  Experiments creating extreme states of matter almost invariably create
non-equilibrium states. These are very interesting in their own right but need
to be understood even if the ultimate goal is to probe high-pressure or
high-temperature equilibrium properties like the equation of state. Here, we
report on the capabilities of the newly developed imaginary time correlation
function (ITCF) technique [1] to detect and quantify non-equilibrium in
pump-probe experiments fielding time resolved x-ray scattering diagnostics. We
find a high sensitivity of the ITCF even to a small fraction of non-equilibrium
electrons in the Wigner distribution. The behavior of the ITCF technique is
such that modern lasers and detectors should be able to trace the
non-equilibrium relaxation from tens of femto-seconds to several 10s of
picoseconds without the need for a model.
