Coulomb Dissociation as a Source of Information on Radiative Capture Processes of Astrophysical Interest

Abstract

The cross sections for radiative capture of α-particles, deuterons and protons by light nuclei at very low relative energies are of particular importance for the understanding of the nucleosynthesis of chemical elements and for determining the relative elemental abundances in stellar burning processes at various astrophysical sites. As examples we quote the reactions α+d→6Li+γ, α+3He→7Be+Y, or α+12C→16O+γ. As an alternative to the direct experimental study of these processes we consider [1,2] the inverse process, the photodisintegration, by means of the virtual photons provided by a nuclear Coulomb field. “The radiative capture process b+c+a+γ is related to the inverse process, the photodisintegration γ+a+b+c by the detailed balance theorem. Except for the extreme case very close to the threshold the phase space favours the photodisintegration cross section as compared to the radiative capture. The disintegration by means of the virtual photons in a Coulomb collision $$ Z + a \to Z + b + c $$ (1) makes use of the high virtual photon number and also of possible kinematical advantages. The fragments b and c have high energies in the lab system and can be conveniently detected. From the kinematics the relative energy Ebc can be accurately deduced (see Ref. 2). Care will have to be taken for “post-acceleration” effects, possibly more serious for fragments with different charge to mass ratios.