Measurements of the total photonuclear cross sections from 30 MeV to 140 MeV for Sn, Ce, Ta, Pb and U nuclei

Abstract

The total photonuclear absorption cross section for Sn, Ce, Ta, Pb and U has been studied from 25 to 140 MeV using a continuously variable monochromatic photon beam obtained from the annihilation in flight of monoenergetic positrons. The basic experimental results are a set of data giving sums of inclusive multiple photoneutron production cross sections of the form σ ( i) ( E γ ) = Σ i= j σ( γ, in: E γ ) for neutron multiplicities ranging from i = 1 to 12. From these data the total photonuclear absorption cross section σ(tot: E γ ) has been deduced. It is concluded that Levinger's modified quasideuteron model describes the total cross sections reasonably well. When these data are combined with lower energy data and integrated to 140 MeV they indicate the need for an enhancement factor K for the Thomas-Reiche-Kuhn sum rule of 0.76 ± 0.10. No evidence was found that would indicate an A-dependence for the enhancement factor.