  We uncover the existence of a universal phenomenon concerning the
electromagnetic optical force exerted by light or other electromagnetic waves
on a distribution of charges and currents in general, and of particles in
particular. This conveys the appearence of underlying reactive quantities that
hinder radiation pressure and currently observed time-averaged forces. This
constitutes a novel paradigm of the mechanical efficiency of light on matter,
and completes the landscape of the electromagnetic force in classical
electrodynamics; widening our understanding in the design of both illumination
and particles in optical manipulation without the need of increasing the
illuminating power, and thus lowering dissipation and heating. We show that
this may be accomplished through the minimization of what we establish as the
reactive strength of canonical (i.e. orbital) momentum, which plays against the
optical force a role analogous to that of the reactive power versus the
radiation efficiency of an antenna. This long time overlooked quantity,
important for current progress of optical manipulation, and that stems from the
complex Maxwell theorem of conservation of complex momentum that we put
forward, as well as its alternating flow associated to the imaginary part of
the complex Maxwell stress tensor, conform the imaginary Lorentz force that we
introduce in this work, and that like the reactive strength of orbital
momentum, is antagonic to the well-known time-averaged force; thus making this
reactive Lorentz force indirectly observable near wavelengths at which the
time-averaged force is lowered.
