Cerium spectra

Impedance results obtained for aluminium substrates (AA2024-T3) treated with cerium-modified silane solutions and treated with a Cr(VI)-based conversion coating. Spectra for the reference silane and spectra for the unmodified aiioy are also included. Samples were immersed in 0.1 M NaCI. For the silane coating modified with cerium, spectra were obtained after 1 and 8 days of immersion. 

The ESR spectrum of the pyridazine radical anion, generated by the action of sodium or potassium, has been reported, and oxidation of 6-hydroxypyridazin-3(2//)-one with cerium(IV) sulfate in sulfuric acid results in an intense ESR spectrum (79TL2821). The self-diffusion coefficient and activation energy, the half-wave potential (-2.16 eV) magnetic susceptibility and room temperature fluorescence in-solution (Amax = 23 800cm life time 2.6 X 10 s) are reported. 

The reaction between Co(III) and Ce(III) has been the subject of a detailed study in a series of papers by Sutcliffe and Weber . Of particular value is the thorough investigation of the influence of anions on the rate in perchlorate media. The reaction was followed by measuring the disappearance of Co(IIl) at its absorption maximum of 650 m/i, a wavelength where both oxidation states of cerium are transparent and Co(II) absorbs only slightly. Changes in temperature and ionic strength affect the spectrum of Ce(III) at the 296 m/i maximum, but the... 

Powder XR diffraction spectra confirm that all materials are single phase solid solutions with a cubic fluorite structure. Even when 10 mol% of the cations is substituted with dopant the original structure is retained. We used Kim s formula (28) and the corresponding ion radii (29) to estimate the concentration of dopant in the cerium oxide lattice. The calculated lattice parameters show that less dopant is present in the bulk than expected. As no other phases are present in the spectrum, we expect dopant-enriched crystal surfaces, and possibly some interstitial dopant cations. However, this kind of surface enrichment cannot be determined by XR diffraction owing to the lower ordering at the surface. 

Optical Absorption Spectra and Electronic Structure The optical spectra of all the doubledeckers are listed in Table I, On first glance, Ce(0EP)2 has a "normal" spectrum (7), However, the spectrum shows extra bands and therefore should be called "hyper", A small band appears at 467 nm (maybe a ligand-to-metal charge transfer band), and broad features extend far into the near infrared (NIR), The latter absorption may be due to exciton interactions. Contrary to the known rare earth monoporphyrins (7), it has been shown for the closely related cerium(IV)... 

Another transient aminoxyl radical has been generated , and employed in H-abstraction reactivity determinations" . Precursor 1-hydroxybenzotriazole (HBT, Table 2) has been oxidized by cyclic voltammetry (CV) to the corresponding >N—O species, dubbed BTNO (Scheme 9). A redox potential comparable to that of the HPI —PINO oxidation, i.e. E° 1.08 V/NHE, has been obtained in 0.01 M sodium acetate buffered solution at pH 4.7, containing 4% MeCN". Oxidation of HBT by either Pb(OAc)4 in AcOH, or cerium(IV) ammonium nitrate (CAN E° 1.35 V/NHE) in MeCN, has been monitored by spectrophotometry , providing a broad UV-Vis absorption band with A-max at 474 nm and e = 1840 M cm. As in the case of PINO from HPI, the absorption spectrum of aminoxyl radical BTNO is not stable, but decays faster (half-life of 110 s at [HBT] = 0.5 mM) than that of PINO . An EPR spectrum consistent with the structure of BTNO was obtained from equimolar amounts of CAN and HBT in MeCN solution . Finally, laser flash photolysis (LFP) of an Ar-saturated MeCN solution of dicumyl peroxide and HBT at 355 nm gave rise to a species whose absorption spectrum, recorded 1.4 ms after the laser pulse, had the same absorption maximum (ca 474 nm) of the spectrum recorded by conventional spectrophotometry (Scheme 9)59- 54... 

The first attempts to record the Bk(IV) solution absorption spectrum were hindered by the presence of cerium impurities (92). The positions of the Bk(IV) absorption bands, superimposed on the strong Ce(IV) bands, suggested the assignment of Sf7 for the electronic configuration of Bk(IV), in agreement with the actinide hypothesis. 

Two binuclear complexes containing 2,2 -bipyridyl (bipy) have been reported in which the imido ligand appears to function in a bridging role. These are [0s2(NH)Cl2(bipy)4](C104)2, made from [Os(bipy)2(NH3)Cl]+ and cerium(TV), and Os2(NH2)(bipy)4, made from Os(bipy)2Cl2 and ammonia.173 The IR spectrum of the first complex has been recorded.294 The oxidation states seem too low for these to be true imido complexes and further investigation would certainly be of interest. 

Radiative transfer plays a role essentially when the absorption band of the acceptor ion is allowed. A photon emitted by an ion is absorbed by an other ion before escaping from the material. This requires overlap of the emission spectrum of the donor with the absorption spectrum of the acceptor. Radiative transfer between identical ions causes a modification of the spectral distribution. This is the case for the Ce + emission when the Stokes shift is small. The cerium emission originates from the lowest 5d state and consists of two bands because the ground state 4f is split by spin-orbit coupling into the states Fs/2 and F7/2 (Figme 5), the shorter-wavelength component 5d 4f( Fs/2) having the... 

All materials used in the construction of a source can contribute to the resultant spectrum emitted by that lamp. Moreover, these materials, some present at very low parts per million, can have either a transitory or permanent effect on the resultant spectrum. Some of these, e.g., the presence of iron or addition of cerium or titanium to glasses, have produced safer and/or more useful (self-cleaning) lamps. 

The spectrum recorded in the particle also contains the cenum lines, whereas only traces of the Tb features could be observed. This suggests a selective incorporation of Ce into the Pi lattice (155). The comparison of the fine structure of the Ce M4, M5 peaks of the support and the particle, Figure 4.28, also reveals some interesting information. Note the 1.8 eV shift to lower enei es, the increase of the M4/M5 intensity ratio and the attenuation of the right side lobes in the spectrum recorded in the particles. All these changes can be interpreted as due to a decrease in the oxidation state of the cerium atoms which have incorporated into the supported particles. In fact these fine structure features are in good agreement with those observed for cerium in intermetallic compounds like CePd, CeAb or in y-Ce. In all these compounds the formal oxidation state of cerium is zero. 

Until very recently the evidence for the existence of the HO2 radical in a condensed phase was based lai gely on kinetic measurements. However, recently it has been reported that the NMR spectrum of the HO2 radical may be observed in ice irradiated at very low temperatures (8, 11) and at room temperature in an aqueous solution (iO), where hydrogen peroxide is being oxidized by cerium (IV). 

A dynamics of nanocrystals formation has been also investigated. The luminescence spectra of colloidal solutions were registered during the reaction. Luminescence was excited by He-Cd laser with the wavelength of 325 nm. Fig. 1 shows the luminescence spectra of CeP04 Tb (15 mol.%) colloidal solution depending on the synthesis time. After 1 h of synthesis, the luminescence spectrum consists of the single intensive broad band with maximum at 370 nm, which corresponds to the luminescence of amorphous cerium phosphate particles. Only after 2 h of synthesis the narrow luminescence bands associated with the Af intrastate transitions of Tb were observed. The Tb ions are not... 

In the present work, the theoretical XANES spectrum for Ce02 is calculated with the DV-X(x method and the peaks therein are assigned to states which are analyzed with wavefunctions, emphasizing the local structural effects. As an application of the present method and the peak assignment, it is clarified how oxygen vacancy affects the spectra for cerium oxides. 

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