The neutron exit channel in 3He-induced break-up reactions

Abstract

Inclusive neutron spectra of 3He-induced reactions with 27A1, 63Cu, 93Nb and 197Au were measured for 26.0, 34.4 and 43.1 MeV projectile energy at laboratory angles from 3° to 177° using time-of-flight techniques. The component remaining after incoherent subtraction of compound and precompound contributions from the inclusive spectra shows a broad continuous bump and is assigned to the direct projectile break-up. Due to Coulomb effects, the position of the bump is shifted from 1 3 E 3 He c.m. to lower and higher energies in neutron- and proton-spectra, respectively. Experimental and theoretical results characterize the projectile break-up as a peripheral process. Break-up neutron yields increase with incident energy and target mass. Experimental spectra are the more underestimated by DWBA model calculations the less the incident energy exceeds the Coulomb barrier of the target nucleus. These discrepancies are attributed to the neglect of reaction mechanisms, e.g. a sequential break-up involving a singlet deuteron as intermediate state or an excitation of the projectile into the continuum followed by an immediate decay.