Liquid-liquid extraction methods for the production of carrier-free 115cd and 89,90sr from fission products

The extraction of fission product elements with 1-phenyl-3-methyl-4-caprylpyrazolone-5 at various pH values has been investigated. The quantitative extraction of cadmium at pH 5.4 and that of strontium at pH 9.0 is utilised in devising procedures for the recovery of ¹¹⁵Cd and ^89,90Sr from the fission products. Good decontamination factors and more than 90% ¹¹⁵Cd and 80% ^89,90Sr activities were recovered.     

A CNDO/2 investigation of the CH3/CF3 substitution effect

The variation of the A-C bond lengths with substitution of methyl by perfluoromethyl in molecules of the kind A(CH₃ )_n is investigated using the CNDO/2 method. Calculations were performed with A as fluorine, oxygen, nitrogen, sulphur and phosphorous and n = 1, 2 or 3. The variation of the A-C bond length can be explained qualitatively by combining two effects, (1) changes in the covalent bond order and (2) changes in the ionic bond strength. While the covalent bond order decreases in all cases, the extent of the decrease depending largely on the electronegativity of A, the ionic bond order increases for fluorine, oxygen, nitrogen and sulphur and decreases in the case of phosphorous. The variations in the ionic bond strength are found to depend on the electronegativity of A as well as on the number of substituted methyl groups.     

Ab initio relativistic self-consistent-field (RSCF) wavefunctions for the diatomics Li2 and Be2

RSCF wavefunctions are calculated using the formalism of the authors. The results essentially agree with the non- relativistic calculations as expected because relativistic effects are negligible for these light atom diatomics.     

Production of the n2 herman infrared system by the energy pooling reaction of N2(Δ3Σ+u) metastable nitrogen molecules

Molecular N₂ emission, observed from an Ar(³Po, 2) and Xe(³P₂) + N₂ flowing afterglow apparatus, indicates that the energy pooling reaction by 2N₂(A ³Σ⁺_u) generates the emission from the Herman infrared system, which is an unassigned nitrogen band system. A lower limit to the formation rate constant for the upper state of the Herman infrared system was found to be 2.5 × 10^-11 cm³ molecule^?1 s^?1. The information presented here may help in the identification of the upper and lower states of the emission system. The 2N₂(A) energy pooling reaction also forms N₂(B³ Π_g, v? 8) but a rate constant cannot be assigned from the present data.     

Vibrational spectra,normal coordinate analysis and mean amplitudes of methyl borate,B(OCH3)3

Infrared spectra for methyl borate, B(OCH₃)₃ were recorded in the gas phase and solutions. Raman spectra were recorded for the same compound in liquid and solid states. The data were interpreted on the basis of a C_3h molecular model. A normal coordinate analysis for the complete model is included. The developed force constants were used to calculate the mean amplitudes of vibration which were compared with recent results from electron diffraction.     

Predissociation of the 3pπ D 1Πu+ state in H2, HD,and D2

Predissociation linewidths and lineshapes are reported for selected vibrational levels of the 3_pπ D ¹Π⁺_u state of H₂, HD, and D₂. We also discuss the effect of a perturbation by the 4_pδ B″B? ¹|gs_u⁺ state on the predissociation rate of the D state.     

A crossed molecular beam study of the chemiluminescent reaction Xe(3P2,0) + BrCN → Xe(1S0) + Br + CN(B2Σ+)

The chemiluminescent interaction of Xe(³P_2,0) and BrCN has been studied under crosscd-beam conditions at collision energies ranging up to 70 kj mol^?1. The CN(B → X) fluorescence spectrum, the excitation function for its production and the fluorescence polarisation - or rather its absence - have been determined. The results can be explained by a two-stage harpooning mechanism involving an inert-gas cyanide (Xe⁺CN^?)¹ intermediate but not by a “sensitisation” mechanism proceeding through electronic energy transfer.     

Calorimetric and spectroscopic studies of the critical phase transition in (CH3NH3)2[SnCl6]

(CH₃NH₃)₂[SnCl₆] undergoes a critical phase transition at 154.32 ± 0.06 K with the critical exponents α = 0.36 ± 0.04, α' = 0.19 ± 0.02, the critical entropy ratio 0.062 and the total transition entropy (1.60 ± 0.18) R. Infrared spectral change favors the order-disorder mechanism of the transition proposed from the thermodynamic data.     

The isomers of Si2H4: disilene and silylsilylene

Geometries and relative energies of the lowest singlet and triplet states of disilene and silylsilylene have been investigated using ab initio SCF and CI methods. At the most reliable level of theory employed, singlet disilene is predicted to be 8–10 kcal/mol more stable than singlet silylsilylene.     

Effect of quadratic interactions on the resonance raman scattering of T × t2 jahn-teller systems

Raman excitation profiles and depolarization dispersion curves are calculated for T × t₂ Jahn-Teller systems that are subject to quadratic vibronic (Renner-Teller) coupling as well as frequency changes of the active vibrational mode.     

1H and 13C NRM and infrared spectral studies on mixed ligand complexes of the type cis-[Co(en)2(Im)Cl]Cl2

A number of mixed ligand complexes of the type [Co(en)₂(Im)Cl]Cl₂ (Im = imidazole or a substituted imidazole) have been synthesized by reaction of trans-[Co(en₂Cl₂]Cl with the imidazole ligands. Electrical conductivity measurements support the ionic (1:2) formulation of the compounds, the electronic spectra is in agreement with an octahedral stereochemistry, and the IR and NMR (¹H and ¹³C) spectra strongly favour the cis configuration for the isolated complexes, [Co(en)₂(Im)Cl]Cl₂.Trans-[Co(en)₂Cl₂]Cl reacts with KNCS to form cis-[Co(en)₂(NCS)₂Cl, the crystal structure of which is briefly reported. This lends additional support in favour of the probable cis configuration of the above complexes.     

