Measurement of the neutron capture cross sections of rhenium up to stellar s - and r -process temperatures at the China Spallation Neutron Source Back-n facility

The neutron capture measurement of natural rhenium was performed with the time-of-flight technique at the Back-n facility of the China Spallation Neutron Source in the energy range from 1 to 500 eV of the resolved resonance region (RRR) and from 5 to 400 keV in the unresolved resonance region (URR). Prompt <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>γ</a:mi></a:math>-rays originating from neutron-induced capture events were detected by four <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msub><b:mi mathvariant="normal">C</b:mi><b:mn>6</b:mn></b:msub><b:msub><b:mi mathvariant="normal">D</b:mi><b:mn>6</b:mn></b:msub></b:mrow></b:math> detectors. The pulse height weighting technique and the double-bunch unfolding method based on the Bayesian theory were used in the data analysis. To obtain reliable measurement results, background subtraction, normalization, and corrections were carefully considered. The multilevel R-matrix Bayesian code was used to extract the resonance parameters in the RRR. An absence of resonance near 392 eV is observed in our measurement, which has been observed in previous works. The average cross sections in the URR of natural rhenium relative to <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mmultiscripts><e:mi>Au</e:mi><e:mprescripts/><e:none/><e:mn>197</e:mn></e:mmultiscripts></e:math> were obtained in logarithmical equidistant energy bins with 20 bins per energy decade. The code was used to describe the average cross sections in the URR; the Maxwellian-averaged cross sections (MACSs) of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mmultiscripts><f:mi>Re</f:mi><f:mprescripts/><f:none/><f:mn>185</f:mn></f:mmultiscripts></f:math> and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mmultiscripts><g:mi>Re</g:mi><g:mprescripts/><g:none/><g:mn>187</g:mn></g:mmultiscripts></g:math> are given from <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mi>k</h:mi><h:mi>T</h:mi><h:mo>=</h:mo><h:mn>5</h:mn></h:mrow></h:math> to 100 keV. At a thermal energy of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:mrow><i:mi>k</i:mi><i:mi>T</i:mi><i:mo>=</i:mo><i:mn>30</i:mn></i:mrow></i:math> keV, the MACS value for <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mmultiscripts><j:mi>Re</j:mi><j:mprescripts/><j:none/><j:mn>185</j:mn></j:mmultiscripts></j:math> (<k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mn>1469</k:mn><k:mo>±</k:mo><k:mn>127</k:mn></k:mrow></k:math> mb) is in good agreement with the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNIS) recommended value (<l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mrow><l:mn>1535</l:mn><l:mo>±</l:mo><l:mn>62</l:mn></l:mrow></l:math> mb) within the error bars. By contrast, the value of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:mrow><m:mn>1361</m:mn><m:mo>±</m:mo><m:mn>118</m:mn></m:mrow></m:math> mb for <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mmultiscripts><n:mi>Re</n:mi><n:mprescripts/><n:none/><n:mn>187</n:mn></n:mmultiscripts></n:math> shows a discrepancy with the recommended value (<o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:mrow><o:mn>1160</o:mn><o:mo>±</o:mo><o:mn>57</o:mn></o:mrow></o:math> mb). Published by the American Physical Society 2024