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Optically pumped laser emission has been observed on the NaK 2(A)1+ 1(X)1+ electronic state transition. The emission occurs between 1.015 and 1.035 m when a sodium-potassium heat-pipe oven is pumped with 695–745 nm pulsed dye laser radiation. The laser emission occurs on many ro-vibrational transitions without the use of cavity mirrors. However, the addition of a simple cavity increases both the number of observed lasing transitions and the amplitude of the emission on each line. We report our results for the dependence of the emission intensity on pump laser power, oven temperature, and buffer gas pressure. 相似文献
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The high temperature phase relations (20°C) of LiH2PO4, NaH2PO4, KH2PO4, RbH2PO4, CsH2PO4, NH4H2PO4, KH2AsO4, RbH2AsO4, CsH2AsO4 and NH4H2AsO4 have been studied. All materials decompose at higher temperatures. Solid—solid transitions are studied when present and transition temperatures, transition enthalpies, decomposition temperatures, decomposition enthalpies and decomposition products are discussed. 相似文献
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Yu Gui Gu Xiaolin Zhang Richard F. Clark Stevan W. Djuric Zhenkun Ma 《Tetrahedron letters》2004,45(15):3051-3053
An intramolecular 1,3-dipolar cycloaddition of azomethine ylide, generated in situ via the reaction of C12-glycinate derivative of macrolide with formaldehyde, provided a novel tricyclic macrolide. The high stereoselectivity of this [2+3] reaction was achieved by introducing a suitable directing group at C-6 position of macrolide. 相似文献
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The role of search theory in the exploitation of natural resources is discussed in this paper. After a brief history and taxonomy of search problems, the mathematics of search is discussed. This includes underlying probability distributions, the differential equations of search, Bayesian use of search information and optimization problems in search theory. The theory is illustrated by applications in fisheries, pest control, animal foraging, and oil and mineral exploration. 相似文献
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Ab initio molecular orbital structures and energies of B2F4, B2Cl4, N2O4, and C2O have been calculated for both perpendicular D2d and planar D2h rotamers. The experimental trend toward greater preference for the D2d forms in going from B2F4 to B2Cl4 is reproduced. N2O4 favors the planar conformation, although the rotation barrier is overestimated at the theoretical levels used. The oxalate dianion is calculated to be more stable in the D2d conformation; the experimental planar arrangement in the solid may be due to crystal packing forces. The preferences for one conformation over another are small; analysis indicates that different effects may predominate in each case: π stabilization for B2F4, hyperconjugation for B2Cl4, lone-pair interactions for N2O4, and electrostatic repulsions for C2O. 相似文献
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G.R. Clark T.J. Collins K. Marsden W.R. Roper 《Journal of organometallic chemistry》1983,259(2):215-232
Reaction of HgR2 with OsHCl(CS)(PPh3)3 yields red, five-coordinate, OsRCl-(CS)(PPh3)2 (R = p-tolyl). From this have been derived the compounds OsRX(CS)(PPh3)2 with X = Br, I, S2CNEt2, O2CMe, O2CCF3. These compounds add an additional ligand, MeCN, CO or CNR to form colourless, six coordinate arylthiocarbonyl complexes, which undergo migratory-insertion reactions to form red, dihapto-thioacyl complexes. The crystal structure of a representative example, Os(η2-CSR)(η1-O2CCF3)(CO)PPh3)2 has been determined. The red equant crystals are orthorhombic, space group P212121, a 11.584(1), b 19.184(2), c 18.90(1) Å, V 4199 Å3, Z 4. The structure was solved by conventional heavy-atom methods and refined by full-matrix least-squares employing anisotropic thermal parameters for all non-hydrogen atoms except the carbon atoms of the triphenylphosphines. The final R factor is 0.057 for 2868 observed reflections.The coordination geometry in the monomeric complex is that of an octahedron distorted by the constraints of the ligands. The triphenyl phosphine ligands are mutually trans; the equatorial plane contains carbonyl, monohapto-trifluoroacetate, and dihapto-thioacyl ligands. Bond distances and angles are OsP 2.405, 2.407(4) Å; POsP 173.9(1)°; OsCO 1.83(2) Å; Os-O (trifluoroacetate) 2.206(11) Å; OsC (thioacyl) 1.91(2); OsS 2.513(6); CS 1.72 Å. The CS bond length implies a reduction in bond order from 2.0 to approx. 1.5 upon coordination to the metal.The η2-thioacyl ligand in Os(η2-CSR)Cl(CNR)(PPh3)2 is methylated with methyl triflate and further reaction with LiCl produces the thiocarbene complex OsCl2(C[SMe]R)(CNR)(PPh3)2. 相似文献