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Gamma-ray angular distribution from the reaction D(p.[Delta])[3]He below 200 KeV Olivo, Miguel Angel

Abstract

The angular distribution of the gamma-rays from the direct radiative capture reaction D(p,ɣ)³He has been measured for 70 KeV and 144 KeV protons in the laboratory system, using thin deuterated polyethylene targets. The study of this particularly simple reaction is of interest for determining some properties of the forces which bind nuclear particles to each other. In addition it plays a role in a number of astrophysical processes. The ground state of ³He is predominantly a symmetric ²S state with admixtures of a ⁴D state and ²S(m) state of mixed symmetry. These admixtues are related to specific components of the two body forces coupling the three particles. The measurements were made with a high current 180 KeV accelerator, built by the author, using an ORTEC duoplasmatron ion source. Technical problems involved in the development of the accelerator and the deuterated targets are discussed. The angular distribution at 144 ± 16 KeV in terms of Legendre polynomials P₁ is given in the centre of mass system by W(ɵ) = Aₒ[Pₒ+(.05±.02)P₁-(.94±.02)P₂-(.05±.02)P₃+(.03±.02)P₄] and at 70 ± 20 KeV the angular distribution is given by W(ɵ) = Aₒ[Pₒ+(.(.06±.04)P₁-(.93±.05)P₂-(.06i±.04)P₃+(.02±.05)P₄] The coefficients in the Legendre polynomial expansion are related to the various transitions between the continuum and bound states. Their significance in terms of the different components of the ³He ground state wave function is discussed. The absolute cross section (i.e. the coefficient Aₒ ) has not been measured. Plans for measuring it in the near future are discussed briefly.

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