D. Miljanić

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.

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

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.

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

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.

4He1H2+ and 4He2H+, exotic impurities in 6He+ beam

(HeH2+)-He-4-H-1 ions were observed as an impurity in a 17.0 MeV He-6(+) beam produced by CYCLONE, with the ratio of Intensities being 1:5400. A (HeH+)-He-4-H-2 beam was also observed, having 60 times weaker intensity and slightly lower magnetic rigidity than original He-6(+) beam

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

In a measurement of the 9Be(7Li, 7Liα)αn reaction at Ei = 52 MeV it is unambigously established for the first time that the 9Be excited states around 6.5 and 11.3 MeV decay into the α + 5He channel. This fact may support previous claims that the 11.3 MeV state is also a member of the ground-state rotational band.

Transfer, sequential decay, and quasi-free reactions induced by 18-MeV 6He beam on 6Li, 7Li, and 12C

The 6He + 6,7Li and 6He + 12C scattering and reactions have been studied using an 18-MeV 6He beam. Experimental results for the elastic scattering on all three targets are in fair agreement with optical model predictions, using the potentials found in the analysis of the 6Li scattering on the same targets and at close beam energies. Several two-body exit channels show clear signatures of a direct reaction mechanism allowing extraction of spectroscopic information. The measured angular distribution for the 6He + 6Li → α + 8Li reaction indicated close similarity between the α + 2n configuration in 6He and the α + d configuration in 6Li. The obtained results for α-particle pickup from both 6Li and 7Li give large values of α spectroscopic factors for some 10Be states, indicating their well-developed α + 6He cluster structure. The exotic two-proton pickup reaction (6He, 8Be) was studied, as well as two-neutron and triton transfer reactions. Quasi-free scattering of 6He on deuteron and α particle in 6Li was also observed. The sequential decay reactions 6He + 6Li → 6He + α + d, 6He + 6Li → 2α + t + n, 6He + 7Li → 6He + α + t, and 6He + 12C → 10Be + 2α were clearly seen, and α clustering of some states in 6,7Li, 8–10Be, and 14C was thus studied. Several new spectroscopic results obtained for some 10Be states support the existence of a molecule-like rotational band in 10Be with a very large moment of inertia.

Excitation function of quasi-free processes in the6Li+6Li → 3α reaction

The6Li+6Li → 3α reaction was studied at energies around the Coulomb barrier. Excitation functions of the quasi-free processes6Li(d,α)4 He with an α-particle spectator either in the target or in the beam were measured.

Quasifree processes in the3H+2H→d+d+n reaction

The quasifree scattering and reaction processes in the3H+2H→d→d+n interaction leaving a neutron as a spectator have been investigated at incident triton energies around 35 MeV. The results compare well with the predictions from Plane Wave Impulse Approximation, arbitrarily normalized to the data. The final energy prescription was used.