Dispersive estimate for the Schrodinger equation with point interactions

We consider the Schrodinger operator in R3 with N point interactions placed at Y=(y1,...,yN), yj (element of)R3, of strength a= (a1,...,aN), aj (element of)R. Exploiting the spectral theorem and the rather explicit expression for the resolvent we prove the (weighted) dispersive estimate for the corresponding Schrodinger flow. In the special case N=1 the proof is directly obtained from the unitary group which is known in closed form.