“Appearance Energy” and Energy Dependence of the Recoil Product Yield in Indium Ethylenediaminetetra-acetate by the In115(γ, γ′)115mIn Reaction

Abstract

The concept of the “appearance energy” has been proposed by observing the recoil product yield as a function of recoil energy in a solid system. The yield of 115mIn3+ ion following the In115(γ, γ′)115mIn reaction in indium ethylenediaminetetraacetate (In–EDTA) was zero in the low-recoil-energy region and it increased from a threshold value of recoil energy, that was named the “appearance energy,” to a saturation yield in the higher energy region. The appearance energy of the 115mIn3+ ion in In–EDTA was about 60 eV with possible errors of factor 2. The meaning of the appearance energy has been discussed in comparison with the displacement energy in solid-state physics. From the energy dependence curve it was suggested that the reaction of the recoil atom might be divided into three categories corresponding to the three parts of the recoil range.