Study of neutron-induced charged particle reactions relevant to the synthesis of ⁴⁰K in massive stars

⁴⁰K is found among other naturally occurring radionuclides to be primarily responsible for the radiogenic heating of terrestrial-type planets. Radiogenic heating, i.e., heating produced by exothermic decays of long-lived radioactive nuclei, has implications in the evolution of habitable environments in extrasolar planetary systems and its study has been intensified over the last decade. State-of-the-art methods of modeling the radiogenic heating in exoplanets currently rely on Galactic Chemical Evolution models for predicting the concertation of ⁴⁰K in the system; within this context, the rate of nuclear reactions relevant to the synthesis of ⁴⁰K in stellar environments can play an important role. ⁴⁰K is formed is massive stars during stellar evolution while its final abundance is particularly sensitive to the ⁴⁰K(n,p)⁴⁰Ar and ⁴⁰K(n,α)³⁷Cl reactions. In this presentation, results from the first direct measurement of ⁴⁰K(n,p)⁴⁰Ar and ⁴⁰K(n,α)³⁷Cl reaction cross-sections with fast neutrons will be discussed. The measurements took place at the Los Alamos Neutron Science Center (LANSCE) using the Low-Energy (n,Z) (LENZ) detector system. Based on the new data, improved stellar reaction rates were extracted that will enhance the accuracy of stellar yield calculations for ⁴⁰K.