MICROCLUSTER IOPTICAL ABSORPTION SPECTRA OF AG-MICROCLUSTERS FORMED BY MATRIX TECHNIQUES

Des microagrégats d'argent ont été préparés par condensation simultanée d'un faisceau d'argent monoatomique et d'un gaz noble en excès sur une cible de saphir refroidie et analysés par spectroscopie optique à transmission dans le domaine UV-VISIBLE. En fonction des paramètres de condensation (i.e. température rapport gaz/métal, taux d'admission du gaz et gaz lui-même) les atomes du métal qui se condensent peuvent soit être isolés, soit former des mélanges d'agrégats à la surface de la matrice en train de croître. Les spectres d'absorption optique de tels mélanges présentent plusieurs bandes d'absorption distinctes dans le domaine 2 000-5 000 Å. Les bandes correspondant à l'argent monoatomique et diatomique peuvent être clairement identifiées, ce qui permet d'attribuer les autres bandes à des particules contenant plus de deux atomes d'argent.Silver microclusters have been prepared by co-condensation of a monoatomic silver beam with an excess of noble gas on a cooled sapphire target and investigated by optical transmission spectroscopy in the U.V.-VIS. range. Depending on the condensation parameters (i.e. temperature, gas/metal ratio, the gas admission rate and the gas itself) the condensing metal atoms can either be isolated as single atoms or as a mixture of aggregates at the surface of the growing matrix layer. The optical absorption spectra of such mixtures show several distinct absorption bands within the range 2 000-5 000 Å. The spectral features of monoatomic and diatomic silver can be clearly identified, allowing the remaining bands to be assigned to multimeric silver particles

Self sacrifice or natural donation? A life course perspective on grandmothering in New Zagreb (Croatia) and East Berlin (Germany)

In this article we explore grandmaternal care and its interpretations in two European capitals of former socialist countries, Zagreb and Berlin. We describe the scope and variety of grandmaternal care practices both field sites and then contrast two grandmotherly interpretations of their intensive caring for grandchildren The different appraisal of their similar practice as self-sacrifice and natural donation respectively is embedded in different life course experiences of these two women. Both grandmothers lived in socialist states and made the experience of profound change with political and economic restructuring. But while socialist eastern Germany and Croatia had many similar traits they also differed in important aspects. While our interlocutors attributed their practice generally to post-socialist developments, they based their judgements on different aspects of state responsibility. While demographic developments might create similar opportunities for child care, national and local contexts vary and local actors attribute different meanings to their actio