Experimental studies of heavy and highly charged ions have made remarkable progress in recent years. Today it is possible
to produce virtually any ion up to hydrogen-like uranium; to study collisions of those ions with atoms, electrons, and solid
surfaces; to excite such an ion and accurately measure the radiation emitted. This progress is largely due to the development of new experimental methods, for instance, the high-energy ion accelerators, laser-produced plasmas, advanced ion
sources and ion traps (such as EBIS, EBIT, ECR, etc.), high temperature magnetically confined plasmas and heavy-ion
storage rings.
The motivations for studies of collisions with highly charged ions and for the understanding of the structure of heavy
atomic systems are multi-faceted. Besides of the basic scientific aspects which are mainly the subject of this symposium,
much incentive is experienced by applications, e.g., the interpretation of spectra from space (solar corona, solar flares and
hot stars), the modelling of stellar atmospheres, the diagnostics of fusion plasma impurities, and the development of
X-ray lasers.
Since quite some time highly charged ions play a key role for high-precision metrology of atomic structure. These studies
have been benchmarks for tests of advanced theories, including many-body theories of interelectronic correlations, relativistic and quantum-electrodynamic (QED) effects, effects due to the finite size of the nucleus and to parity non-conservation (PNC). The interest in QED effects in heavy ions has increased drastically in the last few years. The
remarkable experiment on Li-like uranium, recently reported from Berkeley, has stimulated several groups to perform very
accurate Lamb-shift calculations on such systems, and reports from three groups were given about such work. The agreement between the calculations as well as with experiment was generally very good, which implies that the problem of
evaluating the first-order Lamb shift for any element is now essentially solved. The experimental accuracy is already so high
that also higher-order QED effects become observable, and several groups are now active in trying to evaluate such effects
from first principles.
Another related field where substantial progress has recently been made involves precision measurements of X-ray transitions. This has created an interest in the study of deep inner holes in heavy atoms, where large relativistic and QED effects
appear. These effects are as large as in corresponding highly charged ions, but the interpretation requires that the many-body effects from the surrounding electrons are accurately extracted. This is a big challenge at present.
Atomic collision physics with highly charged ions has been dominated in recent years by the search for a possibility to
describe electron-electron interaction within the dynamics of collisions. The experiments on multielectron transfer reactions
with highly charged ions posed in this respect quite a challenge to the theory. The models developed to meet this were often
based on methods and terminologies developed for describing the inter-electronic interactions in atomic structure. This
caused many controversial discussions, also during this symposium. A new and fast rising field is the interaction of highly
charged ions with solid surfaces. This may become an important link between atomic physics and condensed-matter
physics, stimulated by the opportunity to study effects in coupled many-body systems present in the case when a large
amount of electrons is transferred from the solid to each single ion. Furtheron, collision experiments with cooled ion beams
in ion storage rings open new dimensions also for atomic spectroscopy. It appears possible that transition and binding
energies can be measured in recombination of very heavy ions with a better quality than by conventional Auger electron or
X-ray spectroscopy.
Obviously, it is not possible to cover all the fields mentioned here in a single symposium, and we had to concentrate on
some aspects, mainly based on our own personal interests. Initially, two symposia were planned, one about heavy-ion
spectroscopy with connections to collision phenomena and to atomic structure, and another with focus on relativistic and
QED effects in heavy atoms and ions. Then it was realized that there was a considerable overlap between the two fields,
both regarding the scientific contents and the people that would be involved. Furthermore, we felt that it might be stimulating also to bring people together, who are connected to different aspects of heavy-ion research and who do not have any
natural contact in their research. Therefore, the idea was born to.merge the two symposia into one with the hybrid title
Heavy-Ion Spectroscopy and QED Effects in Atomic Systems. There is always a risk with such an arrangement, namely that
the symposium will split into two parts with only little communication between the two. We actively tried to avoid such a
development by various arrangements, and we believe that we were reasonably successful in that respect.
The symposium was organized in the form of four review sessions and four more specialized mini-symposia. The review
talks covered topics like many-body theory, QED and PNC effects in atoms, electron correlation effects in atomic collisions, electron capture ion-atom collisions and ions in space. Experimental reviews were given about heavy-ion experiments
at Berkeley and Darmstadt. The four-mini symposia were devoted to (i) atomic structure and (ii) QED effects, (iii) multi-
electron transfer reactions, and (iv) PNC effects. In these cases efforts were made to mix people with the main background
in atomic collision physics and atomic structure. The mini-symposium devoted to structure ended with a panel discussion
about the future of atomic structure theory.
Of course, this book can only attempt to summarize the high level of knowledge existing in atomic spectroscopy and
heavy ion collision phenomena. This became evident to us in the excellent lectures given during the symposium. Here we
like to thank our distinguished authors for their enthusiastic cooperation in the task of transmitting the message of the
Nobel Symposium 85 to the science community.