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4.3 Nuclear Structure and Dynamics
4.3.1 Introduction
In Nature strongly interacting matter is found in the form
of atomic nuclei, built from quarks and gluons that are
confined into protons and neutrons (nucleons). The highenergy
bare interaction between constituent particles
is described by QCD, the fundamental theory of strong
interactions. However, at energies characteristic for
nuclear binding the strength and complexity of QCD
complicates immensely the understanding of nuclear
phenomena in terms of these fundamental degrees of
freedom.
Nuclei typically consist of many nucleons, up to 300,
resulting in a rich variety of quantum phenomena. It is
the task of nuclear structure physics to unravel this
myriad of quantum structure and to find the ordering
principles governing nuclei. This endeavour is very broad
in scope, mirroring fields such as solid state physics,
atomic structure physics and atomic collision physics
in which the Coulomb interaction is accompanied by
the much more complicated strong interaction. A correspondingly
versatile set of tools, both theoretical and
experimental, are required to advance our understanding
of this diverse field.
Present and future research in nuclear structure physics
aims at providing answers to key questions:
• How can we describe the rich variety of low-energy
structure and reactions of nuclei in terms of the fundamental
interactions between individual particles
• How can we predict the evolution of nuclear collective
and single-particle properties as functions of mass,
isospin, angular momentum and temperature
• How do regular and simple patterns emerge in the
structure of complex nuclei
• What are the key variables governing the dynamics
between colliding composite systems of nucleons
A real challenge is the understanding of nuclei very
far from stability, these nuclei being the precursors in
the formation process of the stable nuclei on earth. The
advent of the first generation of Radioactive Ion Beam
(RIB) facilities has already opened up new possibilities
to probe these unstable nuclei and access new regions
of the nuclear chart. In the last decade, many of the
important experimental results in nuclear structure
and dynamics have been obtained at these facilities.
However, only circa 3000 of the possibly more than 8000
different nuclei that should exist have been probed or
identified, the large terra incognita being the very neutron-rich
nuclei and super-heavy elements.
With the start-up of new and the upgrade of existing
RIB facilities and innovative experimental techniques,
nuclear research stands on the verge of a new era,
where a much wider range of proton- and neutron-rich
nuclei will become accessible. The availability of a large
variety of unstable projectiles accelerated to different
energy regimes, opens up new physics opportunities,
at the interplay between nuclear structure and reaction
dynamics.
Intense stable-ion beams will retain their vital role in
studies of nuclei at the proton drip-line and even beyond
and to study phenomena driven by spin and temperature.
They are also particularly needed in studies and
production of super-heavy elements.
Recent experimental and theoretical developments,
research challenges together with significant investments
in nuclear structure studies have led to growing connections
with other fields of science and applications.
Particularly in nuclear astrophysics, many questions are
intimately connected to nuclear structure and reaction
problems.
The understanding of excitation properties of nuclei
requires the modeling of the dynamics involved in the
nuclear excitation process. Major advances are being
made in nuclear theory in this regard. However, there is
presently a real need to build a consistent microscopic
theoretical framework unifying the description of bulk
properties, nuclear excitations and reactions.
Light nuclei play a particular role in low-energy nuclear
physics. They exhibit several peculiar features that have
been put into evidence experimentally. They can also be
described by a large variety of theoretical approaches,
starting from the most fundamental ones, the ab initio
methods up to those that can be applied all over the
nuclear chart. Finally, they mix aspects of nuclear structure
and nuclear reactions, with weakly bound states
and nearly bound resonances that are particularly hard
to describe.
For heavy nuclei, methods based on effective forces
(used to build the so called “nuclear energy-density functionals”)
have made huge progress, thanks to theoretical
and computational advances. These methods also need
stringent experimental tests in order to improve the predictive
power of the theory. They are complemented by
symmetry dictated approaches that both identify and
predict the development of simple patterns in complex
nuclei. The identification of simple patterns is possible
only with systematic investigations contributing to the
unraveling of fascinating aspects of the nuclear manybody
system.
The availability of extended asymmetric nucleonic
matter in different forms and conditions will be the basic
ground for exciting research and technical developments
driving nuclear physics in the coming years,
104 | Perspectives of Nuclear Physics in Europe – NuPECC Long Range Plan 2010