  We study the transfer of electromagnetic energy across a subwavelength gap
separating two co-axial metal nanorodes. The absence of spacer in the gap
separating the rods the system exhibits the strong coupling between
longitudinal plasmons in the two rods. The nature and magnitude of this
coupling is studied by varying various geometrical parameters. When the length
of one rod is varied this mode spectrum exhibits the familiar anti-crossing
behavior that depends on the coupling strength determined by the gap width. As
a function of frequency the transmission is dominated by a splitted
longitudinal plasmon peak. The two hybrid modes are the dipole-like "bonding"
mode characterized by a peak intensity in the gap, and a quadrupole-like
"antibonding" mode whose amplitude vanishes at the gap center. When
off-resonant $2-$level emitters are placed in the gap, almost no effect on the
frequency dependent transmission is observed. In contrast, when the molecular
system is resonant with the plasmonic lineshape, the transmission is strongly
modified, showing characteristics of strong exciton-plasmon coupling, modifying
mostly the transmission near the lower frequency "bonding" plasmon mode. The
presence of resonant molecules in the gap affects not only the molecule-field
interaction but also the spatial distribution of the field intensity and the
electromagnetic energy flux across the junction.
