On the dynamic form factor of an electron liquid

The mean field theories of an electron liquid at metallic densities, which go beyond the RPA, and which have been fairly successful so far, are shown to be inadequate when tested against phenomena involving high frequencies. It is also shown that by making a simple Gaussian ansatz for the imaginery part of the response function, χ″(q,ω), and using the zeroth, the first and the third frequency moments of density spectral function to determine the unknown parameters in χ″(q,ω), it is possible to understand at least semiquantitatively the available experimental information regarding the dynamic form factor. Implications of the present analysis as regards the further refinement of the present theories are indicated.     

Synthesis and intramolecular nitrile oxide cycloaddition of 3,5'-ether-linked pseudooligosaccharide derivatives: an approach to chiral macrooxacycles

3,5'-ether-linked pseudooligopentose derivatives were synthesized for the first time from readily available carbohydrate precursors. The 1,2-isopropylidene-protected ether-linked oligopentoses are potentially important as precursors of novel RNA analogues. Intramolecular cycloaddition of the nitrile oxides prepared from these derivatives led to the diastereoselective formation of chiral isoxazolines fused to 10-16-membered oxacycles. The stereochemistry of some of these isoxazolines was established by X-ray diffraction and NOESY analysis.     

A previously unrecognised hydronium di-cation in the crystal structure of a cucurbituril derivative

Examination of the crystal structure of the adduct of hydronium tetrachloroferrate dichloride with cucurbituril resulted in the discovery that the hydronium cation present therein is not the well known H7O3+ species; rather, it is an unprecedented cyclic species of composition (H14O6)2+, templated by the formation of five hydrogen bonds to cucurbituril.     

On the absorption of electromagnetic radiation near a metal surface

We present a discussion on the absorptance of electromagnetic radiation per unit length in the surface region of a free electron like metal. We wish particularly to comment on recent work by Feibelman, Kliewer, Forstmann and Stenscke, who all considered different approximations of the jellium model. We are using a unified treatment from which the results in their models can easily be obtained. Our results confirm the general conclusions by Kliewer about a strong coupling to the electron-hole excitations which lead to a locally negative absorptance. In the model considered by Feibelman there is no such coupling to electron-hole excitations and he obtains the classical results for the absorptance. Forstmann and Stenschke have recently applied a hydrodynamical approach which gives results in disagreement with Kliewer's theory as well as with our own results, and we make some comments about their approach.     

On a field-theoretic formulation of many-electron spin-adaptation

We report the development of a set of spin-adapted creation and annihilation operators which provides a suitable generalisation of the usual many-body apparatus.     

K+N spin-orbit interaction in the constituent quark model

We calculate p-wave phase shifts of the KN system in the framework of the non-relativistic constituent-quark model. We show that the symmetric spin-orbit potential from gluon exchange between quarks leads to KN spin-orbit potentials for the I = 0 and I = 1 states with the correct sign and magnitude. We also discuss the spin-orbit contributions from the naive confinement potential which give the wrong behaviour for the hadron-hadron spin-orbit potential.     

Semiclassical theory of analysing powers for polarised heavy-ion elastic scattering

A unified semiclassical theory of analysing powers of all ranks for polarised heavy-ion elastic scattering from a spin-zero target at energies above the Coulomb barrier is presented. Illustration is provided for by specialising to the two interactions, spin-orbit and tensor. The present approach recovers the phenomenological result, obtained by taking the difference of the nuclear overlap between unpolarised and aligned projectiles (shape-effect model), which successfully explained the structureless pattern of rank-2 observables for aligned ⁷Li + ⁵⁸Ni at E_lab ～ 20 MeV. Deviations observed for ⁷Li + ¹²C (oscillations) are interpreted as due to interference between diffraction (positive-angle) and negative-angle scattering terms.     

Exponents of class groups of real quadratic function fields (II)

Let be an even positive integer. We show that there are polynomials with such that the ideal class group of the real quadratic extensions have an element of order .