2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/195096The freeze out (FO) of the expanding systems, created in relativistic heavy ion collisions, is discussed. We start with kinetic FO model, which realizes complete physical FO in a layer of given thickness, and then combine our gradual FO equations with Bjorken type system expansion into a unified model. We shall see that the basic FO features, pointed out in the earlier works, are not smeared out by the expansion.3 pages, 2 figuresNuclear Theorytext