[en] A stirred aqueous solution of alkali hydroxide or carbonate or ammonium hydroxide or carbonate is reacted with a suitable solid crystalline Ce(IV) salt such as cerium(IV) sulfate or nitrate or ammonium cerium(IV) sulfate or nitrate. The amount of the hydroxide or carbonate must be equal to or higher than the stoichiometric quantity. The Ce salt may contain as much as 50% other rare earth elements. The product can be characterized by the formula CeO₂.xH₂O with x approaching 2, and it roughly retains the macrostructure of the starting solid salt. The procedure is easy to perform and has low energy demands. It can find application as the final step in the preparation of a hydroxide cerium concentrate or as an intermediate step in the preparation of CeO₂. The suspension can be easily filtered, and a product which can be used as a glass polishing powder can be obtained by drying and calcination of the filter cake. (P.A.)

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[en] The level structure of light cerium isotopes has been studied

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[en] In this study, we determined the most appropriate Hamiltonian that is needed for the present calculations of energy levels and B(E2) values of ^128-138Ce nuclei which have a mass around A≅ 130 using the interacting boson model (IBM). Using the best fitted values of parameters in the Hamiltonian of the IBM-2, we have calculated energy levels and B(E2) values for a number of transitions in ^{128,130,132,134,136,138}Ce. The results were compared with the previous experimental and theoretical (PTSM model) data and it was observed that they are in good agreement. Also some predictions of this model have better accuracy than those of PTSM model. It has turned out that the interacting boson approximation (IBA) is fairly reliable for calculating spectra in the entire set of ^{128,130,132,134,136,138}Ce isotopes and the quality of the fits presented in this paper is acceptable. (author)

[en] The decays of the neutron-rich nuclides ¹⁴²La, ¹⁴⁴La, ¹⁴⁶La and ¹⁴⁸La to the levels of the transitional nuclides ¹⁴²Ce, ¹⁴⁴Ce, ¹⁴⁶Ce and ¹⁴⁸Ce, respectively, have been studied using mass-separated sources. Angular correlation studies have been employed to identify new excited 0⁺ levels in ¹⁴⁶Ce and support spin and parity assignments for 1^-, 3^-, 2⁺, 3⁺, 4⁺ and 6⁺ levels in ¹⁴⁴Ce and ¹⁴⁶Ce. An excited 0⁺ level in ¹⁴⁸Ce is indicated by coincidence ratios and electron studies, while no clear evidence can be found for the location an excited 0⁺ level below 2 MeV in ¹⁴⁴Ce. The resulting isotonic and isotopic systematics are discussed in terms of the transition from the closed shells at N = 82 and Z = 50 to the region of deformed nuclides. (orig.)

[en] Cerium is an element of rare earth group which is called lanthanide series. It is found in the ores like monazite and xenotime which are the tailings of tin mines in the south of Thailand. Cerium is used mostly as lens polishing powder besides the applications in other industries. In this study, cerium extracted from monazite ore breakdown by alkaline process was used for the preparation of lens polishing powder. Cerium hydroxide cake from the process was dissolved by hydrochloric acid and precipitated with oxalic acid. The oxalate precipitate then was calcined to oxide powder and its particle size was measured. Precipitation conditions being studied are concentration of feed cerium chloride solution, concentration of oxalic acid used for the precipitation, concentration of sulfuric acid used as precipitation control reagent and the precipitation temperature. It was found that the appropriate precipitation conditions yielded the fine oxide powder with particle size about 12μm. The oxide powder can be ground to the size of 1-3 μm which is suitable for making lens polishing powder

[en] High resolution crossed beam resonance fluorescence laser spectroscopy has been performed on an atomic beam of naturally occurring cerium, and isotope shifts have been measured in several transitions. Changes in mean square charge radius, δ left angle r² right angle, have been extracted using the King plot technique and show the characteristic increase at the N=82 neutron shell closure. The measurements form the basis for further investigations of radioactive isotopes and isomers on both sides of the shell closure. (orig.)

[en] The absorption spectra below the 4d threshold of cerium in Ce metal, CeF₃ and CeO₂ compounds were measured by using a CDM (Constant Deviation Monochromator) at the Photon Factory, KEK. The difference in structure between these spectra is discussed. The structure appeared in CeO₂ were considered to be due to the tetravalent configuration of cerium (Ce⁴⁺) in the ground state. (author)