The αdecay path of the Hoyle state in 12C (Ex = 7:654MeV) represents one ofthe most challenging questions of modern nuclear physics. Its knowledge can help in theunderstanding of cluster ...configurations in light nuclei and the possible existence of Bose-Einstein condensates in nuclei. In stars, it is involved in the so-called 3αprocess, wherethe 12C nucleosynthesis occurs. We studied the 14N(d; α2)12C(7:654) reaction at 10:5MeVincident energy to probe its direct decay component. We found, with a precision higherof a factor 5 than any other previous experiment, an almost total absence of direct decaysby-passing the ground state of 8Be. From our analysis, a new upper limit of such decayis found at 0:043% (95% C.L.). Astrophysical 3α process reaction rate calculations haveto be accordingly revised.
The decay path of the Hoyle state in ^{12}C (E_{x}=7.654 MeV) has been studied with the ^{14}N(d,α_{2})^{12}C(7.654) reaction induced at 10.5 MeV. High resolution invariant mass spectroscopy ...techniques have allowed us 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 3α cluster model calculations, where higher precision limits are needed.
The Hoyle state in 12C(Ex = 7.654MeV) is characterized by a pronounced 3α cluster configuration. It is involved in the so-called 3α process in stars, that is responsible of 12C nucleosynthesis. We ...studied the decay path of the Hoyle state by using the 14N(d, α2)12C(7.654) reaction at 10.5MeV incident energy. We found, with a precision higher of a factor 5 than any other previous experiment, an almost total absence of direct decays by-passing the ground state of 8Be. A new upper limit of such a decay width is placed at 0.043% (95% C.L.). Astrophysical 3α process reaction rate calculations have to be consequently revised.
.
Electron screening has been studied in the
1
H(
7
Li,
)
4
He fusion reaction at lithium beam energies from 0.34 to 2.07 MeV for hydrogen-implanted Pd, Pt, Zn and Ni targets. A large electron ...screening has been observed in all the targets. However, no large electron screening has been observed in the following proton-induced reactions:
55
Mn(p,
)
56
Fe,
55
Mn(p, n)
55
Fe,
113
Cd(p, n)
113
In,
115
In(p, n)
115
Sn,
50
V(p, n)
50
Cr and
51
V(p,
)
52
Cr. Moreover, no shift in the resonance energy for the metallic compared to the insulator environment has been observed within our uncertainties for the studied (p,n) and (
p
,
) reactions. These results raise the question about the validity of the measurements that showed large electron screening potentials in nuclear reactions involving high-
Z
targets, and point to a dependence of the electron screening potential on the position of the target nuclei in the metallic lattice.
Neutron induced reactions are fundamental for the nucleosynthesis of elements in the universe. Indeed, to correctly study the reactions involved in the well-known s-process in stars, which produce ...about half of the elements beyond the iron peak, it is mandatory to know the neutron abundance available in those stars. The
17
O(n, a)
14
C reaction is one of the so-called “neutron poisons” for the pro- cess and it could play an important role in the balance of the neutron abundance. The reaction is therefore investigated in the energy range of astrophysical inter- est between 0 and 350 keV in the center of mass by applying the Trojan Horse Method to the three body reaction
2
H(
17
O, a
14
C)H.
The 02+ state in12C (7.654MeV, the Hoyle state) is important for the understanding of clustering phenomena in nuclei. The pronounced cluster nature of this state allows the triple-α process in stars ...with a reaction rate regulated by its structure properties. To precisely estimate the direct component in the 3α decay mechanism of the Hoyle state, we developed a new experiment using the14N(d,α)12C reaction at 10.5MeV. An anti-coincidence telescope was used to identify the α ejectiles leading the residual12C in the Hoyle state, while its decays in 3α were studied by means of a new hodoscope of silicon detectors, superOSCAR, placed in kinematical coincidence to fully reconstruct the events. Details of the experiment and preliminary results are discussed in the text.
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