The reflectivity of bismuth crystals is measured in the spectral range 50 to 600 cm-l. From the measured data the dielectric function is determined by a'Kramers-Kronig analysis. The dispersion of this function is explained by the dynamical conductivity of a free electron gas. At frequencies above the plasma edge there is a contribution which is due to the excitation of plasmons by the interaction of the free electrons with the Coulomb fields of impurities. This contribution can be expected from model calculations of the dynamical conductivity, considering ionized impurity scattering and screening effects.An Wismut-Kristallen wird das Reflexionsvermogen im Spektralbereich zwischen 50 und 500 cm-I gemessen. Aus den Messungen wird die dielektrische Funktion durch eine Kramers-Kronig-Analyse ermittelt, ihr spektraler Verlauf wird durch die dynamische Leitfiihigkeit des freien Elektronengases erkliirt. Ein Beitrag bei Frequenzen oberhalb der Plasmakante wird Plasmonen zugeschrieben, die durch die Wechselwirkung der freien Elektronen mit den Coulomb-Feldern ionisierter Storstellen angeregt werden. Ein solcher Beitrag wird aus Modellrechnungen fur die dynamische Leitfiihigkeit erwartet, wenn man die Streuung an ionisierten Storstellen und Abschirmeffekte betrachtet.

International audienceIn west-European countries, public policies often argue that heritage - and in particular industrial heritage - could be an effective resource for economic and social development in areas that have been severely affected by de-industrialisation. During the 1990s, the French and British governments proposed two different strategies for the role that industrial heritage might have in repairing the effects of deindustrialisation. From a general point of view, the British promoted tourism, while the French preferred cultural projects. However, concrete examples, such as the ones presented in the present article, show a more complex situation. First, already at that time local authorities and local powers played an important role - especially in Great Britain - in the politics of heritage. Second, these politics are impacted by struggles and tensions between local populations and 'external' agents. Third, the local populations see these heritage-based development projects as being based on a 'mythification' of labour and of the workers' culture. Finally, local populations seem to feel that such projects are imposed from 'the outside', which tends to result in local agents not fully accepting or identifying themselves with such heritage-based projects

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