  When the effects of dispersion are included, neither the Abraham nor the
Minkowski expression for electromagnetic momentum in a dielectric medium gives
the correct recoil momentum for absorbers or emitters of radiation. The total
momentum density associated with a field in a dielectric medium has three
contributions: (i) the Abraham momentum density of the field, (ii) the momentum
density associated with the Abraham force, and (iii) a momentum density arising
from the dispersive part of the response of the medium to the field, the latter
having a form evidently first derived by D.F. Nelson [Phys. Rev. A 44, 3985
(1991)]. All three contributions are required for momentum conservation in the
recoil of an absorber or emitter in a dielectric medium. We consider the
momentum exchanged and the force on a polarizable particle (e.g., an atom or a
small dielectric sphere) in a host dielectric when a pulse of light is incident
upon it, including the dispersion of the dielectric medium as well as a
dispersive component in the response of the particle to the field. The force
can be greatly increased in slow-light dielectric media.
