Direct photoexcitation of appreciable size of domains without lattice motion in neutral-ionic transition systems

In a recent ultrafast pump-probe experiment on a typical neutral-(N-)ionic (I) transition material, tetrathiafulvalene-p-chloranil [S. Iwai, Phys. Rev. Lett. 96, 057403 (2006)10.1103/PhysRevLett.96.057403], it was claimed that an I-phase domain in the N-phase background was very quickly formed even before the lattice started to move. This study proves this idea in terms of an extended Hubbard model that has site-potential alternation and has been frequently used so far. Our focus is on the photoexcited states of the N phase and the optical conductivity spectrum. As a result of accurate spectrum calculation based on a dynamical density-matrix renormalization group technique, we clearly observe photoexcited ionic domains accompanied by no lattice dimerization. Their contribution almost dominates the spectrum near the N-I phase boundary, and we relate this property to the long-tailed spectrum observed in experiments.     

Measurement of azimuthal asymmetries in inclusive production of hadron pairs in e(+)e(-) annihilation at Belle

The Collins effect connects transverse quark spin with a measurable azimuthal dependence in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction methods, we find evidence of statistically significant azimuthal asymmetries for charged pion pairs in e(+)e(-) annihilation at a center-of-mass energy of 10.52 GeV, which can be attributed to a transverse polarization of the primordial quarks. The measurement was performed using a sample of 79 x 10(6) hadronic events collected with the Belle detector.     

Surface characterization of imidazolium ionic liquids by high-resolution Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy

The surface composition of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM] [PF₆]) and 1-butyl-3-methylimidazolium dicyanamide ([BMIM] [DCA]) are studied by high-resolution Rutherford backscattering spectroscopy. Although [BMIM] [PF₆] is almost stoichiometric up to the topmost molecular layer, considerable deviation from the theoretical stoichiometry is observed for [BMIM] [DCA] in a surface layer of ～1.5 nm thickness. Nitrogen is almost completely depleted in this layer while carbon is enhanced. In addition, there are oxygen impurities of ～3 × 10¹⁴ atoms/cm² in this surface layer. With the help of X-ray photoelectron spectroscopy measurements it is concluded that the surface of [BMIM] [DCA] is covered by ～1.7 × 10¹⁴ molecules/cm² of esters and/or carboxylic acids. These contaminant molecules have a preferred orientation, i.e. the carbonyl groups are on the surface of [BMIM] [DCA] and the alkyl chains are pointing towards vacuum. The origin of the contamination layer could be the surface segregation of bulk impurities.     

Resolving vibrational wave-packet dynamics of D2(+) using multicolor probe pulses

We demonstrate the generation and real-time observation of the vibrational wave packet of D(2)(+) by using a sub-10-fs extreme UV high-harmonic pump pulse and a three-color probe laser pulse whose wavelength ranges from near-IR to vacuum UV. This multicolor pump-probe scheme can provide us with a powerful experimental tool for investigating a variety of wave packets evolving with a time scale of ~20 fs.     

Relationships between the anisotropy of longitudinal wave velocity and hydroxyapatite crystallite orientation in bovine cortical bone

Quantitative ultrasound (QUS) is now widely used for evaluating bone in vivo, because obtained ultrasonic wave properties directly reflect the visco-elasticity. Bone tissue is composed of minerals like hydroxyapatite (HAp) and a collagen matrix. HAp crystallites orientation is thus one parameter of bone elasticity. In this study, we experimentally investigated the anisotropy of ultrasonic wave velocity and the HAp crystallites orientation in the axial-radial and axial-tangential planes in detail, using cylindrical specimens obtained from the cortical bone of three bovine femurs. Longitudinal bulk wave propagation was investigated by using a conventional ultrasonic pulse system. We used the one cycle of sinusoidal pulse which was emitted from wide band transmitter. The nominal frequency of the pulse was 1 MHz. First, we investigated the anisotropy of longitudinal wave velocity, measuring the anisotropy of velocity in two planes using cylindrical specimens obtained from identical bone areas. The wave velocity changed due to the rotation angle, showing the maximum value in the direction a little off the bone axis. Moreover, X-ray pole figure measurements also indicated that there were small tilts in the HAp crystallites orientation from the bone axis. The tilt angles were similar to those of the highest velocity direction. There were good correlations between velocity and HAp crystallites orientation obtained in different directions. However, a comparatively low correlation was found in posterior bone areas, which shows the stronger effects of bone microstructure. In the radial-tangential plane, where the HAp crystallites hardly ever align, weak anisotropy of velocity was found which seemed to depend on the bone microstructure.     

Flavour and spin structure of linear baryons

Based on the string picture, we construct a phenomenological model for baryons and study their flavour symmetry, exchange degeneracy pattern and spin structure. Baryons on leading trajectories are assumed to have the configuration of two quarks being attached to the ends of a linear string and the third sitting in the middle, called linear baryons. For such linear baryons, a unitarization scheme can be constructed in a manner similar to the dual unitarity scheme for mesons but without recourse to the $\text{1}\text{N}$ expansion. We find that the interchange interaction of the middle quark with one of the other two quarks at the ends of the string can give rise to a large exchange degeneracy breaking of the baryon spectrum. With this non-planar correction, the model of linear baryons can account for the observed pattern of leading baryon states.     

The thermolysin-catalyzed condensation reactions of n-substituted aspartic and glutamic acids with phenylalanine alkyl esters

The title reactions occur with concurrent peptide synthesis and optical resolutions of racemic substrates. With this method, Z-L-Asp-L-Phe-OME, the precursor to the synthetic sweetner, could be obtained in high yield.