Possible evidences for Giant Quadrupole Resonances within neutron-induced α-particle emission

Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 077125 Bucharest-Magurele, Romania

^* e-mail: vlad.avrigeanu@nipne.ro
^** e-mail: marilena.avrigeanu@nipne.ro

Published online: 14 March 2025

Abstract

A fine agreement of recently measured and presently calculated (n, α) cross sections at a low incident energy almost entirely related to the ground-state activation, supports additionally an α-particle OMP. Further calculated underestimation of the energy dependence of these data, beyond any model parameter uncertainty, is described by a Gaussian distribution around isoscalar giant quadrupole resonance (ISGQR) energy, of ~14.2 MeV, with a peak cross section of 0.36±0.04 mb, width of 1.8±0.1 MeV, and ISGQR-like strength function of 4.3±1.9% energy weighted sum rule (EWSR). The α-particle decay of nuclei excited at ISGQR energies in (n, α) reactions is linked to ISGQR-like strength functions with even around 50% larger uncertainty than ISGQR strengths measured by ³He and α-particle inelastic scattering. An isotope effect is also observed in the corresponding (γ, α) and neutron-induced α-emission data, following the Q-value decrease with the asymmetry parameter (N − Z)/A of the target nuclei.