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Substantial difference- and sum-frequency signals (up to 10−7 W) have been generated and reradiated by mixing the HCN laser radiation at 337 μm with that of a (tunable) millimeter-wave klystron in a metal-semiconductor point-contact or Schottky barrier diode. The magnitude and degree of monochromaticity of the generated power were sufficient for high-resolution spectroscopy as verified by measurements on H2S and CH3OH.
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Bićanić et al. (1978) studied this question.
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