Dynamics of electron-induced manipulation of individual CO molecules on Cu(III)

Electrons tunneling from a scanning tunneling microscope tip to individual CO molecules on Cu(111) can cause their hopping from the surface to the tip if the bias exceeds a threshold of 2.4 V. Polarization-and time-resolved two-photon photoemission identifies the underlying elementary process as intermediate population of a CO 2 pi*-derived level, which exhibits an ultrashort lifetime of 0.8-5 fs. From an isotope effect of 2.7(-0.5)(+0.3) it can be calculated that approximate to 0.05% of the tunneling current transiently occupies this level while a desorption of the excited molecule occurs only in 5 x 10(-9) of the cases. [S0031-9007(98)05403-9].