Isotope and element distributions of the evaporation residues from fusion of 160 MeV 32S with 242526Mg and 27Al

Evaporation residues from fusion reactions induced by 160 MeV 32S on targets of 242526Mg and 27Al were identified by means of a time-of-flight ΔE-E detector telescope. Angular distributions were measured in the range from 30 to 160 and total yields were determined as a function of A and Z of the products. The mass distributions of the evaporation residues (summed over Z) show the typical structure arising from the competition between nucleon and α evaporation in the decay of the highly excited (83 to 90 MeV) compound nuclei, with only little variation between the four systems. It is concluded that the deexcitation mechanism is to a large extent independent of the individual structure of the nuclei in the decay chains. This is also demonstrated by the yield distributions for the individual nuclides, in particular by the similarity of the yield patterns obtained in the N-Z plane for the compound nuclei 59Cu and 57Ni. The data are reproduced very well by evaporation calculations based on the statistical theory. Effects of nuclear deformations due to the high angular momentum on the shape of the yrast line and on the transmission coefficients for the emitted light particles were included. The influence of shell effects in the level densities at high excitation was studied and found to be negligible above 15 MeV excitation