Do Mie plasmons have a longer lifetime on resonance than off resonance?

The dynamics of laser-excited electrons in elliptically shaped silver nano-particles is studied using time-resolved two-photon photo-emission. By changing the polarization of the laser pulse at a fixed frequency, a different dynamics is observed near and far from resonance. To analyze these data , the effect of radiation damping on Mie plasmons of Ag nanoparticles is studied as a function of laser frequency and polarization. It is shown that the off-resonance lifetime can be shorter or longer than the lifetime at resonance, depending on the incidence conditions of the laser light and on the depolarization factors characterizing the optical response of the nano-particles.