Statistical fission parameters for nuclei at high excitation and angular momenta

Experimental fusion/fission excitation functions are analyzed by the statistical model with modified rotating liquid drop model barriers and with single particle level densities modeled for deformation for ground state ($a_{\nu }$) and saddle point nuclei ($a_f$). Values are estimated for the errors in rotating liquid drop model barriers for the different systems analyzed. These results are found to correlate well with the trends predicted by the finite range model of Krappe, Nix, and Sierk, although the discrepancies seem to be approximately 1 MeV greater than the finite range model predictions over the limited range tested. The a priori values calculated for $a_f$ and $a_{\nu }$ are within ±2% of optimum free parameter values. Analyses for barrier decrements explore the importance of collective enhancement on level densities and of nuclear deformation in calculating transmission coefficients. A calculation is performed for the ${}_{}{}^{97}{}_{}{}^{}\mathrm{Rh}$ nucleus for which a first order angular momentum scaling is used for the $J=0\mathrm{}$ finite range corrections. An excellent fit is found for the fission excitation function in this approach. Results are compared in which rotating liquid drop model barriers are decremented by a constant energy, or alternatively multiplied by a constant factor. Either parametrization is shown to be capable of satisfactorily reproducing the data although their $J=0\mathrm{}$ extrapolated values differ markedly from one another. This underscores the dangers inherent in arbitrary barrier extrapolations.