Applications of complete reconstruction of multi-particle final states in fusion-evaporation reactions using a 4π detector

Abstract

Measurement of the energies and directions of one or more charged particles emitted in a fusion-evaporation reaction permits the excitation energy of the remaining system of nucleons to be calculated. The measured excitation energy is strongly linked to the probability that additional particles will be evaporated. Observation of γ-rays in coincidence with the charged particles and forming a two-dimensional matrix of excitation energy vs E γ is thus useful for identifying the reaction channel associated with unknown γ-rays. Here we apply this method to the identification of in-beam γ-rays in 85Zr and 84Y, resulting from the pn and 2pn reactions respectively in the 27Al+ 60Ni system. Peak-to-background enhancements approaching an order of magnitude can be obtained by selection of events using kinematical criteria derived from the analysis. In addition, we demonstrate how the charged particle angular distribution obtained with a 4π detector can be used to identify reactions on light target contaminants because of differences in kinematic focussing.