Isotope Shift in the Dielectronic Recombination of Three-Electron ANd57+

Isotope shifts in dielectronic recombination spectra were studied for Li-like ^ANd⁵⁷⁺ ions with A=142 and A=150. From the displacement of resonance positions energy shifts dE^142?150(2s-2p_1/2)=40.2(3)(6)??meV [(stat)(sys)] and dE^142?150(2s-2p_3/2)=42.3(12)(20)??meV of 2s-2p_jtransitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of ^142?150d?r²?=-1.36(1)(3)??fm². The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.

Energy levels and radiative rates for transitions in Mg-like iron, cobalt and nickel

Energy levels and radiative rates for electric dipole (E1) transitions among the lowest 141 levels of the (IS2 2s(2) 2P(6)) 3l(2) , 3l3l', and 3l4l configurations of Fe XV, Co XVI, and Ni XVII are calculated through the CIV3 code using extensive configuration-interact ion (CI) wavefunctions. The important relativistic effects are included through the Breit-Pauli approximation. In order to keep the calculated energy splittings close to the experimental values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. The energy levels, including their orderings, are in excellent agreement with the available experimental results for all three ions. However, experimental energies are only available for a few levels. Since mixing among some levels is found to be very strong, it becomes difficult to identify these uniquely. Additionally, some discrepancies with other theoretical work (particularly for Ni XVII) are very large. Therefore, in order to confirm the level ordering as well as to assess the accuracy of energy levels and radiative rates, we have performed two other independent calculations using the GRASP and FAC codes. These codes are fully relativistic, but the CI in the calculations is limited to the basic (minimum) configurations only. This enables us to assess the importance of including elaborate Cl for moderately charged ions. Additionally, we report results for electric quadrupole (E2), magnetic dipole (MI), and magnetic quadrupole (M2) transitions, and list lifetimes for all levels. Comparisons are made with other available experimental and theoretical results, and the accuracy of the present results is assessed. (c) 2007 Elsevier Inc. All rights reserved.

Uptake of carbon, nitrogen and phosphorus by phytoplankton along the 20 degrees W meridian in the NE Atlantic between 57.5 degrees N and 37 degrees N

Phytoplankton biomass and rate of production were measured along a transect from 57.54 degreesN to 37.01 degreesN in the northeast Atlantic during July 1996 and at a series of stations over a 7-day period at 37 degreesN 20 degreesW. Surface nutrient concentrations ranged from 4 mu mol l(-1) NO3-, and 0.35 mu mol l(-1) PO43- at 57.54 degreesN to <10 nmol l(-1) NO3- and similar to 10 nmol l(-1) PO43- at 37.01 degreesN. The greatest phytoplankton biomass and production were measured in the vicinity of a frontal system at 50 degreesN, and there was a general decline in total phytoplankton biomass and production to the south of the transect. Production was measured in three size fractions. At the station with the highest chlorophyll concentrations (50.34 degreesN), phytoplankton cells larger than 5 mum dominated the assemblage, accounting for 72% of the chlorophyll concentration (22.9 mg m(-2)) and 51% of primary production (54.1 mmol Cm-2 d(-1)), but picophytoplankton production was also high (43%). At 57 degreesN, carbon fixation by the > 5 mum fraction accounted for 75% of the daily production of 60.75 mmol Cm-2 d(-1). At 37 degreesN, picophytoplankton was the dominant group, accounting for similar to 58% (10 mg m(-2)) of chlorophyll and similar to 64% (46 mmol Cm-2 d(-1)), of primary production. Nitrate, ammonium and phosphate uptake rates also were determined. Although high nitrate uptake rates were measured in the surface water at similar to 50 degreesN, the greatest uptake rates of both depth-integrated nitrate and ammonium were at the south of the transect. At 37 degreesN, a deep euphotic zone was present and light penetrated through the nitracline; total nitrate uptake was enhanced because of assimilation at the base of the euphotic zone. As a consequence, high values of depth-integrated f-ratio were measured in the oligotrophic waters at the south of the transect. Phosphate was predominantly incorporated into the picoplankton fraction, which included heterotrophic and autotrophic components, at all stations and a significant proportion of phosphate uptake occurred in the dark. The C:N:P assimilation ratios were variable throughout the region; phosphate uptake was generally greater than would be expected if nutrient assimilation were in proportion to the Redfield ratio. (C) 2001 Elsevier Science Ltd. All rights reserved.

A quantitative determination of reaction mechanisms from density functional theory calculations: Fischer-Tropsch synthesis on flat and stepped cobalt surfaces

We systematically investigated the mechanism of the C-1 + C-1 coupling reactions using density functional theory. The activation energies of C-1 + C-1 coupling and carbon hydrogenation reactions on both flat and stepped surfaces were calculated and analyzed. Moreover, the coverages of adsorbed C-1 species were estimated, and the reaction rates of all possible C-1 + C-1 coupling pathways were quantitatively evaluated. The results suggest that the reactions of CH2 + CH2 and CH3 + C at steps are most likely to be the key C-1 + C-1 coupling steps in FT synthesis on Co catalysts. The reactions of C-2 + C-1 and C-3 + C-1 coupling also were studied; the results demonstrate that in addition to the pathways of RCH + CH2 and RCH2 + C, the coupling of RC + C and RC + CH also may contribute to the chain growth after C-1. (C) 2008 Elsevier Inc. All rights reserved.

