Search results for "r-process"
showing 4 items of 74 documents
Strong γ-ray emission from neutron unbound states populated in β-decay: Impact on (n,γ) cross-section estimates
2017
J. L. Taín et al. -- 6 pags., 7 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0
Study of beta-delayed neutron emitters in the region of 78ni and its impact on r-process nucleosynthesis
2020
En el presente trabajo hemos estudiado la emisión de neutrones beta-retardada de núcleos alrededor de los núcleo doblemente mágico 78Ni (numero atómico 28, y numero de neutrones 50). Los modelos teóricos a menudo carecen de la precisión necesaria para predecir las propiedades nucleares, en particular, la probabilidad de emitir uno o más neutrones. Se requieren nuevos valores experimentales de vidas medias y probabilidades de emisión de neutrón para mejorar y ampliar nuestro conocimiento actual de tal forma de desintegración. Además, dado que este tipo de desintegración beta es característico de núcleos muy ricos en neutrones, tiene un papel clave en los cálculos de abundancia elemental dura…
The Hamburg/ESO R-process Enhanced Star survey (HERES)
2004
We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe] > 1 dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). Moderate-resolution (~2A) follow-up spectroscopy has been obtained for metal-poor giant candidates selected from the Hamburg/ESO objective-prism survey (HES) as well as the HK survey to identify sharp-lined stars with [Fe/H] < -2.5dex. For several hundred confirmed metal-poor giants brighter than B~16.5mag (most of them from the HES), ``snapshot'' spectra (R~20,000; S/N~30 per pixel) are being obtained with VLT/UVES, with the main aim of finding the 2-3% r-II stars expected to be a…
r Process (n, γ) Rate Constraints from the γ Emission of Neutron Unbound States in β decay
2017
Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of γγ emission from neutron-unbound states populated in the ββ-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission a constraint on the (n, γγ) cross section for highly unstable neutron-rich nuclei can be deduced. A surprisingly large γγ branching was observed for a number of isotopes which might indicate the need to increase by a large factor the Hauser-Feshbach (n, γγ) cross-section estimates that impact on r process abundance calculations. peerReviewed