Interactions between Functional Groups. Part II. Structure of the 2-Dimethylaminobenzenediazonium Cation: Retention of Planarity Despite Excessive Steric Crowding

The crystal structure of 2-dimethylaminobenzenediazonium tetrafluoroborate has been determined at 183 K by X-ray diffraction. The cation is very nearly planar, the strong steric interaction between the ortho-groups being diminished by in-plane angular distoritions.     

Dielectric constant and microwave conductivity of the vanadium bronze Na0.33V2O5

Measurements of the dielectric constant and microwave conductivity are reported for the vanadium bronze Na_0.33V₂O₅. The dielectric constant is highly anisotropic and very large parallel to the highly conducting direction, while the conductivity is strongly dispersive. The results can be consistently interpreted by considering Na_0.33V₂O₅ as a quasi-one-dimensional conductor in which, at low temperatures, a pseudo-gap opens in the open-electron density of states due to inter-site correlations.     

Interaction of surface magnetoplasmons and surface optical phonons in polar semiconductors

A theoretical investigation has been carried out of surface polaritons associated with surface magnetoplasmons coupled to surface optical phonons in polar semiconductors. The coupled mode frequencies are calculated for several orientations of the magnetic field relative to the surface and the direction of propagation in the large wave vector (unretarded) limit. Dispersion curves are calculated for the configuration in which the magnetic field is parallel to the surface and is perpendicular to the wave vector. Experimental possibilities for observing the interaction effects are discussed.     

Configurations arising from maximal arcs

We show that the existence of a maximal arc in a finite projective plane implies the existence of certain block designs and partial geometries. The block designs obtained have interesting resolvability properties.     

Kronecker products and BIBDs

Recursive constructions are given which permit, under conditions described in the paper, a (v, b, r, k, λ)-configuration to be used to obtain a (v′, b′, r′, k, λ)-configuration.     

Higher order temporal and spatial plasma wave echo calculations

The collisionless Boltzmann equation is solved by an iterative characteristic method to calculate temporal and spatial plasma wave echoes of arbitrary order neglecting self-consistent fields. Using this model the measured spatial echo amplitude dependence from the transmitter separation is explained.