Free ions Pr IV (4\text{ f }^{2}) and Tm IV (4\text{ f }^{12}): intermediate versus LS coupling scheme

The intermediate and LS-coupling schemes for the free lanthanide ions $\text{ Pr }^{3+}$ Pr 3 + and $\text{ Tm }^{3+}$ Tm 3 + have been compared by the matrix elements of the tensor operator ${{\varvec{U}}}^{({\varvec{k}})}, \text{ k } = 2, 4, 6$ U ( k ) , k = 2 , 4 , 6 . The necessary eigenvectors and eigenvalues have been computed with the aid of four parameters, $\text{ F }_{2}, \text{ F }_{4}, \text{ F }_{6}$ F 2 , F 4 , F 6 , and $\zeta _{4\mathrm{f}}$ ζ 4 f , known from free-ion spectra of the same ions. It has been found that both coupling types for each ion lead to close values of ${\vert }{{\varvec{U}}}^{({\varvec{k}})}{\vert }^{2}$ | U ( k ) | 2 only for transitions from the ground level to certain lower-lying energy levels within the $4\text{ f }^\mathrm{N}$ 4 f N configuration.     

Spin symmetry conservation rule in free radical reactions

The spin structures of the equilateral and isosceles H₃ radical are characterized on the basis of the magnetic point group. A selection rule in free radical reactions is also derived from magnetic group-theoretical considerations.     

Radial and angular correlation in heliumlike ions

In the framework of nonrelativistic variational formalism a new type of basis set is proposed, to estimate separately the effect of radial and angular correlations on the ground‐state energy for helium isoelectronic sequence H^? to Ar¹⁶⁺. Effect of radial correlation is incorporated by using multiexponential functions arising from product basis sets suitably formed out of Slater‐type one‐particle orbitals. The angular correlation can be switched on by incorporating an expansion in terms of basis involving interparticle coordinates. With a set of six‐term Slater‐type one‐particle basis and five‐term interparticle expansion, the ground‐state energy of helium is estimated as ?2.9037236 (a.u.) compared with the multiterm variational estimates ?2.9037244 (a.u.) due to Pekeris and Thakkar and Smith and Drake. Matrix elements of different operators in the ground state have been calculated and found to be in good agreement with available accurate results. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Spin violation in double-electron capture by Ar4+ ions

Translational energy spectroscopy has been employed to study state-selective double-electron capture by 8 keV Ar⁴⁺ in He and Ne targets, and 12 keV Ar⁴⁺ in He. The capture spectra are dominated by reaction channels which violate spin conservation. The double capture spectra for Ar⁴⁺ in He contain intense peaks which involve capture from the metastable quintet ⁵S⁰ state of Ar⁴⁺, recently identified in single capture spectra for Ar⁴⁺ in He and Ne.     

Spin-free quantum chemistry. XVI. Spin correlation

We discuss the calculation of quasielastic critical neutron scattering for systems defined by a spin-free Hamiltonian. The system dependent property which determines the critical scattering is the thermal average of a spin-free operator called the general unpaired electron correlation operator. For localized models, we obtain the scattering as the Fourier transform of an unpaired site correlation function. The algebraic relationship between this correlation function and the usual spin correlation function is discussed as are its relationships to thermodynamic properties. Correlations in the infinite interaction range model, linear spin wave model, and infinite chain Heisenberg model are given. In the last case, an estimate of the low temperature correlation length is made.     

Rare earth ions in a hexagonal field IV

Energy levels and eigenfunctions of rare earth ions in a crystal field of hexagonal symmetry have been obtained using a Hamiltonian of the form $\text{H}$ = B°₂O°₂ + B°₄O°₄. Results are presented for all J values appearing in the rare earth series. The order of the energy levels has been determined for all relative values of the second and fourth order crystal field intensity parameters, B°₂ and B°₄. This, of course, includes information for the commercially significant RCo₅ compounds, for which the second order term is dominant. The eigenfunctions are pure M states with permanent magnetic moments ± Mg μ_B. The moments are unchanged by a field applied along the c axis.     

