Photoneutron Reaction Data for Nuclear Physics and Astrophysics

Abstract

Abstract. We discuss the role of photoneutron reaction data in nuclear physics and astrophysics in conjunction with the Coordinated Research Project of the International Atomic Energy Agency with the code F41032 (IAEA-CRP F41032). PHOENIX Collaboration for the IAEA-CRP F41032The In this collaboration, we are measuring (,xn) cross sections with x=1-4 for the first compilation (photonuclear data) and (,1n) cross sections near oneneutron threshold for the second compilation (photon strength functions). A list of nuclei to be measured in the PHOENIX Collaboration is given in Table 1. We provide (,xn) cross section data to resolve the long-standing discrepancy between the Livermore and Saclay data of partial photoneutron cross sections. In many cases, Saclay provided larger cross sections for (,1n) reactions than Livermore and vice versa for (,2n) reactions [2]. The ratio of the Saclay data to the Livermore data of integrated total cross sections, Rint  S int / L int , varies from 0.65 to 1.35 over 19 nuclei from 51 V to 238 U. As shown in Fig. 1, the ratio for

Nuclear level density and γ -ray strength function of Ni63

“…The extracted γ SF features a strong up-bend at low energies similar to what has been seen in other Ni isotopes [14][15][16][17][18]20], as well as other nuclei in the same mass region [41][42][43]. Comparing the measured strength function to the M1 strength predicted from the SM calculations in Ref.…”

“…[30] suggest that the enhancement may be due to M1 transitions within the quasicontinuum. Compared with (γ , n) [16] data for 61 Ni there may be a pygmy resonance around 7-8 MeV, but due to the large uncertainties in the absolute value of the measured γ SF we cannot conclude.…”

“…siderably lower. Comparison with the photoabsorption cross section of 61 Ni [16] shows a reasonably good agreement as the giant dipole resonance evolves slowly with mass number. The normalized γ SF has a considerably large uncertainty band with the dominating contributing factor being the uncertainty in the average radiative width.…”

“…This is especially apparent in the unstable neutron-rich nuclei (A = 59,60,64,65,67,69,70 Ni are taken from Refs. [14][15][16][17][18][19]. 67, 69, and 70).…”

“…This makes 63 Ni a very interesting case study as a normalization only considering known discrete levels could resolve the discrepancy. In addition, the γ SFs have previously been measured in several other Ni isotopes and consistently show a strong low-energy enhancement [14][15][16][17][18][19]. With this measurement the NLD and γ SF will have been measured in most stable [14][15][16]20] and several unstable Ni isotopes [17][18][19][20], allowing for investigations into the systematics of the γ SF.…”