The chemist's microscope must be able to resolve the inner workings of a molecule. This requires the characterization of structural and chemical properties with Å-scale spatial resolution. We describe such a multimodal microscope realized by the integration of a scanning tunneling microscope (STM) with tip enhanced Raman scattering (TERS) on a CO-terminated tip. In addition to STM images of the frontier orbitals that determine the space-filling shapes, the CO vibrational frequency shift, intensity, and width can be used to map out the intermolecular forces due to short range Pauli-exchange forces that determine ball and stick shape of the molecule, the chemical potential or electronegativity map of the molecule through the Stark effect, and spring constants of its bonds through vibrational spectro-microscopy. The rich information content of such maps will be highlighted through several examples of interrogated molecules. The measurements also clarify the inseparable processes of TERS and photo-tunneling, through cavity confined light coupled to tunneling plasmons.

Molecular force spectro-microscopy through tip-enhanced Raman scattering

254th National Meeting (2017)

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