Multi-species detection using multi-mode absorption spectroscopy (MUMAS)

The detection of multiple species using a single laser and single detector employing multi-mode absorption spectroscopy (MUMAS) is reported. An in-house constructed, diode-pumped, Er:Yb:glass micro-laser operating at 1,565 nm with 10 modes separated by 18 GHz was used to record MUMAS signals in a gas mixture containing C₂H₂, N₂O and CO. The components of the mixture were detected simultaneously by identifying multiple transitions in each of the species. By using temperature- and pressure-dependent modelled spectral fits to the data, partial pressures of each species in the mixture were determined with an uncertainty of ±2 %.     

Effects of ion motion in intense beam-driven plasma wakefield accelerators

Recent proposals for using plasma wakefield accelerators (PWFA) as a component of a linear collider have included intense electron beams with densities many times in excess of the plasma density. The beam's electric fields expel the plasma electrons from the beam path to many beam radii in this regime. We analyze here the motion of plasma ions under the beam fields, and find for a proposed PWFA collider scenario that the ions completely collapse inside of the beam. Simulations of ion collapse are presented. Implications of ion motion on the feasibility of the PWFA-based colliders are discussed.     

Anion adsorption induced reversal of coherency strain

Experimental results are presented for stress evolution, in vacuum and electrolyte, for the first monolayer of Cu on Au(111). In electrolyte the monolayer is pseudomorphic and the stress-thickness change is -0.60 N/m, while conventional epitaxy theory predicts a value of +7.76 N/m. In vacuum, the monolayer is incoherent with the underlying gold. Using a combination of first-principles based calculations and molecular dynamic simulations we analyzed these results and demonstrate that in electrolyte, overlayer coherency is maintained owing to anion adsorption.     

Hysteretic magnetic moment of YBa2Cu3O7?δ: An angular study

The hysteretic magnetization of an YBa₂Cu₃O_7−δ crystal containing a high density of Y₂BaCuO_x precipitates was investigated by two-axis, quasistatic, de magnetometry. As the eff-axis applied magnetic fieldH was increased and the magnetization magnitude, decreased, its orientation approached a direction near the crystallinec axis. The bulk persistent currentsJ _p predominately flowed parallel to the Cu−O planes for a wide range of temperature and applied field. Even forH almost perpendicular toc, where the deduced irreversibility line maximized as commonly observed, the resulting magnetization was observed to be within 15° of [001]. Managed by Lockheed Martin Energy Research Corp, under contract AC05-96OR22464 with the U. S. Dept. of Energy.     

Fast path and polarization manipulation of telecom wavelength single photons in lithium niobate waveguide devices

We demonstrate fast polarization and path control of photons at 1550?nm in lithium niobate waveguide devices using the electro-optic effect. We show heralded single photon state engineering, quantum interference, fast state preparation of two entangled photons, and feedback control of quantum interference. These results point the way to a single platform that will enable the integration of nonlinear single photon sources and fast reconfigurable circuits for future photonic quantum information science and technology.     

Local moment ferromagnetism in CeRu2Ga2B

Magnetization, specific heat, and electrical resistivity measurements for polycrystalline specimens of CeRu(2)Ga(2)B reveal local moment ferromagnetic order at a Curie temperature T(C) = 16.3 K. Specific heat measurements show that the phase transition is second order and the low temperature behavior indicates that the Ce f-electron states do not hybridize strongly with the conduction electron states. Electrical resistivity measurements demonstrate large spin disorder scattering of conduction electrons for T ≥ T(C). Results for a single crystal are also reported, where T(C) = 15.4 K. While results for the polycrystal and single crystal specimens are qualitatively similar, the differences between them suggest that crystalline disorder plays a role in how the magnetism develops.