Charge separation dynamics relevant to an electron transfer have been revealed by time- and angle-resolved two-photon photoemission spectroscopy for an n-alkanethiolate self-assembled monolayer (SAM) on a Au(111) surface fabricated by a chemical-wet process. The electron was photoexcited into an image potential state located at 3.7 eV above the Fermi level (E F), and it survived well for more than 100 ps on dodecanethiolate (C12)-SAM. The degree of electron separation is precisely controlled by selecting the length of the alkyl chain (C10-C18). We have also evaluated molecular conductivity at the specific electron energy of E F + 3.7 eV. The tunneling decay parameter, β, was fitted by β 90 K = 0.097 Å -1 and β RT = 0.13 Å -1. These values were one order smaller than that at around E F by conventional contact probe methods.
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