  The propagation of the collective surface plasmons, called
plasmon-polaritons, in infinite equidistant ionic sphere chain has been
analyzed. The ideal cancellation of irradiative losses of these ionic
excitations in the chain is demonstrated by inclusion of appropriately retarded
near-, medium and far-field components of dipole interaction between spheres in
the chain. It is proved that the Lorentz friction losses in each sphere are
completely compensated by the energy income from the rest of the chain for a
wide sector of the plasmon-polariton wave vector domain. There is shown that
the damping of plasmon-polariton is reduced to only residual Ohmic losses much
lower than irradiation losses for the separate electrolyte sphere. The
self-frequencies and the group velocities of plasmon-polaritons for
longitudinal and transversal (with respect to the chain orientation)
polarizations are determined and assessed for various ion and electrolyte
parameters. It is proved that there exist weakly damped self-modes of
plasmon-polaritons in the chain for which the propagation range is limited by
relatively small Ohmic losses only. Completely undamped collective waves are
also described in the case of the presence of persistent external excitation of
some fragment of the chain. The possibility of application of the
plasmon-polariton model to describe the so-called saltatory conduction in
periodically myelinated nerve axons is preliminarily discussed.
