Excitation energy deposition in central collisions of 40A MeV Ar40 with Th232

Excitation energy depositions in the reactions of 40A MeV Ar40 with Th232 have been determined from measurements of neutron multiplicities in coincidence with mass identified heavy reaction products. For the most central collisions the derived excitation energies of 880 MeV are 200-300 MeV above previous estimates and in excellent agreement with momentum transfer systematics. Heavy evaporation residues are observed for these collisions indicating apparent dynamic delays in the fission channel of (1-5)×10-20 s. While a massive-transfer simulation incorporating preequilibrium emission is in generally good agreement with the experimental results evidence is also found for strongly damped collisions.