  A new equation for describing physical systems with radiation is obtained in
this paper. Examples of such systems can be found in plasma physics,
accelerator physics (synchrotron radiation) and astrophysics (gravitational
waves). The new equation is written on the basis of the third Vlasov equation
for the probability density distribution function of kinematic quantities:
coordinates, velocities and accelerations. The constructed new Vlasov PSI -
equation makes it possible to describe naturally dissipation systems instead of
phenomenological modifications of the second Vlasov equation, and to construct
conservative difference schemes in numerical simulation.
