Deuterium-deuterium nuclear cross-sections in insulator and metallic environments

The three-dimensional Thomas-Fermi (TF) model is used to simulate the variation of the d+d to t + p cross-section at low impact energies, when the target deuterium nucleus is embedded in metallic or insulator environments. Comparison of the computational results to recent experiments demonstrates that even though the TF model can explain some increase in the low energy cross section for metallic host, a full explanation of the experimental results is still lacking. Possible reasons for the disagreement are discussed.Comment: 6 pages;6 figures. Accepted for publication in Eur. Phys. Jour.

Photoassociation adiabatic passage of ultracold Rb atoms to form ultracold Rb_2 molecules

We theoretically explore photoassociation by Adiabatic Passage of two colliding cold ^{85}Rb atoms in an atomic trap to form an ultracold Rb_2 molecule. We consider the incoherent thermal nature of the scattering process in a trap and show that coherent manipulations of the atomic ensemble, such as adiabatic passage, are feasible if performed within the coherence time window dictated by the temperature, which is relatively long for cold atoms. We show that a sequence of ~2*10^7 pulses of moderate intensities, each lasting ~750 ns, can photoassociate a large fraction of the atomic ensemble at temperature of 100 microkelvin and density of 10^{11} atoms/cm^3. Use of multiple pulse sequences makes it possible to populate the ground vibrational state. Employing spontaneous decay from a selected excited state, one can accumulate the molecules in a narrow distribution of vibrational states in the ground electronic potential. Alternatively, by removing the created molecules from the beam path between pulse sets, one can create a low-density ensemble of molecules in their ground ro-vibrational state.Comment: RevTex, 23 pages, 9 figure

Coherent control with shaped femtosecond laser pulses applied to ultracold molecules

We report on coherent control of excitation processes of translationally ultracold rubidium dimers in a magneto-optical trap by using shaped femtosecond laser pulses. Evolution strategies are applied in a feedback loop in order to optimize the photoexcitation of the Rb2 molecules, which subsequently undergo ionization or fragmentation. A superior performance of the resulting pulses compared to unshaped pulses of the same pulse energy is obtained by distributing the energy among specific spectral components. The demonstration of coherent control to ultracold ensembles opens a path to actively influence fundamental photo-induced processes in molecular quantum gases

Awareness: An Enabling Feature for mediated Interaction in Communities of Practise

The École Polytechnique Fédérale de Lausanne (EPFL) is currently using a Web-based experimentation environment to support laboratory activities in engineering education. The key service for the acceptance of the learning modalities and the appropriation of the environment by the students is a shared electronic notebook called the eJournal. This service is not only used by students to perform the required laboratory work; it is also used to sustain collaboration between students. Additionally it provides support for exchanges with other services integrated in the learning environment. By tracking the creation, the exchanges and the tagging of the digital assets stored in the eJournal database, awareness can be provided. This position paper presents how the eJournal and the associated awareness features are currently enhanced to effectively support interaction in laboratory-oriented communities of practice for members using either desktop or mobile client devices

Real-Time Interaction over the Internet: Model for QOS Adaptation

Real-time Interaction over the Internet (RTI2) is an Internet service that is required typically by remote experimentation applications. From a quality of service (QoS) point of view, RTI2 has constraints that differ from usual real-time multimedia services such as video streaming or video conferencing. The RTI2 QoS can be expressed by three values that represent the level of interaction, the dynamics rendering and the semantic content. The RTI2 metrics, derived from these values, are essential to successfully implement an end-to-end (E2E) control scheme that adapts the transmission parameters to the equivalent E2E infrastructure that encompass not only to the network state, but also to the server and client applications processing capabilities. A model of the end-to-end system is exploited to ensure a minimal transmission time for a given E2E system