  We examine how the magnetic susceptibility obtained by the quench experiment
on isolated quantum systems is related to the isothermal and adiabatic
susceptibilities defined in thermodynamics. Under the conditions similar to the
eigenstate thermalization hypothesis, together with some additional natural
ones, we prove that for translationally invariant systems the quench
susceptibility as a function of wave vector k is discontinuous at k=0.
Moreover, its values at k=0 and the k to 0 limit coincide with the adiabatic
and the isothermal susceptibilities, respectively. We give numerical
predictions on how these particular behaviors can be observed in experiments on
the XYZ spin chain with tunable parameters, and how they deviate when the
conditions are not fully satisfied.
