Study Of The Fusion Mechanism Within The Dinuclear System Model

The low energy heavy ion reaction mechanism leading to super-heavy elements is our interests.The investigation of the heavy ion fusion reactions mechanism covering both fusion and quasi-fission is carried out within the dinuclear system(DNS)concept,in which the capture of the two colliding nuclei and the survive probability are described by a semi-empirical channel coupling model and a statistical model,respectively.Generally,the description of the fusion probability is the most unclear,and the survival probability is also very sensitive to some nuclear structure information.In order to describe the whole process of fusion process more reasonably,the accurate calculation of the capture cross section is particularly important.The calculation in comparison to the prediction of single barrier penetration calculation can well be reproduced when considering the couplings to the rotational states for well deformed colliding nuclei and to the vibrational states for spherical nuclei.In addition,some critical input uncertainties for the calculation of the survival probability are discussed.Through the reliability test of capture cross section and survival probability,the calculation of ERCS can be obtained more reasonably and systematically.The heavy ion fusion process is not yet fully understood,whatever,the QF may be the only direct experimental observation to reveal the fusion process indirectly.On this basis the characteristics of QF products are studied in present work,which may can shed some interesting light on the reaction mechanism.During the fusion process,the two nuclei of the DNS may gradually get deformed due to strong nuclear and Coulomb interactions between them.Thus,the investigation of the characteristics of the QF,including the mass and the total kinetic energy distribution of the QF products,is carried out for the first time using the extended master equation,which is developed to include the deformation variables and mass numbers of projectile-like and target-like nuclei of the DNS configuration,so that the energy dissipation,nucleon exchange,deformation evolutions of the colliding nuclei as well as their correlations can be treated simultaneously.Our results show that dynamical deformations of the projectile-like and target-like nuclei of the DNS configuration play an important role in the process in reproducing the reasonable mass distribution of the QF products.The direct consequence of the introducing the dynamical deformations of the projectile-like and target-like nuclei of the DNS configuration being the dynamical variables is that one must treat the orientation effect properly.In present work,the orientation effect between the two deformed nuclei can be estimated by introducing a barrier distribution function.By further considering the mentioned orientation effect,which mainly contribute the large fluctuation on TKE of fragments,the mean TKE and the variance of the TKE distribution are successfully described.It indicates that in the fusion reaction process,there are may really existing two deformed nuclei,revealing the DNS model has a reasonable theoretical foundation and thus can reliably describe the reaction mechanism.