  We study how the collective effects of nanoparticles arranged in rectangular
arrays influence their temporal plasmon response and field enhancement
property. By systematically changing the lattice constant for arrays containing
identical metal nanorods, we experimentally demonstrate how grating induced
effects affect the position and, more importantly, the broadening of extinction
spectra. We correlate these effects with the achievable field enhancement and
the temporal duration of plasmon transients and formulate criteria for the
generation of enhanced few-cycle localized plasmon oscillations.
