Unusual low-temperature thermodynamic properties of pellet samples of (DMe-DCNQI)<Subscript>2</Subscript>M (<Emphasis Type="Italic">M</Emphasis>=Li,Ag)

Summary We have performed low-temperature heat capacity measurements on pellet samples of (DMe-DCNQI)₂M (M=Li, Ag) which is known to show spin-Peierls transitions at 51 and 86 K, respectively. A linearly temperature-dependent term in the low-temperature heat capacity has been observed for both the samples: It is attributable to the spin-wave excitations induced by the inhomogeneous pressure effects produced in the pellet forming process. Although the temperature dependences of the magnetic susceptibility in both materials are almost the same, the coefficient of T-linear term of the Ag salt becomes three times larger that that of the Li salt. The peculiar electronic state originating from the competition of the spin-Peierls mechanism and the Coulomb repulsion is suggested.     

Fluorescence detection with an immersed flow cell in capillary electrophoresis

An immersed flowcell has been developed for fluorescence detection in capillary electrophoresis (CE) by modifying an ordinary HPLC spectrofluorimetric detector flowcell. The minimum detectability obtained for riboflavine was about 4 fmol. The use of the flowcell to measure a fluorescence spectrum by the stopped-flow method of shutting down the DC high voltage during a wavelength scan, has also been achieved successfully.     

Microwave spectra of deuterated ethanes: Internal rotation potential function and rz structure

The microwave spectra of CH₃CHD₂ in the first excited torsional state and of CH₃CH₂D and CD₃CH₂D in the ground states have been observed by a source-modulation spectrometer and analyzed to determine the two potential constants, V₃ and V₆, simultaneously and also to assess the isotopic effects on the potential function. The results obtained for C₂H₆ are V₃ = 2.882 ± 0.010 and V₆ = 0.020 ± 0.010 kcal/mole. The staggered conformation in ethane was established by observing microwave spectra of gauche CH₂DCH₂D. The r_z structure of ethane was recalculated by adding precise rotational constants obtained in this work to previous microwave and infrared data.     

Emergence of BLOCH bands in a rotating Bose-Einstein condensate

A rotating Bose-Einstein condensate is shown to exhibit a Bloch band structure even in the absence of a periodic potential. Vortices enter the condensate via Bragg reflection if the frequency of a rotating drive is adiabatically increased or decreased, or if the interaction is adiabatically changed at a constant rotating drive. A localized state analogous to a gap soliton in a periodic system is predicted to occur near the edge of the Brillouin zone.     

One-dimensional character of combination modes in the resonance Raman scattering of carbon nanotubes

Resonance Raman spectroscopy with an energy tunable system is used to analyze the 600-1100 cm(-1) spectral region in single-wall carbon nanotubes. Sharp peaks are associated with the combination of zone folded optic and acoustic branches from 2D graphite. These combination modes exhibit a peculiar dependence on the excitation laser energy that is explained on the basis of a highly selective resonance process that considers phonons and electrons in low dimensional materials.     

Backward-wave four-wave mixing and coherent oscillation in CdF<Subscript>2</Subscript>:Ga,Y

Cadmium fluoride doped with Ga and Y is shown to be a suitable medium for backward-wave four-wave mixing with a grating decay time of a few seconds at room temperature. A 3-mm-thick sample ensures amplified phase-conjugate reflectivity and can therefore be used for building a coherent oscillator with a conventional mirror. PACS 42.65.Hw; 42.70.Mp; 42.70.Nq     

Diastereoselective total synthesis of isocarbacyclin from L-ascorbic acid

Diastereoselective total synthesis of isocarbacyclin, which features a fused bicyclic key intermediate available from l-ascorbic acid, is described. The key intermediate was prepared in multigram quantities by the Pauson-Khand reaction of l-ascorbic acid-based (R)-4,4-diallyl-2,2-dimethyl-5-(trimethylsilyl)ethynyl-1,3-dioxolane (3), discriminating diastereotopic groups and faces of the geminal allyl substituents.