焦磷酸盐水溶液中稳定Pr(IV)和Tb(IV)的研究

本文报道了在焦磷酸盐的碱性水溶液中用O~3氧化Pr(III)和Tb(III),从而得到Pr(IV)-P~2O~7^4^-和Tb(IV)-P~2O~7^4^-的配合物溶液,通过对溶液进行化学分析及吸收光谱的研究,证明了溶液中有Pr(IV)和Tb(IV)的存在,其持征吸收分别为λmax=365nm,摩尔消光系数ε=1205L/mol.cm;/.pr(iv)=257nm,ε=929L/mol.cm.在碱性条件下,Pr(IV)和Tb(IV)的还原反应均为拟一级反应.用动力学方法测定了不同条件下Pr(IV)和Tb(IV)的还原速率常数和半衰期,从而探讨了稳定Pr(IV)和Tb(IV)的条件.同时还测定了在反应条件下Pr(IV)/Pr(III)和Tb(IV)/Tb(III)电对的克式电位。     

Effect of crystal structure and ions concentration on luminescence in Yb and Tm codoped fluoride microcrystals

A facile hydrothermal method is used for the preparation of Tm³⁺/Yb³⁺ codoped fluoride microphosphors. The effect of crystal structure and ions concentration on the spectra and lifetimes of the radiative levels of Tm³⁺ ions in the different fluoride microcrystals is studied in detail. XRD analysis of Tm³⁺/Yb³⁺ codoped LaF₃ microcrystals shows that 20% Yb³⁺ doping is sufficient for hexagonal LaF₃ microparticles to crystallize completely in the orthorhombic phase. And lifetime analysis suggests that the average lifetimes of the radiative levels of Tm³⁺ ions increased when the matrix phase structure changing from orthorhombic phase to hexagonal phase with ytterbium dopant concentration changing.     

稀土离子Pr3+和Tm3+多重态间电偶极跃迁约化矩阵元的计算

利用M.F.Reid的f壳层经验程序和P.A.Tanner发表的氯冰晶石Ca2NaLnCl6体系中Pr3+和Tm3+离子的能级参数计算出它们的基组态的中间态波函数14fN?SLJ(共13个),然后将其代入单位张量算符U(?)(?=2,4,6)的约化矩阵元公式中,分别计算出Pr3+和Tm3+离子的各个多重态之间电偶极跃迁的约化矩阵元的值.对该约化矩阵元在分析激发态吸收几率或能量传递几率的应用做了讨论.     

New correlation effects in the photoionization of atoms and ions

Recent advances in experimental and computational capabilities have provided the impetus for highly detailed studies of the photoionization process in atoms and ions. As a result, there have been a number of new phenomena uncovered. And these new phenomena are, in a general sense, of correlation among the atomic electrons, i.e., the breakdown of the single-particle approximation. Of particular interest are cases where correlation is not merely a small perturbation on the single-particle model, but where correlation dominates the process. In this paper, a number of illustrative experimental and theoretical examples are presented in which electron–electron correlation is seen to be a primary determinant of the process.     

Ion-exchange equilibria of metal ions and hydrogen ions on anilinium tin(IV) phosphate

Summary Ion-exchange equilibria of metal ions (Mn^II, Cu^II, Zn^II, Cd^II and Hg^II)/H⁺ systems have been studied at 30, 40, 50 and 60°C on anilinium tin(IV) phosphate (ATP) as a cation exchanger. The exchange isotherms were measured for both forward and reverse reactions with a solution of ionic strength 0.1 by the batch technique. The isotherms are S-shaped for each ion-exchange system. Selectivity coefficients vary linearly with the equivalent fraction of transition metal ion in the exchanger in the range from 0 to 0.6. The selectivity sequence of zero loading is: Zn^II <Mn^II<Cu^II<Cd^II<Hg^II. Overall and hypothetical (zero loading) thermodynamic data are evaluated.     

