WorldWideScience

Sample records for absorption spectra

  1. Absorption Spectra of Astaxanthin Aggregates

    Olsina, Jan; Durchan, Milan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

    2012-01-01

    Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption...

  2. Absorption Spectra of Astaxanthin Aggregates

    Olsina, Jan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

    2012-01-01

    Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption maximum of monomeric astaxanthin (470-495 nm depending on solvent) are caused by excitonic interaction between aggregated molecules. We applied molecular dynamics simulations to elucidate structure of astaxanthin dimer in water, and the resulting structure was used as a basis for calculations of absorption spectra. Absorption spectra of astaxanthin aggregates in hydrated dimethylsulfoxide were calculated using molecular exciton model with the resonance interaction energy between astaxanthin monomers constrained by semi-e...

  3. Optical absorption spectra of Ag-11 isomers

    Martinez, Jose Ignacio; Fernandez, E. M.

    The optical absorption spectra of the three most; stable structural isomers of the Ag-11 cluster were calculated using the time-dependent, density functional theory within the Casida formalism. The slightly different, spectra, of the isomers may permit the identification of the ground-stale confi......The optical absorption spectra of the three most; stable structural isomers of the Ag-11 cluster were calculated using the time-dependent, density functional theory within the Casida formalism. The slightly different, spectra, of the isomers may permit the identification of the ground...

  4. Creating semiconductor metafilms with designer absorption spectra

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-07-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells.

  5. Determination of phytoplankton composition using absorption spectra

    Martínez Guijarro, Mª Remedios; Romero Gil, Inmaculada; Paches Giner, Maria Aguas Vivas; González del Rio Rams, Julio; Martí Insa, Carmen Mª; GIL SEGUÍ, GERMA; Ferrer, Alberto; FERRER, J.

    2009-01-01

    Characterisation of phytoplankton communities in aquatic ecosystems is a costly task in terms of time, material and human resources. The general objective of this paper is not to replace microscopic counts but to complement them, by fine-tuning a technique using absorption spectra measurements that reduces the above-mentioned costs. Therefore, the objective proposed in this paper is to assess the possibility of achieving a qualitative determination of phytoplankton communities by ...

  6. Absorption Features in Soil Spectra Assessment.

    Vašát, Radim; Kodešová, Radka; Borůvka, Luboš; Jakšík, Ondřej; Klement, Aleš; Drábek, Ondřej

    2015-12-01

    From a wide range of techniques appropriate to relate spectra measurements with soil properties, partial least squares (PLS) regression and support vector machines (SVM) are most commonly used. This is due to their predictive power and the availability of software tools. Both represent exclusively statistically based approaches and, as such, benefit from multiple responses of soil material in the spectrum. However, physical-based approaches that focus only on a single spectral feature, such as simple linear regression using selected continuum-removed spectra values as a predictor variable, often provide accurate estimates. Furthermore, if this approach extends to multiple cases by taking into account three basic absorption feature parameters (area, width, and depth) of all occurring features as predictors and subjecting them to best subset selection, one can achieve even higher prediction accuracy compared with PLS regression. Here, we attempt to further extend this approach by adding two additional absorption feature parameters (left and right side area), as they can be important diagnostic markers, too. As a result, we achieved higher prediction accuracy compared with PLS regression and SVM for exchangeable soil pH, slightly higher or comparable for dithionite-citrate and ammonium oxalate extractable Fe and Mn forms, but slightly worse for oxidizable carbon content. Therefore, we suggest incorporating the multiple linear regression approach based on absorption feature parameters into existing working practices. PMID:26555184

  7. Electronic Absorption Spectra of Some Triazolopyrimidine Derivatives

    The electronic absorption spectra of triazolo pyrimidine and some of its derivatives were measured in polar as well as nonpolar solvents. Assignment of the observed transitions is facilitated via molecular orbital calculations. Charge density distributions, dipole moments, and the extent of delocalization of the MOS were used to interpret the observed solvent effects. The observed transitions are assigned as charge transfer (CT), localized, and delocalized according to the contribution of the various configurations in the CI-states. The correspondence between the calculated and experimental transition energies is satisfactory.

  8. Determination of phytoplankton composition using absorption spectra.

    Martínez-Guijarro, R; Romero, I; Pachés, M; Del Río, J G; Martí, C M; Gil, G; Ferrer-Riquelme, A; Ferrer, J

    2009-05-15

    Characterisation of phytoplankton communities in aquatic ecosystems is a costly task in terms of time, material and human resources. The general objective of this paper is not to replace microscopic counts but to complement them, by fine-tuning a technique using absorption spectra measurements that reduces the above-mentioned costs. Therefore, the objective proposed in this paper is to assess the possibility of achieving a qualitative determination of phytoplankton communities by classes, and also a quantitative estimation of the number of phytoplankton cells within each of these classes, using spectrophotometric determination. Samples were taken in three areas of the Spanish Mediterranean coast. These areas correspond to estuary systems that are influenced by both continental waters and Mediterranean Sea waters. 139 Samples were taken in 7-8 stations per area, at different depths in each station. In each sample, the absorption spectrum and the phytoplankton classes (Bacyllariophyceae (diatoms), Cryptophyceae, Clorophyceae, Chrysophyceae, Prasynophyceae, Prymnesophyceae, Euglenophyceae, Cyanophyceae, Dynophyceae and the Synechococcus sp.) were determined. Data were analysed by means of the Partial Least Squares (PLS) multivariate statistical technique. The absorbances obtained between 400 and 750 nm were used as the independent variable and the cell/l of each phytoplankton class was used as the dependent variable, thereby obtaining models which relate the absorbance of the sample extract to the phytoplankton present in it. Good results were obtained for diatoms (Bacillarophyceae), Chlorophyceae and Cryptophyceae. PMID:19269434

  9. HI absorption spectra for Supernova Remnants in the VGPS survey

    Leahy, Denis

    2016-01-01

    The set of supernova remnants (SNR) from Green's SNR catalog which are found in the VLA Galactic Plane Survey (VGPS) are the objects considered in this study. For these SNR, we extract and analyse HI absorption spectra in a uniform way and construct a catalogue of absorption spectra and distance determinations.

  10. Shell structure of pancakes and the absorption spectra of quasars

    The formation of the absorption lines of atomic hydrogen in the spectra of distant quasars is considered. A model is constructed of the formation of shells of a pancake formed in the adiabatic picture of the generation of the large-scale structure of the universe. It is shown that the absorption lines can form doublets and the equivalent widths of the corresponding lines are calculated. The physical conditions corresponding to the observed heavy-element absorption spectra are discussed

  11. Absorption Spectra of Magnesium Sulphite Hexahydrate Doped with Nickel

    Petkova, Petya N.; Bunzarov, Zhelyu I.; Iliev, Ilia A.; Dimov, Todor N.

    2007-04-01

    In the work are presented absorption spectra of MgSO3.6H2O monocrystals doped with Ni. The spectra are measured in a wide spectral range (200 - 1200nm) at room temperature with polarized light. The impurity of Ni changes essentially the absorption of MgSO3.6H2O because it causes the appearance of additional spectral structures.

  12. Quasar absorption spectra and the structure of the universe

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed

  13. Quasar absorption spectra and the structure of the universe

    Doroshkevich, A.G.

    1984-03-01

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed.

  14. Absorption spectra of quasars and the structure of the Universe

    The analysis of the distribution of the distances between the systems of absorption lines in the quasars' spectra and the comparison of this distribution with the distribution of the distances between superclusters in the deep optical surveys are carried out. It is shown that the systems of absorption lines are connected with superclusters of galaxies. The comparison of the absorbing gas parameters with the data for coronae of the Galaxy and of the Magellanic Clouds confirms this connection and permits to revise conclusions of the theory on the properties of superclusters. The problem of unidentified absorption lines in the quasars spectra is discussed

  15. Ultraviolet absorption spectra of mercuric halides.

    Templet, P.; Mcdonald, J. R.; Mcglynn, S. P.; Kendrow, C. H.; Roebber, J. L.; Weiss, K.

    1972-01-01

    The gas phase transitions of the mercuric halides were observed in the UV region by operating at temperatures above 400 K and at vapor pressures on the order of 0.5 mm. Spectral features exhibited by the chloride, bromide, and iodide of mercury correlate energetically with bands previously designated as intermolecular charge transfer transitions. The solution spectra of mercuric iodide and deep color of the crystals (if not due to some solid state interactions) indicate that this molecule may also have longer wavelength transitions.

  16. CO2 Spectroscopy Evaluation Using Atmospheric Solar Absorption Spectra

    Sen, Bhaswar; Brown, Linda R.; Miller, Charles E.; Toon, Geoffrey C.; Toth, Robert A.; Washenfelder, Rebecca A.; Wennberg, Paul O

    2006-01-01

    We evaluated the improvements in successive versions (1996 - 2004) of HITRAN (1) and other molecular line parameter data set (2) to correctly simulate infrared (IR) and near-infrared (NIR) CO 2 transmittance spectra. Understanding the global sources and sinks of CO 2 requires highly accurate measurements (ó 0.3%) and makes extreme de- mands on the spectroscopy. We evaluated the line parameter data sets by fitting solar absorption spectra measured by the JPL MkIV FTIR spectrometer (3) and the ...

  17. Multiple-scattering calculations of x-ray-absorption spectra

    A high-order multiple-scattering (MS) approach to the calculation of polarized x-ray-absorption spectra, which includes both x-ray-absorption fine structure and x-ray-absorption near-edge structure, is presented. Efficient calculations in arbitrary systems are carried out by using a curved-wave MS path formalism that ignores negligible paths, and has an energy-dependent self-energy and MS Debye-Waller factors. Embedded-atom background absorption calculations on an absolute energy scale are included. The theory is illustrated for metallic Cu, Cd, and Pt. For these cases the MS expansion is found to converge to within typical experimental accuracy, both to experiment and to full MS theories (e.g., band structure), by using only a few dozen important paths, which are primarily single-scattering, focusing, linear, and triangular

  18. Sub-millimetre wave absorption spectra of artificial RNA molecules

    Globus, T; Woolard, D; Gelmont, B

    2003-01-01

    We demonstrate submillimetre-wave Fourier transform spectroscopy as a novel technique for biological molecule characterization. Transmission measurements are reported at frequencies 10-25 cm sup - sup 1 for single- and double-stranded RNA molecules of known base-pair sequences: homopolymers poly[A], poly[U], poly[C] and poly[G], and double-stranded homopolymers poly[A]-poly[U] and poly[C]-poly[G]. Multiple resonances are observed (i.e. in the microwave through terahertz frequency regime). We also present a computational method to predict the low-frequency absorption spectra of short artificial DNA and RNA. Theoretical conformational analysis of molecules was utilized to derive the low-frequency vibrational modes. Oscillator strengths were calculated for all the vibrational modes in order to evaluate their weight in the absorption spectrum of a molecule. Normal modes and absorption spectra of the double-stranded RNA chain poly[C]-poly[G] were calculated. The absorption spectra extracted from the experiment wer...

  19. A Parallel Iterative Method for Computing Molecular Absorption Spectra

    Koval, Peter; Foerster, Dietrich; Coulaud, Olivier

    2010-01-01

    We describe a fast parallel iterative method for computing molecular absorption spectra within TDDFT linear response and using the LCAO method. We use a local basis of "dominant products" to parametrize the space of orbital products that occur in the LCAO approach. In this basis, the dynamical polarizability is computed iteratively within an appropriate Krylov subspace. The iterative procedure uses a a matrix-free GMRES method to determine the (interacting) density response. The resulting cod...

  20. Theoretical investigations of absorption and fluorescence spectra of protonated pyrene.

    Chin, Chih-Hao; Lin, Sheng Hsien

    2016-05-25

    The equilibrium geometry and 75 vibrational normal-mode frequencies of the ground and first excited states of protonated pyrene isomers were calculated and characterized in the adiabatic representation by using the complete active space self-consistent field (CASSCF) method. Electronic absorption spectra of solid neon matrixes in the wavelength range 495-415 nm were determined by Maier et al. and they were analyzed using time-dependent density functional theory calculations (TDDFT). CASSCF calculations and absorption and emission spectra simulations by one-photon excitation equations were used to optimize the excited and ground state structures of protonated pyrene isomers. The absorption band was attributed to the S0 → S1 electronic transition in 1H-Py(+), and a band origin was used at 20580.96 cm(-1). The displaced harmonic oscillator approximation and Franck-Condon approximation were used to simulate the absorption spectrum of the (1) (1)A' ← X[combining tilde](1)A' transition of 1H-Py(+), and the main vibronic transitions were assigned for the first ππ* state. It shows that the vibronic structures were dominated by one of the eight active totally symmetric modes, with ν15 being the most crucial. This indicates that the electronic transition of the S1((1)A') state calculated in the adiabatic representation effectively includes a contribution from the adiabatic vibronic coupling through Franck-Condon factors perturbed by harmonic oscillators. The present method can adequately reproduce experimental absorption and fluorescence spectra of a gas phase. PMID:27181017

  1. Model galactic coronae: Ionization structure and absorption-line spectra

    We describe a general model for a gaseous galactic corona, and demonstrate that it is in harmony with a variety of observational and theoretical constraints. We then compute the ionization equilibria of H, He, C, N, O, Si, and S atoms in the corona and determine the strengths of resonance absorption lines arising therein. To this end, we obtain approximate cross sections for ionization of the heavy-element ions by photons of energy E/sub γ/< or =100 eV.We use our results first to discuss the expected absorption spectrum of our Galaxy's corona. Subsequently, we discuss in detail the relevance of our computed equilibria to the suggestion that galactic coronae produce some redshift systems in quasar absorption spectra. Because our model coronae are not isothermal, the ionization structure existing along various lines of sight through them is not in accord with the concept of ''reasonable ionization equilibrium'': a concept assumed to be valid in most analyses of quasar spectra. However, our calculations indicate that typically one well-established redshift system in each quasar absorption spectrum could arise in the corona of an intervening galaxy. This is the number expected from statistical arguments if quasar redshifts are fully cosmological in origin

  2. Absorption spectra variations of EBT radiochromic film from radiation exposure

    Butson, M J [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China); Department of Medical Physics, Illawarra Cancer Care Centre, Crown St, Wollongong, NSW 2500 (Australia); Cheung, T; Yu, P K N [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China)

