Kondo anomaly of impurity spin resonance linewidth

Using the method of Baym and Kadanoff a kinetic equation is derived for the impurity susceptibility in the s-d model. Summing up the most important diagrams the impurity self-energy can be expressed in terms of Suhl's T-matrices t and τ. The contribution of the spin non flip amplitude t to the spin relaxation time is cancelled by a corresponding vertex correction. Thus the final result can be expressed in terms of the spin flip amplitude τ alone which causes an anomalous temperature dependence of the relaxation time.