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Measurement of direct neutron capture by neutron-rich sulfur isotopes  [PDF]
H. Beer,C. Coceva,R. Hofinger,P. Mohr,H. Oberhummer,P. V. Sedyshev,Yu. P. Popov
Physics , 1996, DOI: 10.1016/S0375-9474(97)00244-3
Abstract: Thermal neutron capture cross sections for $^{34}$S(n,$\gamma$)$^{35}$S and $^{36}$S(n,$\gamma$)$^{37}$S have been measured and spectroscopic factors of the final states have been extracted. The calculated direct-capture cross sections reproduce the experimental data.
The thermal neutron capture cross section of the radioactive isotope $^{60}$Fe  [PDF]
T. Heftrich,M. Bichler,R. Dressler,K. Eberhardt,A. Endres,J. Glorius,K. G?bel,G. Hampel,M. Heftrich,F. K?ppeler,C. Lederer,M. Mikorski,R. Plag,R. Reifarth,C. Stieghorst,S. Schmidt,D. Schumann,Z. Slavkovská,K. Sonnabend,A. Wallner,M. Weigand,N. Wiehl,S. Zauner
Physics , 2015, DOI: 10.1103/PhysRevC.92.015806
Abstract: 50% of the heavy element abundances are produced via slow neutron capture reactions in different stellar scenarios. The underlying nucleosynthesis models need the input of neutron capture cross sections. One of the fundamental signatures for active nucleosynthesis in our galaxy is the observation of long-lived radioactive isotopes, such as $^{60}$Fe with a half-life of $2.60\times10^6$ yr. To reproduce this $\gamma$-activity in the universe, the nucleosynthesis of $^{60}$Fe has to be understood reliably. A $^{60}$Fe sample produced at the Paul-Scherrer-Institut was activated with thermal and epithermal neutrons at the research reactor at the Johannes Gutenberg-Universit\"at Mainz. The thermal neutron capture cross section has been measured for the first time to $\sigma_{\text{th}}=0.226 \ (^{+0.044}_{-0.049})$ b. An upper limit of $\sigma_{\text{RI}} < 0.50$ b could be determined for the resonance integral. An extrapolation towards the astrophysicaly interesting energy regime between $kT$=10 keV and 100 keV illustrates that the s-wave part of the direct capture component can be neglected.
Measurements of neutron-induced reactions in inverse kinematics  [PDF]
René Reifarth,Yuri A. Litvinov
Physics , 2013, DOI: 10.1103/PhysRevSTAB.17.014701
Abstract: Neutron capture cross sections of unstable isotopes are important for neutron induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes.
Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics  [PDF]
René Reifarth,Yuri A. Litvinov,Anne Endres,Kathrin G?bel,Tanja Heftrich,Jan Glorius,Alexander Koloczek,Kerstin Sonnabend,Claudia Travaglio,Mario Weigand
Physics , 2015, DOI: 10.1051/epjconf/20159302013
Abstract: Neutron capture cross sections of unstable isotopes are important for neutron-induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes. The idea is to measure neutron-induced reactions on radioactive ions in inverse kinematics. This means, the radioactive ions will pass through a neutron target. In order to efficiently use the rare nuclides as well as to enhance the luminosity, the exotic nuclides can be stored in an ion storage ring. The neutron target can be the core of a research reactor, where one of the central fuel elements is replaced by the evacuated beam pipe of the storage ring. Using particle detectors and Schottky spectroscopy, most of the important neutron-induced reactions, such as (n,$\gamma$), (n,p), (n,$\alpha$), (n,2n), or (n,f), could be investigated.
Reaction Rates of neutron capture by Li- and Be-isotopes  [PDF]
H. Herndl,R. Hofinger,P. Mohr,H. Oberhummer,T. Kajino,N. Terasawa
Physics , 1996,
Abstract: Neutron capture by neutron-rich Li- and Be-isotopes plays a role in big--bang nucleosynthesis, especially in its inhomogeneous version and in the $\alpha$--process occurring in supernovae. New reaction rates for $^{7,8}$Li(n,$\gamma$)$^{8,9}$Li and $^{9,10,11}$Be(n,$\gamma$)$^{10,11,12}$Be have been consistently calculated using direct capture for the nonresonant part and the Breit-Wigner formula for the resonant part. The spectroscopic factors, spin/parity assignments and excitation energies of the final bound and initial resonant states have been taken from existing experimental data whenever possible. For unstable nuclei where this information is not experimentally available the shell model was used to determine these quantities.
