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21.
Furman JD Melot BC Teat SJ Mikhailovsky AA Cheetham AK 《Physical chemistry chemical physics : PCCP》2011,13(17):7622-7629
Three novel inorganic-organic framework compounds containing the organic chromophore ligand 9-fluorenone-2,7-dicarboxylic acid (abbreviated H(2)FDC) and barium (BaFDC), cadmium (CdFDC) and manganese (MnFDC), respectively, have been synthesized and evaluated for their use as phosphor materials for solid state lighting and other applications. The results are compared with two earlier reported structures containing the same ligand with calcium (CaFDC) and strontium (SrFDC). The barium- and cadmium-containing compounds both show blue excited, yellow photoluminescence, while the manganese structure does not. The trends in luminescent efficiency for the Ba, Cd, Ca, and Sr derivatives are discussed in relation to crystallographic, optical, and low-temperature specific heat considerations. 相似文献
22.
23.
Study of magnetoresistance and conductance of bicrystal grain boundary in La0.67Ba0.33MnO3 thin film
La0.67Ba0.33MnO3 (LBMO) thin film is deposited on a 36.7°C SrTiO3 bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics
are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial
magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears
at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic
conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese
atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance
with the increase in temperature is due to enhanced spin-flip scattering process. 相似文献
24.
Subramaniam Ramdas John M. Thomas Paul W. Betteridge Anthony K. Cheetham E. Keith Davies 《Angewandte Chemie (International ed. in English)》1984,23(9):671-679
The unique structural, adsorptive, and catalytic properties of zeolites are particularly amenable to illustration by computer (especially color) graphics. The siting of cations, the accommodation of guest reactant or product species, as well as the occurrence of various kinds of intergrowths (e.g. twin planes and coincidence boundaries) within these microporous solids can all be effectively portrayed by graphical means in such a manner as to emphasize the shape-selective character of the host zeolite. The dynamics of translational and angular motion of guest species (for example benzene) in a channel of molecular dimensions within a typical zeolitic solid (for example silicalite) can also be probed interactively using appropriate potential functions. 相似文献
25.
The structural and conductivity data on silver orthophospate described recently by Deschizeaux-chèuy et al. are considered in the context of earlier work on the same subject. The results of powder neutron (PND) and single crystal X-ray diffraction (SXD) analyses of Ag3P04 provide a consistent picuture of how the I-Ag3P04 structure evolves with temperature. A comparison of independent analyses of II-Na3P04 by PND and SXD demonstrates that solution and refinement of the structures of even highly disordered superionic materials can, in certain cases, be accomplished using powder diffraction data. 相似文献
26.
27.
28.
29.
MJ Singh DO Kataria N Madhavan P Sugathan JJ Das DK Awasthi AK Sinha R Shanker 《Pramana》1999,53(4):743-764
A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer
processes in collisions of 60–120 MeV Si
q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization,
electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated.
The data reported on the present collision system result from a direct measurement in the considered impact energy for the
first time. The total ionization cross-sections for the recoil ions are shown to scale as q
1.7/E
p
0.5
, where E
p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing
recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j
2 upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing
cross-sections σ
qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow
our data for different ionization processes is reviewed and discussed. 相似文献
30.
Using the heavy quark approximation, we have studied the nonleptonic decay mode Λ
b
→Λ
c
a
1. We have included nonfactorizable contributions as well as factorizable ones in our analysis. The estimated branching ratio
for this process is (1.4±0.1)% and the asymmetry parameter α found to be −0.8. 相似文献