Nuclear charge radii and electromagnetic moments of scandium isotopes and isomers in the f7/2 shell

Collinear laser spectroscopy experiments on the ScII transition 3d4s ³D₂→3d4p ³F₃ at λ ≈ 363.1 nm were performed on the ^42–46Sc isotopic chain using an ion guide isotope separator with a cooler–buncher. Isotope and isomer shifts and hyperfine structures of five ground states and two isomers were measured. Preliminary results on the nuclear moments and charge radii changes deduced from these measurements are reported.     

Coadsorption of ethylene and oxygen on an iridium surface

It is established that the hydrocarbon coverage (0<1) formed at T<400 K on the Ir surface is oxidized upon oxygen exposures to CO and H₂O by an adsorption mechanism. Complete oxidation to CO₂ and H₂O is achieved at T350 K after C₂H₄ exposures of the oxygen coverage.

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, (<1), T<400 K Ir, CO H₂O . CO₂ H₂O T350 K C₂H₄ .

     

Accurate isotope shift measurements on short lived neon isotopes

We report on fast beam collinear laser spectroscopy measurements that demonstrate the feasibility of accurate isotope shift measurements for short lived Ne isotopes including the proton halo candidate ¹⁷Ne. Ultra high sensitivity is achieved by the application of an efficient resonance detection scheme based on collisional ionization and ion counting via the β decay. A direct measurement of the kinetic energy of the atomic Ne beam provides the required high accuracy. This revised version was published online in August 2006 with corrections to the Cover Date.     

Near-infrared sensitive organic–inorganic photorefractive device

Organic–inorganic hybrid structure, assembled by Rh-doped Bi₁₂TiO₂₀ crystal and liquid crystal (LC) layer, operating at near-infrared range is proposed and demonstrated. Due to the photorefractive properties of inorganic substrate, light illumination caused a space charge field which acts as a driving force for LC molecules re-alignment and subsequent refractive index modulation. All optically controlled phase retardation ability has been demonstrated supporting possibilities for further infrared applications.     

Vibrational behavior of matrix-isolated ions in Tutton compounds. V. Infrared spectroscopic study of NH4+ and SO42− ions included in zinc sulfates and selenates

Infrared spectra of K₂Zn(SeO₄)₂·6H₂O and (NH₄)₂Zn(SeO₄)₂·6H₂O containing SO₄^2? guest ions and those of K₂Zn(SO₄)₂·6H₂O and K₂Zn(SeO₄)₂·6H₂O containing NH₄⁺ guest ions are presented and discussed in the region of the stretching modes ν₃ and ν₁ of the sulfate ions and in the region of asymmetric bending modes ν₄ of the NH₄⁺ ions, respectively. The SO₄^2? ions matrix-isolated in the selenate matrices (approximately 2 mol%) exhibit three bands for ν₃ and one band for ν₁ in agreement with the low site symmetry C₁ of the selenate host ions. The NH₄⁺ guest ions included in the potassium sulfate matrix are characterized also with three site symmetry components of ν₄. However, the ammonium ions in (NH₄)₂Zn(SeO₄)₂·6H₂O as well as those included in K₂Zn(SeO₄)₂·6H₂O display four infrared bands corresponding to ν₄ probably due to some kind of disorder of the ammonium ions. The extent of energetic distortion of the isomorphously included sulfate ions as deduced from the values of Δν₃ (site-group splitting) and Δν_max (the difference between the highest and the lowest wavenumbered components of the stretching modes) are commented. The spectroscopic experiments reveal that the SO₄^2? guest ions are weaker distorted in the potassium selenate matrix than the same ions in the neat potassium sulfate due to the larger unit-cell volumes of the selenate compounds. However, the SO₄^2? guest ions are stronger distorted in the ammonium selenate matrix as compared to the same ions in the neat ammonium sulfate owing to the formation of hydrogen bonds between the SO₄^2? guest ions and the NH₄⁺ host ions. The analysis of the spectra shows that the band positions of the water librations in the host potassium compounds are affected by the included ammonium cations. The formation of the hydrogen bonds between the NH₄⁺ guest ions and the XO₄^2? host ions leads to a decrease in the proton acceptor capabilities of the anions (anti-cooperative or proton acceptor competitive effect) and as a result the hydrogen bonds formed by the water molecules weaken on going from the neat potassium compounds to the mixed crystals K_1.8(NH₄)_0.2Zn(SO₄)₂·6H₂O and K_1.8(NH₄)_0.2Zn(SeO₄)₂·6H₂O (the bands corresponding to water librations are broadened and shifted to lower frequencies).     

