A new trend in the synergistic extraction of rare-earth(III) complexes with various β-diketones and 1,10-phenanthroline

The synergistic extraction of rare-earth (RE) [La(III), Sm(III), Tb(III) and Lu(III)] complexes, with three β-diketones (HA) [hexafluoroacetylacetone (Hhfa), pivaloyl-trifluoroacetone (Hpta) and benzoylacetone] in the presence of a bidentate ligand (S), 1,10-phenanthroline, in benzene was investigated. The general composition of the adducts formed is expressed as RE(A)₃S. RE(A)₃(S)₂ is also observed in La-Hhfa, La-Hpta and Sm-Hhfa systems. The adduct formation contains β_s,1 and β_s,2 and the synergistic extraction constants K_ex,s,1 were determined. The trend of these constants is discussed in terms of the RE(III), β-diketone, neutral bidentate ligand and organic solvent.     

Reactive resonances in the photodissociation of symmetric triatomic molecules: an interpretation of collinear CO2 in terms of polar coordinates

We discuss the origin of reactive scattering resonances in absorption cross sections following the collinear photodissociation of symmetric triatomic molecules. The analysis of spectra for CO₂ dissociation, previously calculated by Kulander and Light, becomes very simple in terms of polar coordinates. Of particular interest is a symmetry effect which is not observable in ordinary scattering calculations.     

Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. IX: Spectra of protiated and partially deuterated cubic magnesium caesium phosphate hexahydrate

Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO₄·6H₂O (cF100), and its partially deuterated analogues were analyzed and compared to the previously studied spectra of the hexagonal analogue, MgCsPO₄·6H₂O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the regions of HOH stretching and bending vibrations. In the difference IR spectrum of the slightly deuterated analogue (<5% D), one distinctive band appears at 2260 cm⁻¹ with a small shoulder at around 2170 cm⁻¹, but only one band is expected in the region of the OD stretchings of isotopically isolated HDO molecules. The small weak band could possibly result from second-order transitions (a combination of HDO bending and some libration of the same species) rather than statistical disorder of the water molecules. By comparing the IR spectra in the region of external vibrations of water molecules of the protiated compound recorded at RT (room temperature) and at LNT (liquid nitrogen temperature) and those in the series of the partially deuterated analogues, it can be stated with certainty that the bands at 924 and 817 cm⁻¹ result from librations of water molecules, rocking and wagging respectively. And the band at 429 cm⁻¹ can be safely attributed to a stretching Mg–O_w mode. In the ν₃(PO₄) and ν₄(PO₄) region in the infrared spectra, one band in each is observed, at 995 and 559 cm⁻¹, respectively. In the region of the ν₁ modes, in the Raman spectrum of the protiated compound, one very intense band was observed at 930 cm⁻¹ which is only insignificantly shifted to 929 cm⁻¹ in the spectrum of the perdeuterated compound. The band at 379 cm⁻¹ in the Raman spectrum could be assigned to the ν₂(PO₄) modes. With respect to the phosphate ion vibrations, the comparison between the two polymorphic forms of MgCsPO₄·6H₂O and their deuterated compounds shows that ν₁(PO₄) and ν₃(PO₄) appear at lower wavenumbers in the cubic phase than in the hexagonal phase. These data are in full agreement with the lower repulsion potential at the cubic lattice sites compared with that for the hexagonal lattice sites.     

Raman characterization of C60 salts electroformed in aqueous media

Electrochemical intercalation of C₆₀ films from aqueous LiOH, KOH, NaOH, RbOH and CsOH solutions was studied by electrochemical methods and Raman spectroscopy. The intercalation of these alkali metals cations gives rise to reduction peaks at different applied potentials depending on the chemical nature of the cation used. Reduction of the C₆₀ films was observed to rather different extents depending on the composition of the working solution. Electrochemical and Raman experiments show that K⁺ and Cs⁺ ions form the most stables and active salts, while Li⁺, Na⁺ and Rb⁺ are not significantly intercalated. Furthermore, Raman characterization of the K⁺ and Cs⁺ doped films leads to the identification of the its main components, namely the K₂C₆₀ and CsC₆₀ species.     

Vibrational spectrum of bicyclo[1.1.1] pentane

The i.r. and Raman spectra of bicyclo[1.1.1]pentane and of two of its deuterium labeled derivatives are presented. Vibrational assignments have been made and a normal coordinate analysis has been carried out using a valence force field. The resulting force constants are compared with those for cyclobutane and related molecules.     

Infra-red spectrum and force constants of the nitridorhenate(VII) ion

The i.r. spectrum of solid K₂ReO₃N was measured in the region 4000-140 cm⁻¹. All fundamentals of the ReO₃N²⁻ ion were assigned to the observed absorption frequencies, the symmetry of the ion in the crystal being approximately C_3v. The force constants of the ion were calculated using a diagonal F matrix.     

Origin of arrhythmias in a heart model

An investigation of the nonlinear dynamics of a heart model is presented. The model compartmentalizes the heart into one part that beats autonomously (the x oscillator), representing the pacemaker or SA node, and a second part that beats only if excited by a signal originating outside itself (the y oscillator), representing typical cardiac tissue. Both oscillators are modeled by piecewise linear differential equations representing relaxation oscillators in which the fast time portion of the cycle is modeled by a jump. The model assumes that the x oscillator drives the y oscillator with coupling constant $\alpha$. As $\alpha$ decreases, the regular behavior of y oscillator deteriorates, and is found to go through a series of bifurcations. The irregular behavior is characterized as involving a large amplitude cycle followed by a number n of small amplitude cycles. We compute critical bifurcation values of the coupling constant, ${\alpha }_n$, using both numerical methods as well as perturbations.     

Frequent oscillation in a nonlinear partial difference equation

This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation of these partial difference equations is discussed by employing frequency measures.      

Infrared,matrix i.r. and Raman spectra of hexachloro-2-propanol

The i.r. spectra of the alcohol CCl₃CHOHCCl₃ have been recorded in the gaseous and solid phases, in argon, krypton, nitrogen and carbon monoxide matrices and in various solutions. Raman spectra of the solid alcohol and its solutions were also recorded. Assignments of the vibration bands are made on the basis of an approximate normal coordinate calculation. The alcohol exhibits two conformers in the vapour phase and in solutions; the relative stabilities of these conformers are discussed. When the temperature is varied, a reversible interconversion between two species of the alcohol occurs in nitrogen matrices. The self-association tendency of the alcohol is very weak.