in the pre-main-sequence (PMS) phase of stellar evolution, as well as of future fusion reactors. Both the energy dependence and the absolute value of the S(E) factors deviate by more than 15% from the available direct data and existing fitting curves, with substantial variations in the electron screening by more than 50%. As a consequence, the reaction rates for astrophysics experience relevant changes, with a maximum increase of up to 20% at the temperatures of the PMS phase. From a recent primordial abundance sensitivity study, it turns out that the 2H(d,n)3He reaction is quite influential on 7Li, and the present change in the reaction rate leads to a decrease in its abundance by up to 10%. The present reaction rates have also been included in an updated version of the FRANEC evolutionary code to analyze their influence on the central deuterium abundance in PMS stars with different masses. The largest variation of about 10%-15% pertains to young stars (≤1 Myr) with masses ≥1 M ☉.
Journal of Physics G | 2012
L. Lamia; C. Spitaleri; V. Burjan; N. Carlin; S. Cherubini; V. Crucillà; M. Gameiro Munhoz; M. Gimenez del Santo; M. Gulino; Z. Hons; G. G. Kiss; V. Kroha; S. Kubono; M. La Cognata; C. Li; J. Mrazek; A. M. Mukhamedzhanov; R. G. Pizzone; S. M. R. Puglia; Qungang Wen; G. G. Rapisarda; C. Rolfs; S. Romano; M. L. Sergi; E. Somorjai; F. A. Souza; A. Szanto de Toledo; G. Tabacaru; A. Tumino; Y. Wakabayashi
A new measurement of the 11B(p,?0)8Be has been performed applying the Trojan horse method (THM) to the 2H(11B,?80Be)n quasi-free reaction induced at a laboratory energy of 27 MeV. The astrophysical S(E) factor has been extracted from ?600 keV down to zero energy by means of an improved data analysis technique and it has been compared with direct data available in the literature. The range investigated here overlaps with the energy region of the light element LiBeB stellar burning and with that of future aneutronic fusion power plants using the 11B+p fuel cycle. The new investigation described here confirms the preliminary results obtained in the recent TH works. The origin of the discrepancy between the direct estimate of the 11B(p,?0)8Be S(E)-factor at zero energy and that from a previous THM investigation is quantitatively corroborated. The results obtained here support, within the experimental uncertainties, the low-energy S(E)-factor extrapolation and the value of the electron screening potential deduced from direct measurements.
Physical Review Letters | 2008
M. La Cognata; C. Spitaleri; A. M. Mukhamedzhanov; B. F. Irgaziev; R. E. Tribble; A. Banu; S. Cherubini; Alain Coc; V. Crucillà; V. Z. Goldberg; M. Gulino; G. G. Kiss; L. Lamia; J. Mrazek; R. G. Pizzone; S. M. R. Puglia; G. G. Rapisarda; S. Romano; M. L. Sergi; G. Tabacaru; L. Trache; W. H. Trzaska; A. Tumino
The
Physical Review Letters | 2008
M. La Cognata; C. Spitaleri; A. M. Mukhamedzhanov; B. F. Irgaziev; R. E. Tribble; A. Banu; S. Cherubini; Alain Coc; V. Crucillà; V. Z. Goldberg; M. Gulino; G. Kiss; L. Lamia; J. Mrazek; R. G. Pizzone; S. M. R. Puglia; G. G. Rapisarda; S. Romano; M. L. Sergi; G. Tabacaru; L. Trache; W. H. Trzaska; A. Tumino
^{18}{\rm O}(p,\alpha)^{15}{\rm N}
Physical Review C | 2014
C. Spitaleri; L. Lamia; S. M. R. Puglia; S. Romano; M. La Cognata; V. Crucillà; R. G. Pizzone; G. G. Rapisarda; M. L. Sergi; M. Gimenez del Santo; N. Carlin; M. G. Munhoz; F. A. Souza; A. Szanto de Toledo; A. Tumino; B. F. Irgaziev; A. M. Mukhamedzhanov; G. Tabacaru; V. Burjan; V. Kroha; Z. Hons; J. Mrazek; Shu Hua Zhou; Cheng-Bo Li; Qungang Wen; Y. Wakabayashi; H. Yamaguchi; E. Somorjai
reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside AGB stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the
Physical Review C | 2013
M. Gulino; C. Spitaleri; X. D. Tang; G. L. Guardo; L. Lamia; S. Cherubini; B. Bucher; V. Burjan; M. Couder; Paul Davies; R. deBoer; X. Fang; V. Z. Goldberg; Z. Hons; V. Kroha; L. O. Lamm; M. La Cognata; C. Li; C. Ma; J. Mrazek; A. M. Mukhamedzhanov; M. Notani; S. O’Brien; R. G. Pizzone; G. G. Rapisarda; D. Roberson; M. L. Sergi; W. Tan; I. J. Thompson; M. Wiescher
^{18}{\rm O}(p,\alpha)^{15}{\rm N}
Journal of Physics G | 2010
M. Gulino; C. Spitaleri; S. Cherubini; V. Crucillà; M. La Cognata; L. Lamia; R. G. Pizzone; S. Romano; M. L. Sergi; A. Tumino; Li Chengbo; Z. Elekes; E. Somorjai; V. Burjan; V. Kroha; A. M. Mukhamedzhanov
reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances have been deduced and the change in the reaction rate evaluated.
Journal of Physics G | 2008
M. La Cognata; C. Spitaleri; R. E. Tribble; T. Al-Abdullah; A. Banu; S. Cherubini; V. Crucillà; C. Fu; V. Z. Goldberg; M. Gulino; L. Lamia; A. M. Mukhamedzhanov; R. G. Pizzone; S. M. R. Puglia; G. G. Rapisarda; S. Romano; M. L. Sergi; G. Tabacaru; L. Trache; S. Tudisco; A. Tumino; S. Typel; Y. Zhai
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