    2005-07-07

    Gafchromic EBT radiochromic film is one of the newest radiation-induced auto-developing x-ray analysis films available for therapeutic radiation dosimetry in radiotherapy applications. The spectral absorption properties in the visible wavelengths have been investigated and results show two main peaks in absorption located at 636 nm and 585 nm. These absorption peaks are different to many other radiochromic film products such as Gafchromic MD-55 and HS film where two peaks were located at 676 nm and 617 nm respectively. The general shape of the absorption spectra is similar to older designs. A much higher sensitivity is found at high-energy x-rays with an average 0.6 OD per Gy variation in OD seen within the first Gy measured at 636 nm using 6 MV x-rays. This is compared to approximately 0.09 OD units for the first Gy at the 676 nm absorption peak for HS film at 6 MV x-ray energy. The film's blue colour is visually different from older varieties of Gafchromic film with a higher intensity of mid-range blue within the film. The film provides adequate relative absorbed dose measurement for clinical radiotherapy x-ray assessment in the 1-2 Gy dose range which with further investigation may be useful for fractionated radiotherapy dose assessment. (note)

  3. Electronic absorption spectra and geometry of organic molecules an application of molecular orbital theory

    Suzuki, Hiroshi

    1967-01-01

    Electronic Absorption Spectra and Geometry of Organic Molecules: An Application of Molecular Orbital Theory focuses on electronic absorption spectra of organic compounds and molecules. The book begins with the discussions on molecular spectra, electronic absorption spectra of organic compounds, and practical measures of absorption intensity. The text also focuses on molecular orbital theory and group theory. Molecular state functions; fundamental postulates of quantum theory; representation of symmetry groups; and symmetry operations and symmetry groups are described. The book also dis

  4. Infrared absorption spectra of alkaline earth metal metaphosphates

    Infrared absorption spectra of Ba, Sr, Ca, Mg, Be metaphosphates in crystal and glass-like states are studied. Reference of absorption bands to the oscillations of the P=O, P-O- bonds and P-O-P bridges in complex anions is made. It is shown that α-Sr(PO3)2, β-Ca(PO3)0 and Be(PO3)2 are built of the [(POOsup(-)Osub(2/2))sub(4)] sub(infinity) chains of the C1 symmetry. According to spectral data calculated are the main characteristics of the P=o and P-O- bonds (force constants, bond order, interatomic distances). The main structural elements of glass-like metaphosphates are distorted (POO-Osub(2/2)) sub(infinity) chains connected in three-dimentional net

  5. Optical absorption spectra of the pulse irradiated oxide glasses, 2

    Nanosecond pulse radiolysis was applied to binary sodium borate glasses. The induced spectrum was a superposition of the component peaks arising from various defect centers. After the observed spectra were resolved into Gaussian components, their decay behavior was disussed. In the binary glasses the transient spectrum around 1.6 eV, which can not be observed in the X-ray-irradiated glasses, was found to decay slowly with time. Addition of small amounts of foreign ions (Ce, Eu and Ti ions) reduced the intensity of this absorption and accelerated the decay rate. The process may be understood by a competition between scavenging reaction by the foreign ion and a recombination of the initial geminate pairs produced on irradiation. (author)

  6. Absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissues

    Ivashko, Pavlo; Peresunko, Olexander; Zelinska, Natalia; Alonova, Marina

    2014-08-01

    We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

  7. A Parallel Iterative Method for Computing Molecular Absorption Spectra.

    Koval, Peter; Foerster, Dietrich; Coulaud, Olivier

    2010-09-14

    We describe a fast parallel iterative method for computing molecular absorption spectra within TDDFT linear response and using the LCAO method. We use a local basis of "dominant products" to parametrize the space of orbital products that occur in the LCAO approach. In this basis, the dynamic polarizability is computed iteratively within an appropriate Krylov subspace. The iterative procedure uses a matrix-free GMRES method to determine the (interacting) density response. The resulting code is about 1 order of magnitude faster than our previous full-matrix method. This acceleration makes the speed of our TDDFT code comparable with codes based on Casida's equation. The implementation of our method uses hybrid MPI and OpenMP parallelization in which load balancing and memory access are optimized. To validate our approach and to establish benchmarks, we compute spectra of large molecules on various types of parallel machines. The methods developed here are fairly general, and we believe they will find useful applications in molecular physics/chemistry, even for problems that are beyond TDDFT, such as organic semiconductors, particularly in photovoltaics. PMID:26616067

  8. Study of UCI4 structure and absorption spectra

    The two halides ThCl4 and ThBr4, which are isomorphic at room temperature, have a comparable behaviour when the temperature is lowered. The resonance line of the halogen isotope is split into two lines at a temperature of 96 K for ThBr4 and 70 K for ThCl4. These data confirm the observation of a phase transition first detected by Raman Spectroscopy. Though UCl4 is isomorphic with ThCl4 and ThBr4 at room temperature, it behaves differently versus temperature. The experiments performed from 4,2K to room temperature showed there is only one site for the halogen. UCl4 does not present a phase transition. Once some informations have been gathered on the matrices, optical absorption spectra on ThCl4:U4+ and UCl4 monocristals have been recorded in the visible and infrared ranges at 4,2 K and at room temperature. These spectra have many vibronic lines. To give a first interpretation of the pure electronic lines of U4+-ThCl4 and UCl4 studies on U4+-ThBr4 have been used, in particular the zero phonon lines which correspond to a Dsub(2d) symmetry, have been selected in comparison with the work done on ThBr4:U4+. The energy levels in ThCl4:U4+ and UCl4 have been fitted to the electrostatic parameters F0, F2,F4, F6, the spin orbit parameter, the configuration interaction parameters α, β, γ and crystal field parameters B02, B04, B44, B06, B46

  9. An Inverse Modeling Approach to Estimating Phytoplankton Pigment Concentrations from Phytoplankton Absorption Spectra

    Moisan, John R.; Moisan, Tiffany A. H.; Linkswiler, Matthew A.

    2011-01-01

    Phytoplankton absorption spectra and High-Performance Liquid Chromatography (HPLC) pigment observations from the Eastern U.S. and global observations from NASA's SeaBASS archive are used in a linear inverse calculation to extract pigment-specific absorption spectra. Using these pigment-specific absorption spectra to reconstruct the phytoplankton absorption spectra results in high correlations at all visible wavelengths (r(sup 2) from 0.83 to 0.98), and linear regressions (slopes ranging from 0.8 to 1.1). Higher correlations (r(sup 2) from 0.75 to 1.00) are obtained in the visible portion of the spectra when the total phytoplankton absorption spectra are unpackaged by multiplying the entire spectra by a factor that sets the total absorption at 675 nm to that expected from absorption spectra reconstruction using measured pigment concentrations and laboratory-derived pigment-specific absorption spectra. The derived pigment-specific absorption spectra were further used with the total phytoplankton absorption spectra in a second linear inverse calculation to estimate the various phytoplankton HPLC pigments. A comparison between the estimated and measured pigment concentrations for the 18 pigment fields showed good correlations (r(sup 2) greater than 0.5) for 7 pigments and very good correlations (r(sup 2) greater than 0.7) for chlorophyll a and fucoxanthin. Higher correlations result when the analysis is carried out at more local geographic scales. The ability to estimate phytoplankton pigments using pigment-specific absorption spectra is critical for using hyperspectral inverse models to retrieve phytoplankton pigment concentrations and other Inherent Optical Properties (IOPs) from passive remote sensing observations.

  10. The Absorption Spectra of Some Lanthanide (III Ions

    Suresh Purohit

    2013-04-01

    Full Text Available Complexes of some lanthanides such as Pr (Praseodymium, Nd (Neodymium, Sm (Samarium and Tb (Terbium gives absorption bands in the visible region of the spectrum. The Pr(III, Nd(III, Sm(III and Tb(III ions have four, ten, seven and two peaks respectively in their absorption bands. On the other hand Gd (Gadolinium gives absorption band in UV- region and it has two peaks in its absorption band.

  11. A study of luminescence and absorption spectra of GaP

    Experimental luminescence and absorption spectra of GaP at room temperature are presented. A theoretical analysis has been performed on the luminescence and absorption spectra in GaP. The experimental data are in good agreement with the theoretical results. (author). 18 refs, 8 figs

  12. Population Diagnostics of a Hot NaBr Plasma by Detailed Simulation of Absorption Spectra

    JIN Feng-Tao; ZENG Jiao-Long; YUAN Jian-Min

    2006-01-01

    @@ The experimental absorption spectra of a hot NaBr plasma are theoretically studied by using a detailed level accounting model The sodium and bromine absorption spectra have been well reproduced respectively in the approach of local thermodynamic equilibrium, in which the populations between and within ions are obtained by solving the Saha-Boltzmann equation.

  13. Identification of Metal Absorption Lines on Quasar Spectra of SDSS DR9

    Cai-Juan Pan; Cheng-Yu Su; Mu-Sheng Li; Wei-Rong Huang

    2014-09-01

    Absorption lines are an important tool for probing the gas in the Universe. Our group aim to identify the metal absorption lines imprinted on the quasar spectra of the BOSS. In this work, we show the metal absorption lines identified in the spectrum of SDSS J160032.95+323638.7.

  14. Influence of ultrafast carrier dynamics on semiconductor absorption spectra

    In this thesis, we present a theoretical description of the many-body effects in semi-conductor quantum wells and the role they play in the absorption phenomenon. The optical properties of semiconductors and their connections to the thermodynamic properties of the quasi-2D electron-hole plasma are studied in both nonequilibrium and equilibrium regimes. This work was motivated by a series of pump and probe experiments with spin-selective excitation that were performed at Heriot-Watt. The interpretation of the experimental results is non-trivial given the substantial influence of Coulomb and many-body effects which give rise to a rich variety of broadening and energy renormalizations, and hence places heavy demands on the modeling. We constructed a simple model to describe the nonequilibrium thermodynamics of the hot electron/hole plasma. We accounted for various dynamical processes such as: relaxation of the carrier distributions, thermalization, plasma cooling, carrier spin-flip, recombination (radiative and nonradiative) and light hole scattering into heavy holes. A full microscopic treatment of the many-body problem being computationally prohibitive, we focused on a phenomenological approach using rate equations and the associated characteristic times for each of the dynamical process included in our analysis. We computed the time dependent energy renormalization and bleaching of the excitonic resonances by solving the semiconductor Bloch equations together with the set of coupled rate equations. We obtained a good qualitative agreement with experiments and further insight into the interplay between the various dynamical processes by varying the phenomenological parameters entering the rate equations. In particular we found that the carrier spin-flip occurs on a relatively long time scale (several tens of picoseconds) compared to the carrier distributions relaxation and thermalization (a picosecond or less). We also could monitor the time evolution of the plasma

  15. Interpretation of NO2 absorption in twilight sky spectra

    McMahon, B. B.

    1984-07-01

    A multiple scattering model has been developed to calculate nitrogen dioxide (NO2) absorption in the light from the zenith sky during twilight. Model studies show that this absorption is not very sensitive to the atmospheric temperature profile or to tropospheric NO2. The model was used to interpret some ground-based measurements of NO2 sky absorption. Values for the total stratospheric column amount vary from 2 to 12 x 10 to the 15th molec/sq cm, and the mean altitude of the stratospheric concentration profile is around 35 km. These observations are in broad agreement with those of other workers.

  16. Effects of lowly ionized ions on silicon K-shell absorption spectra

    Wei, H. G.; Shi, J. R.; Liang, G. Y.; Wang, F. L.; Zhong, J. Y.; Zhao, G.

    2016-05-01

    Context. In both astrophysical and laboratory plasmas, K-shell absorption spectra have become powerful diagnostic tools to investigate electron density and temperature. These spectra are also widely used to verify the opacity codes in laboratory settings. Aims: We report the effects of the low ionization silicon ions, namely from Si I to Si V, which have rarely been considered in previous models, on the K-shell silicon absorption spectra. Methods: The Si K-shell atomic data were calculated with the flexible atomic code, which is a fully relativistic atomic program with configuration interaction taken into consideration. Detailed level accounting models were employed to calculate the absorption spectra. Results: We calculate the Si absorption spectra in local thermodynamic equilibrium conditions with temperature and density ranges of 20-70 eV and ~1020 cm-3 to ~1022 cm-3, respectively, and show the contributions of the lowly ionized ions to the K-shell absorption spectra of silicon. We also investigate the effects of the different atomic data on the absorption spectra. We find good agreement between our results and these from OPLIB. Conclusions: We find that the contributions from these lowly ionized ions cannot be neglected at relative low temperatures. Accurate experimental measurements are needed to benchmark the theoretical calculations.

  17. Protonation effects on the UV/Vis absorption spectra of imatinib: A theoretical and experimental study

    Grante, Ilze; Actins, Andris; Orola, Liana

    2014-08-01

    An experimental and theoretical investigation of protonation effects on the UV/Vis absorption spectra of imatinib showed systematic changes of absorption depending on the pH, and a new absorption band appeared below pH 2. These changes in the UV/Vis absorption spectra were interpreted using quantum chemical calculations. The geometry of various imatinib cations in the gas phase and in ethanol solution was optimized with the DFT/B3LYP method. The resultant geometries were compared to the experimentally determined crystal structures of imatinib salts. The semi-empirical ZINDO-CI method was employed to calculate the absorption lines and electronic transitions. Our study suggests that the formation of the extra near-UV absorption band resulted from an increase of imatinib trication concentration in the solution, while the rapid increase of the first absorption maximum could be attributed to both the formation of imatinib trication and tetracation.

  18. Invisible structures in the X-ray absorption spectra of actinides

    Highlights: • The X-ray absorption spectra of actinides are discussed with an emphasis atomic multiplet theory, charge transfer theory and crystal field theory. • Resonant inelastic X-ray emission spectra (RIXS) reveal many new features in the X-ray absorption spectra of actinides. • The new range of RIXS beamlines will become an important tool in the determination of the electronic structure of actinides. - Abstract: The X-ray absorption spectra of actinides are discussed with an emphasis on the fundamental effects that influence their spectral shape, including atomic multiplet theory, charge transfer theory and crystal field theory. Many actinide spectra consist of a single peak and it is shown that the use of resonant inelastic X-ray emission spectra (RIXS) has the potential to reveal many new features in the X-ray absorption spectra of actinides. The new range of RIXS beamlines will allow the determination of new structures in the X-ray absorption spectra that have been hitherto invisible. This has the potential to become an important tool in the determination of the electronic structure of actinides

  19. Systematic view of optical absorption spectra in the actinide series

    In recent years sufficient new spectra of actinides in their numerous valence states have been measured to encourage a broader scale analysis effort than was attempted in the past. Theoretical modelling in terms of effective operators has also undergone development. Well established electronic structure parameters for the trivalent actinides are being used as a basis for estimating parameters in other valence states and relationships to atomic spectra are being extended. Recent contributions to our understanding of the spectra of 4+ actinides have been particularly revealing and supportive of a developing general effort to progress beyond a preoccupation with modelling structure to consideration of the much broader area of structure-bonding relationships. We summarize here both the developments in modelling electronic structure and the interpretation of apparent trends in bonding. 60 refs., 9 figs., 1 tab

  20. Near K-edge absorption spectra of III-V nitrides

    Fukui, K. [Fukui Univ. (Japan). Research Center for Development of Far-Infrared Region; Hirai, R.; Yamamoto, A. [Fukui Univ. (Japan). Dept. of Electrical and Electronics Engineering; Hirayama, H.; Aoyagi, Y. [Inst. of Physical and Chemical Research (RIKEN), Wako, Saitama (Japan); Yamaguchi, S.; Amano, H. [Dept. of Materials Science and Engineering, Meijo Univ., Nagoya (Japan); Akasaki, I. [High-Tec Research Center, Meijo Univ., Nagoya (Japan); Tanaka, S. [Research Inst. for Electronic Science, Hokkaido Univ., Sapporo (Japan)

    2001-11-08

    Nitrogen and aluminum near K-edge absorption measurements of wurtzite AlN, GaN and InN, and their ternary compounds (AlGaN, InGaN and InAlN) at various molar fractions have been performed using synchrotron radiation. Using the linear polarization of synchrotron radiation, absorption measurements with different incident light angles were also performed. The spectral distribution of the nitrogen K absorption spectra clearly depends on both the incident light angles and the molar fractions of the samples. That of the aluminum K absorption spectra also shows the clear angle dependence, but it does not show the drastic molar dependence. Spectral shape comparisons among the various molar fractions, different incident angles and between the two ion sites are discussed. The numerical component analysis of the K absorption spectra is also presented. (orig.)

