Electron Transport Properties of Single-Molecule-Bearing Multiple Redox Levels Studied by EC-STM/STS

Multielectron systems as possible components of molecular electronics devices are attracting compelling experimental and theoretical interest. Here we studied by electrochemical scanning tunneling techniques (EC-STMicroscopy and EC-STSpectroscopy) the electron transport properties of a redox molecule endowed with two redox levels, namely, the hydroquinone/quinone (H2Q/Q) couple. By forming self-assembled monolayers on Au(111) of oligo-phenylene-vinylene (OPV) derivatized H2Q/Q moieties, we were able to explore the features of the tunneling current/overpotential relation in the EC-STS setup. The behavior of the tunneling current sheds light onto the mechanism of electron transport involving the redox levels of the H2Q/Q redox pair coupled to tip and substrate electrodes

Observation of semileptonic charmless B meson decays

A detailed study of the lepton momentum spectrum in υ(4S) decays has been made using the ARGUS detector at the DORIS II e+e− storage ring at DESY. In the region from 2.3 to 2.6 GeV/c, which is above the endpoint for contributions from B decays via b→c transitions, we observe 41±10 events in excess of known backgrounds. These events are interpreted as a signal for b→u transitions. A model dependent value of 0.10±0.01 is obtained for the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |Vub|/|Vcv|, using the Altarelli et al. model