Theoretical estimate of the half-life for the radioactive ${}^{134}$Cs and ${}^{135}$Cs in astrophysical scenarios

Abstract

We analyze the ${}_{55}^{134}$Cs${\to }_{56}^{134}$Ba and ${}_{55}^{135}$Cs${\to }_{56}^{135}$Ba ${\beta }^{-}$ decays, which are crucial production channels for Ba isotopes in Asymptotic Giant Branch (AGB) stars. We reckon, from relativistic quantum mechanis, the effects of multichannel scattering onto weak decays, including nuclear and electronic excited states (ES) populated above $\simeq$ 10 keV, for both parent and daughter nuclei. We find increases in the half-lives for $T>10^8$ K (by more than a factor 3 for ${}^{134}$Cs) as compared to previous works based on systematics. We also discuss our method in view of these previous calculations. An important impact on half-lives comes from nuclear ES decays, while including electronic temperatures yields further increases of about 20\% at energies 10-30 keV, typical of AGB stars of moderate mass ($M\lesssim 8M_{\odot }$). Despite properly considering these effects, the new rates remain sensitively lower than the TY values, implying longer half-lives at least above 8-9 keV. Our rate predictions are in substantial accord with recent results based on the shell model, and strongly modify branching ratios along the $s$-process path previously adopted. With our new rate, nucleosynthesis models well account for the isotopic admixtures of Ba in presolar SiC grains and in the Sun.

15 pages, 3 figures, 5 tables. Accepted for publication in ApJ

References in corpus (6)

• Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components
• Electron capture in stars
• s-Processing in AGB Stars Revisited. III. Neutron captures from MHD mixing at different metallicities and observational constraints
• Presolar grain isotopic ratios as constraints to nuclear and stellar parameters of AGB nucleosynthesis
• The stellar beta-decay rate of 134Cs and its impact on the Barium nucleosynthesis in the s process
• The effects of a revised ${}^7$Be e${}^{-}$-capture rate on solar neutrino fluxes

Cited by in corpus (6)

• The s Process and Beyond
• High-temperature ${}^{205}$Tl decay clarifies ${}^{205}$Pb dating in early Solar System
• Slow Neutron-Capture Process: Low-mass AGB stars and presolar silicon carbide grains
• Presolar Silicon Carbide Grains of Types Y and Z: Their Strontium and Barium Isotopic Compositions and Stellar Origins
• Presolar grains
• Advancements in Secondary and Backscattered Electron Energy Spectra and Yields Analysis: from Theory to Applications