Investigation of Residual Oxide Layers on GaAs Surfaces

GaAs(100) and (111) oriented samples, treated by means of different chemical procedures, are studied by X-ray photoelectron spectroscopy (XPS). The thickness and composition of the residual oxide layers are estimated using the intensity ration of Ga 3d and As 3d core levels from the substrate and the oxide overlayers, respectively. Residual oxides containing As₂ O₃ and Ga₂ O₃ on GaAs surface are observed. The thickness of the oxide layers is found to range from 3Å to 15 Å. Optimal conditions for pre-epitaxial surface preparation of GaAs substrates are suggested.     

Hyperfine splitting and isotope shift in the atomic D2 line of 22,23Na and the quadrupole moment of 22Na

The hyperfine structure of the D₂ optical line in ²²Na and ²³Na has been investigated using high resolution laser spectroscopy of a well-collimated atomic beam. The hyperfine splitting constants A and B for the excited 3p ²P_3/2 level for both investigated sodium isotopes have been obtained. They are as follows: A(22) = 7.31(4) MHz, B(22) = 4.71(28) MHz, A(23) = 18.572(24) MHz, B(23) = 2.723(55) MHz. With this data, using the high precision MCHF calculations for the electric field gradient at the nucleus, the electric quadrupole moment of ²²Na has been deduced: Q_s(22) =+0.185(11) b. The sign of Q_s(22), determined for the first time, indicates a prolate nuclear deformation. A precise value of the isotope shift ^22,23Na in the D₂ line has also been obtained. Received: 26 February 1998 / Revised version: 25 June 1998     

Thermal dehydration of the double salts K2Be(XO4)2·2H2O (X = S,Se)

The thermal dehydration of the title compounds was studied by TG, DTA and DSC methods and the enthalpies of dehydration were calculated (87.6 kJ mol^–1 and 167.5 kJ mol^–1 for the sulfate and selenate compound, respectively). The larger value of ΔH_deh of K₂Be(SeO₄)₂·2H₂O is due to the stronger hydrogen bonds formed in the selenate as compared to those formed in the respective sulfate owing to the stronger proton acceptor capabilities of the SeO₄^2– ions. The enthalpies of formation (ΔH_f⁰) of the dihydrates are also calculated from the DSC measurements (– 4467.4 kJ mol^–1 and – 3447.1 kJ mol^–1 for the sulfate and selenate compound, respectively). The anhydrous double salt, K₂Be(SO₄)₂, forms tetragonal crystals with lattice parameters: a = 7.232(2) Å; c = 14.168(2) Å; V = 741.0 ų, while the anhydrous salt, K₂Be(SeO₄)₂, forms monoclinic crystals with lattice parameters: a = 9.217(3) Å; b = 10.645(3) Å; c = 8.989(2) Å; β = 108.52(4)°; V = 836.2 ų. Vibrational spectra (infrared and Raman) of both the dihydrates and the anhydrous compounds are also presented and discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of 1,3-aminonaphthols by diastereoselective Betti-type aminoalkylation of dihydroxy naphthalenes; diastereoselectivity,absolute configuration,and application

Dihydroxy naphthalenes have been applied in Betti-type solventless condensation between aldehydes and (S)-phenylethylamine as a chiral auxiliary. A series of chiral 1,3-aminonaphthols has been synthesized and isolated in diastereoisomerically pure form. The absolute configurations of the aminonaphthols synthesized have been determined by means of advanced NMR experiments and confirmed by X-ray crystallography. The new chiral aminonaphthols have been tested as pre-catalysts for the addition of diethyl zinc and alkynyl-Zn-reagents to aldehydes with enantioselectivities of up to 98% ee.