Experimental investigation of the quasi-continuum γ-ray cascades following 160Gd( α, xn) 164 − xDy reactions

Abstract

Multiplicity shape parameters have been determined for the 160Gd( α, xn) 164 − x Dy reactions with x = 4–8 for E α = 40–110 MeV. Gamma-ray entry lines for the (α, 4n) and (α, 6n) reactions have been deduced from the side-feeding multiplicities as a function of γ-ray energy for various bombarding energies. The γ-ray multiplicities and the excitation energies of the entry lines increase steeply with the bombarding energy in the region of compound-nucleus formation and retain rather constant values when pre-equilibrium decay is important. These saturation effects locate the neutron “drip line” in the energy versus spin plane. The role of angular momentum and of excitation energy on the γ-ray decay process is investigated. The multiplicity data are compared with a combined statistical-master-equation-IBA calculation, which yields insight in the physical parameters that govern the decay process.