  Effect of radiation-reaction force on the dynamics of a charged particle in
an intense focused light wave is investigated using the physically appealing
Hartemann-Luhmann equation of motion. It is found that, irrespective of the
choice of initial conditions, radiation reaction force causes the charge
particle to cross the focal region, thereby enhancing the forward energy gained
by the particle from the intense light wave. This result is in sharp contrast
to the well known result, derived in the absence of radiation reaction forces,
where for certain initial conditions the particle reflects from the high
intensity region of the focused light wave, thereby losing forward energy.
These results, which are of relevance to the present day direct laser
acceleration schemes of charge particle, also agrees with that obtained using
the well known Landau-Lifshitz equation of motion.
