Mass and energy distributions, angular anisotropy of fission fragments, neutron multiplicities, fission cross section, transient fission time and etc. are of particular importance, experimentally and theoretically. Observation of the symmetry characteristic of mass and energy distributions depend on the nature of projectile and target, the energy of projectile, and etc.
As we know the mass and energy distributions of thermal neutron induce fission of {235}^U is asymmetric and be symmetric for fast neutron induced fission of {235}^U. The released energy in the symmetry mode of the induced fission of a given nucleus is more than that one in the asymmetry mode as shown the behavior of total binding energy against the mass number. As a result, we expect to observe a more stable final configuration in symmetry mode of the induced fission of a given fissioning nucleus ( the fission probability as an dependent energy quantity for symmetry fission must be greater than the fission probability of asymmetry fission) in comparison to the asymmetry mode. How to predict the symmetric and asymmetric modes in heavy-ion and light projectile induced fission, theoretically?
Hello! The Strutinsky shell-correction energy to the liquid-drop energy provides asymmetric-mass pathways through the collective potential-energy landscape of the fissioning nucleus, which are energetically more favourable than the symmetric-mass pathway. The collective mass tensor along with the friction tensor and thermal fluctuations are critical for the mass and energy distributions. The fission dynamics is very complex, with many facets, which has been a great challenge for modelling over 75 years. Cheers, Alexis
Dear Alexis
Thank you so much for your answer. Is it possible to predict the symmetry mode of fission in heavy-ion induced fissions by considering the entrance channel mass asymmetry parameter (alpha=(A_T-A_p)/(A_T+A_P)), fissility parameter, and etc?
Hello Saeid! Yes, it is possible. Dynamical models, such as the dinuclear system model or dynamical calculations based on the Langevin equation, can provide information on the symmetric-mass mode in low-energy heavy-ion collisions. The symmetric mass yield include a component of quasi-fission (premature fission) that is very difficult to separate from the standard fission component. From the entrance channel (injection point) there are many, bifurcated trajectories in the collective-potential landscape which contribute to the symmetric-mass mode. Other observables e.g., angular anisotropy or mass-angle correlation measurements) can help separate the different components of the symmetric-mass yield. Cheers, Alexis
Dear Alexis
Thanks a lot, as we know, dynamical models give interesting information on properties of heavy- ion collisions. If the square of standard deviation of mass distribution shows a linear behavior against the nuclear temperature or there is an agreement between the experimental data of angular anisotropy and the prediction of the standard saddle-point statistical model , all of fission events are due to complete fission( in this case, the formation of compound nucleus occurs and all of degrees of freedom reach to the equilibrium except the component of total angular momentum in the direction of symmetry axis). The observation of anomalous behavior in the angular anisotropy is due to the Non-compound nucleus events such as quasi-fission, fast-fission. The average contribution of Non-compound nucleus events in induced fission of a given target by different projectiles and in induced fission of different targets by a given projectile can be predictable as shown in the following paper.
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