  1. Absorption in the spectra of quasi stellar objects and BL Lac objects

    An extensive review is given of the observations of absorption in the spectra of QSOs and BL Lac objects. In Table Ia we summarize all of the information available up to May 1, 1978 on objects which show absorption. Following discussion of the observations in Section II, possible interpretations are critically discussed. (orig.)

  2. Linear optical absorption spectra of mesoscopic structures in intense THz fields: Free-particle properties

    Johnsen, Kristinn; Jauho, Antti-Pekka

    1998-01-01

    We theoretically study the effect of THz radiation on the linear optical absorption spectra of semiconductor structures. A general theoretical framework, based on nonequilibrium Green functions, is formulated and applied to the calculation of linear optical absorption spectrum for several nonequi...

  3. Invisible structures in the X-ray absorption spectra of actinides

    Kvashnina, Kristina O.; De Groot, Frank M F

    2014-01-01

    The X-ray absorption spectra of actinides are discussed with an emphasis on the fundamental effects that influence their spectral shape, including atomic multiplet theory, charge transfer theory and crystal field theory. Many actinide spectra consist of a single peak and it is shown that the use of

  4. Data processing of absorption spectra from photoionized plasma experiments at Z

    Hall, I. M.; Durmaz, T.; Mancini, R. C. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Bailey, J. E.; Rochau, G. A. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1196 (United States)

    2010-10-15

    We discuss the processing of x-ray absorption spectra from photoionized plasma experiments at Z. The data was recorded with an imaging spectrometer equipped with two elliptically bent potassium acid phthalate (KAP) crystals. Both time-integrated and time-resolved data were recorded. In both cases, the goal is to obtain the transmission spectra for quantitative analysis of plasma conditions.

  5. Resonance raman and absorption spectra of isomeric retinals in their lowest excited triplet states

    Wilbrandt, Robert Walter; Jensen, N.-H.; Houee-Levin, C.

    1985-01-01

    The triplet-triplet absorption spectra of 9-cis and all-trans-retinal as well as the time-resolved resonance Raman spectra of the lowest electronically excited triplet states of 9-cis-, 11-cis, 13-cis and all-trans-retinal in aromatic solvents at room temperature were obtained under conditions en...

  6. Infrared absorption spectra of human malignant tumor tissues

    Skornyakov, I. V.; Tolstorozhev, G. B.; Butra, V. A.

    2008-05-01

    We used infrared spectroscopy methods to study the molecular structure of tissues from human organs removed during surgery. The IR spectra of the surgical material from breast, thyroid, and lung are compared with data from histological examination. We show that in malignant neoplasms, a change occurs in the hydrogen bonds of protein macromolecules found in the tissue of the studied organs. We identify the spectral signs of malignant pathology.

  7. Monitoring the Variability of Intrinsic Absorption Lines in Quasar Spectra

    Misawa, Toru; Eracleous, Michael

    2014-01-01

    We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 years (1-3.5 years in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems nor in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable broad absorption lines. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density $\\sim$ 10$^3$-10$^5$ cm$^{-3}$ and upper limits on the distance of the absorbers from the central engine of order a few kpc. Motivate...

  8. Polarized absorption spectra of (2,2) carbon nanotubes aligned in channels of an AEL crystal

    Chen, Yanping; Zhai, Jianpang; Li, Irene Ling; Ruan, Shuangchen; Tang, Zikang

    2015-11-01

    We report polarized absorption spectra for the (2,2) tubes arrayed in the one-dimensional channels of an AlPO4-11 (AEL) single crystal. Strong polarization dependence is observed indicating a preferential optical dipole along the axis of carbon nanotubes. By correlating with the absorption spectra and First-principles local density function (LDA) calculation, the absorption peak at 2.95 eV is uniquely assigned to semiconducting type (2,2) tubes, and peaks at 2.67 and 2.40 eV are corresponding to metallic type (2,2) tubes.

  9. Ultraviolet-visible absorption spectra of solid hydrogen sulphide under high pressure

    Kume, T; Sasaki, S; Shimizu, H

    2002-01-01

    Ultraviolet-visible absorption spectra of solid hydrogen sulphide (H sub 2 S) were measured at various pressures from 0.3 to 29 GPa. The absorption edge observed around 4.8 eV at 0.3 GPa indicated a red-shift with increasing pressure, and positioned below 3 eV at 29 GPa. On the basis of the spectra obtained, the energy gap was determined as a function of pressure. The transition to phase IV at 11 GPa was found to lead to a small jump in its pressure dependence and to yield an Urbach tail in the absorption edge.

  10. Carbon dioxide laser absorption spectra of toxic industrial compounds

    CO2 laser absorption cross-section data are reported for acrolein, styrene, ethyl acrylate, trichloroethylene, vinyl bromide, and vinylidene chloride. These data indicate that sub parts per billion level, interference-free detection limits should be possible for these compounds by the CO2 laser photoacoustic technique. Photoacoustic detectabilities below 40 ppb should be possible for these compounds in the presence of ambient air concentrations of water vapor and other anticipated interferences. These compounds are also found not to be important inerference in the detection of toxic hydrazine-based rocket fuels by CO2 laser spectroscopic techniques

  11. Determining neutrino absorption spectra at Ultra-High Energies

    Scholten, Olaf; Van Vliet, Arjen

    2008-01-01

    A very efficient method to measure the flux of Ultra-high energy (UHE) neutrinos is through the detection of radio waves which are emitted by the particle shower in the lunar regolith. The highest acceptance is reached for radio waves in the frequency band of 100-200 MHz which can be measured with modern radio telescopes. In this work we investigate the sensitivity of this detection method to structures in the UHE neutrino spectrum caused by their absorption on the low-energy relic anti-neutr...

  12. Measurement of XUV-absorption spectra of ZnS radiatively heated foils

    Kontogiannopoulmos, Nikolaos; Thais, Frédéric; Chenais-Popovics, Claude; Sauvan, Pascal; Schott, R; Fölsner, Wolfgang; Arnault, Philippe; Poirier, Michel; Blenski, Thomas

    2008-01-01

    Time-resolved absorption of zinc sulfide (ZnS) and aluminum in the XUV-range has been measured. Thin foils in conditions close to local thermodynamic equilibrium were heated by radiation from laser-irradiated gold spherical cavities. Analysis of the aluminum foil radiative hydrodynamic expansion, based on the detailed atomic calculations of its absorption spectra, showed that the cavity emitted flux that heated the absorption foils corresponds to a radiation temperature in the range 55 60 eV. Comparison of the ZnS absorption spectra with calculations based on a superconfiguration approach identified the presence of species Zn6+ - Zn8+ and S5+ - S6+. Based on the validation of the radiative source simulations, experimental spectra were then compared to calculations performed by post-processing the radiative hydrodynamic simulations of ZnS. Satisfying agreement is found when temperature gradients are accounted for.

  13. Monitoring the variability of intrinsic absorption lines in quasar spectra , ,

    We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 yr (1-3.5 yr in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems or in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable BALs. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density ∼103-105 cm–3 and upper limits on the distance of the absorbers from the central engine of the order of a few kiloparsecs. Motivated by the observed variability properties, we suggest that mini-BALs can vary because of fluctuations of the ionizing continuum or changes in partial coverage while NALs can vary primarily because of changes in partial coverage.

  14. Electron-Vibration Structure of Absorption Spectra of Resazurine

    T.N. Sakun

    2011-01-01

    Full Text Available In the work the experimental and theoretical investigation of the spectral characteristics of a resazurin molecule are carried out. Comparison of results of experimental and theoretical researches has allowed showing, that the spectrum of absorption in the visible region is formed by quantum transitions between electronic states of the molecule, and also by the electron-vibration interaction. In the work the method of reception of theoretical results with the control of molecule symmetry is offered. It has allowed to receive the completely coordinated theoretical and experimental results both by position and by size of the extinction factor and to find out the nature of all quantum transitions and oscillatory frequencies. It is shown, that strips of absorption in the visible region of the spectrum are formed at participation of the totally symmetrical vibrations of the molecule among which the greatest participation stand out vibrations with frequencies in the region of 478 cm – 1, 1467 cm – 1, and also by group of oscillatory frequencies in the region of 1800-2000 cm – 1 which were less than found theoretically for the basic state of the molecule because the degree of loosening of the bonds that responsible for specified vibrations, increases at excitation of the molecule.

  15. The Infrared Spectra and Absorption Intensities of Amorphous Ices

    Gerakines, Perry A.; Hudson, Reggie L.; Loeffler, Mark

    2016-06-01

    Our research group is carrying out new IR measurements of icy solids relevant to the outer solar system and to the interstellar medium, with an emphasis on amorphous and crystalline ices below ~ 120 K. Our goal is to update and add to the relatively meager literature on this subject and to provide electronic versions of state-of-the-art data, since the abundances of such molecules cannot be deduced without accurate reference spectra and IR band strengths. In the past year, we have focused on three of the simplest and most abundant components of interstellar and solar-system ices: methane (CH4), carbon dioxide (CO2), and methanol (CH3OH). Infrared spectra from ∼ 4500 to 500 cm-1 have been measured for each of these molecules in μm-thick films at temperatures from 10 to 120 K. All known amorphous and crystalline phases have been reproduced and, for some, presented for the first time. We also report measurements of the index of refraction at 670 nm and the mass densities for each ice phase. Comparisons are made to earlier work where possible. Electronic versions of our new results are available at http://science.gsfc.nasa.gov/691/cosmicice/ constants.html.

  16. Media effects on the optical absorption spectra of silver clusters embedded in rara gas matrices

    The optical absorption of small mass selected Agn-clusters (n=7, 11, 15, 21) embedded in solid Ar, Kr and Xe has been measured. The absorption spectra show 1 to 3 major peaks between 3 and 4.5 eV, depending on the cluster size. Changing the matrix gas Ar→Kr→Xe induces a redshift which is comparable for all sizes studied and does not affect the main structure of the absorption spectra. We propose a scheme to estimate the gas phase value of the absorption energies which is in fair agreement with an estimation obtained by a simple model based on a Drude metal. (author). 10 refs, 2 figs

  17. Theoretical analysis of electronic absorption spectra of vitamin B12 models

    Andruniow, Tadeusz; Kozlowski, Pawel M.; Zgierski, Marek Z.

    2001-10-01

    Time-dependent density-functional theory (TD-DFT) is applied to analyze the electronic absorption spectra of vitamin B12. To accomplish this two model systems were considered: CN-[CoIII-corrin]-CN (dicyanocobinamide, DCC) and imidazole-[CoIII-corrin]-CN (cyanocobalamin, ImCC). For both models 30 lowest excited states were calculated together with transition dipole moments. When the results of TD-DFT calculations were directly compared with experiment it was found that the theoretical values systematically overestimate experimental data by approximately 0.5 eV. The uniform adjustment of the calculated transition energies allowed detailed analysis of electronic absorption spectra of vitamin B12 models. All absorption bands in spectral range 2.0-5.0 eV were readily assigned. In particular, TD-DFT calculations were able to explain the origin of the shift of the lowest absorption band caused by replacement of the-CN axial ligand by imidazole.

  18. Excitonic and vibronic structure of absorption spectra of Me-PTCDI and PTCDA crystals

    The excitonic and vibronic spectra (exciton + one quantum of intramolecular vibration) of Me-PTCDI and PTCDA crystals are studied in the case of strong mixing of a Frenkel exciton (FE) and charge-transfer excitons (CTEs). The linear optical susceptibility is calculated in the framework of dynamical theory of vibronic spectra. The absorption spectra of both crystals have been modelled. The positions, maximal values and integral intensity of the absorption peaks which correspond to the bound exciton-phonon states and to unbound (many-particle) states have been calculated using FE and CTEs's parameters of Me-PTCDI and PTCDA crystals. The calculated spectra show: (i) the possible recovering of excitonic and vibronic regions; (ii) bigger integral intensity of many-particle states in the case of weak exciton-phonon coupling; (iii) the dominant role of the bound states in the case of intermediate and strong exciton-phonon coupling

  19. Absorption spectra of broadened sodium resonance lines in presence of rare gases

    The pressure broadening of alkali-metal lines is a fundamental problem with numerous applications. For example, the sodium resonance lines broadened by xenon are important in the production of broad spectra emitted in the HPS (High-Pressure Sodium) lamp and they potentially can be used for gas condition diagnostics. Broadened absorption lines of alkali-metal atoms are prominent in the optical spectra of brown dwarfs and understanding the broadening mechanism will help elucidate the chemical composition and atmospheric properties of those stars. The far-line wing spectra of sodium resonance lines broadened by rare gases are found to exhibit molecular characteristics such as satellites and hence the total absorption coefficients for vapors of Na atoms and perturbing rare gas atoms can be modeled as Na-RG (rare gas) molecular absorption spectra. In this work, using carefully chosen interatomic potentials for Na-RG molecules we carry out quantum-mechanical calculations for reduced absorption coefficients for vapors composed of Na-He, Na-Ar, and Na-Xe. Calculated spectra are compared to available experimental results and the agreement is good in the measured satellite positions and shapes

  20. Quantum theory and experimental studies of absorption spectra and photoisomerization of azobenzene polymers

    Pedersen, Thomas Garm; Ramanujam, P.S.; Johansen, P.M.;

    1998-01-01

    The microscopic properties of azobenzene chromophores are important for a correct description of optical storage systems based on photoinduced anisotropy in azobenzene polymers. A quantum model of these properties is presented and verified by comparison to experimental absorption spectra for trans...... and cis isomers of cyano methoxy azobenzene. In addition, the trans --> cis quantum efficiency is measured, and hence the combined experimental and theoretical work allows one to determine the essential molecular properties, including magnitude and anisotropy of the absorption cross section and...

