  In the paper energy dependence of femtoscopy characteristics of pion emission
region at freeze-out is investigated for collisions of various ions and for all
experimentally available energies. For the first time the normalized values of
radii and volume of source are used for energy dependence. This approach allows
us to expand the set of interaction types, in particular, on non-symmetrical
nucleus-nucleus collisions which can be studied in the framework of common
approach. There are no the sharp changing of femtoscopic parameter values, in
particular, $R_{o}/R_{s}$ with increasing of $\sqrt{s_{NN}}$ which were
predicted by some phenomenological models as signature of first order phase
transition in strongly interacting matter. The generalized parameterization for
femtoscopic correlation function is suggested.
