  Electronic conduction through single molecules is affected by the molecular
electronic structure as well as by other information that is extremely
difficult to assess, such as bonding geometry and chemical environment. The
lack of an independent diagnostic technique has long hampered single-molecule
conductance studies. We report simultaneous measurement of the conductance and
the Raman spectra of nanoscale junctions used for single-molecule electronic
experiments. Blinking and spectral diffusion in the Raman response of both
para-mercaptoaniline and a fluorinated oligophenylyne ethynylene correlate in
time with changes in the electronic conductance. Finite difference time domain
calculations confirm that these correlations do not result from the conductance
modifying the Raman enhancement. Therefore, these observations strongly imply
that multimodal sensing of individual molecules is possible in these
mass-producible nanostructures.
