Scaling Laws, Shell Effects, and Transient Times in Fission Probabilities

The fission excitation functions for 14 compound nuclei covering a mass range from $A=186\mathrm{} \mathrm{to} 213$ are shown to scale exactly according to the transition state prediction once shell effects are accounted for. The extracted shell effects correlate closely with those obtained from the ground state masses. No effects of transient times longer than 3 × ${10}^{-20\mathrm{}}$ sec are visible. Pairing effects are noticeable at excitation energies at few MeV above the barrier.