Systematic study of precompound neutron emission in α -particle-induced reactions

Abstract

Background: The precompound emission process in light-ion fusion interactions has been a topic of considerable interest to nuclear physicists for many years. Although widespread theoretical and experimental efforts have been devoted to understand the reaction dynamics of precompound emission, no systematic study has been carried out to determine the driving input parameters in such reactions. Purpose: The importance of this study has large impact on reaction dynamics. In order to get parameters describing the precompound emission, excitation functions have been measured by using an α-particle beam on 141Pr target nuclei. Further, a sensitive analysis of excitation functions has been performed to investigate the systematics of the precompound process with mass number of target nuclei. Method: The off-line γ -ray-spectrometry-based activation technique has been used for the measurement of the excitation functions. The presently measured excitation functions on the system α + 141Pr (and those experimental values taken from literature on the α + 51V, α + 55Mn, α + 93Nb, α + 121Sb, and α + 123Sb systems) have been analyzed within the framework of compound and precompound emissions by using model code ALICE. Results: The analysis performed by using code ALICE with the same set of precompound parameters indicates that the experimentally measured excitation functions could be reproduced only when the precompound emission, simulated theoretically, has been taken into account. The influence of various important precompound parameters of the code ALICE with their physically accepted values for these systems has been judged and a systematics on precompound emission process is achieved with mass number of the target nuclei. Conclusions: The developed systematics for α-induced reactions on target nuclei 51V, 55Mn, 93Nb, 121Sb, 123Sb, and 141Pr indicates that the precompound process is governed by the excitation energy available to the nucleons at the surface the composite systems. Furthermore, mass number of the target nuclei may also play an important role in precompound process at low projectile energies.