Influence of the anion on the electrodeposition of cobalt from imidazolium ionic liquids

Cyclic voltammetry and absorption spectrophotometry were used to examine the complex formation of cobalt (II) in the ionic liquids 1-butyl-3-methylimidazolium chloride ([C(4)mim] Cl) and 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([C(4)mim][Tf2N]). In [C(4)mim]Cl, cobalt(II) is complexed as [CoCl4](2-) at CoCl2 concentrations less than 33 mol %. Cyclic voltammograms show that cobalt cannot be electrodeposited at these concentrations. However, cobalt metal can be electrodeposited at CoCl2 concentrations above the threshold concentration of 33 mol %. In the ionic liquid [C(4)mim][Tf2N] there is no threshold CoCl2 concentration for electrodeposition due to the absence of [CoCl4](2-). (C) 2007 The Electrochemical Society.

Cobalt(II) Complexes of Nitrile-Functionalized Ionic Liquids

A series of nitrile-functionalized ionic liquids were found to exhibit temperature-dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trifluoromethylsulfonyl)imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C1C1CNPyr)2(Tf2N)4] and [Co(C1C2CNPyr)6][Tf2N]8, which were isolated from ionic-liquid solutions, gave an insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt-containing ionic liquids.

V-band 57-65 GHz receiver

A simple V-band radio IQ receiver architecture based around a six-port monolithic microwave integrated circuit (MMIC) is presented. The receiver assembly is designed to cover the 57-65 GHz broadband wireless communication system frequency allocation. The receiver that has an integral 10 dB microstrip antenna consumes 120 mW of dc power and occupies an area of 23 mm x 16 mm. The receiver can be used in heterodyne or in homodyne mode and has the capacity to demodulate quadrature amplitude modulation (QAM), binary phase shift keying (BPSK)/quadrature phase shift keying (QPSK)/offset quadrature phase shift keying (OQPSK). At 60 GHz the receiver can operate over 10 m range for transmitter effective isotropic radiated power (EIRP) of 20 dBm.

The synthesis, characterisation and reactivity of 2-phosphanylethylcyclopentadienyl complexes of cobalt, rhodium and iridium

2-Phosphanylethylcyclopentadienyl lithium compounds, Li[C5R'(4)(CH2)(2)PR2] (R = Et, R' = H or Me, R = Ph, R' = Me), have been prepared from the reaction of spirohydrocarbons C5R'(4)(C2H4) with LiPR2. C5Et4HSiMe2CH2PMe2, was prepared from reaction of Li[C5Et4] with Me2SiCl2 followed by Me2PCH2Li. The lithium salts were reacted with [RhCl(CO)2]2,[IrCl(CO)3] or [Co-2(CO)(8)] to give [M(C5R'(4)(CH2) 2PR2)(CO)] (M = Rh, R = Et, R' = H or Me, R= Ph, R' = Me; M = Ir or Co, R = Et, R' = Me), which have been fully characterised, in many cases crystallographically as monomers with coordination of the phosphorus atom and the cyclopentadienyl ring. The values of nu(CO) for these complexes are usually lower than those for the analogous complexes without the bridge between the cyclopentadienyl ring and the phosphine, the exception being [Rh(Cp'(CH2)(2)PEt2)(CO)] (Cp' = C5Me4), the most electron rich of the complexes. [Rh(C5Et4SiMe2CH2PMe2)(CO)] may be a dimer. [Co-2(CO)(8)] reacts with C5H5(CH2)(2)PEt2 or C5Et4HSiMe2CH2PMe2 (L) to give binuclear complexes of the form [Co-2(CO)(6)L-2] with almost linear PCoCoP skeletons. [Rh(Cp'(CH2)(2)PEt2)(CO)] and [Rh(Cp'(CH2)(2)PPh2)(CO)] are active for methanol carbonylation at 150 degrees C and 27 bar CO, with the rate using [Rh(Cp'(CH2)(2)PPh2)(CO)] (0.81 mol dm(-3) h(-1)) being higher than that for [RhI2(CO)(2)](-) (0.64 mol dm(-3) h(-1)). The most electron rich complex, [Rh(Cp'(CH2)(2)PEt2)(CO)] (0.38 mol dm(-3) h(-1)) gave a comparable rate to [Cp*Rh(PEt3)(CO)] (0.30 mol dm(-3) h(-1)), which was unstable towards oxidation of the phosphine. [Rh(Cp'(CH2)(2)PEt2)I-2], which is inactive for methanol carbonylation, was isolated after the methanol carbonylation reaction using [Rh(Cp'(CH2)(2)PEt2)(CO)].