  1. Temperature dependence of absorption spectra of P-type GaP

    The theoretical analysis of the optical absorption due to band-impurity (impurity-band) electron transitions involving deep impurity levels in semi-conductors is considered. Also the data of the experimental absorption spectra of GaP were performed at room temperature and the results were found to be in agreement with the theoretical results if the electron-phonon interaction is taken into consideration. (author)

  2. Soft X-ray absorption excess in gamma-ray burst afterglow spectra: Absorption by turbulent ISM

    Tanga, M; Gatto, A; Greiner, J; Krause, M G H; Diehl, R; Savaglio, S; Walch, S

    2016-01-01

    Two-thirds of long duration gamma-ray bursts (GRBs) show soft X-ray absorption in excess of the Milky Way. The column densities of metals inferred from UV and optical spectra differ from those derived from soft X-ray spectra, at times by an order of magnitude, with the latter being higher. The origin of the soft X-ray absorption excess observed in GRB X-ray afterglow spectra remains a heavily debated issue, which has resulted in numerous investigations on the effect of hot material both internal and external to the GRB host galaxy on our X-ray afterglow observations. Nevertheless, all models proposed so far have either only been able to account for a subset of our observations (i.e. at z > 2), or they have required fairly extreme conditions to be present within the absorbing material. In this paper, we investigate the absorption of the GRB afterglow by a collisionally ionised and turbulent interstellar medium (ISM). We find that a dense (3 per cubic centimeters) collisionally ionised ISM could produce UV/opti...

  3. Absorption spectra and spectral-kinetic characteristics of the fluorescence of Sanguinarine in complexes with polyelectrolytes and DNA

    The absorption spectra and stationary and time resolved fluorescence spectra of the isoquinoline alkaloid sanguinarine are studied in aqueous media and during interactions with synthetic polyelectrolytes (polystyrene sulfonate and polyallylamine) and a natural polyelectrolyte (DNA). (authors)

  4. Absorption spectra and spectral-kinetic characteristics of the fluorescence of Sanguinarine in complexes with polyelectrolytes and DNA

    Motevich, I. G.; Strekal, N. D.; Nowicky, J. W.; Maskevich, S. A.

    2010-07-01

    The absorption spectra and stationary and time resolved fluorescence spectra of the isoquinoline alkaloid sanguinarine are studied in aqueous media and during interactions with synthetic polyelectrolytes (polystyrene sulfonate and polyallylamine) and a natural polyelectrolyte (DNA).

  5. Oxygen K-edge absorption spectra of small molecules in the gas phase

    Yang, B.X.; Kirz, J.; Sham, T.K.

    1986-01-01

    The absorption spectra of O/sub 2/, CO, CO/sub 2/ and OCS have been recorded in a transmission mode in the energy region from 500 to 950 eV. Recent observation of EXAFS in these molecules is confirmed in this study. 7 refs., 3 figs.

  6. On high-redshift quasar absorption spectra and the Riemannian geometry of the Universe

    It is studied the observed small deviations of high-redshift quasar absorption spectra that are interpreted as a possible evidence for a variable fine structure constant. On the contrary, it was claimed that the effect could be completely attributed to the small amount of cosmic shear beyond the standard Friedmann expanding Universe

  7. Rich magneto-absorption spectra in AAB-stacked trilayer graphene

    Do, Thi-Nga; Chang, Cheng-Pong; Lin, Chiun-Yan; Lin, Ming-Fa

    2015-01-01

    The generalized tight-binding model is developed to investigate the feature-rich magneto-optical properties of AAB-stacked trilayer graphene. Three intragroup and six intergroup inter-Landau-level (inter-LL) optical excitations largely enrich the magneto-absorption peaks. In general, the former are much higher than the latter, depending on the phases and amplitudes of LL wavefunctions. The absorption spectra exhibit the single- or twin-peak structures which are determined by the quantum modes, LL energy spectra and Fermion distribution. The splitting LLs, with different localization centers (2/6 and 4/6 positions in a unit cell), can generate very distinct absorption spectra. There exist extra single peaks because of LL anticrosings. AAB, AAA, ABA, and ABC stackings quite differ from one another in terms of the inter-LL category, frequency, intensity, and structure of absorption peaks. The main characteristics of LL wavefunctions and energy spectra and the Fermi-Dirac function are responsible for the configur...

  8. Optical absorption of nanoporous silicon: quasiparticle band gaps and absorption spectra

    Shi, Guangsha; Kioupakis, Emmanouil

    2013-03-01

    Silicon is an earth-abundant material of great importance in semiconductors electronics, but its photovoltaic applications are limited by the low absorption coefficient in the visible due to its indirect band gap. One strategy to improve the absorbance is to perforate silicon with nanoscale pores, which introduce carrier scattering that enables optical transitions across the indirect gap. We used density functional and many-body perturbation theory in the GW approximation to investigate the electronic and optical properties of porous silicon for various pore sizes, spacings, and orientations. Our calculations include up to 400 atoms in the unit cell. We will discuss the connection of the band-gap value and absorption coefficient to the underlying nanopore geometry. The absorption coefficient in the visible range is found to be optimal for appropriately chosen nanopore size, spacing, and orientation. Our work allows us to predict porous-silicon structures that may have optimal performance in photovoltaic applications. This research was supported as part of CSTEC, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Computational resources were provided by the DOE NERSC facility.

  9. Energy structure and absorption spectra of colloidal CdS nanocrystals in gelatin matrix

    Korolev, N. V.; Smirnov, M. S.; Ovchinnikov, O. V.; Shatskikh, T. S.

    2015-04-01

    We investigate the energy structure of colloidal CdS nanocrystals by measuring the UV-vis absorption spectra. Nanocrystals were synthesized by sol-gel method in a gelatin matrix in the size range from 2.5 to 3.9 (±0.2) nm. In order to interpret the UV-vis absorption spectra we calculate the energy spectrum of electron quasi-stationary states using the model of open nanocrystal as well as the hole stationary spectrum in a two-band approach. It is shown that the main contribution to the absorption spectrum is made by interband transitions 1S3/2→1Se and 1P3/2→1Pe, and its shape is determined by the size distribution of nanoparticles. For this system the estimated values of the effective masses of the heavy hole and light hole are 1.44m0 and 0.28m0, respectively.

  10. Possible spinel absorption bands in S-asteroid visible reflectance spectra

    Hiroi, T.; Vilas, F.; Sunshine, J. M.

    1994-01-01

    Minor absorption bands in the 0.55 to 0.7 micron wavelength range of reflectance spectra of 10 S asteroids have been found and compared with those of spinel-group minerals using the modified Gaussian model. Most of these S asteroids are consistently shown to have two absorption bands around 0.6 and 0.67 micron. Of the spinel-group minerals examined in this study, the 0.6 and 0.67 micron bands are most consistent with those seen in chromite. Recently, the existence of spinels has also been detected from the absorption-band features around 1 and 2 micron of two S-asteroid reflectance spectra, and chromite has been found in a primitive achondrite as its major phase. These new findings suggest a possible common existence of spinel-group minerals in the solar system.

  11. Absorption spectra of PTCDI: A combined UV-Vis and TD-DFT study

    Oltean, Mircea; Calborean, Adrian; Mile, George; Vidrighin, Mihai; Iosin, Monica; Leopold, Loredana; Maniu, Dana; Leopold, Nicolae; Chiş, Vasile

    2012-11-01

    Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in chloroform, N,N'-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). While no signature of assembled PTCDI molecules is observed in chloroform solution, distinct bands assigned to their aggregation have been identified in DMF and DMSO solutions. PTCDI monomers show very similar absorption patterns in chloroform and DMSO solutions. Experimental data, including the vibronic structure of the absorption spectra were explained based on the Franck-Condon approximation and quantum chemical results obtained at PBE0-DCP/6-31+G(d,p) level of theory. Geometry optimization of the first excited state leads to a nice agreement between the calculated adiabatic transition energies and experimental data.

  12. Twin-peaks absorption spectra of excess electron in ionic liquids

    The solvated electron in room temperature ionic liquids (RTILs) has been the subject of several investigations and several reports exist on its nature and absorption spectrum. These studies concluded that the solvated electron exhibits an absorption spectrum peaking in the 1000–1400 nm region; a second absorption band peaking in the UV region has been assigned to the hole or dication radicals simultaneously formed in the system. Here we report on the fate of the excess electron in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, P14+/NTf2− using nanosecond pulse radiolysis. Scavenging experiments allowed us to record and disentangle the complex spectrum measured in P14+/NTf2−. We identified a bi-component absorption spectrum, due to the solvated electron, the absorption maxima located at 1080 nm and around 300 nm, as predicted by previous ab-initio molecular dynamics simulations for the dry excess electron. We also measured the spectra using different ionic liquids and confirmed the same feature of two absorption peaks. The present results have important implications for the characterization of solvated electrons in ionic liquids and better understanding of their structure and reactivity. - Highlights: • The solvated electron (esol−) in the ionic liquids P14+/NTf2− was investigated. • Pulse radiolysis shows a twin-peak absorption spectrum for the esol− in P14+/NTf2−. • The absorption spectrum of the hole was measured using scavenging experiments

  13. Time variations of narrow absorption lines in high resolution quasar spectra

    Boissé, P; Prochaska, J X; Péroux, C; York, D G

    2015-01-01

    Aims. We have searched for temporal variations of narrow absorption lines in high resolution quasar spectra. A sample of 5 distant sources have been assembled, for which 2 spectra - VLT/UVES or Keck/HIRES - taken several years apart are available. Methods. We first investigate under which conditions variations in absorption line profiles can be detected reliably from high resolution spectra, and discuss the implications of changes in terms of small-scale structure within the intervening gas or intrinsic origin. The targets selected allow us to investigate the time behavior of a broad variety of absorption line systems, sampling diverse environments: the vicinity of active nuclei, galaxy halos, molecular-rich galaxy disks associated with damped Lya systems, as well as neutral gas within our own Galaxy. Results. Absorption lines from MgII, FeII or proxy species with lines of lower opacity tracing the same kind of gas appear to be remarkably stable (1 sigma upper limits as low as 10 % for some components on scal...

  14. Intervening Mg II absorption systems from the SDSS DR12 quasar spectra

    Raghunathan, Srinivasan; Campusano, Luis E; Söchting, Ilona K; Graham, Matthew J; Williger, Gerard M

    2016-01-01

    We present the catalogue of the Mg II absorption systems detected at a high significance level using an automated search algorithm in the spectra of quasars from the twelfth data release of the Sloan Digital Sky Survey. A total of 266,433 background quasars were searched for the presence of absorption systems in their spectra. The continuum modelling for the quasar spectra was performed using a mean filter. A pseudo-continuum derived using a median filter was used to trace the emission lines. The absorption system catalogue contains 39,694 Mg II systems detected at a 6.0, 3.0$\\sigma$ level respectively for the two lines of the doublet. The catalogue was constrained to an absorption line redshift of 0.35 $\\le$ z$_{2796}$ $\\le$ 2.3. The rest-frame equivalent width of the $\\lambda$2796 line ranges between 0.2 $\\le$ W$_r$ $\\le$ 6.2 \\AA. Using Gaussian-noise only simulations we estimate a false positive rate of 7.7 per cent in the catalogue. We measured the number density $\\partial N^{2796}/\\partial z$ of Mg II ab...

  15. Modeling absorption spectra for detection of the combustion products of jet engines by laser remote sensing.

    Voitsekhovskaya, Olga K; Kashirskii, Danila E; Egorov, Oleg V; Shefer, Olga V

    2016-05-10

    The absorption spectra of exhaust gases (H2O, CO, CO2, NO, NO2, and SO2) and aerosol (soot and Al2O3) particles were modeled at different temperatures for the first time and suitable spectral ranges were determined for conducting laser remote sensing of the combustion products of jet engines. The calculations were conducted on the basis of experimental concentrations of the substances and the sizes of the aerosol particles. The temperature and geometric parameters of jet engine exhausts were also taken from the literature. The absorption spectra were obtained via the line-by-line method, making use of the spectral line parameters from the authors' own high-temperature databases (for NO2 and SO2 gases) and the HITEMP 2010 database, and taking into account atmospheric transmission. Finally, the theoretical absorption spectra of the exhaust gases were plotted at temperatures of 400, 700, and 1000 K, and the impact of aerosol particles on the total exhaust spectra was estimated in spectral ranges suitable for remote sensing applications. PMID:27168298

  16. Plant phenolics and absorption features in vegetation reflectance spectra near 1.66 μm

    Kokaly, Raymond F.; Skidmore, Andrew K.

    2015-12-01

    Past laboratory and field studies have quantified phenolic substances in vegetative matter from reflectance measurements for understanding plant response to herbivores and insect predation. Past remote sensing studies on phenolics have evaluated crop quality and vegetation patterns caused by bedrock geology and associated variations in soil geochemistry. We examined spectra of pure phenolic compounds, common plant biochemical constituents, dry leaves, fresh leaves, and plant canopies for direct evidence of absorption features attributable to plant phenolics. Using spectral feature analysis with continuum removal, we observed that a narrow feature at 1.66 μm is persistent in spectra of manzanita, sumac, red maple, sugar maple, tea, and other species. This feature was consistent with absorption caused by aromatic Csbnd H bonds in the chemical structure of phenolic compounds and non-hydroxylated aromatics. Because of overlapping absorption by water, the feature was weaker in fresh leaf and canopy spectra compared to dry leaf measurements. Simple linear regressions of feature depth and feature area with polyphenol concentration in tea resulted in high correlations and low errors (% phenol by dry weight) at the dry leaf (r2 = 0.95, RMSE = 1.0%, n = 56), fresh leaf (r2 = 0.79, RMSE = 2.1%, n = 56), and canopy (r2 = 0.78, RMSE = 1.0%, n = 13) levels of measurement. Spectra of leaves, needles, and canopies of big sagebrush and evergreens exhibited a weak absorption feature centered near 1.63 μm, short ward of the phenolic compounds, possibly consistent with terpenes. This study demonstrates that subtle variation in vegetation spectra in the shortwave infrared can directly indicate biochemical constituents and be used to quantify them. Phenolics are of lesser abundance compared to the major plant constituents but, nonetheless, have important plant functions and ecological significance. Additional research is needed to advance our understanding of the spectral influences

  17. F\\"orster resonance energy transfer, absorption and emission spectra in multichromophoric systems: I. Cumulant expansions

    Ma, Jian

    2014-01-01

    We study the F\\"orster resonant energy transfer (FRET) rate in multichromophoric systems. The multichromophoric FRET rate is determined by the overlap integral of the donor's emission and acceptor's absorption spectra, which are obtained via 2nd-order cumulant expansion techniques developed in this work. We calculate the spectra and multichromophoric FRET rate for both localized and delocalized systems. (i) The role of the initial entanglement between the donor and its bath is found to be crucial in both the emission spectrum and the multichromophoric FRET rate. (ii) The absorption spectra obtained by the cumulant expansion method are quite close to the exact one for both localized and delocalized systems, even when the system-bath coupling is far from the perturbative regime. (iii) For the emission spectra, the cumulant expansion can give very good results for the localized system, but fail to obtain reliable spectra of the high excitations of a delocalized system, when the system-bath coupling is large and ...

