Evidence of nonstatistical neutron emission following decay near doubly magic Sn

Heideman, J.*; Grzywacz, R.*; Xu, Z. Y.*; Madurga, M.*; Escher, J. E.*; Kawano, Toshihiko*; Algora, A.*; Andreyev, A. N.; 41 of others*

-delayed neutron emission was observed in the study of the decay of In at ISOLDE CERN. Neutron emission probabilities from the unbound states in Sn to known low-lying, single-particle states in Sn were measured. The neutron energies were determined using the time-of-flight technique and the decay from excited states in Sn was studied by detecting its rays. Individual -delayed neutron emission probabilities were determined by correlating the relative intensities and energies of neutrons and rays. The new results suggest the violation of the assumption that neutrons are emitted statistically via the intermediate compound nucleus. This impacts the neutron-emission probabilities and other properties of nuclei participating in the r-process. A model of neutron emission, which links the observed neutron emission probabilities to nuclear shell effects, is proposed.