21-23 March 2022
Europe/Madrid timezone

Cross section studies of alpha clustering light nuclei

21 Mar 2022, 18:00
Red Temática de Física Nuclear (FNUC) Red FNUC (Red Temática de Física Nuclear)


Vicente García Távora (IEM - CSIC)


There are several reactions that require a better understanding in Nuclear Astrophysics. The most relevant one is 12C(α,γ)16O. The reason for this is both the unmitigated 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 to serve as a resonance for radiative capture in the energy region of interest, the total cross section originates from a sum of resonance tails and direct captures, both, to the ground and excite states of 16O. Among the resonance tails contributing are those of bound subthreshold states, i.e., the 1- state at -45 keV and the 2+ state at -200 keV below the +12C threshold [1]. One of the methods to study these contributions consists in determining all the important reduced α-widths of the subthreshold states by indirect measurements, that are more sensitive to the -width than the direct radiative capture measurement. With this aim, we propose to use the 19F(p,α)16O reaction to populate α-unbound states in 16O [2].

Another reaction of interest is 7Li(3H,n)9Be. Since long, 9Be has been thought to be produced in tiny quantities in big bang nucleosynthesis. However, network calculations of big bang nucleosynthesis yields, indicates that the 7Li(3H,n)9Be reaction, enhances the 9Be abundance by many orders of magnitude compare to that previously found, as [3,4] suggested. A way of estimating the cross section for 7Li(3H, n)9Be would be to infer it from data of the similar reaction, 7Li(3He,p)9Be, as this cross section is more simple to measure.

In this work, we present the experiments that we performed to study both reactions at CMAM facility (Madrid, Spain), one in Nov. 2020 for 19F(p,α)16O reaction and the other one in Feb. 2021. The experimental setup is identical and consists of 14 pixelated silicon detectors in 2x2 that cover forward angles from 27º to 87º [5], three telescopes with multi-segmented silicon detectors in 16x16 in the front that cover from 82º to 171º backwards and behind 3 silicon PAD detectors (just for the 7Li(3He,p)9Be reaction study). The telescope arrangement will allow us the discrimination between the proton channel and the competing deuteron channel originated from the 7Li(3He, d)8Be reaction. We will present an early stage of the analysis process for both reactions.

[1] L. Buchmann. The Astrophysical Journal 468 (1996) L127-L130.
[2] K.Spyrou, et. al. Z. Phys. A 357 (1997) 283-289
[3] J. R. King, et. al. The Astrophysical Journal 478 (1997) 778-786.
[4] M. Kusakabe, https://arxiv.org/abs/1208.4210
[5] L.M. Fraile, J. Äystö. Nuclear Instruments and Methods in Physics Research A 513 (2003) 287-290

Primary authors

Vicente García Távora (IEM - CSIC) Prof. Olof Tengblad (IEM - CSIC) Dr. María José García Borge (IEM - CSIC)

Presentation Materials

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