Spin polarization in 16O-induced heavy-ion reactions

doi:10.1016/0375-9474(84)90525-6

Nuclear Physics A

Volume 422, Issue 2, 25 June 1984, Pages 418-446

https://doi.org/10.1016/0375-9474(84)90525-6 Get rights and content

Abstract

The circular polarization P_γ of γ-rays from ¹⁶O-induced reactions on ²⁷Al, ⁴⁸Ti, ⁵⁸Ni and ⁶²Ni at 100 MeV incident energy has been measured in coincidence with projectile-like fragments detected at angles behind the grazing angle. The dependence of P_γ on the reaction Q-value, on the fragment atomic number and, for ¹⁶O+⁴⁸Ti, on the scattering angle was investigated.

The results show that deep-inelastic (DI) collisions in these fairly light heavy-ion systems are associated with predominantly negative scattering angles. The average value of P_γ(DI) = 0.6 obtained for ¹⁶O + Ni at θ_lab= 35° is consistent with pure negative-angle scattering. The magnitude of P_γ(DI) is smaller for the two lighter systems which is interpreted as mainly arising from the increasing probability for orbiting trajectories leading to scattering angles beyond 180°

Trajectory calculations within a classical friction model were performed, and the parameter dependence of the results was studied. Strong radial friction forces were found necessary to simulate the observed negative-angle cross sections.

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The sign of the mean transverse momentum of non-equilibrium light charged particles was determined from the circular polarization of coincident γ-rays emitted from residual nuclei for $^{14}$ N-induced reactions on $^{154}$ Sm at incident energies, E/A=35, 100 and 155 MeV. Results of the emitted α-particles at mid-central collisions show the predicted transition from mean-field dominated dynamics at low energies to nucleon-nucleon collision dominated dynamics at high energies.
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1990, Nuclear Physics, Section A
The experimentally determined properties of A = 21–44 nuclides are complied and evaluated with special emphasis on nuclear spectroscopy.
Separate tables for each of the nuclides reviewed present the available information about the following properties (in this order):
- •
  - excitation energies E_x,
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  - γ-ray branching ratios b(γ),
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  - γ-ray mixing ratios σ,
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  - lifetimes γ_m or widths Λ,
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  - single-nucleon transfer reactions,
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  - beta-decay,
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  - arguments for spin and parity (J^π) and isospin (T) assignments.
For each nuclide a master table summarizing the “best” or adopted values for E_x, J^π; T and τ_m or Λ precedes the auxiliary tables listed above.
The review of each A-chain concludes with a discussion of isospin multiplets.
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The backward-angle yield from ¹²C + ²⁴Mg has been studied with the technique of inverse kinematics, using ²⁴Mg beams with energies from 90 to 126 MeV. In the different exit channels with 5 ⩽ Z_ejectile ⩽9 the Q-integrated differential cross sections $d σ d θ$ are consistent with isotropy at 130° ⩽ θ_c.m. ⩽ 165°, which is taken as signature of orbiting. The most probable exit energies in the strongly predominant even-Z channels as a function of bombarding energy give evidence for complete damping at angular momenta close to the critical ones for fusion. The results for the weakly populated odd-Z channels suggest that the conditions of damping are affected by the large negative ground-state Q-values.
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^∗: Present address: Brookhaven National Laboratory, Upton, NY 11973, USA.

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Nuclear Physics A

Abstract

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Cited by (14)

Direct observation of the inversion of flow

Energy levels of A = 21-44 nuclei (VII)

Structure phenomena in the orbiting <sup>12</sup>c + <sup>24</sup>Mg system

Gamma-ray spectroscopy with incomplete fusion reactions for the systems <sup>16</sup>O +<sup>58,64</sup>Ni at 100 Me V

Mean field dynamics and non-equilibrium particle emission

Intermediate structure in strongly damped <sup>12</sup>C + <sup>24</sup>Mg reactions of the orbiting type