Chiral unitary approach to the K–deuteron scattering length

Starting from a recent model where the amplitudes are evaluated from the chiral Lagrangians using a coupled-channel unitary method, we evaluate here the scattering length for K⁻–deuteron scattering. We find that the double scattering contribution is very large compared to the impulse approximation and that the charge-exchange contribution of this rescattering is as large as the sequential K⁻ scattering on the two nucleons. Higher-order rescattering corrections are evaluated using coupled channels with K⁻ and within the integral form of the fixed centre approximation to the Faddeev equations. The higher-order corrections involving intermediate pions and hyperons are found negligible.     

Synthesis and Aromaticity of Benzene-Fused Doubly N-Confused Porphyrins

A bicyclo[2.2.2]octadiene(BCOD)-fused bis(dipyrromethane) derivative was reacted with methylal in the presence of trifluoroacetic acid followed by oxidation with chloranil to give a doubly N-confused phlorin derivative, which did not undergo the retro-Diels–Alder reaction extruding an ethylene molecule on heating. In contrast, a 7-tert-butoxybicyclo[2.2.1]heptadiene(7-BuOBCHD)-fused bis(dipyrromethane) yielded benzene-ring-fused doubly N-confused porphyrins by following similar reaction sequences.     

Deuteron form factors and the tensor force

Results of a non-relativistic calculation of deuteron form factors are presented for separable potentials with and without tensor force. The tensor term in triplet state is added in such a way as to keep the values of deuteron binding energy,a _t andr _0t unaltered, so that the difference in the form factors can be regarded as the effect of tensor force only. The calculation has been performed for two different shapes of separable potentials and for three differentD-state probabilities to study their comparative effect.     

Quantum chemistry of ferroelectric solids: Electronic structures and peculiar behavior of zero‐dimensional K3H(SO4)2‐like materials

The main problems of quantum chemistry of H‐bonded ferroelectrics are treated using the zero‐dimensional K₃H(SO₄)₂‐like crystals as suitable examples. Various quantum chemical approaches and computational procedures are applied to evaluate the Ising model coupling parameters that determine different thermodynamic and dielectric properties of these materials. The calculated Ising parameters are employed to describe the peculiarities of ferroelectric behavior of the K₃H(SO₄)₂ family crystals in the framework of mean field approximation. The problems related to the H‐bond proton (deuteron) tunneling are also discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Narrowband Excitation of H Powder Pattern and Its Application to H 1D Exchange Sample-Turning NMR

Frequency-selective narrowband excitation of the ²H powder pattern was examined. Selection of a single spectral band with a linewidth of ca. 15 kHz was achieved by a narrowband ¹H → ²H cross polarization by using the time-averaged precession frequency method. Further narrowing with a ca. 5 kHz linewidth is achieved by DANTE irradiation. The narrowband excitation was applied to transform a recently developed 2D spin-exchange method for obtaining structural information (Chem. Phys. Lett. 260, 159, (1996)) into its 1D analogue. The determination of the D–C–D bond angle was demonstrated for α-glycine-[2,2-d₂]. Further, the intermolecular polarization transfer between two deuterons separated by 0.299 nm was detected with the mixing time of 500 ms.     

A Study of Dipolar Interactions and Dynamic Processes of Water Molecules in Tendon byH andH Homonuclear and Heteronuclear Multiple-Quantum-Filtered NMR Spectroscopy

The effect of proton exchange on the measurement of¹H–¹H,¹H–²H, and²H–²H residual dipolar interactions in water molecules in bovine Achilles tendons was investigated using double-quantum-filtered (DQF) NMR and new pulse sequences based on heteronuclear and homonuclear multiple-quantum filtering (MQF). Derivation of theoretical expressions for these techniques allowed evaluation of the¹H–¹H and¹H–²H residual dipolar interactions and the proton exchange rate at a temperature of 24°C and above, where no dipolar splitting is evident. The values obtained for these parameters at 24°C were 300 and 50 Hz and 3000 s⁻¹, respectively. The results for the residual dipolar interactions were verified by repeating the above measurements at a temperature of 1.5°C, where the spectra of the H₂O molecules were well resolved, so that the¹H–¹H dipolar interaction could be determined directly from the observed splitting. Analysis of the MQF experiments at 1.5°C, where the proton exchange was in the intermediate regime for the¹H–²H dipolar interaction, confirmed the result obtained at 24°C for this interaction. A strong dependence of the intensities of the MQF signals on the proton exchange rate, in the intermediate and the fast exchange regimes, was observed and theoretically interpreted. This leads to the conclusion that the MQF techniques are mostly useful for tissues where the residual dipolar interaction is not significantly smaller than the proton exchange rate. Dependence of the relaxation times and signal intensities of the MQF experiments on the orientation of the tendon with respect to the magnetic field was observed and analyzed. One of the results of the theoretical analysis is that, in the fast exchange regime, the signal decay rates in the MQF experiments as well as in the spin echo or CPMG pulse sequences (T₂) depend on the orientation as the square of the second-rank Legendre polynomial.     

Effect of deuteron density distribution on the deduction of screening potential from the D（d,p）T reaction in Be metals

The D(d,p)T reaction in Be metal environments has been measured to investigate the electron screening effect in metals in an energy region of from 5.5 keV to 10 keV in a center of mass system (CMS) at a temperature of 121 K. The depth distribution of deuteron density in Be metals has an impact on the observed reaction yields. A model of deuteron density distribution in metal has been proposed to obtain the original yields. A screening energy of (116±46) eV has been obtained with the assumed deuteron density distribution model.     

Study of spatial structure and energy spectrum of ion beams by means of LR 115A and PM-355 nuclear track detectors

The paper reports on measurements of pulsed plasma-ion streams, as performed with the selected solid-state nuclear track detectors (SSNTD). The ion-beams were produced by an experimental device (RPI-IBIS) equipped with coaxial electrodes (each made of molybdenum rods) and a fast-acting gas valve. The device was operated at 30 kV/44 kJ, with puffing of pure hydrogen or deuterium. The spatial structure of the ion beams was studied with pinhole cameras equipped with replaceable detectors, and ion mass- and energy-spectra were measured with a Thomson spectrometer. To analyse low-energy ions (below the energy thresholds of LR 115A and PM-355 SSNTD) an additional accelerating system was applied. It was observed that ions of energy are emitted in bunches, and the ion flux amounts to at a distance of 30 cm from the electrodes outlet. Energy spectra of protons and deuterons ranged from about 30 keV to about 400 keV. The ion distributions, as recorded by means of the PM-355 and LR 115A detectors, are similar.     

Deuteron under strong magnetic fields: Skyrme model study

We explore the deuteron under strong magnetic fields in Skyrme models. The effects of the derivative dependent sextic term in the Skyrme Lagrangian are investigated, and the rational map approximation is used to describe the deuteron. The influences of strong magnetic fields on the electric charge distribution and mass of the deuteron are discussed.     

Weak neutral current effects in elastic electron deuteron scattering

We study the effect of weak neutral currents in elastic electron deuteron scattering on both unpolarized and polarized deuteron targets. Theoretical expressions have been derived for the polarized electron asymmetry, polarized target asymmetry and recoil deuteron vector polarization within the framework of impulse approximation. We show that these polarization parameters can give vital information on the space-time and isospin structure of the hadronic weak neutral current. In particular, our numerical estimates show that a measurement of polarized target asymmetry is sensitive to the isoscalar axial vector piece in the hadronic neutral current which, though zero in the Weinberg-Salam model, is not completely ruled out by the data.