Sections efficaces photoneutroniques de I, Ce, Sm, Er et Lu

Abstract

Partial and total photoneutron cross sections for natural I, Ce, Sm, Er and Lu have been measured as a function of photon energy up to 30 MeV using a monoenergetic photon beam created by the annihilation in flight of monochromatic positons. Measured threshold values for σ(γ, n), σ(γ, 2n) and σ(γ, 3n) are in good agreement with theoretical values. From a two Lorentz curve fit to the measured total photonuclear cross sections intrinsic quadrupole moments Q 0, and deformation parameters β 2 have been obtained. Experimental values for the integrated cross sections σ 0, σ −1 and σ −2 are calculated and compared with several theoretical expressions. Finally a set of nuclear density parameters and the corresponding nuclear temperatures are also determined.