Transfer of6Li break-up fragments at6Li projectile energies far above the coulomb barrier

doi:10.1016/0375-9474(79)90293-8

Nuclear Physics A

Volume 329, Issues 1–2, 8–15 October 1979, Pages 259-270

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Abstract

Transfer of beam-velocity fragments has been experimentally investigated in⁶Li induced reactions on²⁰⁸Pb and²⁰⁹Bi in the energy range E_Li = 60–156MeV The experimental techniques involve the observation of the target residues and measurements of the recoil ranges of heavy residual nuclei produced by charged particle bombardment. The determination of the recoil energy enables the discrimination of different reaction paths leading to the same residual nuclei.(⁶Li, xn+p) excitation functions prove to be very similar to (α, (x − 1)n) reactions at E_α ≈23E _Li The results present experimental evidence for a particular reaction type indicated in previous experiments: Dissociation of the⁶Li projectile with capture of the beam-velocity α-particle indicating an (α, xn) reaction (“internal break-up”).

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Cited by (18)

The QQDS magnetic spectrograph "Little John" at the Karlsruhe cyclotron. I. Design and construction
1989, Nuclear Inst. and Methods in Physics Research, A
A magnetic spectrograph for charged-particle spectroscopy, named “Little John”, consisting of two quadrupoles, one dipole and one sextupole magnet was constructed and put into operation at the Karlsruhe isochronous cyclotron. The ion-optically rather simple system covers a particle rigidity of 2.5 Tm and was especially designed for small reaction angle experiments. A modest resolving power of p/Δp = 5200, a momentum acceptance of $(p_{max} − p_{min}) p_{mean} = 20%$ and an acceptance solid angle of ω > 1 msr were the design goals. The momentum dispersion and consequently the acceptance of the spectrograph can be varied by a factor of 2 without varying other imaging properties considerably. The design, construction and equipment of the spectrograph are described.
The QQDS magnetic spectrograph "Little John" at the Karlsruhe cyclotron. II. Experimental procedures and performance
1989, Nuclear Inst. and Methods in Physics Research, A
The measured ion-optical properties of the Karlsruhe magnetic spectrograph “Little John” and the properties of its detector system are described. Moreover, the procedures for an efficient use of the spectrograph, in particular concerning small angle and zero degree experiments, are presented in detail. Characteristic experimental results from ⁶Li-induced nuclear reactions demonstrate the performance of the whole setup.
Comparative study of d- and 6Li-induced reactions on 232Th in terms of breakup and preequilibrium processes
1986, Nuclear Physics, Section A
Excitation functions of (d, xnyp) and $(^{6} Li, αx n y p)$ reactions on ²³²Th with y ⩽ 1 and x ⩽ 4 leading to the same radioactive residual nuclei ^233,232,230pa have been measured from E_d = 8–80 and E_{6_Li} = 28–48 MeV, respectively. The nucleus ²²⁸Pa was only reached with incoming deuterons. The results are compared with exciton-model predictions including compound-nucleus emission and fission competition. While for incoming deuterons these equilibration calculations give reasonable agreement with the data, the prequilibrium model completely fails for the case of ⁶Li. It is found that the breakup of ⁶Li into α and d with subsequent d-induced reactions on ²³³Th seems to be important. Assuming a bump at about $13$ of the ⁶Li energy and a high-energy tail in the corresponding deuteron spectrum, the ⁶Li-induced reaction yields are surprisingly well reproduced by folding the experimental as well as the theoretical d-induced excitation functions on ²³² Th. As in the case of incoming deuterons where stripping to bound states is a very strong reaction channel, the interaction of deuterons from the breakup fusion of ⁶Li leads to strong stripping reactions, too.
The nonelastic projectile break-up cross section from particle-gamma coincidence measurements for the 6li + 40ca reaction at 156 mev
1986, Nuclear Physics, Section A
The cross sections for nonelastic break-up modes have been studied for the ⁶Li + ⁴⁰Ca reaction at E_Li = 156 MeV. Gamma-ray spectra from target-like residual nuclei were measured in coinci- dence with beam-velocity projectile fragments and a value for the nonelastic break-up cross section σ^b.u_non = 582 ± 110 mb has been found. Together with results of inclusive charged-particle measure- ments we infer for the total break-up cross section σ^b.u_tot = 930 ± 115 mb comprising about 50% of the total reaction cross section. The nonelastic contribution of the break-up reaction appears to be less than predicted by the DWBA break-up theory. This result is directly evident from the differential cross sections by comparing inclusive and exclusive results.
Fragmentation processes in nuclear reactions
1984, Physics Reports
Fragmentation processes in nuclear collisions are reviewed. The main emphasis is put on light ion breakup at nonrelativistic energies. The post- and prior-form DWBA theories are discussed. The post-form DWBA, appropriate for the “spectator breakup” describes elastic as well as inelastic breakup modes. This theory can also account for the stripping to unbound states. The theoretical models are compared to typical experimental results to illustrate the various possible mechanisms. It is discussed, how breakup reactions can be used to study high-lying single particle strength in the continuum; how they can yield information about momentum distributions of fragments in the nucleus.
Fusion and nonfusion phenomena in the 6Li + 40Ca reaction at 156 MeV
1984, Nuclear Physics, Section A
Reaction products from ⁶Li-induced reactions on ⁴⁰Ca at 156 MeV have been studied using the dE × E identification as well as the inclusive γ-ray method. The complete fusion cross section has been found to be σ_F = 67 ± 20 mb. The Z-distribution of fusion evaporation residues is compared with statistical model predictions. The Z-spectrum of reaction products shows a maximum at 15 ≲ Z ≲ 20, probably due to transfer and to incomplete fusion. It is suggested that the small value of the fusion cross section is due to the strong competition of ⁶Li break-up processes.

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^†: Institut fu¨r Radiochemie, Kernforschungszentrum Karlsruhe.

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Nuclear Physics A

Abstract

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Cited by (18)

The QQDS magnetic spectrograph "Little John" at the Karlsruhe cyclotron. I. Design and construction

The QQDS magnetic spectrograph "Little John" at the Karlsruhe cyclotron. II. Experimental procedures and performance

Comparative study of d- and <sup>6</sup>Li-induced reactions on <sup>232</sup>Th in terms of breakup and preequilibrium processes

The nonelastic projectile break-up cross section from particle-gamma coincidence measurements for the <sup>6</sup>li + <sup>40</sup>ca reaction at 156 mev

Fragmentation processes in nuclear reactions

Fusion and nonfusion phenomena in the <sup>6</sup>Li + <sup>40</sup>Ca reaction at 156 MeV