THREEFOLD FRAGMENTATION IN HOT NUCLEI WITH MEDIUM MASSES

The threefold massive fragment in hot nuclei with medium mass number h as been measured in Ar-40 + In-115, Rh-103, and Nb-93 reactions at 25M eV/u. The fragments emitted at angles larger than 32 degrees are detec ted by ten parallel plate position-sensitive avalanche counters (PPAC) , each with an area of 25 x 20cm(2). The total kinetic energies (TKE), the yield ratio P-32 of the threefold fragmentation to fission, and t he distributions of the fragment mass, velocity, and relative angle, e tc., are obtained. From the mass ratio of the fragments, a simple empi rical expression is deduced. By analyzing their angular correlation fu nction with a simple space-time model, the time difference between two scission points in the threefold process in the Ar + In reaction syst em is derived. A systematics of P-32 versus Z(2)/A for hot nuclei is o bserved.