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111.
A. T. Bullock G. G. Cameron P. M. Smith 《Journal of Polymer Science.Polymer Physics》1973,11(7):1263-1269
Shape changes in the electron spin resonance spectrum of spin-labeled polystyrene have been studied as a function of temperature in the range 77–340°K. Rotational correlation times have been calculated by using recent theories of slow-motional effects on ESR spectra. Three models were used, namely, Brownian, moderate jump diffusion, and large jump diffusion. The moderate jump model gave correlation times in good accord with those found by other techniques for the δ relaxation in polystyrene. The relaxation was found to be independent of molecular weight. 相似文献
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Self-consistent wavefunctions are obtained in the HFX Xα model for a free water molecule as well as dimers and trimers. The dimer and trimer results are synthesized to deduce the contribution of the hydrogen bond to the Compton profile of water. This offers a very reasonable explanation for a substantial part of the difference between theoretical calculation on a free water molecule and experiment. 相似文献
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115.
Neutron reduced widths Γn0 and Γn1 are reported for about 200 resonances observed in neutron total cross sections of Ca40, 44, Ti48, Cr50, 52, 54, Fe54, 56, Ni58, 60, Sr88, Y89, Sn124, Te130, Ba136, 138, and Pb206, 207, 208, in the energy region 1 to 200 kev. Average parameters , , and have been derived and the Wigner distribution for local spacings and the Porter-Thomas distribution for reduced widths are verified for the resonances in the even-even nuclei Ca40, Fe56, Ni58, and Ni60. A simple method of area analysis which is less tedious and time consuming than the method reported before in Part III is also described. 相似文献
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118.
S. Iversen H. Nann A. Obst Kamal K. Seth N. Tanaka C.L. Morris H.A. Thiessen K. Boyer W. Cottingame C. Fred Moore R.L. Boudrie D. Dehnhard 《Physics letters. [Part B]》1979,82(1):51-54
π+ and π? elastic and inelastic scattering from 18O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio for the 21+ state is 1.86(16), while for the 31? state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 21+ transition and partial neutron blocking for the 31? transition. Optical model analysis of elastic scattering leads to the conclusion that . 相似文献
119.
Heteroleptic copper(II) complexes were synthesized from three different meso-substituted pyridyl- and quinoline-dipyrrinato ligands (3-pyrdpm, 3-quindpm, and 4-quindpm). Metal complexes were prepared with both acetylacetonate (acac) and hexafluoroacetylactonate (hfacac) ancillary ligands. The complexes undergo a self-complementary self-assembly process upon crystallization to generate a range of solid-state topologies including one-dimensional coordination polymers and discrete hexameric rings. The self-assembly of these molecular aggregates is driven by metal-ligand bonding, but is also modulated by fluorine-fluorine interactions. Perfluorination of the spectator ligand tends to generate more compact structures, which is attributed to aggregation of the perfluoromethyl groups. The results presented here demonstrate that fluorine-fluorine contacts can be used to modulate supramolecular structures in the solid state. 相似文献
120.
Mankad NP Rivard E Harkins SB Peters JC 《Journal of the American Chemical Society》2005,127(46):16032-16033
The phosphido-bridged dicopper(I) complex {(PPP)Cu}2 has been synthesized and structurally characterized ([PPP]- = bis(2-di-iso-propylphosphinophenyl)phosphide). Cyclic voltammetry of {(PPP)Cu}2 in THF shows fully reversible oxidations at -1.02 V (Cu1.5Cu1.5/CuICuI) and -0.423 V (CuIICuII/Cu1.5Cu1.5). Chemical oxidation of {(PPP)Cu}2 by one electron yields the class III mixed-valence species [{(PPP)Cu}2]+ (EPR, UV-vis). Structural data establish an unexpectedly large change (0.538 A) in the Cu...Cu distance upon oxidation state. Oxidation of {(PPP)Cu}2 by two electrons yields the dication [{(PPP)Cu}2]2+, an antiferromagnetically coupled dicopper(II) complex. Maintenance of a pseudotetrahedral geometry that is midway between a square plane and an ideal tetrahedron at the copper centers, along with a high degree of flexibility at the phosphide hinges, allows for efficient access to CuICuI, Cu1.5Cu1.5, and CuIICuII redox states without the need for ligand exchange, substitution, or redistribution processes. 相似文献