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Polarized spectra of natural brownish-yellow Fe-rich staurolite from Pizzo Forno (Switzerland) evidence that its color is very likely due to an intervalence charge-transfer transition between [Fe.sup.2+] and [Ti.sup.4+] that causes a broad absorption band at ca. 25 400 [cm.sup.-1] superimposed on an intense high-energy edge. The polarization properties of the band and, also, the visible pleochroism [gamma] > [alpha] >> [beta] of the sample studied, which is found to be different to previously published data viz. [gamma] > [beta] >> [alpha], does not unambiguously give evidence of the structural positions of [Ti.sup.4+] ions involved in the IVCT process. In the NIR-range, we observe a broad structured absorption envelope caused by an electronic spin-allowed band of [sup.IV][Fe.sup.2+] containing three broad components at around 5445, 4625, and 3800 [cm.sup.-1] and strong narrow [beta]- and [gamma]-polarized lines of OH-vibrations in the range 3600 to 3400 [cm.sup.-1]. Curve-fitting analysis suggests that the three crystal field bands are due to lowering of the local symmetry of the tetrahedral [Fe.sup.2+] from [T.sub.d] to ca. [C.sub.2v], so they are assigned to the split electronic [sup.5]E [right arrow] [sup.5][T.sub.2] transition of [sup.IV][Fe.sup.2+]. Noticeable differences in the temperature- and pressure-induced effects on the spin-allowed bands of [sup.IV][Fe.sup.2+] in staurolite compared to spinel--another [sup.IV][Fe.sup.2+]-bearing mineral--are observed. This implies a suppression of the Jahn-Teller effect in staurolite that is normally intrinsic to ions with doublefold degenerate electronic ground state such as [sup.IV][Fe.sup.2+]. Keywords: Staurolite, optical absorption spectra, IVCT, dd-transitions, temperature and pressure effect DO1: 10.2138/am.2010.3207

A new solution to the inversion of Fraunhofer diffraction for particle sizing was introduced. Compared with the well-known Chin-Shifrin inversion, it is an inversion of the form of integral transform and less sensitive to noise. Simulation results with noise-contaminated data were obtained and showed that the new inversion is better than the Chin-Shifrin inversion. Especially when the particle diameter was small, the new inversion still performed well, whereas the Chin-Shifrin inversion did not converge. OCIS codes: 290.0290, 290.2558, 290.3200, 290.5850.

