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Sodium Atom (sodium + atom)
Selected AbstractsInvestigation of structure and dynamics in the sodium metallocenes CpNa and CpNa·THF via solid-state NMR, X-ray diffraction and computational modellingMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2007Cory M. Widdifield Abstract Solid-state 23Na NMR spectra of two organometallic complexes, cyclopentadienylsodium (CpNa) and the tetrahydrofuran (THF) solvate of CpNa (CpNa·THF), are presented. Analytical simulations of experimental spectra and calculated 23Na electric-field gradient (EFG) tensors confirm that both complexes are present in microcrystalline samples of CpNa recrystallized from THF. For the solvate, 23Na NMR experiments at 9.4 T and 11.7 T elucidate sodium chemical shielding (CS) tensor parameters, and establish that the EFG and CS tensor frames are non-coincident. Single-crystal X-ray diffraction (XRD) experiments are used to determine the crystal structure of CpNa·THF: Cmca (a = 9.3242(15) Å, b = 20.611(3) Å, c = 9.8236(14) Å, , = , = , = 90° , V = 1887.9(5)Å3, Z = 8). For CpNa, 23Na NMR data acquired at multiple field strengths establish sodium CS tensor parameters more precisely than in previous reports. Variable-temperature (VT) powder XRD (pXRD) experiments determine the temperature dependence of the CpNa unit cell parameters. The combination of 23Na quadrupolar NMR parameters, pXRD data and calculations of 23Na EFG tensors is used to examine various models of dynamic motion in the solid state. It is proposed that the sodium atom in CpNa undergoes an anisotropic, temperature-dependent, low frequency motion within the ab crystallographic plane, in contrast with previous models. Copyright © 2007 John Wiley & Sons, Ltd. [source] Close coupling approach in optically allowed atomic transitionsANNALEN DER PHYSIK, Issue 12 2007S. Bougouffa Abstract In general the calculations of the cross sections in atomic collisions theory need a treatment of a system of coupled integro-differential equations. We perform a numerical technique for calculations of electrons scattering with sodium atom. The cross sections are evaluated in the close coupling approach, where the problem is formulated in three coupling channel approximation. It is found that the three-channel problem results are typically in good agreement with experiment and two-channel calculations for intermediate energy range. The difference in the other range of energy can be assigned to the number of the used set of coupled differential equations in the 32S , 32P transition of sodium. [source] Crystallographic report: A polymorph of undecasodium decatrimethylsilanolate hydroxide: [Na11(OSiMe3)10(OH)]APPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2004Michael Mehring Abstract The title compound is a polymorph of [Na11(OSiMe3)10(OH)] and was crystallized from a toluene solution containing NaOSiMe3 and water. The molecular structure is best described as being composed of two subunits, a square antiprism built from eight sodium atoms and an Na4O4 heterocubane, both sharing a sodium atom. Copyright © 2004 John Wiley & Sons, Ltd. [source] Computational Investigation of Hydrogen Adsorption by Alkali-Metal-Doped Organic Molecules: Role of AromaticityCHEMPHYSCHEM, Issue 2 2009Kancharlapally Srinivasu Abstract Hydrogen storage: Simple organic molecular systems (CnHn, n=4, 5, 6, 8) are proposed for hydrogen storage purposes based on the concept of aromaticity. The adsorption of hydrogen is attributed to pronounced charge transfer from the sodium atom (green, see picture) to the organic systems and the electrostatic interaction between the ion and hydrogen molecules. Theoretical studies on hydrogen adsorption in small organic molecular systems, such as cyclobutadiene (C4H4), the cyclopentadienyl radical (C5H5), benzene (C6H6), and cyclooctatetraene (C8H8) and their metal-doped modifications, are carried out. Our results reveal that the simple van der Waals surfaces of pure organic molecules are not good enough for hydrogen adsorption due to the weak interaction between hydrogen molecules and the organic molecular surface. However, doping of alkali-metal atoms in the above organic molecular systems increases their hydrogen adsorption ability significantly, mainly due to electron transfer from the metal atom to the carbon surface. This charged surface created around the metal atom is found to enhance the hydrogen adsorption capacity of the complex considerably, both in terms of interaction energy and the number of adsorbed hydrogen molecules, with a hydrogen adsorption capacity ranging from 10 to 12 wt,%. The role of aromaticity in such molecular systems is important in stabilizing these ionized organo-alkali-metal complexes. [source] Convergence radii of the polarization expansion of intermolecular potentialsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2009William H. Adams Abstract A new method is presented to evaluate convergence radii of the polarization expansion of interaction energies for pairs of atoms or molecules. The method is based on an analysis of the variation of the perturbed state vector as a function of the coupling constant , and does not require a calculation of perturbation corrections to high order. The convergence radii at infinite interatomic/intermolecular distances R, as well as a remarkably accurate representation of the R dependence of the convergence radii are obtained from simple calculations involving only monomer wave functions. For the interaction of the lithium and hydrogen atoms, the obtained convergence radii agree well with those obtained previously from the large-order calculations of Patkowski et al. (Patkowski et al., J Chem Phys, 2002, 117, 5124), but are expected to be considerably more accurate. Rigorous upper bounds and reasonable approximations to the convergence radii at R = , are obtained for the pairs of lithium, beryllium, boron, neon, and sodium atoms, as well as for the dimer consisting of two LiH molecules. For all the systems studied, the convergence radii are significantly smaller than the unity and rapidly decrease with the increase of the nuclear charge. It is hoped that the results of this investigation will help to analyze and eventually to compute the convergence radii of the symmetry-adapted perturbation theories which utilize the same partitioning of the Hamiltonian as the polarization expansion. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] The sodium tail of MercuryMETEORITICS & PLANETARY SCIENCE, Issue 9 2002A. E. POTTER However, when the angle of the ecliptic is near maximum in the northern hemisphere, and Mercury is near its greatest eastern elongation, it can be seen against the western sky for about a half hour after sunset. During these times, we were able to map sodium D2 emission streaming from the planet, forming a long comet-like tail. On 2001 May 26 (U.T.) we mapped the tail downstream to a distance of ,40 000 km. Sodium velocities in the tail increased to ,11 km s,1 at 40 000 km as the result of radiation pressure acceleration. On 2000 June 5 (U.T.) we mapped the cross-sectional extent of the tail at a distance of ,17 500 km downstream. At this distance, the half-power full-width of the emission was ,20 000 km. We estimated the transverse velocity of sodium in the tail to range from 2 to 4 km s,1. The velocities we observed imply source velocities from the planet surface of the order of 5 km s,1, or 4 eV. Particle sputtering is a likely candidate for production of sodium atoms at these velocities. The total flux of sodium in the tail was ,1 times 1023 atoms s,1, which corresponds to 1 to 10% of the estimated total production rate of sodium on the planet. [source] Crystallographic report: A polymorph of undecasodium decatrimethylsilanolate hydroxide: [Na11(OSiMe3)10(OH)]APPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2004Michael Mehring Abstract The title compound is a polymorph of [Na11(OSiMe3)10(OH)] and was crystallized from a toluene solution containing NaOSiMe3 and water. The molecular structure is best described as being composed of two subunits, a square antiprism built from eight sodium atoms and an Na4O4 heterocubane, both sharing a sodium atom. Copyright © 2004 John Wiley & Sons, Ltd. [source] |