Probing nuclear dissipation via evaporation residue excitation functions for the ${}^{16,18}\mathrm{O}+{}^{198}\mathrm{Pt}$ reactions

Evaporation residue (ER) cross sections for the ${}^{16,18}\mathrm{O}+{}^{198}\mathrm{Pt}$ reactions are measured in order to investigate fission hindrance. Compound nuclei (${}^{214,216}\mathrm{Rn}$) are formed in the above fusion reactions at excitation energies in the range of 40–68 MeV. The experimental ER cross sections are compared with predictions from the statistical model calculations of compound nuclear decay where Kramers' fission width is used. The strength of nuclear dissipation is treated as a free parameter in the statistical model calculations in order to fit the experimental data.

Figure 1

Cathode ($\Delta E$) vs TOF spectrum for ${}^{16}\mathrm{O}+{}^{198}\mathrm{Pt}$ at 98.4 MeV.

Figure 2

(a) The normalized angular distributions of ERs from ${}^{16}\mathrm{O}+{}^{194}\mathrm{Pt}$ and ${}^{18}\mathrm{O}+{}^{198}\mathrm{Pt}$ reactions at different laboratory energies simulated using the Monte Carlo code TERS. The arrow at $3.{35}^{\circ }$ indicates the angular acceptance of HYRA. (b) Energy distribution for ${}^{18}\mathrm{O}+{}^{198}\mathrm{Pt}$ at lowest and highest energies using TERS. The arrow shows the energy threshold for ER in HYRA.

Figure 3

Variation of (a) ER cross section and (b) ER survival probability with excitation energy for ${}^{16,18}\mathrm{O}+{}^{198}\mathrm{Pt}$ systems.

Figure 4

(a) Fusion cross section for ${}^{16}\mathrm{O}+{}^{198}\mathrm{Pt}$. (b) Fusion cross section for ${}^{18}\mathrm{O}+{}^{198}\mathrm{Pt}$. The total fusion cross sections calculated using the coupled-channels code ccfull are also shown.

Figure 5

Calculated ER excitation functions for different choices of fission barrier along with the experimental ER cross sections: (a) ${}^{16}\mathrm{O}+{}^{198}\mathrm{Pt}$ (full circles), (b) ${}^{18}\mathrm{O}+{}^{198}\mathrm{Pt}$ (full squares).

Figure 6

Calculated ER excitation functions for different values of $\beta$ (in units of ${10}^{21}{\text{s}}^{-1}$) along with the experimental values: (a) ${}^{16}\mathrm{O}+{}^{198}\mathrm{Pt}$ (full circles), (b) ${}^{18}\mathrm{O}+{}^{198}\mathrm{Pt}$ (full squares).