  An analytical formula for the linear complex susceptibility of dipolar
assemblies subjected to thermal agitation, long range interactions and an
externally applied uniform sinusoidal field of weak amplitude is derived using
the forced rotational diffusion equation of Cugliandolo et al. [Phys. Rev. E
91, 032139 (2015)] in the virial approximation. If the Kirkwood correlation
factor of the dipolar assembly gK exceeds unity, a thermally activated process
arising from the interaction-specific component arises while for gK<1, the
susceptibility spectrum normalized by its static value is practically unaltered
with respect to that of the ideal gas phase.
