Bounds on Widths of Resonances for Stark Hamiltonians

Resonances of Schrödinger operators are closely related to the poles of certain meromorphic extension of the resolvent. In this paper, we study the resonances in Stark effect. generated by negative eigenvalues. We give precise location for the reso nances and prove in particular that the widths of resonances are exponentially small-and can be measured by some Agmon's distance.