  In this Letter, we exploit recent breakthroughs in monochromated
aberration-corrected scanning transmission electron microscopy (STEM) to
resolve infrared plasmonic Fano antiresonances in individual nanofabricated
disk-rod dimers. Using a combination of electron energy-loss spectroscopy
(EELS) and theoretical modeling, we investigate and characterize a subspace of
the weak coupling regime between quasi-discrete and quasi-continuum localized
surface plasmon resonances where infrared plasmonic Fano antiresonances appear.
This work illustrates the capability of STEM instrumentation to experimentally
observe nanoscale plasmonic responses that were previously the domain only of
higher resolution infrared spectroscopies.