The (2,0) band of the [B.sup.2][Δ.sub.5/2]-[X.sup.2][Δ.sub.5/2] transition has been recorded with rotational resolution using intracavity laser absorption spectroscopy. The gas phase NiH molecules were produced in an electric discharge using a nickel hollow cathode in a pure hydrogen atmosphere at 2-3 torr total pressure. Peak positions for the NiH isotopologues are presented for these transitions. Large isotopologue splittings are observed for [B.sup.2][Δ.sub.5/2]-[X.sup.2][Δ.sub.5/2] (2,0) transitions. A strong perturbation is observed in the excited state at [J.sub.f] = 6.5. NiH isotopologue ratios in stellar spectra can be used to determine the neutron to proton ratio, with a view to probing models of supernovae and star formation. PACS Nos: 95.55.Qf, 95.75.Fg, 42.62.Fi Nous avons enregistre les bandes (2, 0) de la transition [B.sup.2][Δ.sub.5/2]-[X.sup.2][Δ.sub.5/2] du NiH en utilisant la spectroscopie a absorption laser intracavite. Nous avons produit les molecules de NiH en phase gazeuse par decharge electrique d'une cathode creuse de Ni dans une atmosphere d'hydrogene pur a 2-3 torr de pression totale. Nous presentons la position des pics pour les isotopologues de NiH pour ces transitions. De larges differences entre isotopologues sont observees dans les transitions [B.sup.2][Δ.sub.5/2]-[X.sup.2][Δ.sub.5/2] (2, 0). Nous observons une forte perturbation de l'etat excite [J.sub.f] = 6,5. Les rapports d'isotopologues NiH dans les spectres stellaires peuvent etre utilises pour determiner le rapport neutron/proton, avec comme objectif de verifier les modeles de formation stellaire et de supernovae. [Traduit par la Redaction], Introduction Diatomic transition metal compounds are important molecules as intermediates in various fundamental and applied science areas, such as in astrophysics and surface science. Chemical equilibrium calculations for cool stellar [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.forsciint.2007.02.029 Byline: Craig D. Adam, Sarah L. Sherratt, Vladimir L. Zholobenko Keywords: Ink; UV-vis spectroscopy; Principal component analysis; Forensic Abstract: The technique of principal component analysis has been applied to the UV-vis spectra of inks obtained from a wide range of black ballpoint pens available in the UK market. Both the pen ink and material extracted from the ink line on paper have been examined. Here, principal component analysis characterised each spectrum within a group through the numerical loadings attached to the first few principal components. Analysis of the spectra from multiple measurements on the same brand of pen showed excellent reproducibility and clear discrimination between inks that was supported by statistical analysis. Indeed it was possible to discriminate between the pen ink and the ink line from all brands examined in this way, suggesting that the solvent extraction process may have an influence on these results. For the complete set of 25 pens, interpretation of the loadings for the first few principal components showed that both the pen inks and the extracted ink lines may be classified in an objective manner and in agreement with the results of parallel thin layer chromatography studies. Within each class almost all inks could be individualised. Further work has shown that principal component analysis may be used to identify a particular ink from a database of reference UV-vis spectra and a strategy for developing this approach is suggested. Author Affiliation: Faulds Laboratories, Department of Chemical and Forensic Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK Article History: Received 12 September 2006; Revised 5 February 2007; Accepted 28 February 2007

Magnetosomes are magnetite nanoparticles formed by biomineralization within magnetotactic bacteria. Although there have been numerous genetic and proteomic studies of the magnetosome-formation process, there have been only limited and inconclusive studies of mineral-phase evolution during the formation process, and no real-time studies of such processes have yet been performed. Thus, suggested formation mechanisms still need substantiating with data. Here we report the examination of the magnetosome material throughout the formation process in a real-time in vivo study of Magnetospirillum gryphiswaldense, strain MSR-1. Transmission EM and x-ray absorption spectroscopy studies reveal that full-sized magnetosomes are seen 15 min after formation is initiated. These immature magnetosomes contain a surface layer of the nonmagnetic iron oxide-phase hematite. Mature magnetite is found after another 15 min, concurrent with a dramatic increase in magnetization. This rapid formation result is contrary to previously reported studies and discounts the previously proposed slow, multistep formation mechanisms. Thus, we conclude that the biomineralization of magnetite occurs rapidly in magnetotactic bacteria on a similar time scale to high-temperature chemical precipitation reactions, and we suggest that this finding is caused by a biological catalysis of the process. biomineralization | magnetotactic bacteria | biogenic magnetite | [alpha]-hematite precursor

X-ray absorption spectroscopy is used for investigating the local coordination in gallium nanostructures as a function of temperature and particle size. The nanostructure size has affected the polymorphism of solid gallium and the metastability range of the liquid phase and the surface tension has acted in the same direction as hydrostatic pressure.

An algorithm is presented based on an evolution strategy to retrieve a particle size distribution from angular light-scattering data. The analyzed intensity patterns are generated using the Mie theory, and the algorithm retrieves a series of known normal, gamma, and lognormal distributions by using the Fraunhofer approximation. The distributions scan the interval of modal size parameters 100 [less than or equal to] [bar.[alpha]] [less than or equal to] 150. The numerical results show that the evolution strategy can be successfully applied to solve this kind of inverse problem, obtaining a more accurate solution than, for example, the Chin-Shifrin inversion method, and avoiding the use of a priori information concerning the domain of the distribution, commonly necessary for reconstructing the particle size distribution when this analytical inversion method is used. OCIS codes: 290.0290, 290.3200, 290.4020, 290.5850.

