Photonuclear Probe of Astrophysics

Real photons are a good probe of E1 and M1 $\gamma$-strength functions of nuclei. In stellar conditions, both neutron capture and photodisintgration are sensitive to the $\gamma$- strength function in the low-energy tail of the electric giant dipole resonance (GDR) that are assumed to be built on individual excited states. The $\gamma$-strength function is a key ingredient to improve the reliability of the Hauser-Feshbach model description of neutron capture and photodisintegration. Recently precision determination of photoneutron cross sections of astrophysical importance has become possible with use of quasi-monochromatic $\gamma$ beams from laser Compton backscattering at AIST. These data provide a good insight into the $\gamma$-strength function in the low-energy tail of GDR. This talk covers precision measurements of photodisintegration cross sections in the context of the p-process and s-process nucleosyntheses.