Photonuclear reactions in Ca40

D. Brajnik, D. Jamnik, G. Kernel, U. Miklavžič, and A. Stanovnik
Phys. Rev. C 9, 1901 – Published 1 May 1974
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Abstract

Natural calcium targets were bombarded with γ rays from a 31-MeV betatron at several bremsstrahlung end-point energies. Angular and energy distributions of photoprotons were measured. In addition, the γ-ray spectra emerging from the thick target were recorded at several angles. They were used to study the γ rays accompanying the decay of excited residual nuclei formed in the reactions Ca40(γ,p) and Ca40(γ,n). The analysis yielded the following results for the main reaction channels: the energy dependence of the cross sections, the energy dependence of photoproton angular distributions, and the bremsstrahlung-weighted angular distributions of deexcitation γ rays. According to the experimental results the following amplitudes seem to dominate in the particle channels: f52 waves for the (γ,p0) reaction, p32 waves for (γ,p1), and p waves for reaction channels in which the residual nuclei are left in states above 4.93 MeV. This is consistent with the giant dipole state configuration, predicted on the basis of the shell-model bound-state calculation by Gillet and Sanderson. The agreement with continuum theories is less satisfactory. It is also found that the shapes of cross sections are more uniform and that the angular distributions are less energy-dependent than expected from theory. The (γ,p1) cross section was separated into S=0 and S=1 channel spin contributions of which only the dominant S=0 part shows a resonant structure. Negative-parity hole channels bear evidence for two-step reaction processes and impurities in the ground state of Ca40. Ratios of (γ,p) and (γ,n) cross sections imply an admixture of less than 3% of T=0 strength in the Ca40 giant dipole resonance.

[NUCLEAR REACTIONS Ca40(γ,p), (γ,pγ), and (γ,nγ), Eγ=1130 MeV; measured σ(E,ϑ) to states of residual nuclei; deduced reaction-channel configurations.]

  • Received 29 January 1974

DOI:https://doi.org/10.1103/PhysRevC.9.1901

©1974 American Physical Society

Authors & Affiliations

D. Brajnik, D. Jamnik, G. Kernel, U. Miklavžič, and A. Stanovnik

  • J. Stefan Institute, University of Ljubljana, Ljubljana, Yugoslavia

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Vol. 9, Iss. 5 — May 1974

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