X-ray photoelectron spectra of iron complexes: Correlation of iron 2p satellite intensity with complex spin state

Metal and ligand core-level spectra have been obtained for 36 iron complexes which possess a variety of ligands including carbonyl, nitrosyl, triphenylphosphine,o-phenylenebis(dimethylarsine), halides and pseudohalides. Formal metal oxidation states range from ? 1 to + 3, and complex spin states represented in the series include 0, $\text{1}\text{2}$, $\text{3}\text{2}$, 2 and $\text{5}\text{2}$. A clear correlation between complex spin state and satellite intensity in the Fe 2p spectra is found. The satellite intensities observed experimentally are in approximate quantitative accord with those predicted by a “spin flipping” model. Although the present analysis does not provide a definitive choice between the “sudden approximation” and “spin flipping” models, the agreement between experimental satellite intensities and the intensities predicted by the “spin flipping” model suggests that such a mechanism can be important in the satellite process.     

A study of 75Se by neutron capture and the SU(3)-SU(5) transition in the quadrupole-phonon representation

The γ and e^? spectra following thermal neutron capture in ⁷⁴Se were studied with curved-crystal, β, and pair spectrometers. Precise energies have been obtained for the transitions and levels at low energies. Two primary E2 transitions were found. The neutron separation energy for ⁷⁵Se was determined as 8027.6 keV. Precise γ-energies following the electron capture decay of ⁷⁵Se were also measured, resulting in precise level energies in ⁷⁵As. The calculation of the energy levels in ⁷⁵Se has been performed in the SU(6) particle-vibrational model (PTQM) and 27 theoretical states have been tentatively assigned to the experimental levels. The spectrum of the core nucleus ⁷⁴Se has been calculated in the SU(6) quadrupolephonon model (TQM). The structure of theoretical states, the relation to SU(3) and SU(5) limits, and potential energy surface are discussed. The E2, M1 and E1 transitions have been calculated in PTQM and compared to the experiment. Also, an overview is presented of theoretical explanations of the I = j, j?1, j?2 anomalous triplet emphasizing the rule with shell-model classification corrected for quadrupole phonons.     

Transition probabilities in 134Pr: a test for chirality in nuclear systems

Exited states in 134Pr were populated in the fusion-evaporation reaction 119Sn(19F,4n)134Pr. Recoil distance Doppler-shift and Doppler-shift attenuation measurements using the Euroball spectrometer, in conjunction with the inner Bismuth Germanate ball and the Cologne plunger, were performed at beam energies of 87 MeV and 83 MeV, respectively. Reduced transition probabilities in 134Pr are compared to the predictions of the two quasiparticle + triaxial rotor and interacting boson fermion-fermion models. The experimental results do not support the presence of static chirality in 134Pr underlying the importance of shape fluctuations. Only within a dynamical context the presence of intrinsic chirality in 134Pr can be supported.     

Electrical study of cathodic activation and relaxation of La0,80Sr0,20MnO3

The effect of cathodic activation of sprayed La_0.8Sr_0.2MnO₃ (LSM) films has been studied by electrochemical spectroscopy impedance (EIS). LSM powder was prepared by a citrate route and X-ray diffraction analyses show a complete LSM crystallization without La₂O₃ or La(OH)₃ as side products. Porosity and grain size estimated from scanning electronic microscopy gave values of 33% and 100 nm, respectively. EIS measurement was performed on a Pt/yttria-stabilized zirconia/LSM cell before and after a cathodic current load (300 mA/cm²) on LSM electrode. The relaxation process, which is time-dependent, has been investigated. A drastic decrease of the electrode resistance was noticed just after applying the cathodic current, but after 9 h at optimized valence configuration in air at 850 °C, the recorded polarization resistance gradually enhanced until it almost reached the initial value. The resulting diagrams have been fitted using a Gerischer associated with a resistor and constant phase elements. This simple method has permitted us to observe that only the electrode interfaces are modified by a cathodic activation and the microstructure remains nearly constant.     

Use of an (Hemi) Cellulolytic Enzymatic Extract Produced by Aspergilli Species Consortium in the Saccharification of Biomass Sorghum

This study evaluated the production of lignocellulose-degrading enzymes by solid-state fermentation (SSF) using a microbial consortium of Aspergillus fumigatus SCBM6 and A. niger SCBM1 (AFN extract). The fungal strains were cultivated in sugarcane bagasse (SCB) and wheat bran (WB) as lignocellulosic substrates for 7 days at 30 °C. After SSF, the highest peaks of enzyme production were 150 and 80 U g⁻¹ for β-xylosidase and β-glucosidase at 48 h, 375 U g⁻¹ for xylanase at 96 h, and 80 U g⁻¹ for endoglucanase and 4 U g⁻¹ for cellulase activity on filter paper (FPase) at 144 h. The efficiency of the produced AFN extract was investigated in the enzymatic hydrolysis of crude biomass sorghum (BS) and after the removal of extractives (ES). After saccharification, the glucose and xylose concentrations were 10× superior in ES than in BS hydrolysate (2.5 g L⁻¹ after 12 h). The presence of inhibitors of alcoholic fermentation, such as formic acid, was also reduced in ES hydrolysates, indicating that the removal of extractives positively contributed to the effectiveness of enzymatic hydrolysis of biomass sorghum using AFN extract.

     

Self-aligning method of fiber-to-waveguide pigtailing

An innovative self-aligning technique for the pigtailing of optical fibers to buried channel planar waveguides is presented, based on selective etching. This technique utilizes a plug-and-socket mechanism that is intrinsically self-aligning and mechanically stable. The processes involved have been specifically designed to facilitate the bulk manufacture of pigtailed single or multiple fibers and waveguides. An optimized alignment geometry for the physical connection of fibers to waveguides is presented.     

Optically detected magnetic resonance in the photoexcited triplet states of Ti(IV) and Zr(IV) cylopentadienyl complexes

The class of compounds (RCp)2MX2, where M is a group IV metal, Cp is cyclopentadienyl, R is an alkyl, and X is a halide, has been of continuing interest as precursors for olefin coordination polymerization catalysts. In this communication, we demonstrate that the technique of optically detected magnetic resonance (ODMR) reveals subtle differences in the composition of the frontier molecular orbitals associated with the nature of the alkyl substituents on the Cp rings.     

Spectroscopy of the deformed 126Ce nucleus

The even-even nucleus ¹²⁶Ce was studied via in-beam γ-ray spectroscopy using the ⁴⁰Ca + ⁹²Mo reaction at 190 MeV. Five bands were observed, one of them being identified for the first time. New connecting transitions were identified between the bands, which lead to new spin assignments. The bands are discussed in the framework of the IBM + broken pairs model. Received: 17 July 2002 / Accepted: 23 October 2002 / Published online: 18 February 2003 RID="a" ID="a"e-mail: costel.petrache@unicam.it Communicated by C. Signorini     

SU(6) model for odd-odd nuclei (OTQM/IBOM) and boson-aligned phase diagram inO(6) limit

We introduce the SU(6) model IBOM/OTQM for odd-odd nuclei and discuss the bands in O(6) limit. Bands are characterized by a particular type of phase correlations in the wave functions and exhibit splitting of the SU(3) analogs of Gallagher-Moszkowski bands.