  18. Infrared absorption spectra of anhydrous lutetium orthophosphate activated by Nd3+, Eu3+ and Er3+

    The IR absorption spectra (40Q-1200 cm-1) of LuPO4, activated by Nd3+, Eu3+, Er3+, are obtained. The introduction of active ions of r.e.e. does not cause noticeable distortions of low resolved spectra. During precise investigation of spectra with a high resolution the redistribution of the line intensities, appearance of bends, change of the shape and non-monotonous shift of absorption line position, especially noticeable when Eu3+ and Er3+ are introduced, are observed. Such behaviour of the spectra is explained by the deformation of coordination polyhedron of r.e.e. cation and the change of the force constants when it is substituted for by r.e.e. ion with a higher number of 4f-electrons. A preferable sensitivity of antisymmetric valent vibration νsub(as) (F) of the anion PO43- to the change of the active ion concentration is pointed out. Non-monotonous character of concentrational behaviour of IR spectra is connected with the complexity of interaction in ternary systems

  19. Impact of different visible light spectra on oxygen absorption and surface discoloration of bologna sausage.

    Böhner, Nadine; Rieblinger, Klaus

    2016-11-01

    The objective of this study was to evaluate the influence of several visible light spectra in various intensities on the oxygen absorption and surface color of sliced bologna. Sausage samples were stored in a gastight model packaging system and illuminated at 5°C with six single-colored LEDs covering the main part of the visible light spectrum. The initial oxygen level was set at 0.5% in order to simulate common residual oxygen amounts in conventional packaging. The oxygen absorption and the discoloration measured as changes in CIE a*-value were dependent from the applied light intensity. The color stability of bologna was differently affected by light of various wavelengths. The results show that the use of suitable LEDs with specific spectra for display illumination can help to reduce the light induced deterioration of cured sausages in retail markets. PMID:27343458

  20. Synthesis of rare earth sulfides and their UV-vis absorption spectra

    YUAN Haibin; ZHANG Jianhui; YU Ruijin; SU Qiang

    2009-01-01

    Rare earth sulfides were systematically synthesized via the sulfurization of their commercial oxide powders using CS2 gas to shorten sulfurization time, and their UV-vis absorption spectra were investigated. The appropriate sulfurization conditions were studied. For the rare earth sulfides with the same crystal structure, the sulfurization temperature showed increasing tendency with the decrease of rare earth element atomic radii. The UV-vis absorption spectra of rare earth sulfides did not depend on the crystal structure of rare earth sulfides, but on the 4f electronic structure of rare earth element. The data showed that the optical band gaps of rare earth sulfides were irregular, and the values ranged from 1.65 to 3.75 eV.

  1. Forest of absorption lines in quasar spectra and the structure of the Universe

    The problem of the ''forest'' at absorption lines in the spectra of quasars is discussed in the frame of the A-theory of formation and evolution of the structure of the Universe. It is assumed that the hidden mass is connected with neutrino like particles (possibly instable) with a rest mass of the order of 60-100 eV. An observational test for the hypothesis proposed is discussed

  2. Synthesis, absorption spectra and semiempiric calculations on the photochromism of arylmercuric dithizonate complexes

    S. A. Mostafa

    1999-01-01

    Full Text Available A series of arylmercuric dithizonate complexes have been synthesized and characterized. Optical spectra of dissolved and pure compounds show transition energies around 480 nm which have been rationalized by semiempiric PM3 calculations. All complexes show a pronounced photochromism. The calculations also account for the observed blue absorption of the metastable species when an underlying geometric arrangement according to the proposal of Meriwether's is assumed.

  3. Optical absorption spectra of mercury centres in KCl and NaCl

    Optical absorption spectra of KCl and NaCl monocrystals doped with Hg2Cl2 were recorded at room temperature before and after 60Co #betta#-irradiation and F-light bleaching. It is concluded that gamma irradiation produces all types of Hg centres, that the Hg0 centres grow linearly with time of F-light bleaching, and that F-light bleaching enhances all the bands due to Hg centres

  4. Source brightness fluctuation correction of solar absorption Fourier Transform mid infrared spectra

    T. Ridder

    2011-01-01

    Full Text Available Solar absorption Fourier Transform infrared spectrometry is considered a precise and accurate method for the observation of trace gases in the atmosphere. The precision and accuracy of such measurements are dependent on the stability of the light source. Fluctuations in the source brightness reduce the precision and accuracy of the trace gas concentrations, but cannot always be avoided. Thus, a strong effort is made within the community to reduce the impact of source brightness fluctuations by applying a correction on the spectra following the measurements. So far, it could be shown that the precision and accuracy of CO2 total column concentrations could be improved by applying a source brightness fluctuation correction to spectra in the near infrared spectral region.

    The analysis of trace gas concentrations obtained from spectra in the mid infrared spectral region is fundamental. However, spectra below 2000 cm−1 are generally considered uncorrectable, if they are measured with a MCT detector. Such measurements introduce an unknown offset to MCT interferograms, which prevents a source brightness fluctuation correction.

    Here, we show a method of source brightness fluctuation correction, which can be applied on spectra in the whole infrared spectral region including spectra measured with a MCT detector. We present a solution to remove the unknown offset in MCT interferograms allowing MCT spectra for an application of source brightness fluctuation correction. This gives an improvement in the quality of MCT spectra and we demonstrate an improvement in the retrieval of O3 profiles and total column concentrations.

    For a comparison with previous studies, we apply our source brightness fluctuation correction method on spectra in the near infrared spectral region and show an improvement in the retrieval of CO2 total column concentrations.

  5. Study on the interaction between diphenhydramine and erythrosin by absorption, fluorescence and resonance Rayleigh scattering spectra

    TANG XiaoLing; LIU ZhongFang; LIU ShaoPu; HU XiaoLi

    2007-01-01

    In pH 4.5 Britton-Robinson (BR) buffer solution, erythrosin (ET) can react with diphenhydramine (DP) to form a 1:1 ion-association complex, which not only results in the change of the absorption spectra, but also results in the great enhancement of resonance Rayleigh scattering (RRS) and the quenching of fluorescence. Furthermore, a new RRS spectrum will appear, and the maximum RRS wavelength was located at about 580 nm.In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reaction and the properties of an analytical chemistry were investigated. A sensitive, simple and new method for the determination of DP by using erythrosin as a probe has been developed. The detection limits for DP were 0.0020 μg/mL for RRS method, 0.088 μg/mL for absorption method and 0.094 μg/mL for fluorophotometry. There was a linear relationship between the absorbance, RRS and fluorescence intensities and the drug concentration in the range of 0.0067-2.0, 0.29-6.4 and 0.31-3.2 μg/mL, respectively. The effects of the interaction of diphenhydramine and erythrosin on the absorption, fluorescence and resonance Rayleigh scattering spectra were discussed. In light polarization experiment, the polarization of RRS at maximum wavelength was measured to be P = 0.9779, and it revealed that the RRS spectrum of DP-ET complex consists mostly of resonance scattering and few resonance fluorescence. In this study, enthalpy of formation and mean polarizability were calculated by AM1 quantum chemistry method. In addition, the reaction mechanism and the reasons for the enhancement of scattering spectra and the energy transfer between absorption, fluorescence and RRS were discussed.

  6. UV Absorption and Luminescence Spectra of [2.2]Paracyclophane Phenyl Derivatives

    Nurmukhametov, R. N.; Shapovalov, A. V.; Antonov, D. Yu.

    2016-03-01

    UV absorption, fluorescence emission and excitation, and fluorescence excitation synchronous scanning spectra at 298 K and fluorescence and phosphorescence spectra at 77 K were measured for solutions of 4-phenyl- ( I) and 4,12-( II), 4,15- ( III), and 4,16-diphenyl derivatives ( IV) of [2.2]paracyclophane. Analysis of absorption spectra shows that they are determined by two types of chromophores (biphenyl and paracyclophane). It was shown that their weak long wavelength band (310-340 nm) and fluorescence band are governed by the same electron transition from the ground to an excimer-like excited state, as in the case of the unsubstituted macrocycle. Phenyl substitution shows only a weak influence on the energy of this transition. Strong absorption bands of I- IV at 230-310 nm originate from electronic transitions of biphenyl groups in these molecules. The strong bands of isomeric II- IV (with two biphenyl chromophores) differ significantly. It was supposed that this phenomenon was caused by different resonance interaction between electron oscillators (transitions) of the two biphenyl chromophores leading to different splitting of their excited states.

  7. X-ray absorption and selectively excited X-ray emission spectra of atenolol and nadolol

    Full text: The biological function of a drug given by the oral route is ruled by its degree of absorption in the gastrointestinal tract. These absorption characteristics (dissolution, solubility, permeability, metabolism) of the drug are time consuming and expensive to investigate experimentally. The predictive power of traditional theoretical models is quite limited. This is especially so for solubility, where a model predicting values within one order of magnitude of the experimentally determined solubility is accepted by the research field. Aiming at a more detailed understanding of drug solubility, we are carrying out X-ray absorption and X-ray emission spectroscopy on a series of pharmaceutical model substances in solid form and in water solution. Changes in local geometry and electronic structure primarily associated with changes in the way the drug molecules are hydrogen bonded to surrounding molecules are directly reflected in the spectra. Here we present and analyze the spectra of two solid β-adrenoreceptors, atenolol and nadolol, at the carbon, nitrogen and oxygen K edges. Special attention is given to the influence on the spectra of hydrogen bonding. An increased understanding of hydrogen bonding is essential for improving solubility models

  8. Modeling of multi-exciton transient absorption spectra of protochlorophyllide aggregates in aqueous solution.

    Sytina, Olga A; Novoderezhkin, Vladimir I; van Grondelle, Rienk; Groot, Marie Louise

    2011-11-01

    Protochlorophyllide (Pchlide) is a natural porphyrin, a precursor of chlorophyll, synthesized by plants for its photosynthetic apparatus. The pigment spontaneously forms aggregates when dissolved in neat water solution. We present here calculations of the transient absorption spectra and its comprising components (ground-state bleach, stimulated emission, and excited-state absorption) for a strongly excitonically coupled linear chain of four Pchlide chromophores, using exciton theory with phenomenological Gaussian line shapes and without energetic disorder. A refined multiexciton model that includes static disorder is applied to fit the experimental power-dependent transient absorption spectra of aqueous protochlorophyllide and the kinetics for delay times up to 20 ps after photoexcitation. We show that population up to the 4-exciton manifold is sufficient to explain the pronounced saturation of the bleaching and the shape changes in the instantaneous, t = 0.2 ps transient spectra when the pulse energy is increased from 10 to 430 nJ per pulse. The decay of the multiexciton manifold is relatively slow and is preceded by a spectroscopically distinct process. We suggest that the exciton states in the Pchlide aggregates are mixed with charge-transfer states (CTS) and that the population and repopulation of the CTS coupled to the exciton states explains the relatively slow decay of the multiexciton manifold. The relevance of our results to the optical properties and dynamics of natural photosynthetic complexes and the possible physical origin of CTS formation are discussed. PMID:21936513

  9. Near infrared cavity enhanced absorption spectra of atmospherically relevant ether-1, 4-Dioxane

    Chandran, Satheesh; Varma, Ravi

    2016-01-01

    1, 4-Dioxane (DX) is a commonly found ether in industrially polluted atmosphere. The near infrared absorption spectra of this compound has been recorded in the region 5900-8230 cm- 1 with a resolution of 0.08 cm- 1 using a novel Fourier transform incoherent broadband cavity-enhanced absorption spectrometer (FT-IBBCEAS). All recorded spectra were found to contain regions that are only weakly perturbed. The possible combinations of fundamental modes and their overtone bands corresponding to selected regions in the measured spectra are tabulated. Two interesting spectral regions were identified as 5900-6400 cm- 1 and 8100-8230 cm- 1. No significant spectral interference due to presence of water vapor was observed suggesting the suitability of these spectral signatures for spectroscopic in situ detection of DX. The technique employed here is much more sensitive than standard Fourier transform spectrometer measurements on account of long effective path length achieved. Hence significant enhancement of weaker absorption lines above the noise level was observed as demonstrated by comparison with an available measurement from database.

  10. Absorption Spectra of Ni and Co Nanoparticles using Density Functional Theory

    Metal nanoparticles (NPs) demonstrate excellent electronic properties due to quantum confinement effects and have tremendous applications in catalysts, optics, single-electron devices, bio-chemical sensors, etc. We propose quantum mechanics method for the calculation of absorption spectra of conduction electrons of some transition metal NPs using time-independent Schrodinger equation and approximate the solution by density functional theory. The total energy functional is obtained from the ground-state energy functional of Thomas-Fermi-Dirac- Weizsaecker atomic system. The absorption function was derived and replaced the density function in the final Euler-Lagrange equation. The total energy functional can then be computed numerically for isolated Ni and Co NPs having fcc lattice structure and different nano sizes. The results show a red-shift absorption peak increase with increasing diameter of nanosphere correspond to the number of atoms required to form nanoparticles of respective sizes. (author)

  11. Terahertz absorption spectra of 8-hydroxyquinoline and its some metal complexes

    Liu, Guifeng; Ma, Shihua; Zhao, Hongwei; Ji, Te; Zhang, Zengyan; Wang, Wenfeng

    2009-11-01

    The room temperature terahertz (THz) absorption spectra of 8-hydroxyquinoline (8HQ) and tris(8-hydroxyquinolino)aluminum, bis-(8-hydroxyquinolinato)zinc and copper 8-hydroxyquinoline were clearly measured from 0.3 to 1.8 THz. 8HQ has absorption peaks which occur at 1.02, 1.48, and 1.77 THz. Density functional theory (DFT) was used to predict the vibration frequencies of 8HQ in the frequency range 0-10 THz. Metal complexes have various absorption peaks in the THz region, which may be related to different metal ions and used to distinguish them. These results show that THz-TDS are sensitive tools for characterization of metal complexes.

