VISCOSITY OF SADDLE-TO-SCISSION MOTION IN HOT CF-240 FROM GIANT-DIPOLE RESONANCE GAMMA YIELD

The giant dipole resonance gamma decay of Cf-240 excited to 67 and 93 MeV was measured from the fusion of S-32 + Pb-208. The gamma spectrum and gamma-fission angular correlation are analyzed in terms of prefiss ion and postfission gamma-ray yields using a statistical model with nu clear viscosity in the fission process. The results show a strong incr ease in the prescission gamma yield from 67 to 93 MeV. A saddle to sci ssion time tau(ssc) = 30 X 10(-21) s is extracted from this gamma yiel d, equivalent to a normalized viscosity gamma almost-equal-to 5 and fu ll one-body dissipation.