Effects of nuclear orientation on fusion and fission in the reaction using238U target nucleus

K Nishio,H Ikezoe,S Mitsuoka,S Hofmann,K Hirose,Y Nagame,I Nishinaka,T Ohtsuki

doi:10.1051/epjconf/20100210001

Abstract

Fission fragment mass distributions in the reaction of 30 Si+ 238 U were measured around the Coulomb barrier. At the above-barrier energies, the mass distribution s howed a Gaussian shape. At the sub- barrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at AL/AH≈ 90/178. The asymmetric fission should be attributed to quasifission from the re sults of the measured evaporation residue (ER) cross-sections for 30 Si+ 238 U. The cross-section for 263 Sg at the above- barrier energy agree with the statistical model calculation which assumes th at the measured fission cross-section originates from fusion-fission, whereas the one for 264 Sg measured at the sub-barrier energy is smaller than the calculation, which suggests the presence of quasifission.

Highlights

In the production of superheavy nuclei (SHN) based on the actinide target nuclei and 48Ca beams [1] the cross-sections do not drop at increasing atomic number, but maintain values of a few picobarn even for the production of the heaviest elements
We report the measurement of fission fragment mass distributions for 30Si + 238U from above- to sub-barrier energies
Fission fragment mass distributions in the reaction of 30Si + 238U were measured around the Coulomb barrier

Summary

Introduction

In the production of superheavy nuclei (SHN) based on the actinide target nuclei and 48Ca beams [1] the cross-sections do not drop at increasing atomic number, but maintain values of a few picobarn even for the production of the heaviest elements. The relatively large cross-sections for actinide based reactions are explained by a high survival probability of the compound nuclei in competition with fission due to large fission barriers of nuclei in the vicinity of the N = 184 shell closure [1]. Another possible reason could be higher fusion probability. The crosssection for 264Sg at the sub-barrier energy are lower than a Josef Buchmann-Professor Laureatus the calculation, which suggests the presence of fusion hindrance in polar collisions In this case two different process should be involved in fissions. We expect the asymmetric fission to appear in the sub-barrier region from the measured ER cross-section at the sub-barrier energy

Experiment

Experimental results and discussions

Conclusions