Single crystals of Ca2+, Sr2+, Ba2+, and Pb2+ beta″ alumina were prepared from sodium beta″ alumina by ion exchange. The ionic conductivities of Ca2+, Sr2+, and Ba2+ beta″ alumina are comparable, about 3 × 10?2 (ohm-cm)?1 at 300°C. Surprisingly, Pb2+ beta″ alumina is much more conductive, 1.5 × 10?1 (ohm-cm)?1 at 300°C and 4.6 × 10?3 (ohm-cm)?1 at 40°C. Its conductivity approaches that of sodium beta″ alumina at temperatures below 25°C. The diffusion coefficient for Sr2+ in beta″ alumina at 600°C was estimated from radiotracer experiments. It is consistent with that expected from conductivity measurements. 相似文献
High-resolution translational-energy spectroscopy (up to 0.1 eV) has been carried out on 8 V beams of NO? and NO2?. Several features in the spectrum of NO4 are assigned to the transitions within the triplet manifold of this ion. The observed transitions originate in several excited electronic states, indicating long lifetimes (> 10 μs) for the states involved. Two electronic transitions in NO2' have been observed at low energies which are attributed to excitations to the first two excited states of this ion. 相似文献
Lifetimes of selected vibrational levels of the predissociated Ã2Σ+ and Ã2Π electronic states of N2O+ and COS+, re- spectively, have been measured. These values have been used in conjunction with previous data on fluorescence quantum yields to obtain predissociation rates for the various vibrational levels. 相似文献
The B3LYP/6-311++G (d,p) density functional approach was used to study the gas-phase metal affinities of Guanosine (ribonucleoside)
for the Li+, Na+, K+, Mg2+, Ca2+, Zn2+, and Cu+ cations. In this study we determine coordination geometries, binding strength, absolute metal ion affinities, and free energies
for the most stable products. We have also compared the results for Guanosine, with our previously reported results for 2′-Deoxyguanosine.
Based on the results, it is obvious that MIA is strongly dependent on the charge-to-size ratio of the cation. Guanosine interacts
more strongly with Zn2+ than do with Mg2+, Ca2+, and Cu+ and therefore stronger interactions lead to higher MIA. In both free molecules and their complexes, the Syn orientation of
the base is stabilized by an intramolecular O5′–H···N3 hydrogen bond and the anti orientation of the base is stabilized by
an intramolecular C–H···O hydrogen bond formed between the (C8-H8) and the O5′ atom of the sugar moiety. It is also interesting
to mention that linear correlation between calculated MIA values and the atomic numbers (Z) of the metal ions of Li+, Na+, and K+ were found. Furthermore, the influences of metal cationization on the strength of the N-glycosidic bond, torsion angles,
angle of pseudorotation (P), and intramolecular C–H···O and O–H···O hydrogen bonds have been studied. Natural bond orbital (NBO) analysis was performed
to calculate the charge transfer and natural population analysis of the complexes. Quantum theory of atoms in molecules (QTAIM)
was also applied to determine the nature of interactions. 相似文献