Experimental measurements of evaporation residue (ER) cross sections for the ${}^{19}F$ + ${}^{194,196,198}\mathrm{Pt}$ reactions forming ${}^{213,215,217}\mathrm{Fr}$ compound nuclei are reported. The cross sections are measured at beam energies in the range of 101–137.3 MeV. The survival probability of the ${}^{213}\mathrm{Fr}$ compound nucleus with neutron number $N=126$ is found to be lower than the survival probabilities of ${}^{215}\mathrm{Fr}$ and ${}^{217}\mathrm{Fr}$ with neutron numbers $N=128$ and 130 respectively. Statistical model analysis of the ER cross sections show that an excitation energy dependent scaling of the finite-range rotating liquid drop model fission barrier is necessary to fit the experimental data. The fitted scaling factors for ${}^{213}\mathrm{Fr}$ are found to be smaller than those of ${}^{215}\mathrm{Fr}$ and ${}^{217}\mathrm{Fr}$ for almost the entire range of excitation energies.

• Received 17 November 2013

DOI:https://doi.org/10.1103/PhysRevC.89.024609