Elsevier

Nuclear Physics A

Volume 554, Issue 2, 15 March 1993, Pages 173-188
Nuclear Physics A

The (γ, p) reaction at Eγ ∼60 MeV

https://doi.org/10.1016/0375-9474(93)90337-WGet rights and content

Abstract

A study of the (γ, p) reaction on 12C, 14N, 27Al and 51V targets, at photon energies Eγ ∼60 MeV, is reported. Angular distributions in the range tp = 60°-120° are presented for transitions leading to the ground state and several low-lying states in each residual nucleus. The relative population of residual nucleus slates is similar to those found in (e, e'p) and (d, 3He) experiments, apart from the well-known exception of the peak at 6.8 MeV in the 12C(γ, p) reaction. Direct-knockout calculations fail to account for the magnitude of the (γ, p) results, which indicates the need for calculations that include effects such as meson exchange or short-range correlations. Strength seen at higher excitation energies is attributed to inclusive (γ, p) events. The excitation-energy spectra have been compared with quasi-deuteron model calculations which assume a (γ, np) reaction where the neutron goes undetected. The shape of the 51V(γ, p) excitation spectrum is compared to a pre-equilibrium model calculation. The results appear to indicate that two-nucleon absorption of the photon is important.

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    Present address: NIKHEF-K, Postbus 4395, 1009 AJ Amsterdam, The Netherlands.

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