Microwave spectrum of CH3OD

The microwave spectrum of CH₃OD has been observed in the frequency region between 14 and 92 GHz. All the ground-state transitions with J ≤ 8 and J = 2 ← 1, a-type transitions in the excited torsional states (v = 1 and v = 2) have been observed. The spectrum has been analyzed and rotational constants, torsional constants, torsion-vibration-rotation interaction constants, and centrifugal distortion constants have been evaluated. The Stark effect measurements have been made and the dipole moment components have been determined as μ_a = 0.833 ± 0.008 D and μ_b = 1.488 ± 0.015 D.     

Novel soft chemical method for optically transparent Ru(bpy)3-K4Nb6O17 thin film

A unique guest-guest ion exchange method was developed for preparing a thin film of a nano-layered K(4)Nb(6)O(17).3H(2)O that possesses both (1) optical transparency and (2) ion-exchangeability under ambient conditions without calcination at high temperature. An optically transparent Ru(bpy)(3)(2+)-K(4)Nb(6)O(17) hybrid thin film, a photoresponsive electrode, was successfully prepared by the guest-guest exchange method by use of the intercalation compound MV(2+)-K(4)Nb(6)O(17) as a precursor. The optically transparent Ru(bpy)(3)(2+)-K(4)Nb(6)O(17) hybrid thin films have been characterized by X-ray diffraction, SEM, AFM, IR, and UV spectroscopies, as well as elemental analysis. The electrochemical behavior of the ITO/Ru(bpy)(3)(2+)-K(4)Nb(6)O(17) hybrid thin film electrode was studied; it also exhibits swift photoresponse in the visible region.     

Texture in the superconducting order parameter of CeCoIn5 revealed by nuclear magnetic resonance

We present a 115In NMR study of the quasi-two-dimensional heavy-fermion superconductor CeCoIn5 believed to host a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state. In the vicinity of the upper critical field and with a magnetic field applied parallel to the ab plane, the NMR spectrum exhibits a dramatic change below T*(H) which well coincides with the position of reported anomalies in specific heat and ultrasound velocity. We argue that our results provide the first microscopic evidence for the occurrence of a spatially modulated superconducting order parameter expected in a FFLO state. The NMR spectrum also implies an anomalous electronic structure of vortex cores.     

Spectroscopic observation of bipolaronic point defects in Ba(1-x)KxBiO3

An infrared-absorption band centered at 0.85 eV, which is below the big optical absorption at the charge-density-wave (CDW) gap energy of 1.85 eV, has been observed for semiconducting single crystalline Ba(1-x)KxBiO3. With substituting K for Ba, the spectral weight of the new band increases with x, while that of the CDW-gap excitation decreases. Since the impurity state with the K substitution is known to be nonmagnetic at low temperatures, Bi3+ the state with 6s2 electrons surrounded by the six Bi5+ ions forms a small bipolaron by losing a pair of electrons in the Rice-Sneddon model. The new band is assigned to a transition from the lower-Peierls band to a state of the bipolaronic point defect.     

Iridium complex-catalyzed highly enantio- and diastereoselective [2+2+2] cycloaddition for the synthesis of axially chiral teraryl compounds

An asymmetric [2+2+2] cycloaddition of an alpha,omega-diyne, possessing ortho-substituted aryl groups on its terminus, and a monoalkyne with oxygen functionalities gave various axially chiral teraryl compounds. The coupling proceeded with extremely high enantio- (>99.5% ee) and diastereoselectivities (dl/meso = >95/5) when catalyzed by an iridium-chiral phosphine complex. As the products were readily transformed into diol compounds by deprotection without racemization, the present procedure provides access to a new chiral pool of diol compounds with C2 symmetry.     

Observation of a liquid-gas-type transition in the pyrochlore spin ice compound Dy2Ti2O7 in a magnetic field

Low temperature magnetization measurements on the pyrochlore spin ice compound Dy2Ti2O7 reveal that the ice-rule breaking spin flip, appearing at H approximately 0.9 T applied parallel to the [111] direction, turns into a novel first-order transition for T<0.36 K which is most probably of a liquid-gas type. T-linear variation of the critical field observed down to 0.03 K suggests the unusual situation that the entropy release across the transition remains finite [approximately 0.5 (J/K) x mol-Dy] as T-->0, in accordance with a breaking of the macroscopic degeneracy in the intermediate "kagomé ice" state.     

Field-induced thermal metal-to-insulator transition in underdoped La(2-x)Sr(x)CuO(4+delta)

The transport of heat and charge in cuprates was measured in single crystals of La(2-x)Sr(x)CuO(4+delta) (LSCO) across the doping phase diagram at low temperatures. In underdoped LSCO, the thermal conductivity is found to decrease with increasing magnetic field in the T-->0 limit, in striking contrast to the increase observed in all superconductors, including cuprates at higher doping. In heavily underdoped LSCO, where superconductivity can be entirely suppressed with an applied magnetic field, we show that a novel thermal metal-to-insulator transition takes place upon going from the superconducting state to the field-induced normal state.     

Reversible light-driven structural changes between the mono- and bilayer stacking alignments in 4-octadecyloxystilbazolium arylcarboxylate films

The present investigation deals with the light-driven morphological changes in multilamella films of N-methyl-4-octadecyloxystilbazolium arylcarboxylates (C18OStz+X-) cast on glass slides. The results of XRD analysis show a photostimulated layer expansion and shrinkage of the stacked thin films along the c-axis under alternative illumination at >350 and 254 nm, respectively. It was revealed that such lamellar changes could be switched either way by a reversible transformation between the mono- and bilayer units in these stacked multilamella films. Moreover, such controlled structural adjustments in the alignment could be initiated by the photocyclodimerization of the stilbazolium moieties of the arylcarboxylate salts; i.e., a monolayer-to-bilayer transformation could be induced at a stage of only 10% cyclodimer formation. The photoinduced patterning on the surface of the films was also analyzed by SEM and fluorescence microscopic investigations.