Anomaly of CH4 molecular assembly confined in single-wall carbon nanohorn spaces

Vibrational-rotational properties of CH(4) adsorbed on the nanopores of single-wall carbon nanohorns (SWCNHs) at 105-140 K were investigated using IR spectroscopy. The difference vibrational-rotational bands of the ν(3) and ν(4) modes below 130 K show suppression of the P and R branches, while the Q branches remain. The widths of the Q branches are much narrower than in the bulk gas phase due to suppression of the Doppler effect. These results indicate that the rotation of CH(4) confined in the nanospaces of SWCNHs is highly restricted, resulting in a rigid assembly structure, which is an anomaly in contrast to that in the bulk liquid phase.     

Traffic states induced by slowdown sections on two-lane highway

We study the traffic states and jams occurring on a two-lane highway with a few slowdown sections. We derive the fundamental diagrams (flow-density diagrams). The fundamental diagrams on first and second lanes depend highly on the configuration of slowdown sections. The occupancy fraction of vehicles on first and second lanes varies with configuration of slowdown sections and also changes with density for the definite configuration. When a jam is formed on a lane, the flow (current) saturates on the lane. The saturated flow is given by the maximal value of the current of the slowdown section. The relationship between the densities before and after the jam is derived analytically. The dependence of jam lengths on density is derived numerically and analytically.     

Probing lattice defects in Sr2MgSi2O7:Eu2+,Dy3+

The Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺ materials were prepared with a solid state reaction and their microscopic structure (at 295 K only) and luminescence were studied at selected temperatures between 150 and 295 K. Undisturbed Sr crystal planes were common in the TEM images of the undoped Sr₂MgSi₂O₇ material, whereas with Eu²⁺ doping more disturbed planes were observed even in the nanometer scale. With Dy³⁺ co-doping, a large number of small lattice domains created by the discontinuities in the crystal structure was observed. The domains with different orientations seem to be centered around point defects. The decay curves of Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺ showed fast (ms scale) persistent luminescence. The intensity of persistent luminescence increased considerably between 200 and 250 K while remaining constant in the ranges of 150–200 and 250–295 K. The changes were used to study the depth of the traps. In general, Dy³⁺ co-doping was found to deepen the traps.     

Mixed-valence states of biferrocene derivatives having long alkyl chains

Mixed-valence states of biferrocene derivatives having long alkyl chains such as ditetradecyl, dihexadecyl, and doctadecyl substituents were investigated. A little shortening in the inter-layer length by recrystallization from CH₂Cl₂ was observed in ditetradecyl and dihexadecyl derivatives, while no difference was observed in dioctadecyl derivative. Samples having a longer inter-layer length showed a temperature independent trapped-valence state. On the other hand, samples having a shorter inter-layer length showed a temperature dependence, in which two doublets observed at 80 K approach each other with an increase of temperature to converge into one doublet which is ascribed to an averaged-valence state. The results obtained in the present study prove the fact that the crystal structure affects the mixed-valence states.     

Time-dependent57Fe-species in57Co-labeled cobalt(II) iodate studied by means of coincidence Mössbauer spectroscopy

A lifetime of unstable⁵⁷Fe(II)-species formed through EC-decay of⁵⁷Co-labeled Co(IO₃)₂ was estimated using a coincidence technique. KX-ray-gated and time-resolved emission Mössbauer spectra were measured at room temperature. No remarkable difference was found ont he relative intensity ratio of⁵⁷Fe(II)/⁵⁷Fe(III) between the X-ray-gated and time-integral emission spectra. A mean lifetime of the unstable⁵⁷Fe(II)-species was estimated to be 43±5 ns from the time-resolved emission Mössbauer spectroscopy.     

Magnetic properties of lanthanum orthoferrites containing lattice defects

Polycrystalline lanthanum orthoferrites were prepared by firing coprecipitated hydroxides of La³⁺ and Fe³⁺ at elevated temperatures. The materials fired at temperatures below 1100°C were characterized by the coexistence of such lattice vacancies that the concentration ratio of V_La:V_Fe:V_o is always equal to that of the constituent atoms of LaFeO₃. They exhibited a large magnetic susceptibility, a low Néel temperature, and a small spontaneous magnetization, in comparison with lanthanum orthoferrite without these vacancies. These characteristics originated essentially from a local reduction in anisotropic superexchange interaction at vacant sites. The lowering of Néel temperature characteristic of these materials was interpreted in terms of a decrease in the number of Fe³⁺OFe³⁺ linkages due to the existence of oxygen and iron vacancies.     

Application of Ab initio calculations to nuclear internal conversion: Repulsion energies of highly charged HBr ions

Ab initio MO calculations were applied to the evaluation of repulsion energies in highly charged HBr ions. Net charges of H and Br atoms were obtained from the Mulliken atomic population, and repulsion energies were estimated by a simplified model based on the Coulomb repulsion. The repulsion energy of HBr⁸⁺ was calculated to be 71.5 eV.     

Oxidative aromatization of 9,10-dihydroanthracenes using molecular oxygen promoted by activated carbon

Substituted 9,10-dihydroanthracenes were oxidatively aromatized to the corresponding anthracenes effectively by using molecular oxygen as an oxidant and activated carbon (Darco KB, Aldrich, Inc.) as a promoter in xylene.     

Room-Temperature Phosphorescence Emitters Exhibiting Red to Near-Infrared Emission Derived from Intermolecular Charge-Transfer Triplet States of Naphthalenediimide−Halobenzoate Triad Molecules

Room-temperature phosphorescence (RTP) emitters have attracted significant attention. However, purely organic RTP emitters in red to near-infrared region have not been properly investigated. In this study, a series of naphthalenediimide−halobenzoate-linked molecules are synthesized, one of which exhibits efficient RTP properties, showing red to near-infrared emission in solid and aqueous dispersion. Spectroscopic studies and single-crystal X-ray diffraction analysis have shown that the difference in the stacking modes of compounds affects the optical properties, and the formation of intermolecular charge-transfer complexes of naphthalenediimide−halobenzoate moiety results in a bathochromic shift of absorption and RTP properties. The time-dependent density functional theory calculations showed that the formation of charge-transfer triplet states and the external heavy atom effect of the halogen atom enhance the intersystem crossing between excited singlet and triplet states.