Oxidation of silicon: New electron spectroscopy results

New X-ray photoemission spectroscopy data and high resolution electron scattering spectroscopy data are presented which indicate that a peroxide-like model of the oxygen chemisorption on silicon surface is correct. These results are discussed in light of a recent double-bonded oxygen atom model due to Ludeke and Koma.     

Photoénolisation—VIII: Stéréospécificitéet régiospécificitéde la réaction de diels-alder avec les photodiénols issus de la benzyl-2 et de l'éthyl-2 benz

Photoenols derived from 2-benzyl- and 2-ethylbenzophenone have been trapped by maleic anhydride, methyl fumarate and phenyl fumarate. Stereochemical determinations of the single adduct obtained in each case in high yield have shown unequivocally that the Diels-Alder addition proceeds from the (E,E)-dienol by an endo approach, an interaction between the dienol hydroxylic group and one of the dienophile carbonyl group being strongly determinant. These results do not eliminate the possibility that an unreactive (Z,E)-dienol be formed during the photochemical step.     

Experimental demonstration of a controlled-NOT wave-packet gate

We report the experimental demonstration of a controlled-NOT (CNOT) quantum logic gate between motional and internal-state qubits of a single ion where, as opposed to previously demonstrated gates, the conditional dynamics depends on the extent of the ion's wave packet. Advantages of this CNOT gate over one demonstrated previously are its immunity from Stark shifts due to off-resonant couplings and the fact that an auxiliary internal level is not required. We characterize the gate logic through measurements of the postgate ion state populations for both logic basis and superposition input states, and we demonstrate the gate coherence via an interferometric measurement.     

Palladium Catalyzed Additions to Allylic Hydroxy Phosphonates: Applications in the Enantioselective Synthesis of Enterolactone and Turmerone

Reaction of nonracemic allylic hydroxy phosphonates, prepared by the asymmetric phosphonylation of unsaturated aldehydes, with methyl chloroformate in pyridine yields the corresponding carbonates. The carbonates are excellent substrates for the palladium-catalyzed addition of nucleophiles. Addition of the nucleophile is highly regioselective, resulting in n -substituted vinyl phosphonates. The reaction of the allylic carbonates with aryl stannanes and malonates has been investigated. Progress in the application of these reactions to the synthesis of turmerone and enterolactone is reported.     

Dynamics of interacting edge defects in copolymer lamellae

It is known that terraces at the air-polymer interface of lamella-forming diblock copolymers do not make discontinuous jumps in height. Despite the underlying discretized structure, the height profiles are smoothly varying. The width of a transition region of a terrace edge in isolation is typically several hundreds of nanometres, resulting from a balance between surface tension, chain stretching penalties, and the enthalpy of mixing. What is less well known in these systems is what happens when two transition regions interact with one another. In this study, we investigate the dynamics of the interactions between copolymer lamellar edges. We find that the data can be well described by a model that assumes a repulsion between adjacent edges. While the model is simplistic, and does not include molecular level details, its agreement with the data suggests that some of the the underlying assumptions provide insight into the complex interplay between defects.     

Unoccupied surface and conduction band states on Ge (111) from energy loss spectroscopy

Unoccupied surface states are observed on Ge (111) by measuring 3d-core level to conduction-band transitions using electron energy loss spectroscopy. These experiments also yield values for conduction band density-of-states features.