Semiquantitative Infrared Analysis of Diketones and Anhydrides in a Reaction Mixture

The ozonolysis of a hydroxymethylene ketone yields a mixture of diketone and anhydride. Treatment of hydroxymethylene camphor with ozone affords, in addition to the expected camphor quinone, a surprisingly large amount of camphoric anhydride (56%) via Baeyer-Villager reaction. Use of infrared absorption to analyze the relative amounts of camphor quinone and camphoric anhydride in a reaction mixture was studied by comparing peak heights of their carbonyl stretching bands

High-Frequency Measurements Of The Spectrum Of Sagittarius A*

We report near-simultaneous interferometric measurements of the spectrum of Sagittarius A* over the 5-354 GHz range and single-dish observations that have yielded the first detection of Sgr A* at 850 GHz. We confirm that Sgr A*'s spectrum rises more steeply at short millimeter wavelengths than at centimeter wavelengths, leading to a near-millimeter/submillimeter excess that dominates its luminosity. Below 900 GHz, Sgr A*'s observed luminosity is 70 +/- 30 L.. A new upper limit to Sgr A*'s 24.3 mu m flux, together with a compilation of other extant IR data, imply a far-infrared spectral turnover, which can result from either an intrinsic synchrotron cutoff or excess extinction near Sgr A*. If the former applies, Sgr A*'s total synchrotron luminosity is <10(3) L., while in the latter case it is <3 x 10(4) L. if spherical symmetry also applies.NSF AST96-15025, AST96-13717Astronom

Investigating neutron-proton pairing in sd -shell nuclei via (p, He 3) and (He 3,p) transfer reactions

Neutron-proton pairing correlations are investigated in detail via np transfer reactions in N = Z sd-shell nuclei. In particular, we study the cross-section ratio of the lowest 0+ and 1+ states as an observable to quantify the interplay between T = 0 (isoscalar) and T = 1 (isovector) pairing strengths. The experimental results are compared to second-order distorted-wave Born approximation calculations with proton-neutron amplitudes obtained in the shell-model formalism using the universal sd-shell interaction B. Our results suggest underestimation of the nonneglible isoscalar pairing strength in the shell-model descriptions at the expense of the isovector channel.Séptimo Programa Marco de la Comisión Europea-FP7/2007-2013 00376National Science Foundation (NSF) de los Estados Unidos-PHY-1404442US Department of Energy, Office of Science, Office of Nuclear Physics-DE-AC02-05CH1123

Charge density waves and surface Mott insulators for adlayer structures on semiconductors: extended Hubbard modeling

Motivated by the recent experimental evidence of commensurate surface charge density waves (CDW) in Pb/Ge(111) and Sn/Ge(111) sqrt{3}-adlayer structures, as well as by the insulating states found on K/Si(111):B and SiC(0001), we have investigated the role of electron-electron interactions, and also of electron-phonon coupling, on the narrow surface state band originating from the outer dangling bond orbitals of the surface. We model the sqrt{3} dangling bond lattice by an extended two-dimensional Hubbard model at half-filling on a triangular lattice. We include an on-site Hubbard repulsion U and a nearest-neighbor Coulomb interaction V, plus a long-ranged Coulomb tail. The electron-phonon interaction is treated in the deformation potential approximation. We have explored the phase diagram of this model including the possibility of commensurate 3x3 phases, using mainly the Hartree-Fock approximation. For U larger than the bandwidth we find a non-collinear antiferromagnetic SDW insulator, possibly corresponding to the situation on the SiC and K/Si surfaces. For U comparable or smaller, a rich phase diagram arises, with several phases involving combinations of charge and spin-density-waves (SDW), with or without a net magnetization. We find that insulating, or partly metallic 3x3 CDW phases can be stabilized by two different physical mechanisms. One is the inter-site repulsion V, that together with electron-phonon coupling can lower the energy of a charge modulation. The other is a novel magnetically-induced Fermi surface nesting, stabilizing a net cell magnetization of 1/3, plus a collinear SDW, plus an associated weak CDW. Comparison with available experimental evidence, and also with first-principle calculations is made.Comment: 11 pages, 9 figure