Optical characterization and manipulation of alkali metal nanoparticles in porous silica |
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Authors: | A Burchianti A Bogi C Marinelli C Maibohm E Mariotti S Sanguinetti L Moi |
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Institution: | 1.CNISM and Physics Department,University of Siena,Siena,Italy;2.Mads Clausen Institute,NanoSYD, University of Southern Denmark,S?nderborg,Denmark;3.Physics Department,University of Pisa,Pisa,Italy |
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Abstract: | Rubidium and cesium metal nanoparticles were grown in nanoporous silica samples placed in alkali vapor cells. Their size and
shape were investigated by measuring the sample optical transmittance. Spectral changes due to photodesorption processes activated
by weak light were also analyzed. Alkali atoms photoejected from the silica walls diffuse through and out of the nanopores,
modifying both the nanoparticle distribution in the silica matrix and the atomic vapor pressure in the cell volume. The number
of rubidium and cesium atoms burst out of the samples was measured as a function of photon energy and fluence. The optical
absorption measurements together with the analysis of the photodesorption yield give a complete picture of the processes triggered
by light inside the nanopores. We show that atomic photodesorption, upon proper choice of light frequency and intensity, induces
either growth or evaporation of nanosized alkali metal clusters. Cluster size and shape are determined by the host-guest interaction. |
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Keywords: | PACS" target="_blank">PACS 78 67 Bf Nanocrystals and nanoparticles 68 43 Tj Photon stimulated desorption 64 70 Nd Structural transitions in nanoscale materials |
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