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Population Transfer (population + transfer)

Distribution by Scientific Domains
Physics and Astronomy40%

Selected Abstracts

NMR in photo-induced chemical exchange systems.

CONCEPTS IN MAGNETIC RESONANCE, Issue 5 2006
-dipyridyl)ethene photoisomerization kinetics, Double-resonance inverse fractional population transfer application for investigation of
Abstract The analytical expression describing the dynamics of nuclear magnetization with the use of double-resonance NMR by the procedure of inverse fractional population transfer in requirements of photo-induced chemical exchange (PICE) is obtained in this article. Laser-induced (, = 308 nm) photoisomerization of 1,2-(2,2,-dipyridyl)ethene was studied by NMR and UV absorption spectroscopy under irreversible and photostationary conditions. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 337,346, 2006 [source]

NMR in photoinduced chemical exchange systems: Theoretical basis of double-resonance inverse fractional population transfer

CONCEPTS IN MAGNETIC RESONANCE, Issue 4 2006
S.P. Babailov
Abstract The analytical expression describing dynamics of the nuclear magnetization with the use of double-resonance NMR in the transfer of inverse fractional population under photoinduced chemical exchange is obtained. An experimental procedure for the definition of effective rate constants and quantum yield of responses is considered. The technical approach created allows for planning experimental strategies for the study of photoinduced chemical exchange in any solvable substances. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 299,305, 2006 [source]

Solid-state NMR characterization of 69Ga and 71Ga in crystalline solids

MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2006
Jason T. Ash
Abstract Gallium model systems containing four- and six-coordinate gallium sites have been investigated using solid-state NMR. Measurement of the isotropic chemical shift and electric field gradient (EFG) have been performed at 9.4 T on ,-Ga2O3, ,-Ga2O3, LiGaO2, NaGaO2, KGaO2, Ga2(SO4)3, and LaGaO3 using a variety of techniques on both NMR active nuclei (69Ga and 71Ga) including static, high speed magic-angle spinning (MAS), satellite transition (ST) spectroscopy, and rotor-assisted population transfer (RAPT). The chemical shift is found to correlate well with the coordination number, with four-coordinate gallium having values of approximately 50 ppm and six-coordinate gallium having values near 225 ppm (referenced to 1 M gallium nitrate solution). The magnitude of the EFG is found to be correlated to the distortion of the gallium polyhedra, with the strained systems having EFGs of 3 × 1021 Vm,2 or more, while the less strained systems have values of 1.5 × 1021 Vm,2 or less. A plot of chemical shift versus EFG suggests that solid-state NMR of gallium oxyanions can be more discriminating than liquid state NMR chemical shifts alone. Copyright © 2006 John Wiley & Sons, Ltd. [source]

HD in the primordial gas

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000
D. R. Flower
We study the role of HD in the thermal balance of the primordial gas, beyond the redshift, z, at which the temperatures of radiation and matter have decoupled (z , 300). Statistical arguments are used to derive the rate constants for the forward and reverse reactions, D+(H2, HD)H+, involving reactant and product molecules in excited rotational states. The degree of chemical fractionation of HD is enhanced, compared with the value calculated by taking account of reactions between ground-state molecules only, by a factor of about 2. In spite of its low abundance (10,3), relative to H2, HD contributes comparably to the rate of heating of the gas, through rotationally inelastic collisions with H and He. The much larger rate coefficients for collisional population transfer within HD, compared with H2, and the tighter rotational level spacing are responsible for this finding. We conclude that HD is about as important as H2 in the thermal balance of the primordial gas. [source]

Dynamical model for coherent optical manipulation of a single spin state in a charged quantum dot

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2009
Gabriela Slavcheva
Abstract The optically-induced coherent spin dynamics of a single spin confined in a charged quantum dot (QD) is theoretically studied employing coupled vector Maxwell-pseudospin formalism. Generalized pseudospin master equation is derived for description of the time evolution of spin coherences and spin populations including spin population transfer and dissipation in the system through spin relaxation processes. The equation is solved in the time domain self-consistently with the vector Maxwell equations for the optical wave propagation coupled to it via macroscopic medium polarisation. Using the model the long-lived electron spin coherence left behind a single resonant ultrashort optical excitation of the electron-trion transition in a charged QD is simulated in the low- and high-intensity Rabi oscillations regime. Signatures of the polarised photoluminescence (PL), predicted by the model, such as the appearance of a second echo pulse after the excitation and characteristic PL trace shape, are discussed for realization of high-fidelity schemes for coherent readout of a single spin polarisation state. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]