Effects of motional narrowing on the plasmon resonance in small metal clusters

A model accounting for the time dependence of shape fluctuations in metal microclusters and their effect on the damping width of the plasmon resonance is discussed. An estimate of the relaxation time of the quadrupole shape is given, and calculations demonstrating the effects of time-dependent thermal fluctuations on the plasmon in K ₉ ⁺ are presented.Lee A. DuBridge research fellow in Physics     

Diffusivity of Lattice Gases

We consider one-component lattice gases with local dynamics and a stationary product Bernoulli measure on ${\mathbb{Z}^d}$ . We study the scaling exponents of the space-time correlations of the system in equilibrium at a given density. We consider a variance-like quantity computed from the correlations called the diffusivity (connected to the Green–Kubo formula) and give rigorous upper and lower bounds on it that depend on the dimension and the local behavior of the macroscopic flux function. Our results identify the cases in which the system scales superdiffusively; these cases have been predicted before, using non-rigorous scaling arguments. Our main tool is the resolvent method: the estimates are the result of a careful analysis of a complicated variational problem.     

Spectrum and intensity of light scattered from SF6 along the coexistence curve

Our two groups have measured independently the “Rayleigh linewidth” (Γ), the reduced compressibility (??/?μ)_T, and the pressure (P) of SF₆ along the liquid and vapor sides of the coexistence curve. We find that (??/?μ)_T = 1.67 × 10^-10 (1 - T/T_c)^{-1.22 ± 0.015}g²erg^-1cm^-3 and (?P/?T)lχ = (7094 ± 0.1) × 10⁵ dyne/cm² ° We analyze our linewidth measurements in terms of the Kadanoff-Swift-Kawasaki mode-mode coupling theory using estimates for the viscosity and correlation range.     

Radioactive decay of Os191 and Os191m

Beta and gamma spectra of Os¹⁹¹ were studied using a magnetic double-focusing beta-spectrometer and a scintillation spectrometer. The isomeric state Os^191m decays through the 74·4 ± 0·1 keV (E3/M4=50) transition with a half-lifeT _1/2=13·0 ± 0·5 hours. A continuous beta spectrum withE _max=147 ± 3 keV and the gamma transitions 41·83 ± 0·05 keV (E3), 82·5 ± 0·3 keV and 129·4 ± 0·1 keV (70%M1 + 30%E2) were observed in the decay of the ground state of Os¹⁹¹. The conversion coefficient of the last transition was determined as 1·94 ±± — 0·10. Gamma transitions with energies of 47 keV and 185·8 keV were not observed.     

Interface Energies for Carbide Precipitates in TiAl

Carbon has been extensively investigated as an additive to TiAl alloys to improve high-temperature mechanical properties. The ternary-carbide-precipitate phases that have received most attention are Ti₃AlC (cubic perovskite), and Ti₂AlC (hexagonal). The perovskite (P) precipitates in the form of needles along the 001 direction of -TiAl, and the hexagonal phase (H) primarily forms platelets perpendicular to 111 directions. Using the first-principles density functional theory code VASP, calculations of host-precipitate interface energies were performed for these two carbides. An atomic-scale formulation of the interface energy is adopted. Calculations for the coherent interfaces are performed to determine the preferred terminations and translation states. An approximate correction to the interface energy for the effect of misfit is applied to estimate the energy of incoherent interfaces. The relative interface properties of the P-type and H-type carbides are determined by, in addition to the misfit strains, (i) the stronger bonding of the P-type than the H-type precipitate with the host at the interface, and (ii) the more pronounced variations of the interatomic potentials as a function of parallel translation state across non-close-packed (100) P layers than those across close-packed (0001) H layers.