Effects of diabaticity on fusion of heavy nuclei in the dinuclear model ...

Chapter 1
The elements existing in nature are ordered according to their atomic (chemical) properties
in the periodic system which was developed by Mendeleev and Lothar Meyer. The heaviest
element <strong>of</strong> natural origin is uranium. The transuranium elements range from neptunium (Z=93)
via californium (Z=98) and fermium (Z=100) up to lawrencium (Z=103). For the heaviest
systems the Coulomb repulsion between the increasing number <strong>of</strong> protons grows faster than
the attractive nuclear forces. The heavy nuclear systems are macroscopically instable, their
existence is determined by shell effects. Theoretical nuclear physicists ([1], [2]) predicted that
so-called closed proton and neutron shells should counteract the repelling Coulomb forces.
Atomic nuclei with these special ”magic” proton and neutron numbers and their neighbours
could again be rather stable. These magic proton (Z) and neutron (N) numbers were thought to
be Z=114, N=184 or 196. Studies <strong>of</strong> the shell structure <strong>of</strong> superheavy elements in the framework
<strong>of</strong> the meson field theory and the Skyrme-Hartree-Fock approach have recently shown that the
magic shells in the superheavy region are very dependent on isotopes [3]. According to these
investigations, the region <strong>of</strong> maximum stability may be near Z=120 or Z=126.
The synthesis <strong>of</strong> new nuclear species relies on the constituents <strong>of</strong> the premordial nuclei
available in nature. The available nuclei are limited in their neutron-to-proton ratio by the
beta decay and in size by charged-particle decay and fission due to the increasing electrostatic
repulsion between the constituent protons. The first method used to produce transuranium
elements, which is still used to synthesize larger quantities <strong>of</strong> specific isotopes <strong>of</strong> elements from
neptunium to einsteinium, was the consecutive capture <strong>of</strong> neutrons by uranium isotopes and
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