News

EPJ D - Electrons go unperturbed in a matter-wave interferometer

Details: Published on 19 April 2010

Photodetachment microscopy provides the best electron affinity measurements on atoms and molecules. Photodetachment of a negative ion produces a nearly free electron, hardly perturbed by the residual atomic core. Applying an external electric field does not only concentrate the photoelectron current in a round spot, but also gives rise to an electron interference pattern, due to the existence of a pair of possible trajectories bound to every point of the spot. This very fundamental matter-wave interferometer produces extraordinarily robust interferograms. Although magnetic fields, even in the sub-microT range, causes fluxes between the interfering trajectories that can be huge compared to the quantum unit of magnetic flux, a magnetic perturbation of the system appears to only produce a global deviation of the spot, without any modification of the interference pattern. The main result of the recent paper published in EPJ D by Chaibi et al. is that even in higher magnetic fields (typically 100 microT) the electron interference phase, or number of interference rings, remain unperturbed. This comfirms photodetachment as a highly accurate method for electron spectrometry and electron affinity measurements.

To read the full paper ‘Effect of a magnetic field in photodetachment microscopy’ by W. Chaibi et al., Eur. Phys. J. D (2010) click here

Quantum memories set to go a long way

Details: Published on 14 April 2010

Quantum memories are essential elements for many potential applications of quantum technology. Research on the development of such memories is currently very lively, with a particular emphasis on memories that can interface with photons, which are the best carriers of quantum information over long distances. A Colloquium paper in the May issue on EPJ D reviews a number of different approaches to this challenge, with a focus on the approaches that were represented in the large European Union Integrated Project "Qubit Applications". This Colloquium covers solid-state atomic ensembles, nitrogen-vacancy centres, quantum dots, single atoms and atomic gases. Since the considered approaches are very diverse, an important part of the work was to establish criteria that allow a meaningful comparison. The authors discuss both the current experimental state of the art and the potential long-term performance of the various systems.

To read the full paper ‘Quantum Memories’ by C. Simon et al. click here

Liquid crystals straighten up

Details: Published on 06 April 2010

Grazing incidence X-ray diffraction, performed by Grelet and colleagues, reveals that thin films of discotic liquid crystals typically prefer to lie flat in columns oriented along the surface of their substrate. These materials are potentially useful for organic solar cells, but to achieve good performance from such devices, the column axis should rather be oriented vertical to the conducting substrate. However, the authors of this EPJ E paper have discovered a specific thermal process that makes it possible to change the column alignment from planar to vertical and achieve the best conditions for charge transport in photovoltaic devices.

To read the full paper ‘Morphology of open films of discotic hexagonal columnar liquid crystals as probed by grazing incidence X-ray diffraction’ click here

Giving light a good squeeze

Details: Published on 01 March 2010

Multi-mode optical systems can improve precision measurements in the domain of quantum imaging and metrology. In this context, mastering quantum fluctuations and correlations in complex optical systems is crucial. In a recent EPJ D paper, the authors G. Patera, N. Treps, C. Fabre and G.J. de Valcárcel present the quantum model for an optical parametric oscillator synchronously pumped by a mode locked laser. To cope with the complexity of a system that usually involves about 100 000 modes, the authors introduce new physical objects that they call supermodes, which are proper combinations of standard modes. Their dynamics is studied from both a classical and a quantum point of view with respect to the experimental condition considered. This study shows that a synchronously pumped optical parametric oscillator is a suitable and malleable source of highly multimode non-classical light in the temporal domain.

To read the full paper "Quantum theory of synchronously pumped type I optical parametric oscillators: characterization of the squeezed supermodes" Eur. Phys. J. D 56, 123-140 (2010) click here

Athene Donald wins Glamour award

Details: Published on 11 January 2010

Athene Donald, the former editor in chief of EPJ E and current member of its advisory editorial board, has won the Science & Technology Award issued by women’s magazine Glamour.

Daan Frenkel becomes Editor in Chief of EPJ E

Details: Published on 05 January 2010

EPJ E welcomes Daan Frenkel as new Editor in Chief, next to Richard Jones and Frank Jülicher. Daan Frenkel is a computational physicist who's research focuses on numerical exploration of routes to design novel, self-assembling structures and materials. Currently he is a professor at the universities of Cambridge, Amsterdam, Utrecht and Beijing. He is a foreign member of the British Royal Society and he has many received prestigious awards such as the Aneesur Rahman Prize of the APS, the Spinoza Prize of the Dutch Research Council and the Berni J. Alder CECAM Prize.

Nigel Mason becomes Editor in Chief of EPJ D

Details: Published on 04 January 2010

We are pleased to announce that from January 2010 Nigel Mason, Professor of Physics at the Open University, UK, will be leading EPJ D, together with Kurt Becker and Claude Fabre. Nigel Mason brings to the journal an interdisciplinary approach to the AMOP field. His research covers a wide range of AMOP topics spanning physics and chemistry including astrochemistry, atmospheric science, surface science and spectroscopy. Since the 1990s he has studied the spectroscopy of over 100 molecules (mainly of atmospheric interest) using synchrotron radiation quantifying their photolysis rates and global warming potential. Research on the formation of molecules by irradiation of low temperature (20K) ices has led to a new research programme exploring processes on planetary systems and in the interstellar medium. Most recently his research has extended to study radiation damage processes within biomolecular systems including DNA.

First proton–proton collisions at the LHC as observed with the ALICE detector

Details: Published on 14 December 2009

Figure shows the first pp collision candidate by the event display in the ALICE counting room (3D view).

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam, allowing all LHC experiments to report first collision candidates.

284 such candidates were recorded by the ALICE experiment, allowing the events to be immediately reconstructed and analyzed. The results obtained by measuring the spatial distribution (specifically, the pseudorapidity density) of charged primary particles in the central region, were found to be consistent with previous measurements in proton-antiproton interactions at the same centre-of-mass energy at the CERN SppS collider (UA5 Collaboration, G.J. Alner et al., Z Phys. C 33 (1986), DOI 10.1007/BF01410446).

To read this paper click here

J Schukraft, the ALICE spokesman, said: This important benchmark test illustrates also the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.
The paper is published open access on SpringerLink.com and distributed under the Creative Commons Attribution Noncommercial License.

To read the full paper click here

Atom interferometry in free flight

Details: Published on 10 December 2009

Philippe Bouyer and co-workers in France performed a range of impressive experiments with an atom interferometer in free flight, onboard an Airbus aircraft making "micro-gravity jumps". These experiments successfully demonstrate that when atoms are sufficiently cooled and controlled, their wave properties can be used to perform interferometry in a way analogous to standard interferometry with light. This moves the field closer to the implementation of a range of sensors for e.g. gravity, rotation and inertia with unprecedented accuracy. Such devices will be potentially very useful in satellites and in space missions.

To read the full paper by Philippe Bouyer et al. on "Light-pulse atom interferometry in microgravity" click here

Tidal waves on liquid Helium-4

Details: Published on 17 November 2009

An analytical theory explains why a probe molecule such as Na₂ on the surface of a liquid ⁴He droplet creates soft vibrations which can be used to study the dynamics of the droplet surface with optical spectroscopy.

To read the full paper by Hizhnyakov, Tehver and Benedek click here