Neutron angular distribution in ( γ , n) reactions with linearly polarized γ -ray beam generated by laser Compton scattering

In 1957, Agodi predicted that the neutron angular distribution in ( γ , n) reactions with a 100% linearly polarized γ -ray beam for dipole excitation should be anisotropic and universally described by the simple function of a + b ⋅ cos ⁡ ( 2 ϕ ) at the polar angle θ = 90 ° , where ϕ is the azimuthal angle. However, this prediction has not been experimentally confirmed in over half a century. We have verified experimentally this angular distribution in the ( γ , n) reaction for 197 Au, 127 I, and natural Cu targets using linearly polarized laser Compton scattering γ -rays. The result suggests that the ( γ → , n) reaction is a novel tool to study nuclear physics in the giant dipole resonance region.