  In this paper we study the behaviour of the continuous spectrum of the
Laplacian on a complete Riemannian manifold of bounded curvature under
perturbations of the metric. The perturbations that we consider are such that
its covariant derivatives up to some order decay with some rate in the geodesic
distance from a fixed point. Especially we impose no conditions on the
injectivity radius. One of the main results are conditions on the rate of
decay, depending on geometric properties of the underlying manifold, that
guarantee the existence and completeness of the wave operators.
