The s-process branchings at W-185 and Re-186

Neutron physics of the Re/Os clock. I. Measurement of the (n,γ) cross sections ofOs186,187,188Mosconi1, Fujii2, Mengoni3 et al. 2010Phys. Rev. C311160View full textAdd to dashboardCite

“…Therefore, the radiogenic contribution to the abundance of 187 Os could be determined by subtraction of the s-process component from the observed abundance value. The branchings at 185 W and 186 Re require a corresponding correction of the radiogenic component, which can be determined by a detailed analysis of the s-process reaction flow using a reliable set of stellar (n,γ ) cross sections [9][10][11].…”

“…The first issue could be settled by a measurement of the half-life of fully stripped 187 Re atoms [12] and by subsequent analyses, which demonstrated that the astration effect related to the destruction of 187 Re in later stellar generations is not crucial for the reliability of the clock [13]. Similarly, the s-process contributions to 187 Re due to the branchings at 185 W and 186 Re were shown to have no significant impact either [9,11,14].…”

Neutron reactions and nuclear cosmo-chronology

“…The neutron inelastic scattering cross section of 187 Os was measured at the 3.7 MV Van de Graaff of Forschungszentrum Karlsruhe using the 7 Li( p, n) 7 Be reaction for obtaining a 'monoenergetic' neutron beam of 30 keV. The energy of the pulsed proton beam (∆t = 10 ns) was adjusted right at the ( p, n) threshold to produce kinematically collimated neutrons, which are emitted in a narrow cone with an opening angle of no more than 13 deg and an energy spread of less than 10 keV.…”

“…The first issue could be settled by a measurement of the half-life of fully stripped 187 Re atoms [5] and by subsequent analyses, which demonstrated that the astration effect related to the destruction of 187 Re in later stellar generations is not crucial for the reliability of the clock [6]. Similarly, the s-process contributions to 187 Re due to the branchings at 185 W and 186 Re were shown to have no significant impact either [7][8][9].…”

The s-process branching at $^{186}$Re revised

“…The s-process branching at 186 Re is important for the understanding of the s-process nucleosynthesis pattern in this mass region, and it affects the 187 Re-187 Os cosmochronology [1,2]. A direct measurement of the neutron capture cross section of 186 Re is extremely difficult because of its short half-life of t 1/2 = 3.72 d. Instead, two recent experiments have measured the inverse photodisintegration cross section of 187 Re(γ,n) 186 Re, and statistical model calculations were used to derive the 186 Re(n,γ) 187 Re capture cross section [2,3].…”