Table of contents

Transits of single atoms through higher-order Hermite–Gaussian transverse modes of a high-finesse optical cavity are observed. Compared to the fundamental Gaussian mode, the use of higher-order modes increases the information on the atomic position. The experiment is a first experimental step towards the realisation of an atomic kaleidoscope.

In this paper we overview recent results on the formation of translationally cold molecules. While there are some methods relying on direct cooling of molecules, we shall concentrate on the photoassociation technique that starts from laser-cooled atoms. The detection methods for the ultra-cold molecules will be presented together with a report on the trapping techniques. The treatment is mainly focused on the results obtained by our group on rubidium dimers.

In this paper I review a number of recent results in the field of exotic atoms. Recent experiments or ongoing experiments with muonic, pionic and antiprotonic hydrogen, as well as recent measurement of the pion mass are described. These experiments provide information about nucleon-pion or nucleon-antinucleon interaction as well as information on the proton structure (charge or magnetic moment distribution).

With a single s-electron in the outer shell, alkali atoms are the building blocks of the simplest metal clusters. While aggregates of several dozen atoms have been found to resemble finite size samples of electrical conductors, trimers or tetramers offer the opportunity for detailed studies of interactions that are typical for highly symmetric metal lattices but can hardly be disentangled in the large clusters. Our work examines vibronic couplings in two- and three-state electronic systems of sodium trimers. Spectroscopic information was collected through cw laser excitation followed by laser ionization and mass selective detection in a molecular beam experiment. A significant experimental advantage was gained by utilizing optical–optical double resonance methods with probing through the A state of the molecule. Narrowband Resonant Two-Photon Ionization (RTPI) detection through this long-lived state is extremely efficient and can accurately probe the population of individual rotational ground state levels. Scanning another narrowband laser through the short-lived B-X and B'-X transitions leads to the depletion of these probed levels and allowed for the first high resolution spectroscopy of the coupled B/B' system including rotational assignments. Theoretical analysis of the spectra within the framework of a Jahn–Teller formalism suggests that the B'-X system corresponds to transitions into the middle part of a three-surface potential that is the consequence of both Pseudo Jahn–Teller and Jahn–Teller interactions while the B state represents the lower part.

A combination of scanning tunneling luminescence (STL) and current-voltage scanning tunneling spectroscopy (STS) has been employed to image the charge density of the confined electronic states and to spatially resolve the extent of the orbitals of InGaAs quantum dots produced by epitaxial Stranski–Krastanow growth. The selective investigation of isolated dots and coupled dots (dot-to-dot distance of the order of few nm) clearly reveals the formation of atomic-like and molecular-like states. The tunneling current images have been compared with calculated tunneling current profiles and the observed tunneling current contrast has been associated with the localized quantum dot states.

The development of space-based observatories has heralded the need for atomic data which in the past had seemed unimportant, and for much greater accuracy in the data which did already exist. This review examines the types of calculations of atomic data, particularly oscillator strengths, which are important for the analysis of observational data. Some examples are presented which show how a careful analysis of the atomic data can be used to assess the accuracy of that data. Particular emphasis is placed on transitions in Fe II.

This article reviews some recent experiments with ultracold quantum-degenerate atomic gases at MIT that were presented at the 35th EGAS Conference, including studies of a degenerate strongly interacting Fermi gas, the collective scattering of light from a Bose–Einstein condensate, and the manipulation of condensates in microstructured magnetic potentials.

A general introduction, on an intuitive level, is presented to discrete symmetries of physical laws: P, C, T and CPT. The accurate measurement of the weak nuclear charge in atomic cesium serves as a precision test of the Standard Model. The discovery of the nuclear anapole moment, a new P odd electromagnetic multipole, in the cesium experiment gives a first-rate information on parity-nonconserving nuclear forces. New prospects in the field are discussed. Upper limits on the dipole moments of elementary particles and atoms are presented, and their physical implications discussed. The atomic experiments are demonstrated to be as informative in this respect as the neutron ones. Tremendous progress in the field can be expected from experiments at ion storage rings and linear electrostatic traps.

Weak transitions in single cold trapped ions are highly reproducible as optical frequency standards on account of the high quality factors and stabilities achievable. In recent years, there has been a quickening pace in the development of these optical frequency standards, particularly due to the emergence of femtosecond laser combs for relating the optical frequency directly to the Cs standard. This paper reports progress on optical frequency standards based on the quadrupole transition in a single cold ion of ⁸⁸Sr⁺ and the octupole transition in a single cold ion of ¹⁷¹Yb⁺.

A method has been developed and applied for the determination of the electronic g-factor of single hydrogen-like ions stored in a Penning trap. The method is based on mode coupling of the ion trapping motions and is conceptionally advantageous as compared to previously used methods. It has been applied to hydrogen-like oxygen ¹⁶O⁷⁺ and yields a value for the g_J-factor which is in agreement with previously determined values. Experimental requirements and possibilities of the new method are discussed.

