Excitation functions for production of heavy actinides from interactions of 40Ca and 48Ca ions with 248Cm

Excitation functions have been measured for production of isotopes of Bk through Fm in bombardments of 248Cm with 234- to 294-MeV 40Ca ions and with 239- to 318-MeV 48Ca ions. The maxima of the isotopic distributions for these elements occur at only 2 to 3 mass numbers larger for 48Ca than for 40Ca reactions. The shapes of the distributions and the half-widths of about 2.5 mass numbers are quite similar to those observed previously for reactions of 16O, 18O, 20Ne, and 22Ne with 248Cm. In general, the excitation functions for 40Ca show maxima near the Coulomb barrier while those for 48Ca are about 20 MeV above the barrier. The cross sections decrease rather slowly with increasing projectile energy over the energy range studied, indicating that the additional projectile energy is not manifested as excitation energy of these actinide products