Continuous Decoupling of Dynamically Expanding Systems

The question of decoupling and freeze-out is revisited. Starting from an exact manybody expression transparent semi-classical decoupling formulae are microscopically derived which provide a smooth decoupling in time both, for single and two particle inclusive spectra. They generalise frequently employed instantaneous freeze-out procedures and provide simple relations between the damping width and the duration of the decoupling process. The implications on physical phenomena in the context of the phase transitions and freeze-out processes of the highly compressed hadronic matter generated in high energy nuclear collisions are discussed.