This review highlights current (and future) hot topics in astrophysics where atomic or molecular input data are (or will be) essential, with special emphasis on topics relating to nucleosynthesis and cosmochemistry.

We first discuss issues (like the abundances of oxygen and iron in the Sun, and that of lithium in post-AGB stars) where the use of poor-quality atomic or molecular data have led to spurious astrophysical puzzles which sparked fancy astrophysical models or theories. We then address issues where the advent of new instruments (like the ultraviolet high-resolution spectrographs—GHRS onboard HST, Keck-HRS or VLT-UVES—or future infrared satellites) calls for new and accurate atomic or molecular data.

We report velocity map imaging experiments on the behaviour of electrons that are strongly driven by electric fields that vary over a wide range of timescales (from DC electric fields to laser fields at optical frequencies). We show how in slow photoelectron imaging using DC electric fields direct and indirect photoionization events can be distinguished and that a quantummechanical interference between several competing pathways that take the electron from the atom to the detector can be observed. We show that with a half-cycle THz pulse Rydberg states can be ionized, that the electrons can be accelerated (though the final kinetic energy of the electrons is small) and that the initial momentum distribution of the prepared Rydberg state can be observed. Finally, we show that—at optical frequencies—high harmonic generation can lead to the formation of trains of attosecond laser pulses, with a striking dependence of the appearance time of the attosecond pulses on the harmonic generation gas.

We report on the realization of a single photon source relying on the pulsed excitation of a single organic molecule at room temperature, and the study of its intensity fluctuations over 4 orders of magnitude of the observation time scale. On a time scale of a few excitation periods, sub-poissonian statistics is clearly observed and the probability of multiphoton events is 10 times smaller than for equivalent Poissonian pulses. An excess of noise appears on longer timescale, due to the blinking produced by the molecular triplet state.

Organizing the 35th Conference of the European Group of Atomic Spectroscopy was a very exciting experience. We felt from the participants that this event, involving around 200 scientists with a participation of 10–15% young PhD students, was successful. The scientific program was established on the basis of 15 plenary sessions given by the invited speakers and 40 talks organized in 14 sessions. 130 communications were presented in two separate poster sessions covering Atomic, Molecular and Optical Sciences in a wide sense—more specifically: the structure of atoms and molecules, theory, atomic and molecular spectra and interactions with photons, instruments and techniques, collision processes, quantum optics, cold atoms and molecules, laser spectroscopy and applications, highly charged ions and x-ray spectroscopy, plasma physics, physics of clusters, etc.

All the abstracts have been collected in the Europhysics Conference Abstracts booklet. The present proceedings collect the invited speakers' contributions. Convincing them to write their contribution is one thing but getting their contribution in final form is another. We are very grateful to the invited speakers who kindly accepted to contribute to the present Physica Scripta Topical Issue.

We would like to warmly thank our colleagues and very good friends, Michel Carleer, Michel Herman, Daniel Hurtmans, Jacky Liévin, Jean Vander Auwera, from the `Service de Chimie quantique et Photophysique' of Université Libre de Bruxelles (ULB), for their role in the `local organizing committee', but also Emile Biémont (UMH/ULg), Henri-Pierre Garnir (ULg) and Pascal Quinet (UMH/ULg) who gave us a tremendous help in setting the final program and in editing the EPS abstracts booklet. Thanks also to Paul Geerlings (VUB), Renaat Gijbels (UIA) and Bernard Piraux (UCL) who also contributed to the success of the 35th EGAS conference by attending our `National committee' meetings from which helpful guidelines emerged. Michelle Leclercq, Athéna Rizopoulos, Sophie Fally, Brigitte Foucart, Pierre-François Coheur and Xavier Dimartinelli have helped us a lot in solving hundreds of practical problems, before and during the event. Thanks also to Raymond Pétrisse, Jean-Pierre Walgraeve and the PhD students for their kind assistance, in particular to Emilie Cauët and Nathalie Rinskopf at the registration desk.

The role of the international EGAS board members was crucial too, not only in guiding the choice of the invited speakers, but also in following the conference organization on a regular basis.

The 35th EGAS conference got the label of `Europhysics Conference' from the European Physical Society that supported the participation of nine young physicists through the Young Physicists Fund and the East West Fund. We had the honour to have Prof. Martin C E Huber, chairman of the EPS, with us and it was a pleasure to listen to his kind and encouraging words at the official conference opening time.

The 35th EGAS conference budget was balanced, thanks to the support of the Fonds National de la Recherche Scientifique (FNRS), the Nationaal Fonds voor Wetenschappelijk Onderzoek (FWO), the Ministère de la Communauté française de Belgique, the Ministère de la Région Bruxelles-Capitale, Brussels City, the Académie royale des Sciences, des Lettres et des Beaux-Arts de Belgique and the Société Royale de Chimie.

There is a french proverb Jamais deux sans trois. Hopefully, we have not yet reached the point of agreeing to organize a second EGAS meeting in Brussels, although we really enjoyed in organizing the 35th edition.