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The optical and dielectric properties of water in the vacuum ultraviolet are presented and discussed. Optical constants at energies up to 14.6 eV were obtained by a Kramers-Kronig analysis using ref lectances measured in this study between 9.2 and 14.9 eV and ref lectances calculated from data in the literature below 9.9 eV. Structure in the complex part of the dielectric constant and the energy-loss function of water is compared with molecular excitations observed in water vapor. A sum-rule calculation indicates approximately 1 as the effective number of electrons per water molecule participating in absorption processes in the liquid state up to 14, 6 eV.

Optical properties of polystyrene in the form of thin films were determined for photon energies between 0.6 and 82 eV from transmission measurements. The results for k, the extinction coefficient, were combined with previous experimental results in the soft and hard x-ray regions up to 8050 eV. Analyses were made on several sum rules for the optical properties in this unusually wide energy range. induding a sum rule for the refractive index n derived recently by Altarelli et al. Redistribution of the oscillator strength corresponding to 2.7% of the total electrons was found between the valence and core excitations of carbon. Using the complex dielectric function and the energy-loss function obtained, the average photoexcitation energy and the average energy loss for fast-charged particles over the entire oscillator strength distribution were evaluated to be 25.1 and 36.8 eV. respectively. 3243 3244 INAGAKI, ARAKAWA, HAMM, AND WILLIAMS 15

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Optical constants have been obtained for glassy carbon from 0 to 82 eV by means of reflection measurements. The data have been analyzed by analogy with those for graphite in terms of single electron excitations and of collective oscillations of the π and σ electrons.

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