Resonant Scattering of Phonons. II. KCl and KBr Doped with NO2- Ions

It is shown that the ${\omega }^4$ dependence of the phonon resonant-scattering relaxation rate $\tau _r^{}{}_{}{}^{-1\mathrm{}}$ does not explain the phonon conductivity results on KCl:N${\mathrm{O}}_2^{-}$ and KBr:N${\mathrm{O}}_2^{-}$ systems. The results in the KC1:N${\mathrm{O}}_2^{-}$ system can, however, be very well explained by the formula $\tau _r^{}{}_{}{}^{-1\mathrm{}}\propto \frac{{\omega }^2}{{({\omega }^2-\omega _0^{}{}_{}{}^2)}^2}$, as obtained by Kwok on the basis of a Green's-function approach in the case of $n-\mathrm{Ge}$. The agreement between the theoretical and experimental values of the phonon conductivity in KBr:N${\mathrm{O}}_2^{-}$ is, however, not so good.