Stark effect of adsorbate vibrations

The theory of the vibrational Stark effect of adsorbates is discussed. In particular, the reported linear variation of CO vibrational frequency with potential difference across the Pt-electrolyte interface is shown to be consistent with a recent measurement of the Stark tuning rate of CO on Ni [110] in UHV and the differential capacitance of the Pt-electrolyte interface. We also demonstrate that the Stark tuning rate of CO on Ni [110] is itself in agreement with theoretical prediction. Our vibrational Hamiltonian applies to atomic adsorbates and molecules. It relates frequency shifts of the adsorbate to the local electric field at an adsorbate free surface.