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Photoelectron spectra of single crystals of eight aromatic compounds were measured at several UV wavelengths. Useful results were obtained when sample charging was eliminated by inducing photoconduction through subsidiary illumination of the sample crystal with low energy light, and/or by a vapor-deposited gold grid on the sample surface. The threshold ionization potential obtained for a single crystal was found always to be lower than that for the corresponding polycrystalline film.
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Sato et al. (1985) studied this question.
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