The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm was used to study the dissociation of methanol between 1591 and 2865 K. The values obtained for reaction C[H.sub.3]OH Kr -> C[H.sub.3] OH Kr and C[H.sub.3]OH Kr -> C[H.sub.2] [H.sub.2]O Kr were found to be in agreement with the result data for earlier experimental determination and also for OH C[H.sub.3] -> products.

An experiment which explores the interaction between Cu(II) ion and tetraglycine (TetraGly) as an excellent model of a protein fragment is presented. The analysis has allowed the students to determine the coordination modes of TetraGly with varying pH.

Surface sensitive x-ray absorption spectroscopy (XAS) is compared to bulk sensitive electron energy loss spectroscopy (EELS) studies of vanadium oxide nanotubes, which are synthesized via sol-gel route. The obtained spectra have helped in distinguishing single-wall from multiwall [V.sub.2][O.sub.5] nanotubes.

The detection of vapors of dinitrobenzenes and dinitrotoluenes by UV cavity ringdown spectroscopy (CRDS) was investigated. Absorption cross sections at 248 nm were estimated by measurements on saturated vapors and compared with solution-phase values. The computed subparts per [10.sup.9] detection sensitivity with no effort at preconcentration was demonstrated through measurements on diluted flows. The factors affecting measurements on 1 atm total pressure were considered, and it was demonstrated that Rayleigh scattering by air will reduce the detection sensitivity by 5%-10%. The UV absorption spectra of these compounds are broad, resulting in a relatively poor selectivity for single-wavelength measurements with the UV CRDS technique. OCIS codes: 280.3420, 300.1030, 300.6390.

A multiline absorption spectroscopy technique was investigated based on the single-line absorption spectroscopy technique. An open-path methane-detecting system was designed. An LED was used as a broadband source, and a Fabry-Perot interferometer whose transmission peaks matched the methane R-branch absorption lines was used to enhance the detectable sensitivity. We demonstrate a minimum-detectable concentration of 7600 [+ or -] 10% ppm (parts per million) with a multiline differential absorption spectroscopy technique and a concentration of 1000 [+ or -] 10% ppm with a multiline wavelength modulation spectroscopy technique.

We present a statistical analysis of a large set of absorption spectra of phytoplankton, measured in natural samples collected from ocean water, in conjunction with detailed pigment concentrations. We processed the absorption spectra with a sophisticated neural network method suitable for classifying complex phenomena, the so-called self-organizing maps (SOM) proposed by Kohonen [Kohonen, Self Organizing Maps (Springer-Verlag, 1984)]. The aim was to compress the information embedded in the data set into a reduced number of classes characterizing the data set, which facilitates the analysis. By processing the absorption spectra, we were able to retrieve well-known relationships among pigment concentrations and to display them on maps to facilitate their interpretation. We then showed that the SOM enabled us to extract pertinent information about pigment concentrations normalized to chlorophyll a. We were able to propose new relationships between the fucoxanthin/Tchl-a ratio and the derivative of the absorption spectrum at 510 nm and between the Tchl-b/Tchl-a ratio and the derivative at 640 nm. Finally, we demonstrate the possibility of inverting the absorption spectrum to retrieve the pigment concentrations with better accuracy than a regression analysis using the Tchl-a concentration derived from the absorption at 440 nm. We also discuss the data coding used to build the self-organizing map. This methodology is very general and can be used to analyze a large class of complex data.

