Astrophysical reaction rates forNi58,60(n,γ) from new neutron capture cross section measu

Abstract

New neutron capture cross sections of 58,60 Ni were measured in the energy range from 100 eV to 600 keV using the Oak Ridge Electron Linear Accelerator. The combination of these new neutron capture data with previous transmission data allowed a resonance analysis up to 900 keV using R-matrix theory. The theoretically determined direct capture cross sections were included in the analyses. From these resonance parameters and the direct capture contribution, new (n,γ ) astrophysical reaction rates were determined over the entire energy range needed by the latest stellar models describing the so-called weak s process.

Measurement of the stellarNi58(n,γ)Ni59cross section with accelerator mass spectrometry

“…The following Table VII shows the calculated MACS from this work in comparison to the MACS from ENDF/B-VII.1 and experimental data from recent TOF measurements [18,19]. Our result of σ 30keV = 30.4 (23) syst (9) stat mbarn is slightly lower (∼ 10%) than the two TOF measurements from [18,19] but still agrees within the uncertainties.…”

“…The 58 Ni(n, γ) 59 Ni cross section has been measured at stellar energies in several time-of-flight (TOF) experiments [14][15][16][17][18][19]. The overview in the "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars" (KADoNiS) [20] (see also Table VIII) reveals that "older" measurements which were performed before 1993 [14][15][16][17] yield a systematically higher Maxwellian-averaged cross section at kT = 30 keV (MACS30) compared to the two more recent TOF measurements from ORELA [18] and n TOF [19].…”

“…The overview in the "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars" (KADoNiS) [20] (see also Table VIII) reveals that "older" measurements which were performed before 1993 [14][15][16][17] yield a systematically higher Maxwellian-averaged cross section at kT = 30 keV (MACS30) compared to the two more recent TOF measurements from ORELA [18] and n TOF [19]. The latter two are in agreement and were used for the derivation of the new recommended MACS at kT = 30 keV of σ 30keV = 34.1 (15) mbarn in the most recent release of the KADoNiS v1.0 database.…”

“…Due to this and the perfect agreement with the following publication from the ORNL group [18] and the independently measured data from the n TOF group [19] we used only the cross section from the ENDF/B-VII.1 library for our calculation of the MACS.…”

Databases and tools for nuclear astrophysics applications

“…4) for 1 ≤ A ≤ 16 targets; -the NACRE data (Angulo et al 1999), when not superseded by NACRE II, or by other more recent compilations than NACRE listed below; -the compilation of the rates of Big-Bang reactions based on the R-matrix model (Descouvemont et al 2004); -the 2010 evaluation of Monte Carlo-based rates of resonant proton capture reactions on targets in the 20 ≤ A ≤ 40 range (Iliadis et al 2010); -the proton-induced reaction rates on stable and unstable target nuclei in the 20 < A < 40 region (Iliadis et al 2001); -when not available in the above-mentioned compilations, the reaction rates proposed by Caughlan & Fowler (1988); -the compilation of Bao et al (2000) for radiative neutron capture rates; -various radiative neutron capture rates made available between 2000 and 2011 that supersede the compilation of Bao et al (2000) (Abbondanno et al 2004;Aerts et al 2006;Best et al 2001;Blackmon et al 2002;Borella et al 2007;Dillmann et al 2006bDillmann et al , 2009Dillmann et al , 2010Domingo-Pardo et al 2006a,b, 2007aEsch et al 2008;Guber et al 2002Guber et al , 2010Heil et al 2005Heil et al , 2008aKatoh et al 2003;Koehler et al 1998Koehler et al , 2000Koehler et al , 2001Lederer et al 2011;Marrone et al 2006;Marganiec et al 2009aMarganiec et al ,b, 2010Meierhofer et al 2010;Mohr et al 1999;Mosconi et al 2010;Nakamura et al 2003;Noguere et al 2006;…”