Low-lying magnetic excitation of the Shastry-Sutherland model

By using perturbation calculation and numerical diagonalization, the low-energy spin dynamics of the Shastry-Sutherland model is investigated with particular attention to the two-particle coherent motion. In addition to spin-singlet- and triplet-bound states, we find novel branches of coherent motion of a bound quintet pair, which are usually unstable because of repulsion. Unusual dispersion observed in neutron-scattering measurements is explained by the present theory. The importance of the effects of phonons is also pointed out.     

Glycerophosphocholines of the earthworm, Pheretima asiatica.

The lipid composition of the earthworm, Pheretima asiatica (Annelida), was analyzed. Four glycerophospholipids, together with four known glycosphingolipids, were isolated in pure form. The former four were 1-alkyl 2-acyl glycerophosphocholines possessing a C17:0 and/or C18:1 fatty acid residue. Their structures, including the position and geometry of the double bond, were determined on the bases of chemical and spectral data.     

Observation of micropores in hard-carbon using Xe NMR porosimetry

The existence of micropores and the change of surface structure in pitch-based hard-carbon in xenon atmosphere were demonstrated using ¹²⁹Xe NMR. For high-pressure (4.0 MPa) ¹²⁹Xe NMR measurements, the hard-carbon samples in Xe gas showed three peaks at 27, 34 and 210 ppm. The last was attributed to the xenon in micropores (<1 nm) in hard-carbon particles. The NMR spectrum of a sample evacuated at 773 K and exposed to 0.1 MPa Xe gas at 773 K for 24 h showed two peaks at 29 and 128 ppm, which were attributed, respectively, to the xenon atoms adsorbed in the large pores (probably mesopores) and micropores of hard-carbon. With increasing annealing time in Xe gas at 773 K, both peaks shifted and merged into one peak at 50 ppm. The diffusion of adsorbed xenon atoms is very slow, probably because the transfer of molecules or atoms among micropores in hard-carbon does not occur readily. Many micropores are isolated from the outer surface. For that reason, xenon atoms are thought to be adsorbed only by micropores near the surface, which are easily accessible from the surrounding space.     

Measurements of Liquid-Phase Adsorption under High Pressure

Adsorption equilibria at about 1000 atm were measured for aqueous solutions of aromatic compounds. No significant difference between the isotherms at atmospheric pressure and at 1000 atm was found for nitrobenzene and ethylbenzene on activated carbon fiber. The decrease in the amount adsorbed due to the solubility increase with pressure and the increase in the amount adsorbed caused by compression of the adsorbed phase were considered to cancel each other. On the other hand, pressure had a marked effect on the adsorption of L-phenylalanine on a macroreticular adsorbent, resulting in a 1.5 to 2 times larger amount adsorbed at 1500 atm. The pressure effect was greater with larger amounts adsorbed. This implies that the molar volume of the adsorbed state is smaller than those of the pure state and dissolved state, and varies with the amount adsorbed.     

Rotational and vibrational states of excitonic molecules in CuBr studied by the two-photon-resonant Raman scattering

Excited states of excitonic molecules are found in the study of the two-photon-resonant Raman scattering. These states consist of four levels and have binding energies of 1.0–1.8 meV, which are very small compared with those of the ground states. They are considered to be the rotational and vibrational states of excitonic molecules.     

Mean thickness measurement of distributed fine particles by using alpha-ray absorption curves (author's transl)

The mean superficial density of fine particles, such as polystyrene latex particles or ion exchange resin particles, dispersed on a thin supporting film was measured by means of the thickness gauge which used the absorption curves of alpha-rays. The measured absorption curves coincided with the ones calculated from the particle diameter, density, number of particles per unit area and equivalent film thickness to an absorption gas of 1 mmHg. On the other hand, when the particle diameter exceeded a certain limit, the measured mean superficial density which was derived from the pressure displacement of absorption curve considerably differed from the true mean superficial density. This limit can be calculated from the shape of absorption curve, which depends on the alpha-ray spectrum emitted from the source. In the case of the 241Am source used in this study, the limit was about 450 microgram/cm2 for polystyrene latex particles. The mean superficial density of a sample can easily be obtained by measuring the pressure displacement of absorption curve when the maximum thickness difference is below the limit. However, when the maximum thickness difference exceeds the limit, it is necessary to estimate the whole shape of absorption curves.