  We explored the effects of relative motion on the excitation of
surface-plasmon-polariton (SPP) waves guided by the planar interface of a metal
film and a dielectric slab, both materials being isotropic and homogeneous.
Electromagnetic phasors in moving and non-moving reference frames were related
directly using the corresponding Lorentz transformations. Our numerical studies
revealed that, in the case of a uniformly moving dielectric slab, the angle of
incidence for SPP-wave excitation is highly sensitive to (i) the ratio $\beta$
of the speed of motion to speed of light in free space and (ii) the direction
of motion. When the direction of motion is parallel to the plane of incidence,
the SPP wave is excited by $p$-polarized (but not $s$-polarized) incident plane
waves for low and moderate values of $\beta$, while at higher values of $\beta$
the total reflection regime breaks down. When the direction of motion is
perpendicular to the plane of incidence, the SPP wave is excited by
$p$-polarized incident plane waves for low values of $\beta$, but $s$-polarized
incident plane waves at moderate values of $\beta$, while at higher values of
$\beta$ the SPP wave is not excited. In the case of a uniformly moving metal
film, the sensitivity to $\beta$ and the direction of motion is less obvious.
