Inducing and observing the abstraction of a single hydrogen atom in bimolecular reactions with a scanning tunneling microscope

A variable-temperature scanning tunneling microscope (STM) was used to init iate and observe the abstraction of a single hydrogen atom in a simple bimo lecular reaction. Dicarbon (CC) on the Cu(001) surface reacted separately w ith hydrogen sulfide (H2S) and water (H2O) to form CCH + SH and CCH + OH, r espectively. At 9 K, hydrogen abstraction from H2O occurred spontaneously u pon contact between CC and thermally diffusing H2O molecules. Hydrogen abst raction from H2S was effected at 9 K by inducing H2S diffusion via excitati on with tunneling electrons. The thermal diffusion and reaction of HPS and CC were also observed at 45 K. By removing a single hydrogen atom from H2S and H2O using tunneling electrons, we established the identities of the sul fhydryl (SH) and hydroxyl (OH) reaction products. SH and OH did not react w ith CC under conditions that led to the reaction of the parent molecules. T he bimolecular reactions H2O + O --> 2OH and H2S + O --> SH + OH did not oc cur thermally at 9 K but were induced by tunneling electrons.