M. Lattuada

The Bare Astrophysical S(E) Factor of the 7Li(p, α)α Reaction

The astrophysically important 7Li(p, α)α reaction has been studied via the Trojan horse method in the energy range E = 10-400 keV. A new theoretical description, based on the distorted-wave Born approximation approach, allows one to extract information on the bare astrophysical S-factor, Sb(E), with Sb(0) = 55 ± 3 keV barns. The results are compared with direct experimental data leading to a model-independent value of the electron screening potential energy, Ue = 330 ± 40 eV, much higher than the adiabatic limit Uad = 175 eV.

Indirect investigation of the {ital d}+{sup 6}Li reaction at low energies relevant for nuclear astrophysics

The indirect investigation of low-energy charged-particle reactions relevant for nuclear astrophysics is considered, employing statistical tensor analysis. Data from the quasi-free contribution to the {sup 6}Li({sup 6}Li, 2{alpha}){sup 4}He reaction at projectile energies above the Coulomb barrier are analyzed in order to extract the excitation function of the {sup 6}Li({ital d},{alpha}){sup 4}He reaction at very low relative energy. The results are compared with an astrophysical factor extracted from the free-reaction cross section data. The limits of the method are discussed. {copyright} {ital 1996 The American Astronomical Society.}

6He + α clustering in 10Be

In a kinematically complete measurement of the 7Li(7Li,α6He)4He reaction at Ei = 8 MeV it was observed that the 10Be excited states at 9.6 and 10.2 MeV decay by 6He emission. The state at 10.2 MeV may be a member of a rotational band based on the 6.18 MeV 0+ state.

Proton-induced lithium destruction cross-section and its astrophysical implications

Knowledge of the primordial nucleosynthesis offers a powerful tool to retrieve information on the baryon density of the Universe. In this context lithium isotopes play a crucial role and in particular we stress how important the bare nucleus cross-section for the 7 Li(p,

Indirect measurement of nuclear reaction cross sections at astrophysical energies

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The alpha-C-12 scattering studied via the Trojan-Horse method

He reaction is. Recent application of the Trojan Horse Method led to an indirect measurement of that cross-section. In the present paper its astrophysical implications are examined in the case of the Solar lithium problem and of the primordial nucleosynthesis.

The quasi-free 9Be(3He, αα)4He reaction between 3 and 12 MeV

Abstract In order to extract the cross sections for thermonuclear fusion reactions in the region of astrophysical energies we have used a method based on a quasi-free reaction mechanism, called ‘Trojan horse’. In particular, information regarding the 7 Li ( p , α ) 4 He reaction is obtained from an analysis of the three-body 7 Li ( d , 2 α ) n process.

8Li + α decay of 12B and its possible astrophysical implications

Abstract: The Trojan-horse method has been suggested as a means to study a two-body reaction at astrophysical energies via a three-body breakup reaction. In order to test this method the 6Li(12C,α12C)2H reaction was studied in a kinematically complete experiment at an incident energy of 18 MeV. Coincidence spectra show the presence of the quasi-free α-12C scattering process. The excitation function of the three-body reaction is calculated in the plane wave impulse approximation assuming quasi-free scattering and is compared with the experimental data. Also, the excitation function of the virtual α-12C elastic scattering is extracted from the three-body reaction cross section at low deuteron momenta and compared with the behaviour of the free scattering cross section.

A procedure for the analysis of the data of a three body nuclear reaction

The 9Be(3He, αα)4He reaction was studied in a kinematically complete experiment in the energy range E = 3–12 MeV in order to extract information about the energy dependence of the quasi-free process proceeding through the virtual 5He(3He, α)4He reaction. The excitation function of this process was extracted from the data and the momentum distribution of the 4He-5He motion in 9Be was deduced. The behaviour of the excitation function around and above the Coulomb barrier is discussed.

α-5He decaying states and the ground-state rotational band of 9Be

The 12B excitation energy spectrum has been obtained from coincidence measurements of the 9Be + 7Li → 2α + 8Li reaction at E0 = 52 MeV. The decay of the states at excitations between 10 and 16 Mev into α + 8Li has been observed for the first time. Observed α-decay indicates possible cluster structure of the 12B excited states. The influence of these states on the cross-section of the astrophysically important 8Li(α,n)11B and 9Be + t reactions is discussed and the results are compared with existing results.