Optische Eigenschaften dünner Cäsium-Schichten im Wellenlängenbereich von 0,3 bis 0,9 μ und ihr elektrischer Widerstand
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Optical properties of thin cesium films in the wavelength region between 0.3 and 0.9 μ and their electrical resistance
Electrical resistance and optical transmission, reflexion and absorption of thin films of the alkali metal cesium were measured as a function of thickness, the latter for ∥ and ⊥ polarised monochromatic radiations having wavelengths between 3000 and 9000 Å incident from the vacuum side as well as from the quartz-support side at angles of 45 ° and ca 30 ° resp. The films were prepared by evaporation in static ultra-high vacuum (∼10−10 Torr) onto a cooled (70 K) smooth surface of a thin, plane-parallel plate of polycrystalline quartz. The thickness of the slowly condensing films was varied continuously from zero to some thousand Angström-units corresponding to the bulk metal.
The results obtained permit, on the one side, by means of the size effect in the resistance, the determination of the mean free path of the conduction electronsl and of the productp∞ ·l, a constant characterising fundamental electronic properties of the respectiv metal in bulk; they permit, on the other side the identification of the volume- or the surface character of the different plasma oscillations, the determination of their resonance frequency, a quantitative analysis of their development with increasing film thickness, and finally of the optical constants.
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