Theory of the Isotopic Impurity in Solid Helium and Neon

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Abstract
A theory is presented to predict the size of the strain field about an isotopic impurity in solid helium and neon. The theory is based on the self-consistent harmonic approximation, as recently formulated by Koehler. In contrast to previous treatments, the theory computes the long-range behavior of the strain field and scattering rates for long-wavelength phonons. Good qualitative agreement with experimental results is found for the pressure dependence of the scattering rate for helium, but the quantitative agreement is dependent on the assumptions used in determining parameters of the theory. The theory predicts the existence of an appreciable strain field in neon.