SYSTEMATICS OF α-DECAY HALF-LIVES OF THE HEAVIEST ELEMENTS

The systematics of alpha-decay half-lives of super heavy nuclei with Z=102-120 and N=150-180 vs decay energy or number of valence nucleons is investigated in several approximation schemes. Half-lives given by self-consistent models for the alpha-clustering and resonance scattering are compared with empirical estimates. The calculated values of log(10)T(alpha)(th.) (sec) with alpha-formation and resonance reaction amplitudes, plotted vs Z(d)(0.6)Q(alpha)(-1/2), fall on a straight line given by log(10)T(alpha)(th.) (sec) = 9.6533.*(Z(d)(0.6)Q(alpha)(-1/2))-52.2369 (rms=0.4187), where Z(d) is the charge number of the daughter nucleus, Q(alpha) is the decay energy given in MeV units, and rms is the standard error. The experimental values of log(10)T(alpha)(exp.) (sec) plotted vs Z(d)(0.6)Q(alpha)(-1/2) are shown to fall also on a straight line given by log(10)T(alpha)(exp.) (sec)=9.6205*(Z(d)(0.6)Q(alpha)(-1/2))-51.0626 (rms=0.5515). The major influence of the pairing, deformed shell closures and screening corrections is evidenced and provides a convenient basis for the interpretation of observed trends of the data and for prediction of new results. The very small widths of alpha-resonances observed experimentally in fusion-evaporation reactions, are interpreted as resonance levels of radioactive products, and such a correlation contributes directly to the study of the nuclear structure on the basis of decay data. From the ratio between experimental and theoretical results we can obtain alpha-preformation factors. In few cases, the observed large discrepancies between the experimental data and theoretical results could indicate wrong data and might be eliminated by improving the accuracy of further measurements.