Strong erbium luminescence in the near-infrared telecommunication window

A new type of near-infrared emitting rare-earth complex has been synthesised, consisting of three bis(perfluoroalkylsulfonyl)imide ligands and one 1,10-phenanthroline molecule. The chelate rings formed by the rare-earth ion and the bidentate ligands do not contain any carbon atoms and can hence be considered as 'inorganic' chelate rings. The absence of C-H stretching vibration modes in the first coordination sphere of the rare-earth ion and the presence of a light-harvesting moiety (1,10-phenanthroline) bound to the rare-earth ion result in a complex that can be efficiently excited and exhibits intense near-infrared luminescence. (C) 2004 Elsevier B.V. All rights reserved.

Convergence of partial-wave expansions for energies, scattering amplitudes and positron annihilation rates

We use many-body theory to find the asymptotic behaviour of second-order correlation corrections to the energies and positron annihilation rates in many- electron systems with respect to the angular momenta l of the single-particle orbitals included. The energy corrections decrease as 1/(l+1/2)4, in agreement with the result of Schwartz, whereas the positron annihilation rate has a slower 1/(l+1/2)2 convergence rate. We illustrate these results by numerical calculations of the energies of Ne and Kr and by examining results from extensive con?guration-interaction calculations of PsH binding and annihilation.

Ireland's Innovation Performance: 1991-2005

In this paper we use data from the five waves of the Irish Innovation Panel (IIP) to profile the innovation performance of manufacturing plants in Ireland and Northern Ireland over the period 1991 to 2005. Despite considerable public sector investment on both sides of the border levels of innovation activity have remained broadly similar throughout this period although somewhat different trends are evident in Ireland and Northern Ireland. In terms of product innovation for example, the proportion of manufacturing plants making product changes has increased 5 per cent in Ireland and just over 7 per cent in Northern Ireland. In terms of process innovation a decline of almost 7 per cent in Ireland has been accompanied by a 7 per cent increase in Northern Ireland. These trends provide some evidence of convergence in innovation performance over the 1991 to 2005 period. This is evident in the narrowing gap between the proportion of product innovators in Ireland and Northern Ireland, convergence in the proportion of plants undertaking process innovation and in terms of the increasingly similar proportions of sales derived from innovative products. Looking in more detail at the determinants of manufacturing innovation emphasises the importance of R&D and backwards supply chain linkages as sources of new knowledge for innovation. Other external linkages prove less important suggesting the value of policy initiatives designed to promote knowledge sharing. We also find a significant negative innovation effect from legislative restrictions on plants’ product innovation. Public support for both product and process innovation are having positive effects on innovation outputs at the level of the individual plant. Future research interest centres on the contrast between this strong positive result at firm level and the more modest increases in innovation among the population of firms in Ireland and Northern Ireland.

Environmental context explains Levy and Brownian movement patterns of marine predators

An optimal search theory, the so-called Levy-flight foraging hypothesis(1), predicts that predators should adopt search strategies known as Levy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey(2-4). Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Levy behaviour has recently been questioned(5,6). Consequently, whether foragers exhibit Levy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory's central predictions. Here we use maximum-likelihood methods to test for Levy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Levy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Levy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Levy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Levy-flight foraging hypothesis(1,7), supporting the contention(8,9) that organism search strategies naturally evolved in such a way that they exploit optimal Levy patterns.

Simulation of a collisionless planar electrostatic shock in a proton-electron plasma with a strong initial thermal pressure change

The localized deposition of the energy of a laser pulse, as it ablates a solid target, introduces high thermal pressure gradients in the plasma. The thermal expansion of this laser-heated plasma into the ambient medium (ionized residual gas) triggers the formation of non-linear structures in the collisionless plasma. Here an electron-proton plasma is modelled with a particle-in-cell simulation to reproduce aspects of this plasma expansion. A jump is introduced in the thermal pressure of the plasma, across which the otherwise spatially uniform temperature and density change by a factor of 100. The electrons from the hot plasma expand into the cold one and the charge imbalance drags a beam of cold electrons into the hot plasma. This double layer reduces the electron temperature gradient. The presence of the low-pressure plasma modifies the proton dynamics compared with the plasma expansion into a vacuum. The jump in the thermal pressure develops into a primary shock. The fast protons, which move from the hot into the cold plasma in the form of a beam, give rise to the formation of phase space holes in the electron and proton distributions. The proton phase space holes develop into a secondary shock that thermalizes the beam.

Direct versus delayed pathways in strong-field non-sequential double ionization

We report full-dimensionality quantum and classical calculations of double ionization (DI) of laser-driven helium at 390 nm. Good agreement is observed. We identify the relative importance of the two main non-sequential DI pathways, the direct|with an almost simultaneous ejection of both electrons|and the delayed. We find that the delayed pathway prevails at small intensities independently of total electron energy but at high intensities the direct pathway predominates up to a certain upper-limit in total energy which increases with intensity. An explanation for this increase with intensity is provided.

Strong-field approximation for Coulomb explosion of H-2(+) and D-2(+) by short intense laser pulses

We present a simple quantum mechanical model to describe Coulomb explosion of H-2(+) and D-2(+) by short, intense infrared laser pulses. The model is based on the length gauge version of the molecular strong-field approximation and is valid when the process of dissociation prior to ionization is negligible. The results are compared with recent experimental data for the proton kinetic energy spectrum [Th. Ergler , Phys. Rev. Lett. 95, 093001 (2005); D. S. Murphy , J. Phys. B 40, S359 (2007)]. Using a Franck-Condon distribution over initial vibrational states, the theory reproduces the overall shape of the spectrum with only a small overestimation of slow protons. The agreement between theory and experiment can be made perfect by using a non-Frank-Condon initial distribution characteristic for H-2(+) (D-2(+)) targets produced by strong-field ionization of H-2 (D-2). For comparison, we also present results obtained by two different tunneling models for this process.

Convergence of bimodules over maximal abelian selfadjoint algebras

We prove a continuity result for the map sending a masa-bimodule to its support. We characterise the convergence of a net of weakly closed convex hulls of bilattices in terms of the convergence of the corresponding supports, and establish a lower-semicontinuity result for the map sending a support to the corresponding masa-bimodule.

Redistribution of vibrational population in a molecular ion with nonresonant strong-field laser pulses

We present an experimental demonstration of nonresonant manipulation of vibrational states in a molecule by an intense ultrashort laser pulse. A vibrational wave packet is generated in D-2(+) through tunnel ionization of D-2 by a few-cycle pump pulse. A similar control pulse is applied as the wave packet begins to dephase so that the dynamic Stark effect distorts the electronic environment of the nuclei, transferring vibrational population. The time evolution of the modified wave packet is probed via the D-2(+) photodissociation yield that results from the application of an intense probe pulse. Comparing the measured yield with a quasiclassical trajectory model allows us to determine the redistribution of vibrational population caused by the control pulse. ©