Speaker
Description
Several reactions of light nuclei require a better understanding at the energies relevant for Nuclear As- trophysics. The most relevant one is 12C(α,γ)16O. The reason for this is the importance of the reaction, and the complexity of its cross section at the relevant energies of static helium burning (300 keV) which uncertainty is still undesirably large. As there is no state of natural parity in 16O near the alfa-threshold to serve as a resonance for radiative capture in the energy region of interest, the total cross section orig- inates from a sum of resonance tails and direct captures, both, to the ground and excited states of 16O. Among the resonance tails contributing are two bound subthreshold states, i.e., the 1- state at -45 keV and the 2+ state at -200 keV below the α+12C threshold [1]. One of the methods to estimate these contri- butions consists in determining all the important reduced α-widths of the subthreshold states by indirect measurements, that are more sensitive to the α-width than the direct radiative capture measurement.
With this aim, a study of the 19F(p,α)16O reaction is being performed at CMAM facility (Madrid, Spain), using a proton beam with energies between 1.3 and 2.9 MeV to populate α-unbound states in 16O [2]. The experimental setup consists in 14 pixelated silicon detectors forming a quarter sphere configuration that cover forward angles from 27o to 87o [3] with an angular resolution of 9o. In the backward direction, three multi-segmented silicon detectors that cover from 82o to 171o backwards with an angular resolution of 3o, and an array of four scintillator units of 4 cm LaBr3(Ce) coupled with 6 cm LaCl3(Ce).
In this work we will present branching ratios to the population of the different 16O levels at different energies, measured, for the first time, through the study of the α-particles and γ-rays emitted in the reaction simultaneously in this energy range. We will conclude discussing the relative cross section obtained for those subthreshold levels that were highly populated at these energies.
References
[1] L. Buchmann. The Astrophysical Journal 468 (1996) L127-L130.
[2] R. J. deBoer, et. al. Physical Review C 103, 055815 (2021).
[3] L.M. Fraile, J. A ̈ysto ̈. Nuclear Instruments and Methods in Physics Research A 513 (2003) 287-290
