Vibration-Assisted Rotation and Deprotonation of a Single Formic Acid Molecule Adsorbed on Ni(110) Studied by Scanning Tunneling Microscopy

We have studied the reaction of a single molecule of formic acid adsorbed on the Ni(110) surface using a scanning tunneling microscope (STM) at cryogenic temperatures. At 50 K, formic acid molecules, having an O−H bond, were converted to formate via thermal dissociation of the O−H bond, whereas deuterated formic acid molecules, having O−D, are adsorbed intact. By injecting tunneling electrons from the STM tip into individual formic acid molecules, we have selectively controlled two types of reactions: rotational motion and O−H bond dissociation to form formate. Injection of the tunneling electrons at various voltages indicates that significant enhancements in the reaction probability are due to the excitation of specific vibrational modes, that is, C−O stretching and O−D stretching modes of formic acid.