Volume 110, Issue 6, 08 February 1999
Index of content:
110(1999); http://dx.doi.org/10.1063/1.477875View Description Hide Description
Charge inversion mass spectra of ions produced by electron impact from HC≡CH and were measured using K and Cs targets. Clear differences in the charge inversion spectra between HC≡CH and indicate that the ion formed from is The lifetime of is found to be longer than 8.5 μs, and the state is proposed to be the ground-state rather than the state.
110(1999); http://dx.doi.org/10.1063/1.477876View Description Hide Description
Excitation and detection of high-order multiple quantum (MQ) coherences among nuclear spins in singly--labeled organic solids is demonstrated experimentally. MQ signals involving at least ten quanta of spin angular momentum are observed in nuclear magnetic resonance(NMR)measurements on polycrystallineL-methionine-methyl- and L-alanine- using a time-reversible multiple pulse excitation sequence modified specifically for experiments on systems with weak homonuclear dipole–dipole couplings and strong inhomogeneous interactions such as anisotropicchemical shifts. The feasibility of high-order MQ excitation and detection in -labeled organic solids promises to expand significantly the range of applications of MQ NMR as a structural tool, to include such systems as -labeled synthetic polymers and biopolymers.
110(1999); http://dx.doi.org/10.1063/1.477973View Description Hide Description
Detailed balance is an overly strict condition to ensure a valid Monte Carlo simulation. We show that, under fairly general assumptions, a Monte Carlo simulation need satisfy only the weaker balance condition. Not only does our proof show that sequential updating schemes are correct, but also it establishes the correctness of a whole class of new methods that simply leave the Boltzmann distribution invariant.
High density adsorbed oxygen on Rh(111) and enhanced routes to metallic oxidation using atomic oxygen110(1999); http://dx.doi.org/10.1063/1.477877View Description Hide Description
Exposure of Rh(111) to atomic oxygen leads to the facile formation of a full-coverage and ordered (1×1)-O monolayer which is stable at room temperature. This result differs markedly from the half-coverage (2×1)-O overlayer which forms at saturation when using molecular oxygen. This demonstrates that kinetic rather than thermodynamic constraints inhibit the formation of dense oxygen overlayers when is the oxidant. We also report that O absorption into the bulk proceeds much more readily when using O rather than a finding with direct implications for enhanced methods of low-temperature metallic oxidation. These results demonstrate that there are important fundamental differences in the way in which low-energy beams of atomic and molecular oxygen interact with metals.