The development of a new concurrent multiaxis (CMAX) sky viewing spectrometer to monitor rapidly changing urban concentrations of nitrogen dioxide is detailed. The CMAX differential optical absorption spectroscopy (DOAS) technique involves simultaneous spectral imaging of the zenith and off-axis measurements of spatially resolved scattered sunlight. Trace-gas amounts are retrieved from the measured spectra using the established DOAS technique. The potential of the CMAX DOAS technique to derive information on rapidly changing concentrations and the spatial distribution of N[O.sub.2] in an urban environment is demonstrated. Three example data sets are presented from measurements during 2004 of tropospheric N[O.sub.2] over Leicester, UK (52.62[degrees]N, 1.12[degrees]W). The data demonstrate the current capabilities and future potential of the CMAX DOAS method in terms of the ability to measure real-time spatially disaggregated urban N[O.sub.2]. OCIS codes: 010.1120, 120.0280, 300.0300.

The modified nucleic acid base, 1-cyclohexyluracil is examined by femtosecond transient absorption spectroscopy in protic and aprotic solvents of varying polarity. The transient absorption signals reveal ultrafast branching in the initial bright state prepared by ultraviolet absorption, and while a fraction of the population decays through ultrafast internal conversion to [S.sub.0], a significant fraction of 40% decays to a dark [sup.1]n[pi.sup.*] state, which decays to [S.sub.0] on a slower time scale.

The structures of [C.sub.7][H.sub.9.sup.} ions generated by protonation of toluene are examined by using gas-phase infrared spectroscopy in conjunction with labeling experiments and complementary mass spectrometric studies. The results have confirmed the structural predictions derived from theory and have provided evidence for the existence of protonated cycloheptatriene, but have posed some questions about the comparability of intensities in multiphoton dissociation and linear absorption spectra.

Abstract -- Amidinothiourea immobilized glass bead (AGB) was applied as the microcolumn packing for the flow-injection online separation and preconcentration of Au(III) and Pd(II) coupled with FAAS determination. The peak-area [...]

A report on the mechanism for the photoreaction of trans-4'-benzyl-5-styrylfuran (trans-BSF) in the absence and presence of oxygen during picosecond (ps) or nanosecond (ns) laser flash photolysis (LFP) is presented. Transient fluorescence and absorption spectra assigned to the singlet excited trans-BSF are observed during the 30-ps LFP.

Absorption and emission spectra of asFP595 are similar to those of a number of cloned GFP-like red proteins of the DsRed subfamily. It is reported that asFP595 chromophore is actually very close in chemical structure to that of zFP538, a yellow fluorescent protein.

It is shown that spherical reverse micelles induce the spheres and also various other particle shapes like cubes, tetrahedral and ellipsoidal particles. A comparison of the HRTEM and transmission electron micrographs (TEM) results with the DNA simulations made for various shapes indicates that the additional resonance band is the proof of the presence of mainly decahedral nanocrystals with ellipsoidal particles and trigonal prisms.

The electrooxidation of CO is studied on reconstructed gold single-crystal surfaces by a combination of electrochemical (EC) and infrared reflection absorption spectroscopy (IRAS) measurements. The IRAS/EC data indicate that the kinetics of CO oxidation is structure sensitive.

The (0,0) band of the electronic transition of VN near 450.5 nm is investigated using the technique of laser vaporization/reaction with free jet expansion and cavity ring-down laser absorption spectroscopy. A comparison of the observed electronic states of VN to those of the isoelectronic TiO molecule supports the assignment.

The high potential and current status of the research involving the use of ultrafast X-ray absorption spectroscopy (XAS), the boundary conditions of the technique and the implementation of XAS, is presented. XAS helps in providing the electronic and structural information on the system.

An investigation conducted to determine the effect of surface modification on the back electron transfer (BET) reaction of Alz-sensitized TiO2 nanoparticles using the femtosecond transient absorption technique in the visible and near-IR region is presented. It is shown that on surface modification, the rate of the BET reaction can be reduced drastically in the dye-sensitized TiO2 nanoparticle system.

