Experimental study of ³⁷Cl(α,n)⁴⁰K reaction in order to constrain the reaction rate of destruction of ⁴⁰K in stars

¹ Department of Physics, Central Michigan University, Mt. Pleasant, MI 48859, USA
² Department of Physics & Astronomy,Ohio University, Athens, OH 45701, USA
³ Facility for Rare Isotope Beams, East Lansing, MI 48824, USA
⁴ Los Alamos National Laboratory, Los Alamos, NM 87545, USA
⁵ Joint Institute for Nuclear Astrophysics –Center for the Evolution of the Elements, East Lansing, MI48824, USA

^* e-mail: dimt2n@cmich.edu

Published online: 3 February 2023

Abstract

⁴⁰K is one of the main isotopes responsible for the radiogenic heating of the mantle in Earth-like exoplanets [1] and hence, plays a very important role in the internal geophysical dynamics of a planet. The abundance of ⁴⁰K in the mantle and the core of such planets is not always possible to be determined by astrophysical observations, although constraining the nuclear reaction rates of ⁴⁰K during stellar evolution can also lead to constraining the present amount of ⁴⁰K in these planets, which will improve our understanding on the habitability potential of Earth-like exoplanets. This study aims to constrain the ⁴⁰K(n,α)³⁷Cl reaction rate, one of the two major destruction paths of ⁴⁰K in stellar nucleosynthesis,by measuring the reverse reaction ³⁷Cl(α,n)⁴⁰K and applying the principle of detailed balance as we have done before for the 40K (⁴⁰K(n,p)⁴⁰Ar reaction rate) [2]. During the first set of measurements we performed differential cross-section measurements of the ³⁷Cl(α,n₁γ)⁴⁰K, ³⁷Cl(α,n₂γ)⁴⁰K and ³⁷Cl(α,n₃γ)⁴⁰K reaction channels, for six different center of mass energies in the range between 5.1 and 5.4 MeV. The experiment took place at the Edwards Accelerator Laboratory of Ohio University. The gamma rays from the reaction channels mentioned above were detected by two LaBr³ scintillators. Using the swinger facility to change the angle of the beam-target system with respect to the detection system, we were able to take measurements for the differential cross-section at six different angles between 20° and 120° in the lab system.