  12. Decoupling multimode vibrational relaxations in multi-component gas mixtures: Analysis of sound relaxational absorption spectra

    Zhang Ke-Sheng; Wang Shu; Zhu Ming; Ding Yi; Hu Yi

    2013-01-01

    Decoupling the complicated vibrational-vibrational (V-V) coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures.In our previous work [Acta Phys.Sin.61 174301 (2012)],an analytical model to predict the sound absorption from vibrational relaxation in a gas medium is proposed.In this paper,we develop the model to decouple the V-V coupled energy to each vibrationaltranslational deexcitation path,and analyze how the multimode relaxations form the peaks of sound absorption spectra in gas mixtures.We prove that a multimode relaxation is the sum of its decoupled single-relaxation processes,and only the decoupled process with a significant isochoric-molar-heat can be observed as an absorption peak.The decoupling model clarifies the essential processes behind the peaks in spectra arising from the multimode relaxations in multi-component gas mixtures.The simulation validates the proposed decoupling model.

  13. The high resolution vacuum ultraviolet absorption spectra of the group VI dihydrides and deuterides Rydberg series

    Mayhew, C A

    1984-01-01

    The high resolution absorption spectra of the important group VI dihydrides and deuterides in the vacuum ultraviolet below, and up to, their first ionisation potentials are presented. These spectra were recorded using synchrotron radiation as the background light source in conjunction with a 3m normal incidence vacuum spectrograph, equipped with holographic gratings. Due to the nature of the originating orbital for the majority of optical transitions in the VUV well developed Rydberg series are observed. One particular series can be followed up to fairly high n, so that accurate values of the first ionisation potential are determined. The identifications of the Rydberg series are made from arguments relating to their oscillator strengths, quantum defects, symmetries and from comparisons with the spectra of the corresponding united atoms i.e. the inert gases. Examples of the symmetry assignments for Rydberg series from rotational band contour analyses of the lower Rydberg members for the H sub 2 S, H sub 2 Se ...

  14. Infrared absorption spectra of transition metals-doped soda lime silica glasses

    Infrared (IR) absorption spectra of some prepared undoped and transition metals-doped soda-lime-silicate glasses have been studied in the region of 400-4000 cm-1. IR spectra were analyzed to determine and differentiate the various vibrational modes by applying a deconvolution method to the IR spectra. Although the first sight reveals close similarity between the different transition metal- (TM) doped samples; careful inspection indicates some minor differences depending on the type of TM ions. These observed data are correlated with similar energy of the 3d orbitals of TM atoms in the neutral state and when the atoms are ionized, the 3d orbitals becomes more stable than the 4 s orbitals.

  15. Absorption features in the spectra of X-ray bursting neutron stars

    Rauch, Thomas; Werner, Klaus

    2008-01-01

    The discovery of photospheric absorption lines in XMM-Newton spectra of the X-ray bursting neutron star in EXO0748-676 by Cottam and collaborators allows us to constrain the neutron star mass-radius ratio from the measured gravitational redshift. A radius of R=9-12km for a plausible mass range of M=1.4-1.8Msun was derived by these authors. It has been claimed that the absorption features stem from gravitationally redshifted (z=0.35) n=2-3 lines of H- and He-like iron. We investigate this identification and search for alternatives. We compute LTE and non-LTE neutron-star model atmospheres and detailed synthetic spectra for a wide range of effective temperatures (effective temperatures of 1 - 20MK) and different chemical compositions. We are unable to confirm the identification of the absorption features in the X-ray spectrum of EXO0748-676 as n=2-3 lines of H- and He-like iron (Fe XXVI and Fe XXV). These are subordinate lines that are predicted by our models to be too weak at any effective temperature. It is m...

  16. X-ray-absorption spectra in KrF2 and FeCl2: theory

    Theoretical x-ray-absorption near-edge structure (XANES) and extended x-ray-absorption fine structure (EXAFS) of molecular and crystalline KrF2 and gas-phase FeCl2 have been obtained by using a modified Xα scattered-wave procedure. EXAFS calculations are made in the single-scattering approximation. Effects of multiple scattering near the absorption edge have been investigated by comparing predicted XANES and EXAFS spectra in the near-edge region. Two exchange-correlation potentials, Xα and energy-dependent Dirac (ED), were incorporated in the EXAFS calculations. Comparison between experimental and theoretical results confirm that the ED potential is more valid for EXAFS spectra. Molecular field splitting as well as resonance coupling were demonstrated by comparing the theoretical XANES of the isolated KrF2 molecule to that of FeCl2. The single-particle XANES calculation of molecular FeCl2 is compared with the experimental crystalline FeCl2 results of Stern. 37 references, 8 figures, 1 table

  17. Vibronic bandshape of the absorption spectra of dibenzoylmethanatoboron difluoride derivatives: analysis based on ab initio calculations.

    Rukin, Pavel S; Freidzon, Alexandra Ya; Scherbinin, Andrei V; Sazhnikov, Vyacheslav A; Bagaturyants, Alexander A; Alfimov, Michael V

    2015-07-14

    The nature of absorption bandshapes of dibenzoylmethanatoboron difluoride (DBMBF2) dye substituted in ortho-, meta-, and para-positions of the phenyl ring is investigated using DFT and TDDFT with the range-separated hybrid CAM-B3LYP functional and the 6-311G(d,p) basis set. The solvent effects are taken into account within the polarized continuum model. The vibronic bandshape is simulated using a time-dependent linear coupling model with a vertical gradient approach through an original code. For flexible chromophores, the spectra of individual conformers are summed up with Boltzmann factors. It is shown that the long-wavelength absorption bandshape of DBMBF2 derivatives is determined by three factors: the relative statistical weights of conformers with different electronic absorption patterns, the relative position and intensity of the second low-energy electronic transition, and the vibronic structure of individual electronic peaks. The latter is governed by the relationship between the hard vibrational modes, which contribute to vibronic progression, and soft modes, which provide broadening of the peaks. The simulated spectra of the dyes in the study are generally consistent with the available experimental data and explain the observed spectral features. PMID:26062782

  18. Optical absorption spectra of semiconductors and insulators: ab initio calculation of many-body effects

    A method for the inclusion of self-energy and excitonic effects in first-principle calculations of absorption spectra, within the state-of-the-art plane wave pseudopotential approach, is presented. Starting from a ground state calculation, using density functional theory (DFT) in the local density approximation (LDA), we correct the exchange-correlation potential of DFT-LDA with the self-energy applying Hedin's GW approximation to obtain the physical quasiparticles states. The electron-hole interaction is treated solving an effective two-particle equation, which we derive from Hedin's coupled integral equations, leading to the fundamental Bethe-Salpeter equation in an intermediate step. The interaction kernel contains the screened electron-hole Coulomb interaction and the electron-hole exchange effects, which reflect the microscopic structure of the system and are thus also called local-field effects. We obtain the excitonic eigenstates through diagonalization. This allows us a detailed analysis of the optical properties. The application of symmetry properties enables us to reduce the size of the two-particle Hamiltonian matrix, thus minimizing the computational effort. We apply our method to silicon, diamond, lithium oxide and the sodium tetramer. Good agreement with experiment is obtained for the absorption spectra of Si and diamond, the static dielectric constant of diamond, and for the onset of optical absorption of Li2O due to discrete bound excitons. We discuss various approximations of our method and show the strong mixing of independent particle transitions to a bound excitonic state in the Na4 cluster. The influence of ground state calculations on optical spectra is investigated under particular consideration of the pseudopotential generation and we discuss the use of different Brillouin zone point sampling schemes for spectral calculations. (author)

  19. Index of Refraction and Absorption Coefficient Spectra of Paratellurite in the Terahertz Region

    Unferdorben, Márta; Buzády, Andrea; Hebling, János; Kiss, Krisztián; Hajdara, Ivett; Kovács, László; Péter, Ágnes; Pálfalvi, László

    2016-07-01

    Index of refraction and absorption coefficient spectra of pure paratellurite (α-TeO2) crystal as a potential material for terahertz (THz) applications were determined in the 0.25-2 THz frequency range at room temperature by THz time domain spectroscopy (THz-TDS). The investigation was performed with beam polarization both parallel (extraordinary polarization) and perpendicular (ordinary polarization) to the optical axis [001] of the crystal. Similarly to the visible spectral range, positive birefringence was observed in the THz range as well. It was shown that the values of the refractive index for extraordinary polarization are higher and show significantly larger dispersion than for the ordinary one. The absorption coefficient values are also larger for extraordinary polarization. The measured values were fitted by theoretical curves derived from the complex dielectric function containing independent terms of Lorentz oscillators due to phonon-polariton resonances. The results are compared with earlier publications, and the observed significant discrepancies are discussed.

  20. Efficient Calculation of Electronic Absorption Spectra by Means of Intensity-Selected TD-DFTB

    Rüger, Robert; Lu, You; Frenzel, Johannes; Heine, Thomas; Visscher, Lucas

    2014-01-01

    During the last two decades density functional based linear response approaches have become the de facto standard for the calculation of optical properties of small and medium-sized molecules. At the heart of these methods is the solution of an eigenvalue equation in the space of single-orbital transitions, whose quickly increasing number makes such calculations costly if not infeasible for larger molecules. This is especially true for time-dependent density functional tight binding (TD-DFTB), where the evaluation of the matrix elements is sufficiently cheap so that relatively large systems can be studied. We propose to do an oscillator strength based truncation of the single-orbital transition space to reduce the computational effort of TD-DFTB based absorption spectra calculations. We show that even a sizeable truncation does not destroy the principal features of the absorption spectrum, while naturally avoiding the unnecessary calculation of excitations with small oscillator strengths. We argue that the re...

  1. Absorption Spectra of a Three-Level Atom Embedded in a PBG Reservoir

    ZHANG Ke; ZHANG Han-Zhuang

    2007-01-01

    We introduce the 'decay rate' terms into the density matrix equations of an atom embedded in a photonic band gap (PSG)reservoir successfully.By utilizing the master equations,the probe absorption spectra and the refractivity properties of a three-level atom in the PBG reservoir are obtained.The interaction between the atom and the PBG reservoir as well as the effects of the quantum interference on the absorption of the atom has also been taken into account.It is interesting that two different types of the anomalous dispersion relations of refractivity are exhibited in one dispersion line.The methodology used here can be applied to theoretical investigation of quantum interference effects of other atomic models embedded in a PBG reservoir.

  2. Multielectron excitations in x-ray absorption spectra of Rb and Kr

    In the K-edge x-ray absorption of rubidium vapour and gaseous krypton, comprehensive spectra of collective excitations down to the relative probability of 5x10-5 are extracted. After removal of the asymptotic Victoreen trend, the region ∼100 eV above the edge exhibits a steep decrease of the absorption coefficient attributed to core relaxation and post-collision interaction in the Auger decay. With an exponential model for the decrease, the entire spectrum of multielectron excitations is recognized as a succession of consecutive resonant, shake-up and shake-off channels. They can be identified as coexcitations of electrons from successively deeper subshells, from 5s down to 3s. The identification of excited states is aided by a quantitative modelling of subshell contributions and by natural-width deconvolution. The valence and subvalence coexcitations are shown to follow the pattern of the lighter homologues potassium and argon. (author)

  3. Dielectric tensor of tetracene single crystals: the effect of anisotropy on polarized absorption and emission spectra.

    Tavazzi, S; Raimondo, L; Silvestri, L; Spearman, P; Camposeo, A; Polo, M; Pisignano, D

    2008-04-21

    The full UV-visible dielectric tensor and the corresponding directions of the principal axes of triclinic tetracene crystals are reported as deduced either by polarized absorption and ellipsometry measurements or by calculations based on the molecular and crystallographic data. The results allow the attribution of the polarized bands observed in both absorption and photoluminescence emission spectra. In particular, the spectral line shape and polarization of the emission are found to depend on the sample thickness, and the effect is attributed to the modification of the state of polarization of the emitted light during its propagation inside the crystal. Indeed, the directions of polarization of the lowest optical transitions and the directions of the principal axes of the dielectric tensor are demonstrated not to coincide, in contrast to the assumptions typically made in the literature, thus causing the mixed transverse/longitudinal character of light propagation. PMID:18433260

  4. Collision-induced absorption (CIA) spectra and ground-state potentials of inert gas mixtures

    Collision-induced absorption spectra of the rare gas systems He-Ne, He-Ar, He-Kr, He-Xe, Ne-Kr, Ne-Xe, Ar-Kr and Ar-Xe at different temperatures with the pressure second virial coefficients, viscosity and thermal conductivity have been used for deriving the empirical models of the induced dipole moment and the interaction potential. Theoretical zeroth, first and second moments of the binary spectra using various models for the induced dipole moment and interatomic potential are compared with the experimental values performed by the groups of Marteau, Bosomworth, Bucktoyarova, Bar-Ziv, Ryzhov and Frommhold. In addition, mixture diffusion coefficients and isotopic thermal factors calculated for these models are compared with experimental ones. The results show that these models are the most accurate models reported to date for these mixtures.

  5. Pressure dependence of Hexanitrostilbene Raman/ electronic absorption spectra to validate DFT EOS

    Farrow, Darcie; Alam, Kathleen; Martin, Laura; Fan, Hongyou; Kay, Jeffrey; Wixom, Ryan

    2015-06-01

    Due to its thermal stability and low vapor pressure, Hexanitrostilbene (HNS) is often used in high-temperature or vacuum applications as a detonator explosive or in mild detonating fuse. Toward improving the accuracy of the equation of state used in hydrodynamic simulations of the performance of HNS, we have measured the Raman and electronic absorption spectra of this material under static pressure in a diamond anvil cell. Density functional theory calculations were used to simulate the pressure dependence of the Raman/Electronic spectra along the Hugoniot and 300K isotherm for comparison and to aid in interpreting the data. We will discuss changes in the electronic structure of HNS under pressure, validation of a DFT predicted equation of state (EOS), and using this data as a basis for understanding future pulsed Raman measurements on dynamically compressed HNS samples.

  6. Solvent effect on electronic absorption spectra of cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids

    VERA V. KRSTIC

    2000-06-01

    Full Text Available The ultraviolet absorption spectra of cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were determined in six protic and nine aprotic solvents in the wavelength range from 200 to 400 nm. The position of the lmax of the two examined acids showed that the ultraviolet absorption maximums of cyclohex-1-enylcarboxylic acid were at consistently longer wavelengths in protic solvents than those of methylcyclohex-1-enylcarboxylic acid. The opposite was true in aprotic solvents. In order to explain the obtained results, the ultraviolet absorption frequencies of the electronic transitions in the carboxy carbonyl group of the examined acids were correlated using a total solvatochromic equation of the form: n = n0 + sp* + aa + bb, where p* is a measure of the solvent polarity, b represents the scale of solvent hydrogen bond acceptor basicities and a represents the scale of solvent hydrogen bond donor acidities. The correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The opposing solvent effects on the ultraviolet absorption maximums of the two examined acids were discussed.

