Stellar(n,γ)Cross Section ofNi62

Abstract

The 62Ni(n,gamma)63Ni(t(1/2)=100+/-2 yr) reaction plays an important role in the control of the flow path of the slow neutron-capture (s) nucleosynthesis process. We have measured for the first time the total cross section of this reaction for a quasi-Maxwellian (kT=25 keV) neutron flux. The measurement was performed by fast-neutron activation, combined with accelerator mass spectrometry to detect directly the 63Ni product nuclei. The experimental value of 28.4+/-2.8 mb, fairly consistent with a recent calculation, affects the calculated net yield of 62Ni itself and the whole distribution of nuclei with 62<A<90 produced by the weak s process in massive stars.

Erratum:Ni62(n,γ)andNi63(nLederer1, Massimi2, Berthoumieux3 et al. 2015Phys. Rev. CSelf Cite5020View full textAdd to dashboardCite

“…For kT < 30 keV, the n_TOF data are in agreement with the results of Alpizar-Vicente et al [19]. At 25 keV and 30 keV, our MACS is in excellent agreement with activation measurements of Nassar et al [20] and Dillmann et al [22], while being significantly lower than a previous time-of-flight measurement by Tomyo et al [18]. Towards higher kT values, our data start to deviate from the results of Alpizar-Vicente et al [19], being systematically lower up to a factor of 1.8.…”

“…[15]. In this section, [19], Nassar et al [20], Dillmann et al [22], and Tomyo et al [18]). The results obtained with data from the JENDL-4.0 evaluation (dashed line, [27]) and the recommended MACS values of the KADONIS compilation (solid line, [51]) are included as well.…”

“…This paper describes the measurement and data analysis of the (n,γ ) experiments on 62 Ni and 63 Ni. Current data on 62 Ni(n,γ ) include time-of-flight measurements [16][17][18][19] as well as activation measurements to directly determine the MACS at kT = 25 keV [20][21][22]. Neutron capture resonances have been analyzed over a large energy range (E n < 200 keV) by Beer and Spencer [17], while there are a few other measurements investigating only the first strong = 0 resonance at 4.6 keV [23][24][25].…”

Thesprocess: Nuclear physics, stellar models, and observations

“…A prominent example is the case of the 62 Ni(n, γ) 63 Ni cross section, where the effect was discussed first Guber, 2002, 2005;Rauscher et al, 2002). This problem has triggered a series of experimental studies on that isotope (Alpizar-Vicente et al, 2008;Lederer et al, 2010;Nassar et al, 2005;Tomyo et al, 2005) and on other key reactions of the weak s process between Fe and Sr, which could be considerably improved (e.g. Heil et al, 2008b,c).…”

Stellar neutron capture rates – key data for thesprocess

“…The main feature of AMS is the unsurpassed sensitivity for specific nuclides, much higher than can be obtained with conventional mass spectrometry, disadvantages are often elaborate sample preparation and the destruction of the sample by the measurement. AMS has first been applied to neutron capture reactions in s-process environments for 62 Ni by Nassar et al [45] and subsequently to a number of target nuclei including 40 Ca, 58 Ni, 62 Ni, and 78 Se [46][47][48]. The 13 C(n, ) 14 reaction was studied as part of a recently completed series of measurements [49] and represents a typical example for combining activation at keV neutron energies with subsequent AMS detection of the long-lived reaction product 14 C.…”