Fission fragment mass distribution in the ¹³C+¹⁸²W and ¹⁷⁶Yb reactions

Shell effects can play a prominent role in fission fragment mass distributions. For lighter systems in the region of A∼180-200, mass distributions were generally expected to be symmetric. However, a recent experiment showed that fission of ¹⁸⁰Hg following electron capture of ¹⁸⁰Tl leads to an asymmetric mass split. Recent calculations by various groups indicate that the mechanism of asymmetric fission could be very different in this mass region compared to the actinide region. To investigate the role of shell effects in this mass region, we have measured the fission fragment mass distribution for the ¹³C+¹⁸²W, ¹⁷⁶Yb reactions forming the compound nuclei ¹⁹⁵Hg and ¹⁸⁹Os respectively, at lab bombarding energies of 60, 63 and 66 MeV using the CUBE detector setup located at the ANU Heavy Ion Accelerator Facility. The experimental data were fitted with single and double Gaussian distributions. The results indicate an asymmetric mass split for ¹⁹⁵Hg, whereas for ¹⁸⁹Os, the mass distribution is well fitted with a single Gaussian distribution.