  Stationary scattering problem (when the distance $r$ tends to infinity) and
dynamical scattering problem (when the time $t$ tends to infinity) are
considered for the 3D Schr\"odinger equation. A simple interconnection between
the scattering amplitude (stationary case) and scattering operator (dynamical
case) is given in the paper. This result is a quantum mechanical analog of the
ergodic formulas in the classical mechanics.
