Test of statistical model predictions for alpha-particle decay of ${}_{}{}^{90}{}_{}{}^{}$,92,94,96Ru compound nuclei

The α decay of Ru compound nuclei populated in ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ on ${}_{}{}^{58}{}_{}{}^{}$,60,62,64Ni reactions at $E_{\mathrm{beam}=135\mathrm{}–}$185 MeV has been studied. Experimental data have been compared with statistical model calculations performed with two different computer codes. The quality of the agreement between calculations and experimental data was found, in one case, to depend on the compound nucleus populated. Comparing the results from the two computer codes, deviations in the predicted cross sections are evidenced which are due to the different parametrization of nuclear properties employed in the calculations. Statistical model calculations describe well the shape of experimental spectra if account is taken of changes in the phase space available to the decaying nucleus which are related to the onset of deformations at high spins. Fission competition strongly determines the alpha-particle cross sections at the higher bombarding energies which are systematically underestimated by the model calculations if transmission coefficients computed from optical model potentials are used.