Measurements of mass-angle distributions (MADs) for Cr + W reactions, providing a wide range in the neutron-to-proton ratio of the compound system, (N/Z)CN, have allowed for the dependence of quasifission on the (N/Z)CN to be determined in a model-independent way. Previous experimental and theoretical studies had produced conflicting conclusions. The experimental MADs reveal an increase in contact time and mass evolution of the quasifission fragments with increasing (N/Z)CN, which is indicative of an increase in the fusion probability. The experimental results are in agreement with microscopic time-dependent Hartree-Fock calculations of the quasifission process. The experimental and theoretical results favor the use of the most neutron-rich projectiles and targets for the production of heavy and superheavy nuclei.

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Energy dissipative processes play a key role in how quantum many-body systems dynamically evolve towards equilibrium. In closed quantum systems, such processes are attributed to the transfer of energy from collective motion to single-particle degrees of freedom; however, the quantum manybody dynamics of this evolutionary process are poorly understood. To explore energy dissipative phenomena and equilibration dynamics in one such system, an experimental investigation of deepinelastic and fusion-fission outcomes in the 58 Ni+ 60 Ni reaction has been carried out. Experimental outcomes have been compared to theoretical predictions using Time Dependent Hartree Fock and Time Dependent Random Phase Approximation approaches, which respectively incorporate onebody energy dissipation and fluctuations. Excellent quantitative agreement has been found between experiment and calculations, indicating that microscopic models incorporating one-body dissipation and fluctuations provide a potential tool for exploring dissipation in low-energy heavy ion collisions.The dynamic evolution of perturbed quantum manybody systems towards equilibrium is a topic of great interest in many fields, including quantum information [1], condensed matter [2-5], and nuclear physics [6][7][8][9][10]. Energy dissipation-the transfer of energy from collective motion to internal or external degrees of freedomshapes this dynamic evolution, playing a significant role in whether and how such complex systems achieve full equilibration. To date, a great deal of effort has focused on quantum systems in which energy dissipation is brought about via contact with an external environment (e.g., gas, photons, etc.) [11,12]. Much less is known about energy dissipation that arises from internal degrees of freedom [2, 5,13].One testing ground for the exploration of energy dissipation due to internal degrees of freedom can be found in heavy ion collisions. The nuclear collision process results in a closed composite quantum system that is isolated from external environments during the time of the collision (a timescale of several zeptoseconds, prior to particle emission), rapidly evolves towards equilibration in many degrees of freedom, and undergoes significant excitation and internal rearrangement throughout the equilibration process. Through the manipulation of collision entrance channel parameters (projectile-target combinations and energies), a range of factors with the potential to affect energy dissipation can be explored. Typical timescales for energy dissipation in such systems could in principle vary from isospin and mass equilibration times on the order of 0.3-0.5 zs [14,15] and ∼5 zs [16,17], respectively.In nuclear reactions, the observation of the total kinetic energy of the reaction products (TKE) offers a direct measure of energy dissipation. The observation of the masses of reaction products via direct or indirect methods offers a measure of system equilibration in a key degree of freedom, and can be used to explore fluctuations in reaction product mas...

Complete fusion cross sections have been measured using the off-line γ -ray spectroscopy method for the 6 Li + 90 Zr system around barrier energies. Statistical and coupled-channel calculations have been performed to investigate the effect of coupling on complete fusion. It is observed that the complete fusion is suppressed by 34 ± 8% compared to the coupled channel predictions. The effect of breakup coupling is estimated using the continuum discretized coupled channels (CDCC) method and it is found to reduce the complete fusion probability. Contrary to earlier predictions, a universal behavior of complete fusion suppression factor for the 6 Li projectile with target charge is observed.

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