Volume 113, Issue 6, 08 August 2000
Index of content:
113(2000); http://dx.doi.org/10.1063/1.482014View Description Hide Description
The coherent control of bimolecular processes typically requires that the system be initiated in a superposition of correlated translational and internal reactant states. We show that by colliding identical molecules one bypasses many of these complexities, allowing for direct studies of coherently controlled collision phenomena.
113(2000); http://dx.doi.org/10.1063/1.482015View Description Hide Description
Nuclear magnetic resonance(NMR) is well-suited to implement quantum algorithms experimentally. However, there are serious problems associated with the noisy mixed initial state that is described by the thermal equilibrium density operator of NMR spectroscopy. Here we present a new strategy to dramatically increase the sensitivity of a NMRquantum computing experiment. Para hydrogen can be used to prepare a density operator in a suitable molecule that is very close to a pure state, an improvement on the order of compared to “conventional” NMRquantum computing. Our strategy is demonstrated experimentally solving the Deutsch–Jozsa problem based on para hydrogen and Vaska’s complex.
Localized excess negative charges in surface states of the clean Ga-rich reconstruction as imaged by scanning tunneling microscopy113(2000); http://dx.doi.org/10.1063/1.482016View Description Hide Description
Scanning tunneling microscopyimages of the Ga-rich surface exhibit vivid long-range patterns consisting of bright spots (“ghosts”) which are attributed to localized excess charge rather than atomic clusters. The nearly planar geometry of the -hybridized gallium dimer atoms results in localized π states made up of a combination of the Ga orbitals. These states in the upper half of the band gap form the lowest unoccupied band. Surface or bulk defects lead to excess negative charge flowing into these localized states. Repulsion between the trapped negative excess charges leads to the observed “ghost” pattern.
Adsorbate phase transformations and the coverage-dependent oscillation of electron transfer probabilities113(2000); http://dx.doi.org/10.1063/1.482017View Description Hide Description
We report a study of the effects of chlorine adsorption on the interaction of positive ions with a Ag(111) surface from the submonolayer Cl chemisorption to initial stages of AgCl formation. Cl adsorption on Ag(111) proceeds through different phases and we observed that the neutralization probabilities oscillate in this range, attaining an intermediate minimum at about 2/3 coverage and reach a maximum at full coverage. The subsequent appearance of AgCl phase again leads to a reduction in neutralization. These results are described in terms of changes in Auger neutralization rates due to modifications in the adsorbatedensity of states.