Transient times of fission in sup 40 Ar+ sup 232 Th peripheral collisions

Peripheral {sup 40}Ar+{sup 232}Th collisions at a bombarding energy {ital E}/{ital A}=30 MeV were studied by measuring coincidences of fission fragments with projectile fragments detected near the grazing angle. It is found that the sequential fission of the highly excited target residue nuclei is severely hindered if their excitation energies, determined from the measured recoil momenta, exceed a value of abour 50--75 MeV. A transient time of fission of the order of 10{sup {minus}20} s is deduced.