Photon strength function of ¹¹⁵In and evaluation of neutron-capture cross section for ¹¹⁴In

The photon strength function (PSF) is an important quantity to estimate the neutron capture cross section for the understanding of astrophysical processes and applications to nuclear engineering. In the last half century, the giant dipole resonance (GDR) has been studied well. Recently, the PSF on the low-energy tail of the GDR below the neutron threshold is of particular interest because of the appearance of an extra enhancement of E1 strength called Pygmy dipole resonance (PDR), or M1 strength in addition. The nuclei heavier than iron is mainly produced via s-, r-, or p-processes. The origin of p-nuclei is said to be production via photodisintegration in the O/Ne layers of core-collapse of massive stars explosions of supernovae type I or II, or/and s-, r- processes. However, one of the p-nuclei, ¹¹⁵Sn still cannot be explained with its production abundance. Recently, the s-process contribution is tried to be explained at the branching point of neutron capture reaction and β-decay at ¹¹³Cd^m by the following reactions: ¹¹²Cd(n,γ)¹¹³Cd^m(β-)¹¹³In(n,γ)¹¹⁴Sn(n,γ)¹¹⁵Sn. It was found that an s-process contribution from ¹¹³Cd^m is not sufficient to explain the production problem of ¹¹⁵Sn. In this study, we would like to shift the view point to the ¹¹⁵In region, which is produced via the main s-process. In this region, 3 possible reactions compete between ¹¹⁵In(γ,n)↔¹¹⁴In(β-)¹¹⁴Sn(γ,n)↔¹¹⁵Sn. However, both the photodisintegration rate for ¹¹⁵In and the neutron capture rate for ¹¹⁴In have not been known experimentally well. Hence, we measured the ¹¹⁵In(γ,γ^,),¹¹⁵In reaction to estimate the photodisintegration rate and the rate of the inverse ¹¹⁴In(n,γ)¹¹⁵In reaction. (author)