Sequential decay analysis of 235U(nth, f ) reaction using fragmentation approach

Abstract

Abstract Numerous experimental and theoretical observations have concluded that the probability of the three fragment emission (ternary fission) or binary fission increases when one proceeds towards the heavy mass region of nuclear periodic table. Many factors affect fragment emission, such as the shell effect, deformation, orientation, and fissility parameter. Binary and ternary fissions are observed for both ground and excited states of the nuclei. The collinear cluster tripartition (CCT) channel of the U(n , f) reaction is studied, and we observe that the CCT may be a sequential or simultaneous emission phenomenon. To date, different approaches have been introduced to study the CCT process as a simultaneous or sequential process, but the decay dynamics of these modes have not been not fully explored. Identifying the three fragments of the sequential process and exploring their related dynamics using an excitation energy dependent approach would be of further interest. Hence, in this study, we investigate the sequential decay mechanism of the U(n , f) reaction using quantum mechanical fragmentation theory (QMFT). The decay mechanism is considered in two steps, where initially, the nucleus splits into an asymmetric channel. In the second step, the heavy fragment obtained in the first step divides into two fragments. Stage I analysis is conducted by calculating the fragmentation potential and preformation probability for the spherical and deformed choices of the decaying fragments. The most probable fragment combination of stage I are identified with respect to the dips in the fragmentation structure and the corresponding maxima of the preformation probability ( ). The light fragments of the identified decay channels (obtained in step I) agree closely with the experimentally observed fragments. The excitation energy of the decay channel is calculated using an iteration process. The excitation energy is shared using an excitation energy dependent level density parameter. The obtained excitation energy of the identified heavy fragments is further used to analyze the fragmentation, and the subsequent binary fragments of the sequential process are obtained. The three identified fragments of the sequential process agree with experimental observations and are found near the neutron or proton shell closure. Finally, the kinetic energy of the observed fragments is calculated, and the middle fragment of the CCT mechanism is identified.