Evaporation residue formation in reactions with 40 AMeV argon beams

A study of nuclear reactions resulting from 40 AMeV Ar beams on Th{dollar}sp{lcub}232{rcub},{dollar} Au{dollar}sp{lcub}197{rcub},{dollar} Tb{dollar}sp{lcub}159{rcub},{dollar} Mo{dollar}sp{lcub}100{rcub}{dollar} and Ni{dollar}sp{lcub}58{rcub}{dollar} is presented. Excitation energies derived from neutron multiplicity measurements are shown to be consistent with the massive transfer model. Excitation energies for the most central collisions in order of decreasing mass of the target nucleus range from 900 MeV to 600 MeV. The highest of these are at least 200 MeV higher in energy than that deduced in previous studies based on the most probable neutron multiplicities in similar systems.; Comparisons between the experiment and a massive transfer model and statistical models are made. For the heavier systems formed in the reactions of Ar on Th and Au targets massive residues are seen. These residues are shown to be evaporation products of compound nuclei formed in central collisions which have avoided fission. The experiments are found to be consistent with the massive transfer model when a dynamical fission delay on the order of 10{dollar}sp{lcub}-20{rcub}{dollar} sec is included.