Actinide production from the interactions of 40Ca and 44Ca with 248Cm and a comparison with the 48Ca+248Cm system.

Excitation functions have been measured for production of isotopes of Th through Fm in bombardments of {sup 248}Cm with 231- to 323-MeV {sup 44}Ca ions and for the production of isotopes of Th through Cm in bombardments of {sup 248}Cm with 230- to 291-MeV {sup 40}Ca ions, respectively, using radiochemical methods. Upper production cross section limits were established for nuclides that were not positively detected. The experimental data were compared with the results of previous reaction studies in the systems {sup 40}Ca+{sup 248}Cm and {sup 48}Ca+{sup 248}Cm. The half-widths of the Gaussian isotopic distributions were about 2.5 mass numbers for above-target elements and 5 to 5.5 mass numbers for below-target elements in all three systems. The majority of the cross section for the production of above-target nuclides was assigned to predominantly quasielastic reactions, whereas below-target nuclides were formed in deeply inelastic and asymmetric quasifission reactions. The maxima of the isotopic distributions were shown by others to closely follow the minimum of the potential energy surface in experiments with {sup 48}Ca, whereas in reactions with {sup 40}Ca and {sup 44}Ca we found that a transfer of 4 to 5 protons in either direction was required to reach the minimum in potentialmore » energy.« less