10 research outputs found

    Measurement of Population Dynamics In Stimulated Raman Adiabatic Passage

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    The temporal evolution of populations has been directly measured for a three-level ladder system undergoing coherent excitation by stimulated Raman adiabatic passage (STIRAP). The measurement technique makes use of charge transfer as diagnostic. The method is model independent and has a temporal resolution of a few nanoseconds. The temporal evolution is measured for several values of the delay between the pump and Stokes laser pulses that are part of the STIRAP excitation scheme. The corresponding quantum Liouville equations are solved and the results of the calculations are compared with experiment

    The Physics of the B Factories

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    Partitioning of C into κ-carbides by Si addition and its effect on the initial deformation mechanism of Fe-Mn-Al-C lightweight steels

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    The effect of Si addition on the initial deformation mechanism of Fe–30Mn–9Al–0.9C–0.5Mo cast lightweight steel has been investigated. Atomic-scale analysis by three-dimensional atom-probe tomography confirmed that Si addition accelerates the formation kinetics of the κ-carbide, and increases remarkably the partitioning coefficient of carbon by more than 2 times. Promotion of C partitioning into κ-carbides by Si addition leads to deformation localization in an aged state. This is attributed not only to the increase of the κ-carbide size associated with higher coherency strain, but also to higher frequency of Al-C bonding formation. First-principles calculations indicated that the energy required for a/2<110> shearing of κ-carbide in the aged 1%-Si steel is higher (561 mJ/m2) than that in the aged Si-free steel (494 mJ/m2). Therefore, Si addition leads to a significant energy difference for shearing and results in different shear bands formation. The operative deformation mechanism can be calculated for this alloy system as a function of precipitates volume fraction and size. It was determined that deformation proceeds primarily by κ-carbide shearing as long as the radius of κ-carbides is smaller than 13.4 nm. © 2018 Elsevier B.V.FALS

    Photosynthetic Adjustment to Temperature

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