Many fascinating aspects of the
structure of atomic nuclei — from their extreme single-particle
properties to their highly collective states — can be investigated
through diverse nuclear reaction mechanisms such as fragmentation,
induced fission, multi-nucleon transfers etc.
Heavy-ion fusion is also of enormous importance, being frequently used to create compound nuclei whose “evaporation residues” (left after rapid cooling by emission of neutrons, protons and alpha particles) could be super-heavy nuclei, or strongly deformed systems at very high spins, or nuclei with exotic neutron/proton ratios... The fusion reaction depends strongly on the internal structure of the colliding target and projectile, especially when they possess highly collective vibrational or rotational modes. Barrier distributions measured over many years in various laboratories worldwide confirm our understanding of fusion as an aspect of “quantal tunneling in the presence of an environment”, a phenomenon arising in many other branches of physics and chemistry.
These successes allow us to exploit our
results in areas where experimental data are particularly sensitive to
entrance-channel effects, such as the spin distributions of very heavy
nuclei, whose properties may yield valuable information on the
single-particle states responsible for the existence of an “island of
stability” for superheavy elements. But there remain important unsolved
problems that we are actively studying, such as for instance, the rapid
decrease of the fusion probability at energies far below the Coulomb
barrier, the possible effect of the multiple weakly-coupled channels, or
the preference for heavy systems for “quasi-fission” instead of an
equilibrated compound nucleus.