Effect of radiation-reaction on charged particle motion in an intense focused light wave

Effect of radiation reaction force on charged particle dynamics in an intense plane focussed light wave is investigated using the Hartemann-Luhmann equation of motion [ F. V. Hartemann and N. C. Luhmann, Phys. Rev. Lett. 74, 1107 (1995) ]. It is found that, irrespective of the choice of initial conditions radiation reaction completely nullifies the well known criterion for reflection from the focal region [ P. K. Kaw and R. M. Kulsrud, Physics of Fluids 16, 321 (1973) ] and thereby enhances the energy gained by the particle from the intense plane wave due to focussing alone. This energy gain is found to be independent of the choice of polarization of the wave. These results, which are of relevance to the direct laser acceleration scheme of particle acceleration, agrees with the results obtained using the well known Landau-Lifshitz equation of motion.