New experimental constraint on the 185^{185}W(n,γn,\gamma)186^{186}W cross section

In this work, we present new data on the $^{182,183,184}$W($\gamma,n$) cross sections, utilizing a quasi-monochromatic photon beam produced at the NewSUBARU synchrotron radiation facility. Further, we have extracted the nuclear level density and $\gamma$-ray strength function of $^{186}$W from data on the $^{186}$W($\alpha,\alpha^\prime\gamma$)$^{186}$W reaction measured at the Oslo Cyclotron Laboratory. Combining previous measurements on the $^{186}$W($\gamma,n$) cross section with our new $^{182,183,184}$W($\gamma,n$) and ($\alpha,\alpha^\prime\gamma$)$^{186}$W data sets, we have deduced the $^{186}$W $\gamma$-ray strength function in the range of $1 < E_\gamma < 6$ MeV and $7 < E_\gamma < 14$ MeV. Our data are used to extract the level density and $\gamma$-ray strength functions needed as input to the nuclear-reaction code \textsf{TALYS}, providing an indirect, experimental constraint for the $^{185}$W($n,\gamma$)$^{186}$W cross section and reaction rate. Compared to the recommended Maxwellian-averaged cross section (MACS) in the KADoNiS-1.0 data base, our results are on average lower for the relevant energy range $k_B T \in [5,100]$ keV, and we provide a smaller uncertainty for the MACS. The theoretical values of Bao \textit{et al.} and the cross section experimentally constrained on photoneutron data of Sonnabend \textit{et al.} are significantly higher than our result. The lower value by Mohr \textit{et al.} is in very good agreement with our deduced MACS. Our new results could have implications for the $s$-process and in particular the predicted $s$-process production of $^{186,187}$Os nuclei.Comment: 17 pages, 15 figures; to be submitted to Phys. Rev.

Evolution of the γ\gamma-ray strength function in neodymium isotopes

The experimental gamma-ray strength functions (gamma-SFs) of 142,144-151Nd have been studied for gamma-ray energies up to the neutron separation energy. The results represent a unique set of gamma-SFs for an isotopic chain with increasing nuclear deformation. The data reveal how the low-energy enhancement, the scissors mode and the pygmy dipole resonance evolve with nuclear deformation and mass number. The data indicate that the mechanisms behind the low-energy enhancement and the scissors mode are decoupled from each other.Comment: 14 pages and 10 figure

New experimental constraint on the 185W(n,γ)186W cross section

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New experimental constraint on the W-185(n, & gamma;) W-186 cross section

In this work, we present new data on the 182,183,184W(; gamma; , n) cross sections, utilizing a quasi-monochromatic photon beam produced at the NewSUBARU synchrotron radiation facility. Further, we have extracted the nuclear level density and ; gamma; -ray strength function of 186W from data on the 186W(; alpha;, ; alpha;'; gamma; ) 186W reaction measured at the Oslo Cyclotron Laboratory. Combining previous measurements on the 186W(; gamma; , n) cross section with our new 182,183,184W(; gamma; , n) and (; alpha;, ; alpha;'; gamma; ) 186W data sets, we have deduced the 186W ; gamma; -ray strength function in the range of 1 E ; gamma; 6 MeV and 7 E ; gamma; 14 MeV. Our data are used to extract the level density and ; gamma; -ray strength functions needed as input to the nuclear-reaction code TALYS, providing an indirect, experimental constraint for the 185W(n, ; gamma; ) 186W cross section and reaction rate. Compared to the recommended Maxwellian-averaged cross section (MACS) in the KADoNiS-1.0 database, our results are on average lower for the relevant energy range kBT ; ISIN; [5, 100] keV, and we provide a smaller uncertainty for the MACS. The theoretical values of Bao et al. [At. Data Nucl. Data Tables 76, 70 (2000)] and the cross section experimentally constrained on photoneutron data of Sonnabend et al. [Astrophys. J. 583, 506 (2003)] are significantly higher than our result. The lower value ingredient in simulations for investigating the neutron density and the 186,187Os production in the s process.European Research Council [325714]; Research Council of Norway [OISE-1927130, 118846]; F.R.S.-FNRS; National Science Foundation [316116]; National Research Foundation of South Africa; [637686]The authors would like to thank J. C. Mueller, P. A. Sobas, and J. C. Wikne at the Oslo Cyclotron Laboratory for operating the cyclotron and providing excellent experimental conditions. We sincerely thank T. W. Hagen, S. J. Rose, and F. Zeiser for helping with the OCL experiment, Y. -W. Lui for helping with the NewSUBARU experiments, and S. N. Liddick for inspiring discussions. A.C.L. gratefully acknowledges funding of this research by the European Research Council through ERC-STG-2014 under Grant Agreement No. 637686, and from the Research Council of Norway, Project Grant No. 316116. S.G. acknowledges the support from the F.R.S.-FNRS. This work was supported in part by the National Science Foundation under Grant No. OISE-1927130 (IReNA) . The photoneutron cross section measurement was performed as part of the IAEA CRP on Updating the Photonuclear Data Library and generating a Reference Database for Photon Strength Functions (F41032) . A.G., V.W.I., and S.S. gratefully acknowledge financial support from the Research Council of Norway, Project Grant No. 325714. This work is in part based on the research supported partly by the National Research Foundation of South Africa (Grant No. 118846)