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Synthesis of a terminal Ce(iv) oxo complex by photolysis of a Ce(iii) nitrate complex.
Reaction of [Ce(NR2)3] (R = SiMe3) with LiNO3 in THF, in the presence of 2,2,2-cryptand, results in the formation of the Ce(iii) "ate" complex, [Li(2,2,2-cryptand)][Ce(κ2-O2NO)(NR2)3] (1) in 38% yield. Photolysis of 1 at 380 nm affords [Li(2,2,2-cryptand)][Ce(O)(NR2)3] (2), in 33% isolated yield after reaction work-up. Complex 2 is the first reported example of a Ce(iv) oxo complex where the oxo ligand is not supported by hydrogen bonding or alkali metal coordination. Also formed during photolysis are [Li(2,2,2-cryptand)]2[(μ3-O){Ce(μ-O)(NR2)2}3] (3) and [Li(2,2,2-cryptand)][Ce(OSiMe3)(NR2)3] (4). Their identities were confirmed by X-ray crystallography. Complex 4 can also be prepared via reaction of [Ce(NR2)3] with LiOSiMe3 in THF, in the presence of 2,2,2-cryptand. When synthesized in this fashion, 4 can be isolated in 47% yield. To rationalize the presence of 2, 3, and 4 in the reaction mixture, we propose that photolysis of 1 first generates 2 and NO2, via homolytic cleavage of the N-O bond in its nitrate co-ligand. Complex 2 then undergoes decomposition via two separate routes: (1) ligand scrambling and oligomerization to form 3; and, (2) abstraction of a trimethylsilyl cation to form a transient Ce(iv) silyloxide, [CeIV(OSiMe3)(NR2)3], followed by 1e- reduction to form 4. Alternatively, complex 4 could form directly via ·SiMe3 abstraction by 2
Regularization of Vertical-Cavity Surface-Emitting Lasers emission by periodic non-Hermitian potentials
We propose a novel physical mechanism based on periodic non-Hermitian
potentials to efficiently control the complex spatial dynamics of broad-area
lasers, particularly in Vertical-Cavity Surface-Emitting Lasers (VCSELs),
achieving a stable emission of maximum brightness. Radially dephased periodic
refractive index and gain-loss modulations accumulate the generated light from
the entire active layer and concentrate it around the structure axis to emit
narrow, bright beams. The effect is due to asymmetric-inward radial coupling
between transverse modes, for particular phase differences of the refractive
index and gain-loss modulations. Light is confined into a central beam with
large intensity opening the path to design compact, bright and efficient
broad-area light sources. We perform a comprehensive analysis to explore the
maximum central intensity enhancement and concentration regimes. The study
reveals that the optimum schemes are those holding unidirectional inward
coupling but not fulfilling a perfect local PT-symmetry.Comment: 4 pages, 4 figure
Search for Higgs Bosons Decay Using Vector Boson Fusion
The sensitivity of the ATLAS experiment to low mass SM Higgs produced via
Vector Boson Fusion mechanism with is invest igated. A cut
based event selection has been chosen to optimize the expected signal
significance with this decay mode. A signal significance of 2. 2 may
be achieved for M_H=130 \gev with 30 fb of accumulated luminosity
Coal/rock interface detection by sensitized pick, part A
In order to increase the operating margins of the detector for safe, reliable operation under difficult in-mine conditions the transmitted signal strength was increased to provide additional signal margin for in-mine conditions and the transmitter section was redesigned to reduce frequency pulling of the transmitter frequency with variations in antenna load. The linearity of the pick load SCO signal with true pick load was increased, and hysteresis effects were minimized. The sensitized pick hardware was ruggedized for rough inmine use. The sensitized pick and telemetry system provided excellent, high quality signals proportional to cutting load under all conditions experienced during testing
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