The influence of electron screening on half-lifes

Abstract

Electron screening strongly changes nuclear reaction cross sections at energies below 1000 times the screening energy U e . It has been found that U e can be one order of magnitude larger than predicted by theory [1] if the target atoms are hosted in a metallic environment. As a consequence, a change of lifetimes of low-energy β and α emitters may also be considered if they are situated in a metal. In addition, a temperature dependence of the screening effect has been proposed [2], dramatically changing some half-lifes if the metal is cooled [3,5]. We checked these claims experimentally by measuring the decay rate of 22 Na in a piece of aluminum activated by a 70 MeV proton beam. We observed the 22 Na activity both at room temperature and when cooled down to nearly LN 2 temperatures. As a result, a 10% increase as proposed by [3] can be clearly excluded. Furthermore, a 1/ √ T temperature dependence of U e as it was proposed by [3,5] when the Debye-Hückel model is applied is unlikely.