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Attenuation at temperatures low enough that rotons can be ignored and the phonon mean free path is much greater than the wavelength of sound, is considered. The attenuation constant resuiting from three phonon processes is calculated. A perturbation calculation is performed in which the phonon dispersion spectrum is neglected. Agreement with observed values is obtained below 0.4 deg K. (L.N.N.)
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Kyozi Kawasaki (1961) studied this question.
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