Study on the extraction of trivalent lanthanide ions with N,N′-dimethyl-N,N′-diphenyl-malonamide and diglycolamide

The extraction of trivalent lanthanide (Ln(III) ions with two diamides: (1) N,N′-dimethyl-N,N′-diphenyl-malonamide (MA) and (2) N,N′-dimethyl-N,N′-diphenyl-diglycolamide (DGA) from nitric acid solution was studied. Chemical bond properties of extracted complexes were investigated by UV-VIS and FT-IR spectroscopies. The chemical bond strength between Ln(III) ions and the ligands in extracted complexes was closely related with the magnitude of the distribution ratios of Ln(III) ions: the extracted complex having a stronger bond between Ln(III) ion and the ligand showed a higher magnitude of the distribution ratio of Ln(III) ion.     

Si nanocrystallites in SiO2 with intense visible photoluminescence synthesized from SiOx films deposited by laser ablation

We observed very intense and highly reproducible photoluminescence (PL) spectra for SiO_x films obtained by laser ablation of Si targets in 50-mTorr oxygen gas followed by proper annealing. It was found that the PL peak continuously changes from 1.4 eV at the center of the samples to 1.8 eV at the sample edge. The optimum values of the oxygen component in SiO_x was x=1.3-1.4 and the optimum annealing temperature was 1000 °C for intense PL. From transmission electron microscopy images of annealed films, Si nanocrystallites are found to be formed in the matrix of SiO₂ grown from the SiO_x and have diameters of 2-3 nm. These indicate that a high density of Si nanocrystallites with diameters of 2-3 nm in the SiO₂ phase are probably responsible for the PL and that the Si nanostructure is well formed from the as-deposited, metastable SiO_x (x=1.3-1.4) films by annealing at 1000 °C.     

High-resolution gamma-ray spectroscopy of ΛLi

We report on the first observation of hypernuclear γ transitions using germanium detectors. Using a large-acceptance Ge detector system, we observed two γ transitions in _Λ⁷Li, the spin-flip transition at 689±4keV and the transition at 2050±2 keV (preliminary). The strength of the ΛN spin-spin interaction is derived from the energy of the former transition. As for the latter transition, B(E2) was measured to be 3.9±0.6±0.4 e²fm⁴ (preliminary), which indicates a shrinkage of the nuclear size of _Λ⁷Li from ⁶Li and confirms “glue-like role” of Λ.     

Excess Thermal Expansion Factors of Polar Mixtures and Aqueous Solutions

Excess thermal expansion factor of non-polar mixtures is the order of 10^–6 K^–1 and within an experimental error. On the other hand, those of polar mixtures and aqueous solutions are very large and the order of 10^–5 K^–1, up to the order of 10^–4 K^–1 in an extreme case. The excess thermal expansion factors express well the excesses of entropy volume cross fluctuation and enthalpy volume cross fluctuation estimated from thermal expansion factor and molar volume. Those of aqueous solutions are, however, reduced by small molar volume of water.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis and properties of calixarene analogs incorporating a thiophene unit in the macrocyclic ring

Calixarene analogs containing a thiophene unit in the macrocyclic ring were prepared by a stepwise method. The macrocycles adopt a cone‐like form as the preferred conformation in solution. The induced chemical shift change, nOe experiment, and ¹H relaxation time (T₁) measurement supported the fact that the macrocycle forms a complex with the N‐methylpyridinium salt. In contrast, O‐tetramethylated macrocycles and linear phenol‐formaldehyde tetramer, could not efficiently include the N‐methylpyridinium salt.     

Quantum dynamics of ultrafast photoinduced processes in organic semiconductors: exciton dissociation at polymer heterojunctions

A molecular-level, quantum-dynamical analysis of phonon-driven exciton dissociation in semiconducting polymers is presented, using a linear vibronic coupling model in conjunction with a recently developed hierarchical chain representation. Quantum-dynamical simulations in 20-30 dimensions are carried out using efficient multiconfigurational techniques. The decay of the exciton towards a charge-separated state is shown to be an ultrafast, coherent process of pronounced non-equilibrium character, which cannot be modeled by conventional kinetic equations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Anomalous delay of phonons reflected from the surface of a superlattice

We study theoretically the propagation of acoustic phonons in a superlattice (SL) with a free surface. A phonon incident normally on the SL from a substrate is perfectly reflected, but it comes back to the substrate either with a time delay or with a time advance. Specifically the time delay is enhanced considerably if the frequency of the incident phonon coincides with an eigenfrequency of the vibrational modes localized at the surface of the SL. This suggests the observability of the surface vibrational modes by a time-resolved phonon reflection experiment.     

Multi-step-direct-reaction analysis of continuum spectra of (p, α) reaction

Application of multi-step direct reaction theory to transfer reactions is demonstrated by successfully fitting continuous spectra of the ⁵³Fe(p, α)⁵¹Mn reaction taken as an example.