Mass-asymmetric barriers from excitation functions for complex-fragment emission.

The conditional saddle-point heights (conditional barriers) that preside over the emission of complex fragments (Z = 2—11) from compound nuclei have been obtained from the excitation functions of individual fragments in the reaction He+""Ag. The magnitudes of the barriers and their dependence on mass asymmetry may be used to verify important features of the potential-energy surface including shell effects at the conditional saddle and to verify the validity of the liquid-drop model and recent refinements such as finite-range effects and surface diffuseness.