Analysis of angular distributions in three-particle reactions

doi:10.1016/0375-9474(73)90208-X

Nuclear Physics A

Volume 205, Issue 2, 30 April 1973, Pages 249-256

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Abstract

A model-independent description for angular distributions of sequential decay processes is given. The method and the notation are in close analogy to the treatment for two-particle processes given by Welton. In particular arbitrary ranks of tensor polarization of the final particles can be described. It is shown that from the angular distribution information about the quantum numbers J, π and the polarization of the unstable recoil nucleus can be gained. A simple application of the formalism to the ¹⁰ (α,2α) ⁶Li reaction is given.

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Angular correlation experiments in the reactions 2H(α, nα)p and 2H(α, pα)n and comparison with the Faddeev theory and the resonating group method
1985, Nuclear Physics, Section A
At the Hamburg Isochronous Cyclotron angular correlation experiments were carried out in the reactions ²H(α, nα)p and ²H(α, pα)n, in order to determine the tensor polarization of the ground-state resonances $^{5} Li (32^{−})$ and $^{5} He (32^{−})$ , respectively. We find that the observables for the two mirror reactions $^{2} H (α, n)^{5} Li and^{2} H (α, p)^{5} He$ are charge-dependent. This result is interpreted as evidence for a violation of charge symmetry.
In the whole phase-space region absolute break-up cross sections are generally well reproduced by the Faddeev theory. On the other hand, we find that the resonating group method which has up to now been mainly applied to two-body reactions can also provide valuable information for break-up reactions. The predictions of Hackenbroich, Schütte and coworkers are in quite good agreement with the measured tensor polarization of ⁵He and ⁵Li and the corresponding angular correlation functions.
Spectroscopy of intermediate 16F states with the reaction 14N(3He, np)15O
1985, Nuclear Physics, Section A
Excited states of ¹⁶F have been investigated with the reaction ¹⁴N(³He, np)¹⁵O at E = 10.5 and 12 MeV in kinematically complete experiments. Proton groups corresponding to the decays of intermediate ¹⁶F states were observed at various angles with counter telescopes in time coincidence with the associated neutrons detected at θ_n^lab = 0° with a time-of-flight spectrometer. Excitation energies and decay widths Γ_p0 of these states have been extracted from the proton spectra. Lower limits for the orbital angular momentum in the decay channel and for the spin of the states have been deduced from the obtained angular correlations. By comparison with the reaction ¹⁴N(³He, pp)¹⁵N measured at E = 13 MeV, pairs of $T = 1^{16} F$ parent/¹⁶O analog states have been identified. J^π assignments and shell-model configurations are discussed on the basis of the selectivity of the reactions measured.
Reaction mechanism and spin information in the sequential breakup of 18O at 82 MeV
1984, Nuclear Physics, Section A
The α-decays of states in ¹⁸O have been studied in the sequential breakup reaction $^{12} C (^{18} O,^{18} O^{∗} →^{14} C α)$ at 82MeV. Double-differential cross sections have been obtained for the states excited in ¹⁸O. A conventional analysis of the decay correlations does not yield unambiguous information on the spins of the states excited. However a systematic dependence of the correlations on the angle of the ¹⁸O^∗ in the c.m. frame is observed, allowing the determination of the transferred angular momentum. The double-differential cross sections have been analysed with the DWBA and a strong absorption model. The latter allows the extraction of quantitative information on spins and reaction mechanism from the data.
Angular distribution of tensor polarizations in 2H(α, 5Heg.s)p from the sequential decay reaction 2H(α,p)5Heg.s(α)n
1977, Nuclear Physics, Section A
The sequential decay reaction ²H(α,p)⁵He^g.s(α)n has been studied at E_α = 22.5 MeV in kinematically complete p-α coincidence experiments with special regard to the tensor moments of even rank of the intermediate state $^{5} He^{32−}$ . From the measured absolute differential cross section of this reaction, the angular distributions of the second step for the ⁵He^g.s c.m. production angles from 45.6 to 119.8 were extracted. By applying Welton's formalism to the second step the tensor moments of even rank of the intermediate ⁵He system were deduced and compared to calculations in the cluster-model formalism. They as well as the absolute differential cross sections for ²H(α,pα)n were found to be in good agreement with the sequential decay model. Small deviations seem to arise from Coulomb interaction between p and α in the final channel and from the restriction to partial waves l ≦ 2.
Cluster model description of the d(α, αp)n break-up as two-step reaction
1974, Physics Letters B
The ⁶Li scattering system has been described in the framework of the multichannel cluster model reaction theory. Under the assumption of sequential decay, cross sections for the ⁴He  d → ⁵He  p → ⁴He  n - p process have been calculated. Comparison of the theoretical results with recent experimental data shows good agreement for those kinematical situations, in which the sequential decay mechanism dominates.
The sequential decay 10B(α, α)10B*(α)6Li at E<inf>α</inf> = 24 MeV
1974, Nuclear Physics, Section A
In the break-up reaction $^{10} B (α, 2α)^{6} Li$ at E_α = 24 MeV, the sequential decay via excited levels of ¹⁰B is found to be the dominant mechanism. Expected contributions of α-α quasifree scattering and sequential decay via ⁸Be levels are negligible. The kinematically complete, coplanar α-α coincidence measurements at various angle combinations could not be analysed consistently without postulating 17 new levels of ¹⁰B with excitation energies between 8.665 and 16.0 MeV. Angular distributions of the second-step decay are well described by model independent calculations including the polarization of the intermediate nucleus. Lower limits for the spins of six levels could be extracted.

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Nuclear Physics A

Abstract

References (14)

Nucl. Phys.

Nucl. Phys.

Phys. Rev.

Rev. Mod. Phys.

Can. J. Phys.

Phys. Rev.

Phys. Rev.

Cited by (23)

Angular correlation experiments in the reactions <sup>2</sup>H(α, nα)p and <sup>2</sup>H(α, pα)n and comparison with the Faddeev theory and the resonating group method

Spectroscopy of intermediate <sup>16</sup>F states with the reaction <sup>14</sup>N(<sup>3</sup>He, np)<sup>15</sup>O

Reaction mechanism and spin information in the sequential breakup of <sup>18</sup>O at 82 MeV

Angular distribution of tensor polarizations in <sup>2</sup>H(α, <sup>5</sup>He<sup>g.s</sup>)p from the sequential decay reaction <sup>2</sup>H(α,p)<sup>5</sup>He<sup>g.s</sup>(α)n

Cluster model description of the d(α, αp)n break-up as two-step reaction

The sequential decay <sup>10</sup>B(α, α)<sup>10</sup>B<sup>*</sup>(α)<sup>6</sup>Li at E<inf>α</inf> = 24 MeV