  7. Absorption and fluorescence spectra of gallium phosphide(GaP) nanoparticles

    YUE Long-yi; ZHANG Zhao-chun; CHEN Xu

    2006-01-01

    The optical absorption spectrum ranging from 200 to 800 nm and fluorescence spectra ranging from 300 to 650 nm of GaP nanoparticles at room temperature were reported. From the optical absorption spectrum it is inferred that the GaP nanoparticles exhibit a direct transition of about 410 nm (3.02 eV) and an indirect transition around 480 nm (2.58 eV). In addition, an absorption peak at about 308 nm (4.02 eV) corresponding to the direct transition at higher energy was observed. The absorption peak was attributed to the transition from the spin-orbit-split valence band to the lowest conduction band along the A direction. By observing the fluorescence of the GaP nanoparticles, it follows that multiple emission bands corresponding to the violet, blue, and yellow light are shown peaking at about 400.4-414.1 nm (3.097-2.994 eV), 450.1-466.8 nm (2.755-2.656 eV), and 582.4 nm (2.129 eV),respectively. The violet and blue light emissions are ascribed to the direct and indirect transitions from conduction band to valence band of the GaP nanoparticles. As to the weak yellow emission, it may be attributed to the radiative recombination from defect centers. The spin-orbit-splitting of the GaP nanoparticles is determined as about 100 meV.

  8. Atomic calculations and search for variation of the fine-structure constant in quasar absorption spectra

    Dzuba, V. A.; Flambaum, V. V.

    A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.

  9. Atomic calculations and search for variation of the fine structure constant in quasar absorption spectra

    Dzuba, V A

    2008-01-01

    A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.

  10. IR absorption and surface-enhanced Raman spectra of the isoquinoline alkaloid berberine

    Strekal', N. D.; Motevich, I. G.; Nowicky, J. W.; Maskevich, S. A.

    2007-01-01

    We present the IR absorption and surface-enhanced Raman scattering (SERS) spectra of the isoquinoline alkaloid berberine adsorbed on a silver hydrosol and on the surface of a silver electrode for different potentials. Based on quantum chemical calculations, for the first time we have assigned the vibrations in the berberine molecule according to vibrational mode. The effect of the potential of the silver electrode on the geometry of sorption of the molecule on the surface is considered, assuming a short-range mechanism for enhancement of Raman scattering.

  11. Decay heat and anti-neutrino energy spectra in fission fragments from total absorption spectroscopy

    Rykaczewski, Krzysztof

    2015-10-01

    Decay studies of over forty 238U fission products have been studied using ORNL's Modular Total Absorption Spectrometer. The results are showing increased decay heat values, by 10% to 50%, and the energy spectra of anti-neutrinos shifted towards lower energies. The latter effect is resulting in a reduced number of anti-neutrinos interacting with matter, often by tens of percent per fission product. The results for several studied nuclei will be presented and their impact on decay heat pattern in power reactors and reactor anti-neutrino physics will be discussed.

  12. Modulated microwave absorption spectra from Josephson junctions on a scratched niobium wire

    Modulated microwave absorption (MMA) spectra from Josephson junction formations on a scratched Nb wire have been studied at 9.3 GHz and 4 K. The peak-to-peak separation, δH of the Josephson lines was found to vary linearly with P1/2, where P is the applied microwave power, in contrast to a recent interpretation of junction formation in pressed lead pieces by Rubins, Drumheller, and Trybula. The interpretation of the MMA data on Nb are given in terms of the theory of Vichery, Beuneu, and Lejay for superconducting loops containing weak links. copyright 1997 The American Physical Society

  13. Infrared absorption spectra of Tb3+-ions in Bi2TeO5 single crystal

    Bismuth tellurite Bi2TeO5 (BTO) is a photorefractive crystal with special capability of self-fixing hologram recording. Single crystals of BTO:Tb were grown by the Czochralski technique. Five infrared transitions were identified and analyzed in the high resolution absorption spectra from the 7F6 ground state to the 7F4, 7F3, 7F2, 7F1, and 7F0 manifolds together with their Stark components. The features of the Tb3+ transitions are in accordance with the single site Tb substitution to one of the slightly different Bi-site.

  14. Electronic properties and absorption spectra of ZnSnP2 using mBJ potential

    We present the energy bands and density of states of ZnSnP2 using full potential linearized augmented plane wave method with modified Becke Johnson potential. It is found that this compound has a direct band gap of about 2.01 eV at Γ point, which originates from the energy difference between P-3p and Sn-5s states. In addition, we have also calculated absorption spectra in the solar energy range and compared it with that of bulk Si to explore the applicability of ZnSnP2 in photovoltaic and optoelectronic devices

  15. Appraisal of Surface Hopping as a Tool for Modeling Condensed Phase Linear Absorption Spectra.

    Petit, Andrew S; Subotnik, Joseph E

    2015-09-01

    Whereas surface hopping is usually used to study populations and mean-field dynamics to study coherences, in two recent papers, we described a procedure for calculating dipole-dipole correlation functions (and therefore absorption spectra) directly from ensembles of surface hopping trajectories. We previously applied this method to a handful of one-dimensional model problems intended to mimic the gas phase. In this article, we now benchmark this new procedure on a set of multidimensional model problems intended to mimic the condensed phase and compare our results against other standard semiclassical methods. By comparison, we demonstrate that methods that include only dynamical information from one PES (the standard Kubo approaches) exhibit large discrepancies with the results of exact quantum dynamics. Furthermore, for model problems with nonadiabatic excited state dynamics but no quantized vibrational structure in the spectra, our surface hopping approach performs comparably to using Ehrenfest dynamics to calculate the electronic coherences. That being said, however, when quantized vibrational structures are present in the spectra but the electronic states are uncoupled, performing the dynamics on the mean PES still outperforms our present method. These benchmark results should influence future studies that use ensembles of independent semiclassical trajectories to model linear as well as multidimensional spectra in the condensed phase. PMID:26575927

  16. X-Ray Absorption Near Edge Structure Spectra as a basis for the speciation of lead

    For this study several inorganic lead (II) compounds were measured at the Pb-L3-(13035 eV), L1- (15860 eV) and M5- (2484 eV) edge using X-Ray Absorption Near Edge Structure Spectroscopy (XANES) to determine experimentally which edge is most sensitive to the coordination environment. Each edge probes a different electronic configuration because of the selection rules and has a different resolution because of life-time broadening. Pb-L1-XANES spectra are only sensitive to the first coordination shell. Pb-M5-XANES spectra show a better energy resolution which is due to decreased lifetime broadening, but the pure lead spectra are also sensitive only to the first coordination shell. Spectra at the Pb-L3-edge show the highest sensitivity: differences in coordination out to the third shell could be distinguished. Therefore, even though Pb-L1- and M5-edges have some advantages, because of physical conditions compared to the L3-edge, these advantages do not result in increased sensitivity.

  17. Extracting interstellar diffuse absorption bands from cool star spectra: Application to bulge clump giants in Baade's window

    Chen, Hui-Chen; Babusiaux, Carine; Puspitarini, Lucky; Bonifacio, Piercarlo; Hill, Vanessa

    2012-01-01

    Interstellar diffuse bands are usually extracted from hot star spectra because they are characterized by smooth continua. It introduces a strong limitation on the number of available targets, and reduces potential studies of the IS matter and the use of absorptions for cloud mapping. We have developed a new automatic fitting method appropriate to interstellar absorptions in spectra of cool stars that possess stellar atmospheric parameters. We applied this method to the extraction of three DIBs in high resolution VLT FLAMES/GIRAFFE spectra of red clump stars from the bulge. By combining all stellar synthetic spectra, HITRAN-LBLRTM atmospheric transmission spectra and diffuse band empirical absorption profiles, we determine the 6196, 6204, and 6284 A DIB strength toward the 219 target stars and discuss the sources of uncertainties. In order to test the sensitivity of the DIB extraction, we intercompare the three results and compare the DIB equivalent widths with the reddening derived from an independent extinct...

  18. Transient absorption and luminescence spectra of K9 glass at sub-damage site by ultraviolet laser irradiation

    Highlights: • Transient absorption and luminescence spectra at sub-damage site of K9 glass by laser irradiation at 355 nm are presented. • As the energy density increases to 2.54 J/cm2, the absorption intensity reaches to about 0.2. • The mechanism of two-photon ionization mainly plays a critical role at sub-damage site. • Intensity of Raman spectra is very high at low energy density and decreased with respect to high energy density. -- Abstract: Transient absorption and luminescence spectra at sub-damage site of K9 glass by laser irradiation at 355 nm are presented. The dependence of transient absorption on laser energy and number of pulses was investigated. As the energy density increases to 2.54 and 3.18 J/cm2, the transient absorption intensity reaches to about 0.20 range from 400 to 480 nm. With the increase of number of pulses the process of residual absorption appears, which can be used to explain the fatigue effect of K9 glass. The defects in K9 glass were investigated by fluorescence and Raman spectra. The fluorescence band centered at about 410 nm is attributed to oxygen deficiency centers. The mechanism of two-photon ionization plays a critical role at sub-damage site. Compared to the Raman spectra of pristine site, intensity of Raman spectra is very high at a lower energy density, while it decreased at a higher energy density

  19. Gas phase UV and IR absorption spectra of CxF2x+1CHO (x=1-4)

    Hashikawa, Y; Kawasaki, M; Waterland, RL;

    2004-01-01

    The UV and IR spectra of CxF2x+1 CHO (x = 1-4) were investigated using computational and experimental techniques. CxF2x+1CHO (x = 1-4) have broad UV absorption features centered at 300-310 nm. The maximum absorption cross-section increases significantly and shifts slightly to the red with increas...

  20. Identifying Student and Teacher Difficulties in Interpreting Atomic Spectra Using a Quantum Model of Emission and Absorption of Radiation

    Savall-Alemany, Francisco; Domènech-Blanco, Josep Lluís; Guisasola, Jenaro; Martínez-Torregrosa, Joaquín

    2016-01-01

    Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two…

  1. Multi-state extrapolation of UV/Vis absorption spectra with QM/QM hybrid methods

    Ren, Sijin; Caricato, Marco

    2016-05-01

    In this work, we present a simple approach to simulate absorption spectra from hybrid QM/QM calculations. The goal is to obtain reliable spectra for compounds that are too large to be treated efficiently at a high level of theory. The present approach is based on the extrapolation of the entire absorption spectrum obtained by individual subcalculations. Our program locates the main spectral features in each subcalculation, e.g., band peaks and shoulders, and fits them to Gaussian functions. Each Gaussian is then extrapolated with a formula similar to that of ONIOM (Our own N-layered Integrated molecular Orbital molecular Mechanics). However, information about individual excitations is not necessary so that difficult state-matching across subcalculations is avoided. This multi-state extrapolation thus requires relatively low implementation effort while affording maximum flexibility in the choice of methods to be combined in the hybrid approach. The test calculations show the efficacy and robustness of this methodology in reproducing the spectrum computed for the entire molecule at a high level of theory.

  2. A wavelet analysis for the X-ray absorption spectra of molecules

    We present a Wavelet transform analysis for the X-ray absorption spectra of molecules. In contrast to the traditionally used Fourier transform approach, this analysis yields a 2D correlation plot in both R- and k-space. As a consequence, it is possible to distinguish between different scattering pathways at the same distance from the absorbing atom and between the contributions of single and multiple scattering events, making an unambiguous assignment of the fine structure oscillations for complex systems possible. We apply this to two previously studied transition metal complexes, namely iron hexacyanide in both its ferric and ferrous form, and a rhenium diimine complex, [ReX(CO)3(bpy)], where X = Br, Cl, or ethyl pyridine (Etpy). Our results demonstrate the potential advantages of using this approach and they highlight the importance of multiple scattering, and specifically the focusing phenomenon to the extended X-ray absorption fine structure (EXAFS) spectra of these complexes. We also shed light on the low sensitivity of the EXAFS spectrum to the Re-X scattering pathway.

  3. Fullerene-Based Photoactive Layers for Heterojunction Solar Cells: Structure, Absorption Spectra and Charge Transfer Process

    Yuanzuo Li

    2014-12-01

    Full Text Available The electronic structure and optical absorption spectra of polymer APFO3, [70]PCBM/APFO3 and [60]PCBM/APFO3, were studied with density functional theory (DFT, and the vertical excitation energies were calculated within the framework of the time-dependent DFT (TD-DFT. Visualized charge difference density analysis can be used to label the charge density redistribution for individual fullerene and fullerene/polymer complexes. The results of current work indicate that there is a difference between [60]PCBM and [70]PCBM, and a new charge transfer process is observed. Meanwhile, for the fullerene/polymer complex, all calculations of the twenty excited states were analyzed to reveal all possible charge transfer processes in depth. We also estimated the electronic coupling matrix, reorganization and Gibbs free energy to further calculate the rates of the charge transfer and the recombination. Our results give a clear picture of the structure, absorption spectra, charge transfer (CT process and its influencing factors, and provide a theoretical guideline for designing further photoactive layers of solar cells.

  4. Multi-state extrapolation of UV/Vis absorption spectra with QM/QM hybrid methods.

    Ren, Sijin; Caricato, Marco

    2016-05-14

    In this work, we present a simple approach to simulate absorption spectra from hybrid QM/QM calculations. The goal is to obtain reliable spectra for compounds that are too large to be treated efficiently at a high level of theory. The present approach is based on the extrapolation of the entire absorption spectrum obtained by individual subcalculations. Our program locates the main spectral features in each subcalculation, e.g., band peaks and shoulders, and fits them to Gaussian functions. Each Gaussian is then extrapolated with a formula similar to that of ONIOM (Our own N-layered Integrated molecular Orbital molecular Mechanics). However, information about individual excitations is not necessary so that difficult state-matching across subcalculations is avoided. This multi-state extrapolation thus requires relatively low implementation effort while affording maximum flexibility in the choice of methods to be combined in the hybrid approach. The test calculations show the efficacy and robustness of this methodology in reproducing the spectrum computed for the entire molecule at a high level of theory. PMID:27179466

  5. Photosynthetic complex LH2 – Absorption and steady state fluorescence spectra

    Nowadays, much effort is devoted to the study of photosynthesis which could be the basis for an ideal energy source in the future. To be able to create such an energy source – an artificial photosynthetic complex, the first step is a detailed understanding of the function of photosynthetic complexes in living organisms. Photosynthesis starts with the absorption of a solar photon by one of the LH (light-harvesting) pigment–protein complexes and transferring the excitation energy to the reaction center where a charge separation is initiated. The geometric structure of some LH complexes is known in great detail, e.g. for the LH2 complexes of purple bacteria. For understanding of photosynthesis first stage efficiency, it is necessary to study especially optical properties of LH complexes. In this paper we present simulated absorption and steady-state fluorescence spectra for ring molecular system within full Hamiltonian model. Such system can model bacteriochlorophyll ring of peripheral light-harvesting complex LH2 from purple bacterium Rhodopseudomonas acidophila (Rhodoblastus acidophilus). Dynamic disorder (coupling with phonon bath) simultaneously with uncorrelated static disorder (transfer integral fluctuations) is used in our present simulations. We compare and discuss our new results with our previously published ones and of course with experimental data. - Highlights: • We model absorption and steady state fluorescence spectra for B850 ring from LH2. • Fluctuations of environment is modelled by static and dynamic disorder. • Full Hamiltonian model is compared with the nearest neighbour approximation one. • Simulated fluorescence spectrum is compared with experimental data

  6. Infrared absorption spectra of a Nd0.5Ho0.5Fe3(BO3)4 crystal

    Gerasimova, Yu. V.; Sofronova, S. N.; Gudim, I. A.; Oreshonkov, A. S.; Vtyurin, A. N.; Ivanenko, A. A.

