Abstract

the tunneling current with increasing voltage because of tunneling through the NIR state (21). Based on I(V) measurements for other adsorbates on NaCl films, we estimate that tunneling through the NIR state increases the tunneling current by about two orders of magnitude. The extrapolation of I to z 10.5 Å and V 1.4 V thus gives a current on the order of one electron per second, corresponding to a quantum yield on the order of unity. This extremely high yield is consistent with a cap-ture of electrons tunneling into the NIR state. Further support for this interpretation comes from the experimentally suggested position of a resonance level at ENIR 1.4 eV above EF or