Single-mode transmitting modules for fiber-optics lines operating at wavelengths 1.3 and 1.55 μm

Optoelectronic sources for the 1.3- and 1.55-m bands have been developed on the basis of InGaAsP/InP heterostructures in the form of modules that include a Peltier microcooler, a temperature sensor, and a photodiode monitor. The properties of single-mode sources are presented and the technique of is discribed of coupling them to single-mode fibers using a taper and a microlens lightguide pigtail. Data on the influence of parasitic and some results on high-frequency modulation and information transmission are given.Optoelectronics Laboratory, Lebedev Physics Institute. Translated from Preprint No. 137 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

A theoretical investigation of α-substituents on the structure,proton affinities and inversion barriers of silyl anions

Geometries, optimised at the double-zeta level, are reported for silanes SiH₃X and silyl anions SiH₂X^? where X = H, BH₂, CH₃, NH₂, OH and F. The anions are pyramidal with larger out-of-plane angles than their carbanion analogues and inversion barriers are large, varying from 34.3 $\text{kcal}\text{mole}$ for X = H up to 57.3 $\text{kcal}\text{mole}$ when X = F. The silylborane anion is planar at both boron and silicon and has a Si-B bond length shorter by 0.15 than in silylborane. Silyl anions are more stable than methyl anions by between 55 and 66 $\text{kcal}\text{mole}$.     

Fast isolation of short-lived osmium isotopes by nickel-potassium hexacyanoferrate

An ion-exchange system is described for the separation of short-lived isotopes.     

Solvent Effect of Dimethyl Sulfoxide on the Chemical Shifts of Phenyl Vinyl Ketones

In our study on the 1D and 2D NMR spectra of synthetic chalcones in DMSO‐d₆, we found that, contrary to our expectation, the signals of α‐carbon correlated to the olefinic protons resonating at lower field whereas the signals of β‐carbon correlated to the olefinic protons resonating at higher field in the spectra of chalcones. To further investigate such solvent effect, four α,β‐unsaturated ketones were prepared and studied separately in CDCl₃ and DMSO‐d₆. The result indicated that the α,β‐unsaturated ketones that possess benzoyl moiety experienced solvent effect in DMSO‐d₆ to result in an anomalous chemical shift. The shift arose from the complexation of solute molecule with DMSO that fixed the steric conformation of solute molecule so that H_β was kept apart from its benzene ring whereas its H_α became more accessible by its benzene ring. Thus, these two olefinic protons would experience a different extent of anisotropic effect exerted by the neighboring benzene ring.     

Improvement for α-energy resolution in determination of low level plutonium by liquid scintillation counting

An improvement of -energy resolution for determining low level plutonium has been investigated using combined solvent extraction-low level liquid scintillation counter. In the present work, -energy resolution of 270–290 keV for liquid scintillation spectra of²³⁶Pu and²³⁹Pu is attained. Thus the simultaneous determination of low level plutonium with -liquid scintillation spectrometry may be practized.     

Growth and sintering of Pd clusters on alpha-Al2O3(0001)

The growth and sintering of Pd nanoparticles on alpha-Al(2)O(3)(0001) have been studied by noncontact atomic force microscopy (NC-AFM), low-energy ion scattering spectroscopy (LEIS), temperature-programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). This is the first study of metal nanoparticles on a well-defined oxide surface where both NC-AFM and LEIS are used for characterization. These prove to be a powerful combination in assessing particle dimensions. The clean alumina surface showed atomically flat, 200-700 nm wide terraces. The sharp step edges are straight (within our resolution) for lengths of >300 nm and have heights in multiples of 0.2 nm. The Pd grows initially as two-dimensional (2D) islands at 300 K, with the transition to 3D particle growth at 0.25 ML (ML=monolayers). Upon heating at 1 K/s, the Pd starts to sinter below 400 K, and sinters at a nearly constant rate with increasing temperature, covering approximately 50% less of the alumina surface by approximately 1000 K, with a doubling in particle diameter and an eightfold decrease in particle number density. By approximately 1000 K, the number density was approximately 9 x 10(11)cm(2) for 0.8 ML of Pd, with an average diameter of 5 nm and an average thickness of 1 nm.     

Formation of Alkyne Bridged Multicobalt Carbonyl Complexes with Tris(2‐Thienyl)Phosphine or Bis(Trimethylsilylethynyl)Phenylphosphine Ligand

Treatment of Co₄(CO)₁₂ with an excess of trimethylsilylacetylene (TMSA) in the presence of tri(2‐thienyl)phosphine in THF at 25 °C for 2 hours yielded six compounds. Two pseudo‐octahedral, alkyne‐bridged tetracobalt clusters, [Co₄(μ₄‐η²‐HC≡CSiMe₃)(CO)₁₀(μ‐CO)₂] ( 4 ) and [Co₄(μ₄‐η²‐HC≡CSiMe³)‐(CO)₉(μ‐CO)₂{P(C₄H₄S)₃}] ( 6 ), along with an alkyne‐bridged dicobalt complex, [Co₂(CO)₅(μ‐HC≡CSiMe₃)‐{P(C₄H₄S)₃}] ( 5 ), were obtained as new compounds. The addition of the thienylphosphine ligand, in fact, facilitates the reaction rate. Reaction of an alkyne‐bridged dicobalt complex, [(η²‐H‐C≡C‐SiMe₃)Co₂(CO)₆] ( 3 ), with a bi‐functional ligand, PPh(‐C≡C‐SiMe₃)₂, yielded an unexpected six‐membered, cyclic compound, {(Ph)(Me₃Si‐C≡C)P‐[(η²‐C≡C‐SiMe₃)Co₂(CO)₅]}₂ ( 7 ). All of these new compounds were characterized by spectroscopic means; the solid‐state structures of ( 5 ), ( 6 ) and ( 7 ) have been established by X‐ray crystallography.     

Reactions of bis(trifluoromethyl)nitroxyl with tris(pentafluorophenyl)-phosphine arsine and stibine

Tris(pentafluorophenyl)phosphine is oxidised by bis(trifluoromethyl)nitroxyl to form tris(pentafluorophenyl)phosphine oxide and perfluoro(2,4-dimethyl-3-oxa-2,4-diazapentane). With the corresponding arsine and stibine, addition products are obtained, namely tris(pentafluorophenyl)-arsenicdi[bis(trifluoromethyl)nitroxide] and tris(pentafluorophenyl)-antimonydi[bis(trifluoromethyl)nitroxide] respectively. Some reactions of the new derivatives are described.