A method used to create strong luminescent, diffraction-limited clusters of small, stable sliver nanoparticles using a conventional confocal microscope setup is discussed. The distribution of silver nanoparticles is likely to contain predominantly very small particles with radii on the order to a few nanometers.

Two geometrically constrained Cu(I)-monophennthroline complexes are investigated in order to study that ligand constraints have on the excited-state dynamics of copper-phenanthroline complexes. The conclusion states that femtosecond transient absorption spectroscopy enables o spectrally and temporally resolve the effect of ligand constraints on the flattening rearrangement dynamics in photoexcited Cu(I)-monophenanthroline complexes.

The photochemical reactions occurring after irradiation at 200 nm of the aqueous nitrate ion, No3(super -1)(aq) is examined. The formation and subsequent relaxation of the primary photoproducts of nitrate photolysis is characterized using the femtosecond transient absorption spectroscopy over the range 194-388 nm.

Laser-assisted size-reduction and network formation of gold nanoparticles were performed in pure water and in a sodium dodecyl sulfate (SDS) solution and the mechanisms were studied by applying optical absorption spectroscopy and electron microscopy. Results reveal that the laser-assisted size reduction and network formation of gold nanoparticles is a promising method for preparing nanoscale devices consisting of nanoparticles and nanowires with a desired size.

The transient absorption spectra in the visible region and their decay dynamics following excitation of synthetic pheomelanin and Sepia eumelanin at 303 nm are compared. An enhanced photoreactivity of the red melanin, pheomelanin compared to the black melanin, eumelanin is invoked to explain why fair skinned individuals are more prone to skin cancers.

The near-IR transient absorption studies of carotenoid spirilloxanthin after excitation to the S2 state, both in an n-hexane solution and in the light-harvesting (LH1) complex of Rhodospirillum rubrum is reported. Upon excitation of spirilloxanthin, both in solution and in the LH1 complex, an intense ESA band appears instantly at approximately 1200 nm and decays with a lifetime of

The series of amorphous nitrided galloaluminophosphate 'AlGaPON' catalysts with nitrogen contents varying from 0 to 23.3 wt% were obtained by nitriding Al(sub 0.5)Ga(sub 0.5)PO(sub 4) precursor under ammonia flow at 750 degreeC in a tubular furnace. The results compared by using X-ray absorption spectroscopy (XAS) and X-ray photoelectrons spectroscopy on five samples is described.

The first eight valence excited states of the three conformers of n-Si4Me10, transoid, ortho, and gauche, is described using the mutistate complete active space second-order pertubation theory (MS-CASPT2) method. The results show the dependence of the UV absorption spectrum of the tetrasilanechromophore on the skeletal dihedral angle in terms of avoided crossings of both B and A symmetry states.

The absolute absorption spectrum of the benzyl radical in the visible region measured by ring-down spectroscopy in the visible region measured by cavity ring-down spectroscopy is presented. The absorption cross sections reported would facilitate the quantification of the benzyl radical in future kinetic studies.

Layer-by-layer thin films are prepared by the alternate deposition of clay particles and ionic organic compounds from solution onto a rigid support. A close examination of the absorption spectra of the donor -acceptor systems reveals that an interaction occurs in the assembly that results in excess acceptor dye being incorporated into the film.

Electroabsorption (Stark) spectroscopy is used to study the dye sensitized interfacial electron transfer in Fe(super II)(CN)(sub 6)(super 4-) donor complex bound to a TiO2 nanoparticle. The average charge-transfer distance determined from the Stark spectra is 5.3 angstrom.

A study was conducted, by using the time-resolved infrared spectroscopy (TRIR), laser flash photolysis with UV-vis detection, fluorescence quenching, absorption spectroscopy, and density functional theory calculations, to investigate the photoreaction between riboflavin tetraacetate and nucleosides. The TRIR spectroscopy demonstrates that triplet riboflavin tetraacetate reacts with G' to form a neutral hydroflavin radical by an electron transfer-proton transfer mechanism.

