The Production of Neutron-Rich Nuclides in the Heavy-Element Region via 3He Induced Reactions

We have measured the production cross sections for 233Th and 231Th from the bombardment of 238U with 3He ions at 46-, 53-, and 60-MeV at the Brookhaven 60-in. isochronous cyclotron. We have also attempted to observe the decay of 233Ac produced via 238U(3He, 8B) or equivalent reactions using 61 MeV 3He ions by first separating thorium from actinium and then perf orming chemical purifications on the second thorium sample into which the actinium has decayed. In the four experiments we performed, three gave results consistent with the 3 half-life of 233Ac somewhat longer than 120 s and the production cross section from this target-projectile combination in the order of 1-2 ¿b.