Speaker
Description
40K is the main isotope responsible for radiogenic heating of the mantle in Earth-like exoplanets during the preliminary stages of their formation. The high levels of 40K typically found in the interiors of exoplanets are from the events that enriched interstellar gas clouds such as supernovae explosions. These supernovae develop from the massive stars which are part of a large clusters. The radioisotopes such as 40K produced at supernovae sites enrich the discs present near the forming stars which eventually develop into planets. This indicates that this energy dispersion of particles after stellar explosions disperses enhanced levels of radioisotopes observed in the planets. The decay of 40K is an exothermic process that generates heat, which in turn keeps an Earth-like planet’s mantle hot for billions of years following its birth. This radiogenic heating and its evolution since a planet’s formation are critically connected to the initiation and sustainability of tectonic activity of a planet as well as of other planetary functions which control CO2 levels in a planet’s atmosphere.
The long-lived, 40K isotope is also produced by slow capture of neutrons by 39K and in massive stars during oxygen burning when lighter elements fuse. The reaction channel, 40Ar(p,n)40K, has been studied previously by our group to constrain the destruction rate of 40K via (n,p) channel [1]. In this work, we study the 37Cl(a,n)40K reaction, which will be used to find the destruction rate of 40K into radioactive 37Cl in the stellar environments. The experiment was performed at various energies, 4.25 MeV< Elab < 5.80 MeV, which produces the effective energy for the inverse reaction in the range of interest for astrophysical s-process. The experiment was performed at the Edwards Accelerator Laboratory at Ohio University using the 4.5 MV tandem accelerator. The neutrons were detected by the 4π HeBGB detector [2] with a detection efficiency of (7.5 ± 1.2%) at the neutron energies produced in this reaction. A complementary study, by our collaborators, was carried out at Los Alamos National Laboratory, where the direct reaction, 40K(n,α)37Cl has been measured to find the reaction rate for the same. In future, we plan to compare their results with our findings.
During the conference, we will discuss more about the reaction cross-section at experimental energies. The Hausher-Feshbach code, TALYS [3] is used to extract the reaction rates for the 37Cl(α,n)40K reaction. These calculations will provide parameters to constrain the theoretical calculations for inverse reaction and the destruction rate for 40K.
References:
[1] D.D. Clayton and E.W. Stanford, Rev Mod Phys 46, 755 (1974).
[2] P. Gastis, et al, Phys Rev C 101, 055805 (2020).
[3] K. Brandenburg, Jou Inst 17, P05004 (2022).
[4] A.J. Koning, et al, EDP Sciences, 211 (2008).