Static dielectric properties of Stockmayer fluids

Dielectric constants for the Stockmayer fluid are computed both from the equilibrium fluctuations of the polarization and from the polarization response to an applied field in a molecular dynamics simulation with periodic boundary conditions and with the dipole interactions treated by the Ewald method. The dielectric constant at finite wavelength is obtained from a Kirkwood-like expression, while for uniform polarization fluctuations a different expression applies due to the absence of surface effects in the Ewald calculation. The results are nearly independent of the number (up to 500) of particles investigated, even at large values of the dipole moment. The dielectric constants obtained from the approximate solution of the hypernetted chain integral equation are considerably larger than the molecular dynamics results except at low dielectric constants. The external field simulation permits study of the non-linear dependence of the dielectric constant on the magnitude of the applied electric field.     

Electroproduction of π+ mesons in the resonance region

Results on the reaction ep→e′nπ⁺ are presented in the mass range 1.355 ?W ?1.775 GeV at q₂=1GeV² and in the range 1.415 ? W ? 1.595 GeV at q²=0.6 GeV². From the angular distribution of the π⁺ meson the polarization terms σ_u + ?σ_L, σ_p and σ_I have been determined in the range of production angles 0 <θ_π⁺ ?63°     

The ppπ0 coupling constant and electromagnetic effects in p-p forward dispersion relations

We show that a “Coulomb-renormalized” ppπ⁰ coupling constant can be defined and deduced from experiment by applying a forward dispersion relation to Coulomb-modified p-p scattering amplitudes. The value determined in this model-independent way from the Livermore phase shifts is G²_ppπ⁰ = 15.3 ± 0.3.     

Messung von Positronstrahlern in kosmischen Staubproben

Ohne Zusammenfassung     

Evaluation of time correlation functions from a generalized Enskog equation

Numerical results for the density and current correlation functions in dense hard-sphere fluids are obtained from a kinetic equation which is the extension of the linearized Enskog equation to finite wavelengths in order to demonstrate the convergence of the method of solution. Comparison is made to a previously proposed approximate solution.This work was performed in part under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48 and in part supported by the National Science Foundation.     

The design and development of a multichannel atomic absorption spectrometer for the simultaneous determination of trace metals in hair

A multichannel atomic absorption spectrometer capable of analysing up to nine elements simultaneously in human hair has been designed. Light from an array of hollow-cathode lamps is passed through an electrically heated graphite tube into a direct reading spectrometer. The photomultiplier output is fed into a novel transient signalprocessing device which separates the absorption pulse from the continuous background and increases linear range and sensitivity. Solutions containing Ni, Co, Si, Mn, Al, Cu, Ag, Cr and Fe in nanogram and sub-nanogram amounts can be determined with reasonable precision.     

Electronic excitation and ionization temperature measurements in a high frequency inductively coupled argon plasma source and the influence of water vapour on plasma parameters

Excitation temperatures measured from Fe I lines with a wide range of upper energy levels have shown that the environment of the central channel of an argon ICP is not in a state of local thermal equilibrium, as predicted from Griem's criterion. Deviations from a Boltzmann distribution have been observed in the population of the excited states of Fe I. The significance of water in providing extra electrons by ionization in the ICP is demonstrated and discussed.