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The influence of the alignment and density of dye molecules on the spectroscopic properties of aggregates can be studied particularly well in J‐aggregates of 1,7‐bis(dimethylamino)heptamethine (BDH⊕). Four different arrangements of BDH⊕ molecules can be obtained without changing the molecular structure simply by using different counterions. The relationship between structure and linear spectroscopic properties—including the color of crystals containing BDH⊕–is discussed.

Electroabsorption measurements are performed with solution cast films of poly-(dodecylthiophene) and poly-(phenylphenylenevinylene). The spectra are described within the framework of second-order Stark effect acting on an excitonic transition including field-induced transfer of oscillator strength to higher lying states. The spatial extent of the exciton is two to three repeat units of the polymer backbone consistent with the notion that the absorbers are ordered subunits of the conjugated chain.Es werden Elektroabsorptionsmessungen an Poly-(dodecy1thiophen)-und Poly-(phenylphenylenviny-1en)-Filmen durchgefuhrt, die aus der Losung abgeschieden worden waren. Zur Interpretation wird ein Stark-Effekt xweiter Ordnung, der auf einen exzitonischen obergang wirkt, herangezogen unter Berucksichtigung der Umverteilung von Oszillatorstarke zu hoheren Zustanden. Die Ausdehnung des Exzitons wird zu zwei bis drei Wiederholungseinheiten der Polymerkette abgeschatzt.

The GridPP Collaboration is building a UK computing Grid for particle physics, as part of the international effort towards computing for the Large Hadron Collider. The project, funded by the UK Particle Physics and Astronomy Research Council (PPARC), began in September 2001 and completed its first phase 3 years later. GridPP is a collaboration of approximately 100 researchers in 19 UK university particle physics groups, the Council for the Central Laboratory of the Research Councils and CERN, reflecting the strategic importance of the project. In collaboration with other European and US efforts, the first phase of the project demonstrated the feasibility of developing, deploying and operating a Grid-based computing system to meet the UK needs of the Large Hadron Collider experiments. This note describes the work undertaken to achieve this goal. S Supplementary documentation is available from stacks.iop.org/JPhysG/32/N1. References to sections S1, S2.1, etc are to sections within this online supplement.