The absorption spectrum of gaseous fluoride ion has been observed in shock-heated vapors of CsF, RbF, and KF. The spectrum is a continuum with two sharp thresholds at 3595 and 3542 Å, similar to those of the other halide ions. The electron affinity determined from the low-energy threshold is 3.448±0.005 eV. The cross-section for photodetachment at 3565 Å is about 2.5±2×10−18 cm2 and at 3525, about 3.3±2×10−18 cm2. The electron affinities of chlorine, bromine and iodine are revised, respectively, to 3.613, 3.363, and 3.063 eV, all with uncertainties of 0.003 eV.
The crystal structure of a 1 : 1 cupric nitrate-pyrazine complex, Cu(NO3)2. (C4N2H4), was determined by single-crystal X-ray diffraction techniques. This compound crystallizes in the orthorhombic system with a= 6.712, b= 5.142, and c= 11.732/~, space group Pmna, Q= 2.19 g.cm -3 and Z= 2. The intensities of 642 unique reflections were recorded by the 20-scan method and the structure was solved by an analysis of the three-dimensional Patterson map. The structure is a coordination polymer and consists of linear -Cu-pyrazine-Cu-pyra7ine-chains. The nitrate groups lie in mirror planes normal to the chain axes and they are coordinated to the Cu H ion unsymmetrically through two oxygen atoms. Refinement by anisotropie least-squares analysis gave an R value of 0.04.
The crystal and molecular structure of tetrakispyrazole-nickel chloride, Ni(C3H4N2)4C12, was determined by single-crystal X-ray diffraction techniques. Ni(C3H4N2)4CI2 crystallizes in the monoclinic system with a= 13.876+0.001, b=9.263 +0.006, c= 14.451 +0.003/~, p= 116.83+0.01 o, space group C2/c, 0o = 1.61 g.cm-3 and Z= 4. Three-dimensional data (2401 reflections) were used and the structure solved by an analysis of the Patterson map. The Ni(C3HaN2)4C12 molecule is centrosymmetric with the nickel atom at the center of an octahedron formed by two chlorine atoms and a nitrogen atom from each of the four pyrazole molecules. One pair of coordinated nitrogen atoms lies 2-097 A and the other pair 2.087/~ from the nickel atom. The nickel-chlorine vector makes an angle of 0.4 ° with the normal to the plane of the coordinating nitrogen atoms and the chlorine atoms lie 2.507 It from the nickel atom. The pyrazole rings were found to be planar within experimental error. Final refinement by a three-dimensional anisotropic least-squares analysis resulted in an R value of 5"4 ~.
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