  Using the UrQMD/coarse graining approach we explore the kinetic freeze-out
stage in central Au + Au collisions at various energies. These studies allow us
to obtain detailed information on the thermodynamic properties (e.g.
temperature and chemical potential) of the system during the kinetic decoupling
stage. We explore five relevant collision energies in detail, ranging from
$\sqrt{s_{NN}}=2.4\,\mathrm{GeV}$ (GSI-SIS) to
$\sqrt{s_{NN}}=200\,\mathrm{GeV}$ (RHIC). By adopting a standard Hadron
Resonance Gas equation of state, we determine the average temperature $\langle
T \rangle$ and the average baryon chemical potential
$\langle\mu_{\mathrm{B}}\rangle$ on the space-time hyper-surface of last
interaction. The results highlight the nature of the kinetic freeze-out as a
continuous process. This differential decoupling is an important aspect often
missed when summarizing data as single points in the phase diagram as e.g. done
in Blast-Wave fits. We compare the key properties of the system derived by
using our approach with other models and we briefly review similarities and
differences.
