Shell corrections at the saddle point for mass $~200$

Statistical model analysis of the measured evaporation residue and fission excitation functions indicates the presence of shell corrections to the liquid drop energy at the saddle point deformations for nuclei of mass $~200$, if one attempts to fit simultaneously the measured prefission neutron multiplicities.

Figure 1

A schematic representation of the potential energy of deformation of a nucleus with shell correction.

Figure 2

(Top panels) The experimental fusion, evaporation residue, and fission excitation functions are compared with model calculations for the ${}^{12}\mathrm{C}$+${}^{194,198}\mathrm{Pt}$ and ${}^{19}\mathrm{F}$+${}^{188,192}\mathrm{Os}$ systems. The dot-dashed line represents the coupled channels calculation using CCDEF for fusion excitation function. The continuous, the dotted, the short dashed, the dot-dot-dashed, and the long dashed lines are the statistical model predictions for the 3$n$, 4$n$, 5$n$, and 6$n$ evaporations and the fission, respectively, using the parameters given in Table (Set A). (Bottom panels) The statistical model predictions of prefission neutron multiplicities for various sets of values of ($k_f,{\tilde{a}}_f/{\tilde{a}}_n$), which produce equally good fits to the ER and fission excitation functions, are compared with the data (filled diamonds) for $Z=82\text{−}87$ [17] and the systematics [18] (gray band). The gray bands with diagonal lines are obtained from the systematics [18] (gray bands) after correction due to estimated dynamical neutron emission corresponding to a dynamical delay of $30\times {10}^{-21}$ (see text).

Figure 3

(Top panels) The experimental fission probabilities are compared with the statistical model calculations for the ${}^{16}\mathrm{O}$+${}^{181}\mathrm{Ta}$,${}^{16}\mathrm{O}$+ ${}^{182}\mathrm{W}$, and ${}^{19}\mathrm{F}$+${}^{194,198}\mathrm{Pt}$ systems. The continuous lines are the statistical model predictions for the fission probability using the parameters given in Table (Set A). (Bottom panels) The statistical model predictions of prefission neutron multiplicities for various sets of values of ($k_f,{\tilde{a}}_f/{\tilde{a}}_n$), which produce equally good fits to the fission probabilities, are compared with the data (filled diamonds) for $Z=82\text{−}87$ [17] and the systematics [18] (gray bands). The gray bands with diagonal lines are obtained from the systematics [18] (gray bands) after correction due to estimated dynamical neutron emission corresponding to a dynamical delay of $30\times {10}^{-21}$ (see text).