The correlation potential for two-electron atomic ions

The correlation potential is computed for two electron atomic ions with atomic numbers from 1 to 10 using the charge density reconstructed from a natural orbital expansion of a Kinoshita-like atomic wave function. Over the wide range of densities involved, the correlation potentials are not even approximately a local function of the density.     

Spectroscopic properties of Pr3+ ions in a PbWO4 single crystal

Site-selective fluorescence laser spectroscopy of Pr (3+) ions in lead tungstate single crystal were investigated at temperatures from 10 to 300 K. The site-selective emission spectra and fluorescence decays from the (3)P J ( J = 0, 1, 2) and (1)D 2 states were analyzed. The (3)P J ( J = 0, 1, 2) level shows its predominantly radioactive character with the typical greenish-blue luminescence ascribed to (3)P J transition. The emission from the (1)D 2 level is only observed when this level is directly excited. The decay kinetic of the (1)D 2 level was measured under site-selective excitation and discussed in terms of cross-relaxation. The up-conversion emission from levels (3)P 1 and (3)P 0 following excitation of the (1)D 2 state was observed in the PbWO 4 crystal between 10 and 300 K. The main up-conversion mechanism, together with the understanding the quenching of the (1)D 2 fluorescence in this Pr (3+) heavily doped PbWO 4 were discussed. The presence of the complex structures of the emission spectra and different decay profiles indicate that several processes contribute to the quenching of the (1)D 2 fluorescence of Pr (3+) ions. It was found that the up-conversion fluorescence intensity had a quadratic dependence on the laser input power. The temporal behavior of the up converted emission indicates that an energy-transfer up-conversion is the dominant process.     

Emission and excitation spectra of Ce3+ and Pr3+ ions in hexafluoroelpasolite lattices

The emission and excitation spectra of Ce(3+) and Pr(3+) doped into the cubic host Cs(2)NaYF(6) have been recorded at room temperature and ～10 K using synchrotron radiation. The two 5d(1) T(2g) states of Ce(3+) have been located from the excitation spectra, whereas the E(g) state is placed above the host band gap. Decay measurements of the 5d(1) → 4f(1) Ce(3+) emission, and spectra collected using selective excitation, indicate the occupation of more than one type of site by Ce(3+) in this host lattice. By contrast, the location of features in the 4f(1)5d(1) → 4f(2) emission of Pr(3+) is independent of the excitation wavelength. Assignments are presented for some of the 4f(1)5d(1) levels and for the Pr(3+)-F(-) charge transfer band. The 5d emission lifetimes for Ce(3+) and Pr(3+) in the Cs(2)NaYF(6) host are 42 and 29 ± 1 ns, respectively, and are not temperature-dependent.     

Reactions of pentaamminechloroplatinum(IV) with iodide and sulfite ions

The reactions of pentaamminechloroplatinum(IV) with potassium iodide and sodium sulfite are studied. In the presence of an equimolar amount of the iodide, the chloride ions are completely substituted without subsequent displacement of the ammonia molecules that are in the trans position to the entering iodide ions. The reaction with sodium sulfite is accompanied by the reduction of Pt(IV) to Pt(II). The reaction kinetics of pentaamminechloroplatinum(IV) with potassium iodide at 22, 40, and 50°C are studied. The rate constants and activation energy of this reaction are calculated.     

Chromatographic behaviour of metal ions on tin(IV) and titanium(IV) antimonate papers

Summary The chromatographic behaviour of 49 metal ions has been studied on papers impregnated with Sn(IV) and Ti(IV) antimonates in aqueous HNO₃ and mixed solvent systems containing dimethyl sulphoxide. Numerous separations have been achieved and the Alberti equation, for Sn(IV) and Ti(IV) antimonate papers, in the modified form: –nloga K⁺=R_M + constant (a K⁺=activity of K⁺), has been verified. The effect of the concentration of impregnating reagents on these papers has been determined and compared with other papers. The effect of pH on R_f, R_i, log R_f and R_M values of metal ions has also been examined in aqueous systems.