Reaction rates for Neutron Capture Reactions to C-, N- and O-isotopes to the neutron rich side of stability  [PDF]
H. Herndl,R. Hofinger,J. Jank,H. Oberhummer,J. Goerres,M. Wiescher,F. -K. Thielemann,B. A. Brown
Physics , 1999, DOI: 10.1103/PhysRevC.60.064614
Abstract: The reaction rates of neutron capture reactions on light nuclei are important for reliably simulating nucleosynthesis in a variety of stellar scenarios. Neutron capture reaction rates on neutron-rich C-, N-, and O-isotopes are calculated in the framework of a hybrid compound and direct capture model. The results are tabulated and compared with the results of previous calculations as well as with experimental results.
Production cross section of neutron-rich isotopes with radioactive and stable beams  [PDF]
Myeong-Hwan Mun,G. G. Adamian,N. V. Antonenko,Yongseok Oh,Youngman Kim
Physics , 2014, DOI: 10.1103/PhysRevC.89.034622
Abstract: The production cross section of neutron-rich isotopes of Ca, Zn, Te, Xe, and Pt are predicted in the diffusive multi-nucleon transfer reactions with stable and radioactive beams. With these isotopes one can treat the neutron shell evolution beyond N = 28, 50, 82, and 126. Because of the small cross sections, the production of nuclei near the neutron drip line requires the optimal choice of reaction partners and bombarding energies.
Neutron capture reactions on Lu isotopes at DANCE  [cached]
Roig O.,Jandel M.,Vieira D.J.,Bond E.M.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100205003
Abstract: The DANCE (Detector for Advanced Neutron Capture Experiments) array located at the Los Alamos national laboratory has been used to obtain the neutron capture cross sections for the 175Lu and 176Lu isotopes with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process in astrophysics and for applications as in reactor physics or in nuclear medicine. Three targets were used to perform these measurements. One was natLu foil and the other two were isotope-enriched targets of 175Lu and 176Lu. The cross sections are obtained for now through a precise neutron flux determination and a normalization at the thermal neutron cross section value. A comparison with the recent experimental data and the evaluated data of ENDF/B-VII.0 will be presented. In addition, resonances parameters and spin assignments for some resonances will be featured.
Thermal Neutron Capture onto the Stable Tungsten Isotopes  [cached]
Hurst A.M.,Firestone R.B.,Sleaford B.W.,Summers N.C.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122110005
Abstract: Thermal neutron-capture measurements of the stable tungsten isotopes have been carried out using the guided thermal-neutron beam at the Budapest Reactor. Prompt singles spectra were collected and analyzed using the HYPERMET γ-ray analysis software package for the compound tungsten systems 183W, 184W, and 187W, prepared from isotopically-enriched samples of 182W, 183W, and 186W, respectively. These new data provide both confirmation and new insights into the decay schemes and structure of the tungsten isotopes reported in the Evaluated Gamma-ray Activation File based upon previous elemental analysis. The experimental data have also been compared to Monte Carlo simulations of γ-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. Together, the experimental cross sections and modeledfeeding contribution from the quasi continuum, have been used to determine the total radiative thermal neutron-capture cross sections for the tungsten isotopes and provide improved decay-scheme information for the structural- and neutron-data libraries.
Dependence of direct neutron capture on nuclear-structure models  [PDF]
T. Rauscher,R. Bieber,H. Oberhummer,K. -L. Kratz,J. Dobaczewski,P. Moller,M. M. Sharma
Physics , 1998, DOI: 10.1103/PhysRevC.57.2031
Abstract: The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. We calculate direct neutron capture on the even-even isotopes $^{124-145}$Sn and $^{208-238}$Pb with energy levels, masses, and nuclear density distributions taken from different nuclear-structure models. The utilized structure models are a Hartree-Fock-Bogoliubov model, a relativistic mean field theory, and a macroscopic-microscopic model based on the finite-range droplet model and a folded-Yukawa single-particle potential. Due to the differences in the resulting neutron separation and level energies, the investigated models yield capture cross sections sometimes differing by orders of magnitude. This may also lead to differences in the predicted astrophysical r-process paths. Astrophysical implications are discussed.
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