Mode excitation induced by the scanning tunnelling microscope

The scanning tunnelling microscope (STM) can induce molecular vibrations. This is detected by changes in the tunnelling conductance as the bias voltage matches a vibrational excitation threshold. Vibrational spectroscopy is available for a unique molecule. Nevertheless, the experimental results present several challenges: few modes are detected, certain symmetries are dominant, and site and conformation properties affect the detection. Despite these difficulties, this technique is proving to be of the uttermost importance in the analysis of molecular adsorbates and in their manipulation. We present a general theory that can predict the outcome of STM induced vibrational spectroscopy. The above challenges are analysed and quantitative results are then shown.