The optical second harmonic generation (SHG) was used to study the electrocatalytic oxidation of formaldehyde on Pt(111) under potentiostatic conditions and periodic potential oscillations. The result shows oscillations of the SHG field under galvanostatic conditions, corresponding to the potential oscillations.

The sol-gel derived gold/silica glasses, starting with Au sols prepared by two different methodologies, one without the aid of any external stabilizing agent and the other with silica-coated Au, are presented. The optical absorption spectra show the typical surface plasmon resonance for Au at around 520-530 nm.

Excited-state twisting and relaxation of triarylpyrylium cations is studied with various substituents attached to different parts of the molecule by means of femtosecond pump-probe absorption spectroscopy. The modeling shows that a broad population distribution along the twisting angle in the ground state is transferred to the excited state, causing strong fluorescene broadening, while competition between the excited-state twisting and solvation determines a subsequent reaction path.

The simultaneous presence of Au(I) and zerovalent goldclusters with an average diameter of about 30 Angstorm in MgO-supported catalysts is demonstrated by X-ray absorption near edge spectroscopy (XANES) of the functioning catalysts during steady-state CO oxidation. The initial dispersion and oxidation state of the gold in the catalyst were found not to affect the properties of the catalyst functioning at steady state.

Femtosecond transient absorption spectroscopy and time-integrated photoluminescence (PL) measurements are used to study charge carrier relaxation in colloidal InP quantum dots (QDS). The results suggest that with increasing excitation energy, there arise relaxation pathways involving surface or external energy states exhibiting reduced radiative efficiency.

The use of a quinone functionality in the linkage unit of laterally bridged oligoporphyrins as a switch for controlling electronic coupling between the termini is examined. This provides a paradigm for the use of molecular electronic devices in sensing, control and high-capacity relatively low-speed data storage applications.

The fast solid-solid transformations with millisecond time resolution is investigated using piezo X-ray absorption spectra (XAFS) technique in combination with an in situ cell. The technique records X-ray absorption spectra in a continuous mode by making use of piezo tilt tables in the X-ray monochromator, which are actuated by an oscillatory high voltage.

Interactions due to intermolecular orbital overlap, responsible for energy transport in the triplet state, are the driving force for singlet excitation transport. Triplet excitation transport in the columnar liquid crystal formed by tetrameric triphenylene derivative was carried out by transient absorption spectrascopy with a nanosecond resolution.

The sulfur 1s and oxygen 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of (SO + 20)/Cu(100) are studied by the multiple-scattering cluster (MSC) method. The analysis shows that the Pi orbital breaks into two levels which shift toward higher energy due to the interaction between SO and the substrate.

Theoretical extended x-ray absorption fine-structure (EXAFS) spectra are computed from molecular dynamics (MD) simulation data. Based on MD-generated geometries, EXAFS spectra are generated with the FEFF6 program, commonly used in the analysis of experimental EXAFS spectra.

X-ray absorption spectroscopy was used to study the structural properties of As-Se-S glass system.

The Chini-type Pt carbonyl clusters ([Pt3(CO)6](sub n)(super 2-), n=4, 5, 6) and other CO-stabilized Pt clusters were synthesized by gamma-radiolysis, and their structures, when supported on carbon and alpha-alumina, were investigated by X-ray absorption spectroscopy (XAS). It was found that the stacking prismatic structure of triangular units in Chini clusters were transformed, when supported on carbon, into another structure in which the trimeric units are conserved but are arranged in a planar monolayer.

An examination is done of the photophysical properties of the singlet (S1) and triplet (T1) excited states of p-aminobenzophenone (p-ABP), which is investigated in various organic solvents using steady state as well as transient absorption spectroscopy with picosecond and subpicosecond time resolution. A comparison is made among the photophysical properties of benzophenone (BP), p-hydroxybenzophenone (p-HOBP) and p-ABP.