Computation of impurity Green’s functions in the tight-binding scheme

Summary A general method to calculate electronic Green’s functions in the tight-binding scheme is presented. The integrations are systematically reduced to the irreducible volume of the first Brillouin zone, so that a very short time is necessary for the computer’s work. The importance of symmetry planes, lines and points is stressed.

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Riassunto Si presenta un metodo generale per il calcolo delle funzioni di Green elettroniche nell’approssimazione degli elettroni fortemente legati. Le integrazioni sono sistematicamente ridotte al volume irriducibile della prima zona di Brillouin, in modo da ridurre notevolmente il tempo di calcolo. Si mette in risalto l’importanza di piani, linee e punti di simmetria.

     

Configurational correlations for chiral episulphides and episulphoxides by 1H NMR spectroscopy in optically active solvent

Optically active 2,2,2-trifluorophenylethanol, when used as NMR solvent, causes enantiomeric spectral dissimilarities for chiral episulphides and episulphoxides; the relative field positions of non-equivalent NMR resonances are analysed with respect to the absolute configuration of the solvated compounds.     

The Snowmass Points and Slopes: benchmarks for SUSY searches

The ”Snowmass Points and Slopes” (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present and future experiments. This set of benchmarks was agreed upon at the 2001 ”Snowmass Workshop on the Future of Particle Physics” as a consensus based on different existing proposals. Received: 4 March 2002 / Published online: 26 July 2002     

Stark effect on CH3OH and CH3F FIR lasers: Large frequency tuning and resolved structures

The operation of a cw FIR laser in the presence of a strong electric field is described. A hybrid metal-dielectric waveguide is used and the cavity length is scanned to study how the frequency and power of the laser depend on the field strength. The results have also been checked by heterodyning with a conventional reference laser. We report the results obtained for the 496 μm line of CH₃F and the 70.5 μm and 119 μm lines of CH₃OH. A large frequency tunability of almost ±40 MHz is obtained in the best case with power levels in the mW range. A very simple theoretical model accounts for the experimental results. We also report the appearance of a new FIR line at about 204 μm when CH₃OH is pumped by the 9 μmP(34) of CO₂ in the presence of an electric field larger than 1.2 KV/cm.     

New CH2F2 FIR laser lines pumped by a tunable WG CO2 laser

8 new large offset FIR laser lines of CH₂F₂ have been discovered by pumping with a high tunability waveguide CW CO₂ laser. Optoacoustic measurements of CH₂F₂ have also been performed and the pump offsets of the new and of previously known lines have been measured and checked. Some assignments are proposed and a few assignments found in literature are checked     

Second-harmonic generation in He+-implanted gadolinium calcium oxoborate planar waveguides

What is believed to be the first investigation of second-harmonic generation (SHG) in Ca(4)GdO (BO(3))(3) waveguides is reported. A planar waveguide was formed by 2-MeV-helium implantation. We cut the sample to achieve type I noncritical phase matching of an 823-nm fundamental wave for fundamental light propagating along the y axis and polarized along the z crystallophysic axis of the crystal. SHG was achieved with a relatively low pumping power of a cw Ti:sapphire laser. The results indicate that the nonlinearity of the material remains in the guiding region after ion implantation.     

Analysis of All-Optical State Generator for “Encoding a Qubit in an Oscillator”

The fault-tolerant quantum computation scheme proposed by Gottesman (Phys. Rev. A 64, 012310 (2001)) can be performed using relatively simple linear optical resources and provides a natural protection against arbitrary small errors. On the other hand, preparing the initial GKP states is a difficult task. A few proposals to generate GKP states have been done over the last years. Our objective here is to analyze the performance of a particular GKP generator that uses cat states, linear optical devices, squeezing, and homodyne detection. We use numerical simulations to study the behavior of the fidelity between the generated and the ideal states and show that the proposal in consideration is indeed a promising scheme.     

Quinine‐Catalyzed Asymmetric Synthesis of 2,2′‐Binaphthol‐Type Biaryls under Mild Reaction Conditions

Simple quinine as an organocatalyst mediates the addition of various naphthols to halogenated quinones to afford non‐C₂‐symmetrical, axially chiral biaryl products, which are promising compounds as chiral ligands and organocatalysts. The rotational barrier required to have two distinct atropisomers has been evaluated in the products generated from the addition of naphthols to various quinones by means of DFT calculations and HPLC. The use of halogenated quinones as reagents was necessary to have configurationally stable enantiomeric products which can be obtained in good yield and stereoselectivity. These compounds have also been prepared in gram quantities and recrystallized to near enantiopurity.