Relating localized nanoparticle resonances to an associated antenna problem

On an empirical basis, we indicate the possibility of conceptually unifying the description of resonances existing in some of the analytically studied metallic nanoparticles and optical nanowire antennas. To this end the nanoantenna is treated as a Fabry-P\'erot-like resonator with arbitrary seminanoparticles forming the terminations. We show that the frequencies of the quasistatic dipolar resonances of the considered nanoparticles coincide with those where the round-trip phase of the complex reflection coefficient of the fundamental propagating plasmon polariton mode at the wire terminations amounts to 2π. The lowest order Fabry-P\'erot resonance of the optical wire antenna occurs therefore even for a negligible wire length.