Chemistry of mixed ligand complexes of platinum: crystal and molecular structure of trans-[PtCl(CH3)(PEt3)(AsPh3)]

The dimethyl platinum(II) complex containing mixed ligands, cis-[Pt(CH₃)₂(PEt₃)(AsPh₃)] reacted with one equivalent of hydrogen chloride yielding trans-[PtCl(CH₃)(PEt₃)(AsPh₃)]. The X-ray crystal structure of the molecule shows the trans orientation of the PEt₃ and AsPh₃ ligands.     

Photoinitiated reactions of (η-C5H5)2MH3 (M  Nb,Ta) with Mn2(CO)10: structure of (η-C5H5)2(CO)Ta(μ-H)Mn2(CO)9

The photoreaction of (η-C₅H₅)₂TaH₃ with Mn₂(CO)₁₀ gives, inter alia, (η-C₅H₅)₂(CO)Ta(μ-H)Mn₂(CO)₉, whose crystal structure reveals an open, bent trimetallic framework. Preliminary mechanistic studies show that this and the analogous niobium reaction proceed via a complex sequence of thermal steps following photoinitiation.     

Rate coefficient for the reaction OH + HO2 = H2O + O2 at 1 atmosphere pressure and 308 K

The rate coefficient for the reaction OH + HO₂ =H₂O + O₂ has been determined from measurements of the steady-state absorption of HO₂ at 210 nm, in low-frequency square-wave modulated photolysis of O₃ + H₂O mixtures. The value obtained was (9.9 ± 2.5) × 10^?11 cm³ molecule^?1 s^?1 at 308 K and 1 atm pressure.     

A DWBA study of angular distributions for the state-to-state reactive scattering process of F + H2 → HF + H

Based on our earlier three-dimensional DWBA theory, we discuss angular distributions and the roles of various angular momenta. The theory predicts a relatively small number of partial waves, backward scattering, and broadening of angular distributions with increased energy, for the reaction F+ H₂ (v_a = 0, j_a = 0) → HF (v_b = 2 j_b = 0) + H     

N-lines and chromium-pairs in the luminescence spectra of the spinels ZnAl2O4:Cr3+ and MgAl2O4:Cr3+

It is shown that the N-lines in the luminescence spectra of the two spinels ZnAl₂O₄:Cr³⁺ and MgAl₂O₄:Cr³⁺ exhibit quite similar dependencies on chromium concentration, excitation frequency, and thermal treatment of the samples. While most of these lines are structure dependent, the line N₄ at $\text{ν}{}_{\mathrm{R}}\text{?}\text{ν}\text{≈ 400}\text{cm}{}^{\mathrm{?1}}$ and two very weak lines are in both cases due to chromium-pairs. The exchange Hamiltonian H_ex = JS₁ · S₂ + j(S₁ · S₂)² used for the ground-state splitting is fitted by the parameters J = 40.9 cm^?1, j = 1.5 cm^?1 and J = 45.6 cm^?1, j = 2.0 cm^?1 for ZnAl-spinel and MgAl-spinel, respectively. The differences between the spectra of low-doped and high-doped samples are in both cases caused by the existence of a phonon sideband of the N₄-line, which is in many respects similar to the well-known phonon side band of the R-line.     

EPR kinetic study of the reactions of F and Br atoms with H2CO

The absolute rate constants of the reactions F + H₂CO → HF + HCO (1) and Br + H₂CO → HBr + HCO (2) have been measured using the discharge flow reactor-EPR method. Under pseudo-first-order conditions (¦H₂CO¦?¦F¦or¦Br¦), the following values were obtained at 298 K: k₁ = (6.6 ± 1.1) × 10^?11 and k₂ = (1.6± 0.3) × 10^?12, Units are cm³ molecule^?1s^?1. The stratospheric implication of these data is discussed and the value obtained for k makes reaction (2) a possible sink for Br atoms in the stratosphere.     

Dissolution of Ca3(AsO4)2 · 2H2O in the system CaOAs2O5H2O at 35, 40, 45 and 50°C and the related thermodynamic data

Calcium arsenate dihydrate is precipitated at pH 7.0 and its dissolution in aqueous solutions at temperatures of 35, 40, 45 and 50°C and a pH of between 3.0 and 8.0 is investigated. The thermodynamic parameters ΔG⁰, ΔS⁰ and ΔH⁰ for the process are evaluated. Temperature dependence of solubility is obtained by the equations ?log K_TCA = $\text{9078.138}\text{T}$ ? 34.0468 + 0.0821421 T     

NMR study of water reorientation in molybdic acids: MoO3 · 2H2O and yellow MoO3 · H2O

Proton NMR relaxation times (T₂, T₁, T_1?) are reported for powder samples of MoO₃ · 2H₂O and yellow MoO₃ · H₂O in the temperature range 150–325 K and at 20 and 60 MHz. No translation of hydrogen atoms is detected but the spin-lattice relaxation behavior indicates reorientation of H₂O molecules. The waters coordinated to Mo atoms undergo 180° flips (about their C₂ axes) with similar motional parameters in both compounds. The interlayer waters in MoO₃ · 2H₂O undergo 180° flips with different parameters. An assumed Arrhenius-type temperature dependence of correlation times leads to preexponential factors which are “anomalously” low. The possible involvement of temperature-dependent activation barriers is discussed.     

Franck-condon factors for I2 lines arising from Ar, K and He-Ne laser excitation

We report Franck-Condon factors for the I₂ B → X transitions excited by several lines of Ar⁺, Kr⁺ and He-Ne lasers and observed in fluorescence. The most recent and accurate molecular constants of Luc have been used in the calculation.