  Knowing the characteristic relaxation time of free electrons in a dense
plasma is crucial to our understanding of plasma equilibration and transport.
However, experimental investigations of electron relaxation dynamics have been
hindered by the ultra-fast, sub-femtosecond time scales on which these
interactions typically take place. Here we propose a novel approach that uses
x-rays from a free electron laser to generate well-defined non-thermal electron
distributions, which can then be tracked via emission spectroscopy from
radiative recombination as they thermalize. Collisional radiative simulations
reveal how this method can enable the measurement of electron relaxation time
scales {\it in situ}, shedding light on the applicability and accuracy of the
Coulomb Logarithm framework for modelling collisions in dense plasmas.
