Nuclear Reactions of Astrophysical Interest Involving Light Nuclei

Balogh, W.; Efros, V.D.; Herndl, H.; Hofinger, R.

doi:10.1007/978-3-7091-9427-0_42

Cited by 4 publications

(2 citation statements)

References 22 publications

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“…The study of 7 Be and 8 B dynamical behavior is relevant for the understanding of several processes in the universe [1]: 7 Be is at the top side of the reaction network which describes the primordial nucleosynthesis in the framework of the standard Big Bang, being involved in the production of the primordial lithium; jointly with 8 B, is a main actor in the proton-proton chains of hydrogen burning in the main-sequence stars like our sun; in particular, 7 Be is at the vertex of two reaction chains, being the product of the 3 He+ 4 He fusion; beta decays of 7 Be and 8 B are responsible of the neutrino flux from the Sun, studied for the understanding of neutrino oscillations; finally, 7 Be is involved in additional reaction networks which describe the nucleosynthesis model of the inomogeneus big bang and some supernovae. 7 Be and 8 B are exotic nuclei which are also intriguing for the peculiar structures they exhibit: 8 B is characterized by a proton halo (which was discovered by measuring its quadrupole moment [2]); 7 Be, which is the core of 8 B, shows a cluster structure consisting of a 3 He- 4 He system.…”

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confidence: 99%

⁷Be and ⁸B reaction dynamics at Coulomb barrier energies

et al. 2018

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Abstract. We investigated the reaction dynamics induced by the 7 Be, 8 B+ 208 Pb collisions at energies around the Coulomb barrier. Charged particles originated by both the collisions were detected by means of 6 ∆E-E res telescopes of a newly developed detector array. Experimental data were analysed within the framework of the Optical Model and the total reaction cross-sections were compared together and with the 6,7 Li+ 208 Pb colli- (2018) https://doi.org/10.1051/epjconf/201818402015 9 th European Summer School on Experimental Nuclear Astrophysics sion data. According to the preliminary results, 7 Be nucleus reactivity is rather similar to the 7 Li one whereas the 8 B+ 208 Pb total reaction cross section appears to be much larger than those measured for reactions induced by the other weakly-bound projectiles on the same target.

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Section: Introductionmentioning

confidence: 99%

⁷Be and ⁸B reaction dynamics at Coulomb barrier energies

et al. 2018

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“…In order to show how to implement this method in the case of three-body radiative capture, two examples are worked out: the two-neutron radiative capture by 9 Li to produce 11 Li and by 4 He to produce 6 He. The 9 Li(2n,γ ) 11 Li reaction could appear in the α-process in type II supernovae or in the inhomogeneous big bang [18]. Although the 11 Li formation might not be very relevant for astrophysics, this case is chosen to illustrate the method since reasonable experimental data on inclusive break-up cross sections has been measured recently at TRIUMF [17] at the angles required for the applicability of the present procedure.…”

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Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements

et al. 2016

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A relationship between the Coulomb inclusive break-up probability and the radiative capture reaction rate for weakly bound three-body systems is established. This direct link provides a robust procedure to estimate the reaction rate for nuclei of astrophysical interest by measuring inclusive break-up processes at different energies and angles. This might be an advantageous alternative to the determination of reaction rates from the measurement of B(E1) distributions through exclusive Coulomb break-up experiments. In addition, it provides a reference to assess the validity of different theoretical approaches that have been used to calculate reaction rates. The procedure is applied to 11 Li ( 9 Li + n + n) and 6 He ( 4 He + n + n) three-body systems for which some data exist.DOI: 10.1103/PhysRevC.93.041602Nucleosynthesis occurs in stellar environments, following a complex network of reactions in which heavier nuclei are formed by proton, neutron, or α radiative capture by a lighter nucleus. The knowledge of these radiative capture reaction rates is crucial for the stellar models aiming to describe the evolution in composition, energy production, and temperature structure of different stellar environments (see, for example, Ref.[1] and references therein). The direct experimental measurement of the relevant cross sections is, in principle, possible for two-body reactions [2,3]. In many interesting cases, however, reaction cross sections cannot be measured directly. This may occur if the initial nucleus is short-lived [4] or when the capture process is a three-body reaction [5]. In this case, the inverse reaction to radiative capture, photodissociation, could be measured [4]. Reaction rates are then obtained by integrating the photodissociation cross section for the compound nucleus, weighted with the Maxwell-Boltzmann energy distribution and the relevant phase space factors, from the corresponding energy threshold [6,7]. Direct photodissociation measurements can be done only for stable nuclei, e.g., 12 C [8], sometimes with important discrepancies among different experiments, e.g., 9 Be [5,9]. Thus, for many relevant cases this technique is not feasible (e.g., 17 Ne [10]). In addition, to obtain the reaction rate from experimental photodissociation measurements usually requires, for three-body systems, a sequential description of the formation process, which is questionable at low temperatures if the particles do not have enough energy to populate intermediate resonances [11].At first order, the energy distribution of the photodissociation cross section is determined by the B(E1) distribution, of the compound nucleus, into the continuum of its fragments [12]. Hence, an alternative to obtain this cross section, when the nucleus is short-lived, is to perform exclusive Coulomb breakup experiments at intermediate energies (∼100 MeV/nucleon) on heavy targets, at very forward angles [13,14]. From the exclusive break-up cross section, the B(E1) is extracted * jcasal@us.es assuming Coulomb is dominant at those angles. Howe...

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Reaction rate for two-neutron capture by4He

Efros

Balogh

Herndl

et al. 1996

Z. Physik A — Hadrons and Nuclei

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Recent investigations suggest that the neutrino-heated hot bubble between the nascent neutron star and the overlying stellar mantle of a type-II supernova may be the site of the r-process. In the preceding α-process building up the elements to A ≈ 100, the 4 He(2n,γ) 6 Heand 6 He(α,n) 9 Be-reactions bridging the instability gap at A = 5 and A = 8 could be of relevance. We suggest a mechanism for 4 He(2n,γ) 6 He and calculate the reaction rate within the α+n+n approach. The value obtained is about a factor 1.6 smaller than the one obtained recently in the simpler direct-capture model, but is at least three order of magnitude enhanced compared to the previously adopted value. Our calculation confirms the result of the direct-capture calculation that under representative conditions in the α-process the reaction path proceeding through 6 He is negligible compared to 4 He(αn,γ) 9 Be.

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Nuclear Reactions of Astrophysical Interest Involving Light Nuclei

Cited by 4 publications

References 22 publications

⁷Be and ⁸B reaction dynamics at Coulomb barrier energies

⁷Be and ⁸B reaction dynamics at Coulomb barrier energies

Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements

Reaction rate for two-neutron capture by4He

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Nuclear Reactions of Astrophysical Interest Involving Light Nuclei

Cited by 4 publications

References 22 publications

7Be and 8B reaction dynamics at Coulomb barrier energies

7Be and 8B reaction dynamics at Coulomb barrier energies

Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements

Reaction rate for two-neutron capture by4He

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⁷Be and ⁸B reaction dynamics at Coulomb barrier energies

⁷Be and ⁸B reaction dynamics at Coulomb barrier energies