Spontaneous Fission of Light Californium Isotopes Produced in the 206,207,208 Pb + 34,36 S Reactions; New Nuclide 238 Cf

In bombardments of 206 Pb, 207 Pb, 208 Pb with 34 S and 206 Pb with 36 S, we identified a new spontaneously fissioning isotope 238 Cf with Tsf ∼ T1/2 = 21 ± ms and obtained evidence of the production of a new isotope 237 Cf with T1/2 = 2,1 ± 0,3 s. We measured spontaneous fission branches for 242 Cf and 240 Cf to be bsf ≤ 1,4 x 10-4 and bsf ∼ 2 x 10-2, respectively. For 237 Cf, we estimated bsf to be ∼ 10-1. The measured production cross sections of 238 Cf in the 206,207,208 Pb + 34 S reactions are in the range of 0,3 to 1,1 nb. We probed also the influence of the neutron excess in the N = 20 projectile 36 S on cross sections of fusion-evaporation fusion-evaporation reactions occurring on lead targets. 19 refs., 3 figs., 2 tabs