Dynamics and structure of an aging binary colloidal glass

We study aging in a colloidal suspension consisting of micron-sized particles in a liquid. This system is made glassy by increasing the particle concentration. We observe samples composed of particles of two sizes, with a size ratio of 1:2.1 and a volume fraction ratio 1:6, using fast laser scanning confocal microscopy. This technique yields real-time, three-dimensional movies deep inside the colloidal glass. Specifically, we look at how the size, motion and structural organization of the particles relate to the overall aging of the glass. Particles move in spatially heterogeneous cooperative groups. These mobile regions tend to be richer in small particles, and these small particles facilitate the motion of nearby particles of both sizes.Comment: 7 pages; submitted to Phys. Rev. E. Revised with 1 new figure, improved tex

Optical properties of single crystals of some rare-earth trifluorides, 5-34 eV

The reflectances of single crystals of the trifluorides of La, Ce, Pr, Nd, Dy, and of polycrystalline GdF3 were measured in the 10-34-eV region, along with 5-9-eV transmission measurements on films of these materials. Localized 4f→5d, 6stransitions on the rare-earth ions give rise to the absorption below 10 or 11 eV. Strong interband absorption gives anisotropic reflectance peaks in the 10-15-eV region, presumably from F− 2p valence bands to lanthanide 5d, 6s (and other states) conduction bands, accounting for about one-third of the expected F− 2p osillator strength. Transitions from lanthanide 5p levels cause two types of spectra beginning around 20 eV: transitions of the 5p→5d type, apparently localized on lanthanide ions, but with some an isotropy; and transitions of 5p electrons to the conduction band, giving a peak of very high reflectance at energies above 27 eV

Temperature-Modulated Reflectance of Gold from 6 to 35 eV

The thermoreflectance spectrum of gold has been measured in the 6-35-eV region at about 200 K by using synchrotron radiation. Considerable sharp structure exists throughout this region, showing that lifetime broadening is not large enough to preclude the extension of high-resolution modulation techniques to at least 35 eV. The structure arises from interband transitions of the 5d electrons and from plasmons

Thermomodulation Study of Plasmons and Longitudinal Excitons in Alkali Halides

Thermoreflectance measurements on LiF and KCl were made from 10 to 30 eV using synchrotron radiation. Analysis of the differential dielectric and electron-energy-loss functions shows that the energy-loss peak generally attributed to the valence plasmon actually arises from the plasmon and overlapping longitudinal-exciton-like peak(s)

Thermoreflectance of LiF between 12 and 30 eV

The thermoreflectance spectrum of LiF between 12 and 30 eV was measured and several of the structures interpreted. The absorption-edge region is interpreted in terms of a Wannier exciton series converging to the fundamental band gap Γ15→Γ1. Structure associated directly with the band gap is not manifest, so the Γ15−Γ1 energy is determined indirectly to be 14.2 ± 0.2 eV. The n=1 exciton state generates the first strong structure in Δε̃ and we suggest that the exciton-phonon interaction, along with a central-cell correction, can give a significant contribution to its binding energy. Structures at higher energy have been associated with the interband transitions L3′→L1 and L2′→L1 between the crystal-field-split valence band at L and the lower conduction band. The strong electron-hole interaction modifies the expected line shape and a hyperbolic exciton, associated with the transitions at L, may exist as an antiresonance in the continuum. A strong feature at 22.2 eV in Δε̃ is associated with excitonic transitions at X involving the second d-like conduction band. The corresponding peak at 26.4 eV in Δ[Im(−1ε̃)] overlaps the valence-band plasmon at 24.6 eV. No evidence for double excitations is found around 25 eV in either Δε̃ or Δ[Im(−1ε̃)]. The Δ[Im(−1ε̃)] spectrum shows for the first time which structures in the energy-loss function are generated by longitudinal excitons and which by plasmons

Neutron spectroscopic factors of Ni isotopes from transfer reactions

177 neutron spectroscopic factors for nickel isotopes have been extracted by performing a systematic analysis of the angular distributions measured from (d,p) transfer reactions. A subset of the extracted spectroscopic factors are compared to predictions of large-basis shell models in the full pf model space using the GXPF1A effective interaction, and the (f5/2, p3/2, p1/2, g9/2) model space using the JJ4PNA interaction. For ground states, the predicted spectroscopic factors using the GXPF1A effective interaction in the full pf model space agree very well with the experimental values, while predictions based on several other effective interactions and model spaces are about 30% higher than the experimental values. For low-energy excited states (<3.5 MeV), the agreement between the extracted spectroscopic factors and shell model calculations is not better than a factor of two.Comment: 18 pages, 4 figures, 2 tables. accepted for publication in PR