  We systematically test a quasi-classical spin model of a large spin-lattice
in energy space, with a tunable, reversible Hamiltonian and effective
long-range interactions. The system is simulated by a weakly interacting Fermi
gas undergoing perturbed quantum rewinding using radio-frequency(RF) pulses.
The model reported here is found to be in a quantitative agreement with
measurements of the ensemble-averaged energy-resolved spin density. This work
elucidates the effects of RF detunings on the system and measurements, pointing
the way to new correlation measurement methods.
