Study of pre-scission evaporation for 84Kr + 27AI at 10.6 MeV/u using 3π-phoswich detector system

We measured the pre-scission multiplicity of charged particle for the system of ⁸⁴Kr + ²⁷Al at 10.6 MeV/u. The charge multiplicity of pre-scission is about 80 % of the total charge multiplicity, which is about ten times as large as that calculated by a statistical model code (GEMINI). To reproduce the pre-scission multiplicity it is essential to introduce a fission delay time of the order of 10 ^-20 sec. It makes, however, the significant suppression of the binary fragment cross sections. To reproduce both cross section of binary fragments and pre-scission particle multiplicity simultaneously with the code, the pre-scission particles should not be emitted at the pre-saddle point, but between the saddle and scission points. The another explanation is that the composite system is formed between the saddle and scission points.