The12C* Hoyle state in the inelastic12C +12C reaction and in24Mg* decay

Morelli, L.; Bruno, M.; D’Agostino, M.; Baiocco, G.; Gulminelli, F.; Abbondanno, U.; Barlini, S.; Bini, M.; Casini, G.; Cinausero, M.; Degerlier, M.; Fabris, D.; Gramegna, F.; Mabiala, J.; Marchi, T.; Olmi, A.; Pasquali, G.; Piantelli, S.; Valdré, S.

doi:10.1088/0954-3899/43/4/045110

Cited by 20 publications

(47 citation statements)

References 23 publications

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“…This is not the case for the (C + 3α) channel, and the anomalously high branching ratio of this channel can be tentatively attributed to a possible persistence at high excitation energy of α structure correlations in the 12 C+ 12 C molecular state and/or in the 24 Mg compound. The kinematic characteristics of these non-statistical decays are further studied in the continuation of this work [36].…”

Section: Discussionmentioning

confidence: 97%

Thermal properties of light nuclei from¹²C +¹²C fusion–evaporation reactions

Morelli¹,

Baiocco²,

D’Agostino³

et al. 2014

J. Phys. G: Nucl. Part. Phys.

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Abstract. The12 C+ 12 C reaction at 95 MeV has been studied through the complete charge identification of its products by means of the GARFIELD+RCo experimental set-up at INFN Laboratori Nazionali di Legnaro (LNL). In this paper, the first of a series of two, a comparison to a dedicated Hauser-Feshbach calculation allows to select a set of dissipative events which corresponds, to a large extent, to the statistical evaporation of highly excited 24 Mg. Information on the isotopic distribution of the evaporation residues in coincidence with their complete evaporation chain is also extracted. The set of data puts strong constraints on the behaviour of the level density of light nuclei above the threshold for particle emission. In particular, a fast increase of the level density parameter with excitation energy is supported by the data. Residual deviations from a statistical behaviour are seen in two specific channels, and tentatively associated with a contamination from direct reactions and/or α-clustering effects. These channels are studied in further details in the second paper of the series.PACS numbers: 25.70.z, 24.60.Dr, 27.30.+t, 24.10.Pa NUCLEAR REACTIONS 12C(12C,X), E = 95 AMeV, Measured Fusion-evaporation reactions, Observed deviation from statistical behaviour.

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Section: Discussionmentioning

confidence: 97%

Thermal properties of light nuclei from¹²C +¹²C fusion–evaporation reactions

Morelli¹,

Baiocco²,

D’Agostino³

et al. 2014

J. Phys. G: Nucl. Part. Phys.

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“…was obtained by Kirsebom et al by using the kinematic fitting method [29]. Two more recent experiments by Rana et al [30] and Morelli et al [31] suggested non-zero values of direct decay B.R., respectively of (Γ α − Γ α0 )/Γ α = 0.91% ± 0.14% and 1.1% ± 0.4%. Finally, thanks to a high statistics experiment, Itoh et al [32] determined an improved upper limit of the direct B.R.…”

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confidence: 92%

High-Precision Probe of the Fully Sequential Decay Width of the Hoyle State in C12

Dell’Aquila¹,

Lombardo²,

Verde³

et al. 2017

Phys. Rev. Lett.

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The decay path of the Hoyle state in 12 C (Ex = 7.654MeV) has been studied with the 14 N(d, α2) 12 C(7.654) reaction induced at 10.5MeV. High resolution invariant mass spectroscopy techniques have allowed to unambiguously disentangle direct and sequential decays of the state passing through the ground state of 8 Be. Thanks to the almost total absence of background and the attained resolution, a fully sequential decay contribution to the width of the state has been observed. The direct decay width is negligible, with an upper limit of 0.043% (95% C.L.). The precision of this result is about a factor 5 higher than previous studies. This has significant implications on nuclear structure, as it provides constraints to 3-α cluster model calculations, where higher precision limits are needed.Exploring the structure of 12 C is extremely fascinating, since it is strongly linked to the existence of α clusters in atomic nuclei and to the interplay between nuclear structure and astrophysics. Furthermore, 12 C is one of the major constituents of living beings and ourselves. Our present knowledge traces the origin of 12 C to the so called 3α process in stellar nucleosynthesis environments. The 3α process, which occours in the Heburning stage of stellar nucleosynthesis, proceeds via the initial fusion of two α particles followed by the fusion with a third one [1, 2] and the subsequent radiative deexcitation of the so formed excited carbon-12 nucleus, 12 C * . The short lifetime of the 8 Be unbound nucleus (of the order of 10 −16 s), formed in the intermediate stage, acts as a bottle-neck for the whole process. Consequently, the observed abundance of carbon in the universe cannot be explained by considering a non-resonant two-step process. This fact led Fred Hoyle, in 1953, to the formulation of his hypothesis [3,4]: the second step of the 3α process, α+ 8 Be→ 12 C+γ, has to proceed through a resonant J π = 0 + state in 12 C, close to the α+ 8 Be emission threshold. The existence of such a state was then soon confirmed [5] at an excitation energy of 7.654MeV. This state was then named as the Hoyle state of 12 C [6]. The decay properties of this state strongly affect the creation of carbon and heavier elements in helium burning [7], as well as the evolution itself of stars [8,9]. At typical stellar temperatures of T ≈ 10 8 − 10 9 K, this reaction proceeds exclusively via sequential process consisting of the α + α s-wave fusion to the ground state * dellaquila@na.infn.it † ivlombardo@na.infn.it of 8 Be, followed by the s-wave radiative capture of a third α to the Hoyle state. However, in astrophysical scenarios that burn helium at lower temperatures, like for instance helium-accreting white dwarfs or neutron stars with small accretion rate, another decay mode of the Hoyle state completely dominates the reaction rate: the non-resonant, or direct, α decay [10][11][12], where the two αs bypass the formation of 8 Be via the 92keV resonance. Recent theoretical calculations show that, at temperatures below 0.07GK, the reaction rate...

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“…These characteristics make CsI(Tl) crystals particularly well-suited for being used as residual energy stages for silicon-based telescope systems, enabling the identification of fragments via the so-called ∆E-E technique [2]. Many large acceptance detection systems such as INDRA [3], CHIMERA [4,5], NIMROD-ISiS [6], GARFIELD [7] or FAZIA [8,9], have been used successfully in detecting and identifying particles in wide energy and mass ranges. Recently, detectors based on modular strip Si-CsI telescopes have been developed to provide high angular resolution in addition to high energy resolution for nuclear structure, particle-particle correlation and nuclear reaction studies.…”

Section: Introductionmentioning

confidence: 99%