    2016-01-01

    Infrared absorption spectra of a Nd0.5Ho0.5Fe3(BO3)4 crystal in the spectral range of 30-1700 cm-1 have been measured at temperatures from 6 to 300 K. The experimental spectra have been analyzed based on the semiempirical calculation of the lattice dynamics and the analysis of correlation diagrams of borate complexes. No changes associated with structural phase transitions have been detected in the temperature range of measurements; the effect of magnetic ordering on the infrared absorption spectra has not been observed.

  7. Excitation dynamics in Phycoerythrin 545: modeling of steady-state spectra and transient absorption with modified Redfield theory.

    Novoderezhkin, Vladimir I; Doust, Alexander B; Curutchet, Carles; Scholes, Gregory D; van Grondelle, Rienk

    2010-07-21

    We model the spectra and excitation dynamics in the phycobiliprotein antenna complex PE545 isolated from the unicellular photosynthetic cryptophyte algae Rhodomonas CS24. The excitonic couplings between the eight bilins are calculated using the CIS/6-31G method. The site energies are extracted from a simultaneous fit of the absorption, circular dichroism, fluorescence, and excitation anisotropy spectra together with the transient absorption kinetics using the modified Redfield approach. Quantitative fit of the data enables us to assign the eight exciton components of the spectra and build up the energy transfer picture including pathways and timescales of energy relaxation, thus allowing a visualization of excitation dynamics within the complex. PMID:20643051

  8. Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra

    Murphy, M T; Flambaum, V V

    2003-01-01

    [Abridged] We previously presented evidence for a varying fine-structure constant, alpha, in two independent samples of Keck/HIRES QSO spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2absorption clouds. Assuming that da/a=0 at z_abs=0, the da...

  9. Absorption spectra response of XRQA radiochromic film to x-ray radiation

    Alnawaf, Hani [Centre for Medical Radiation Physics, University of Wollongong, NSW (Australia); Cheung, Tsang [Dept. of Physics and Materials Science, City University of Hong Kong, Kowloon Tong (Hong Kong); Butson, Martin J., E-mail: martin.butson@sesiahs.health.nsw.gov.a [Dept. of Physics and Materials Science, City University of Hong Kong, Kowloon Tong (Hong Kong); Department of Medical Physics, Illawarra Cancer Care Centre, Crown St, Wollongong, P.O. Box 1798, NSW 2500 (Australia); Centre for Medical Radiation Physics, University of Wollongong, NSW (Australia); Yu, Peter K.N. [Dept. of Physics and Materials Science, City University of Hong Kong, Kowloon Tong (Hong Kong)

    2010-01-15

    Gafchromic XRQA, radiochromic film is a high sensitivity auto developing x-ray analysis films designed and available for kilovoltage x-ray, dose and QA assessment applications. The film is designed for reflective analysis with a yellow transparent top filter and white opaque backing materials. This allows the film to be visually inspected for colour changes with a higher level of contrast than clear coated radiochromic films such as Gafchromic EBT version 1. The spectral absorption properties in the visible wavelengths have been investigated and results show two main peaks in absorption located at 636 nm and 585 nm. These peaks are located in the same position as EBT Gafchromic film highlighting a similar chemical monomer/polymer for radiation sensitivity. A much higher sensitivity however is found at kilovoltage energies with an average 1.55 OD units per 20 cGy irradiation variation measured at 636 nm using 150 kVp x-rays. This is compared to approximately 0.12 OD units per 20 cGy measured at 636 nm for EBT film at 6 MV x-ray energy. That is, the XRQA film is more than 10 times more sensitive than EBT1 film. The visual colour change is enhanced by the yellow polyester coating. However this does not affect the absorption spectra properties in the red region of analysis which is the main area for use using desktop scanners in reflection mode.

  10. Polarized absorption spectra of highly oriented two-dimensional aggregates of tetrachlorobenzimidazolocarbocyanine in thin films

    Reaching a control on the mesoscopic morphology and internal molecular arrangement of cyanine aggregates is an important step for realization of devices with tailor-made optical properties. Despite a wealth of research, understanding of the relationship between molecular organization, excitonic states and dynamics of aggregates is still preliminary. To this end, we have employed polarized absorption spectroscopy to investigate the relationship between internal molecular organization and excitonic states of J-aggregates in 1,1',3,3'tetraethyl-5,5',6,6'-tetrachlorobenzimidazolocarbocyanine (TTBC) thin films in poly-vinyl alcohol (PVA). Angular dependence of the UV-vis spectra has been measured at 11 different orientations between the electric field polarization and the macroscopic alignment axis. Aggregate spectral response consisted of an asymmetrically split Davydov pair of bands exhibiting opposite polarization: an H-band (505 nm, Lorentzian-like, polarized along the macroscopic film axis) and a J-band (594 nm, one-dimensional J-aggregate like band shape, polarized perpendicular to the macroscopic film axis). The polarized absorption observations were found to be consistent with a herringbone model for which the internal molecular arrangement, the excited state structure and dynamics have recently been detailed by us upon interpretation of isotropic absorption data in ionic aqueous solution

  11. Polarized absorption spectra of highly oriented two-dimensional aggregates of tetrachlorobenzimidazolocarbocyanine in thin films

    Ozcelik, Serdar [Chemistry Department, Izmir Institute of Technology, Urla 35430, Izmir (Turkey)], E-mail: serdarozcelik@iyte.edu.tr; Guelen, Demet [Physics Department, Middle East Technical University (METU), 06531 Ankara (Turkey)

    2008-05-15

    Reaching a control on the mesoscopic morphology and internal molecular arrangement of cyanine aggregates is an important step for realization of devices with tailor-made optical properties. Despite a wealth of research, understanding of the relationship between molecular organization, excitonic states and dynamics of aggregates is still preliminary. To this end, we have employed polarized absorption spectroscopy to investigate the relationship between internal molecular organization and excitonic states of J-aggregates in 1,1',3,3'tetraethyl-5,5',6,6'-tetrachlorobenzimidazolocarbocyanine (TTBC) thin films in poly-vinyl alcohol (PVA). Angular dependence of the UV-vis spectra has been measured at 11 different orientations between the electric field polarization and the macroscopic alignment axis. Aggregate spectral response consisted of an asymmetrically split Davydov pair of bands exhibiting opposite polarization: an H-band (505 nm, Lorentzian-like, polarized along the macroscopic film axis) and a J-band (594 nm, one-dimensional J-aggregate like band shape, polarized perpendicular to the macroscopic film axis). The polarized absorption observations were found to be consistent with a herringbone model for which the internal molecular arrangement, the excited state structure and dynamics have recently been detailed by us upon interpretation of isotropic absorption data in ionic aqueous solution.

  12. Narrow C IV absorption doublets on quasar spectra of the Baryon Oscillation Spectroscopic Survey

    Zhi-fu, Chen; Luwenjia, Zhou; Yanmei, Chen

    2016-01-01

    In this paper, we extend our works of Papers I and II, which are assigned to systematically survey \\CIVab\\ narrow absorption lines (NALs) with \\zabs$\\ll$\\zem\\ on quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), to collect \\CIV\\ NALs with \\zabs$\\approx$\\zem\\ from blue to red wings of \\CIVwave\\ emission lines. Together with Papers I and II, we have collected a total number of 41,479 \\CIV\\ NALs with $1.4544\\le$\\zabs$\\le4.9224$ in surveyed spectral region redward of \\lya\\ until red wing of \\CIVwave\\ emission line. We find that the stronger \\CIV\\ NALs tend to be the more saturated absorptions, and associated systems (\\zabs$\\approx$\\zem) seem to have larger absorption strengths when compared to intervening ones (\\zabs$\\ll$\\zem). The redshift density evolution behavior of absorbers (the number of absorbers per redshift path) is similar to the history of the cosmic star formation. When compared to the quasar-frame velocity ($\\beta$) distribution of \\MgII\\ absorbers, the $\\beta$ distribution of \\C...

  13. Shape of the absorption and fluorescence spectra of condensed phases and transition energies.

    Lagos, Miguel; Paredes, Rodrigo

    2014-11-13

    General integral expressions for the temperature-dependent profile of the spectral lines of photon absorption and emission by atomic or molecular species in a condensed environment are derived with no other hypothesis than: (a) The acoustic vibrational modes of the condensed host medium constitute the thermodynamic energy reservoir at a given constant temperature, and local electronic transitions modifying the equilibrium configuration of the surroundings are multiphonon events, regardless of the magnitude of the transition energy. (b) Electron-phonon coupling is linear in the variations of the bond length. The purpose is to develop a theoretical tool for the analysis of the spectra, allowing us to grasp highly accurate information from fitting the theoretical line shape function to experiment, including those spectra displaying wide features. The method is illustrated by applying it to two dyes, Lucifer Yellow CH and Coumarin 1, which display fluorescence maxima of 0.41 and 0.51 eV fwhm. Fitting the theoretical curves to the spectra indicates that the neat excitation energies are 2.58 eV ± 2.5% and 3.00 eV ± 2.0%, respectively. PMID:25321927

  14. Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra

    Kausch, W; Kimeswenger, S; Barden, M; Szyszka, C; Jones, A M; Sana, H; Horst, H; Kerber, F

    2015-01-01

    Context: Absorption by molecules in the Earth's atmosphere strongly affects ground-based astronomical observations. The resulting absorption line strength and shape depend on the highly variable physical state of the atmosphere, i.e. pressure, temperature, and mixing ratio of the different molecules involved. Usually, supplementary observations of so-called telluric standard stars (TSS) are needed to correct for this effect, which is expensive in terms of telescope time. We have developed the software package molecfit to provide synthetic transmission spectra based on parameters obtained by fitting narrow ranges of the observed spectra of scientific objects. These spectra are calculated by means of the radiative transfer code LBLRTM and an atmospheric model. In this way, the telluric absorption correction for suitable objects can be performed without any additional calibration observations of TSS. Aims: We evaluate the quality of the telluric absorption correction using molecfit with a set of archival ESO-VLT...

  15. Absorption, phosphorescence and Raman spectra of IrQ(ppy){sub 2} organometallic compound

    Polosan, Silviu, E-mail: silv@infim.ro [National Institute of Materials Physics, R-77125 Bucharest-Magurele (Romania); Ciobotaru, Iulia Corina [National Institute of Materials Physics, R-77125 Bucharest-Magurele (Romania); Tsuboi, Taiju [Kyoto Sangyo University, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan)

    2015-07-15

    The absorption and photoluminescence (PL) spectra, PL decays, Raman spectrum, cyclic voltammetry (CV) and nuclear magnetic resonance of heteroleptic Ir-compound IrQ(ppy){sub 2} compound with two phenylpyridine (ppy) ligands and one quinoline (Q) ligand have been investigated experimentally and theoretically. Two very weak absorption bands due to the transitions to the triplet states are found at about 560 and 595 nm in IrQ(ppy){sub 2} doped in CH{sub 2}Cl{sub 2} solution. IrQ(ppy){sub 2} exhibits a dual emission of red and green phosphorescence bands. The red emission intensity is much higher than the green one in IrQ(ppy){sub 2} powder, but much lower than the green one in lightly IrQ(ppy){sub 2}-doped CH{sub 2}Cl{sub 2} solution and PMMA film. The intensity ratio of the red emission to the green emission, however, is observed to increase with increasing the IrQ(ppy){sub 2} concentration in CH{sub 2}Cl{sub 2} solution and PMMA film. The enhancement of the red emission is suggested to be caused by the Forester energy transfer from Ir-ppy component to Ir–Q components between two neighboring IrQ(ppy){sub 2} molecules. The HOMO energy is estimated to be −4.865 eV from the CV measurement, which is close to the HOMO energy of −4.844 eV calculated using the time dependent density function theory (TD-DFT). The LUMO energy is estimated as −2.856 eV from the HOMO energy and the long-wavelength absorption edge found at 617 nm in the absorption spectrum. The absorption spectrum of IrQ(ppy){sub 2} is calculated by the TD-DFT. Discussion is given on a deviation of the calculated spectrum from the measured spectrum. - Graphical abstract: Display Omitted - Highlights: • IrQ(ppy){sub 2} has red and green emissions of different ratio between film and solution. • Intensity ratio of red to green emissions increases with IrQ(ppy){sub 2} concentration. • Enhancement of red emission is due to energy transfer in two neighboring IrQ(ppy){sub 2}. • Lowest-energy absorption

  16. Absorption, phosphorescence and Raman spectra of IrQ(ppy)2 organometallic compound

    The absorption and photoluminescence (PL) spectra, PL decays, Raman spectrum, cyclic voltammetry (CV) and nuclear magnetic resonance of heteroleptic Ir-compound IrQ(ppy)2 compound with two phenylpyridine (ppy) ligands and one quinoline (Q) ligand have been investigated experimentally and theoretically. Two very weak absorption bands due to the transitions to the triplet states are found at about 560 and 595 nm in IrQ(ppy)2 doped in CH2Cl2 solution. IrQ(ppy)2 exhibits a dual emission of red and green phosphorescence bands. The red emission intensity is much higher than the green one in IrQ(ppy)2 powder, but much lower than the green one in lightly IrQ(ppy)2-doped CH2Cl2 solution and PMMA film. The intensity ratio of the red emission to the green emission, however, is observed to increase with increasing the IrQ(ppy)2 concentration in CH2Cl2 solution and PMMA film. The enhancement of the red emission is suggested to be caused by the Forester energy transfer from Ir-ppy component to Ir–Q components between two neighboring IrQ(ppy)2 molecules. The HOMO energy is estimated to be −4.865 eV from the CV measurement, which is close to the HOMO energy of −4.844 eV calculated using the time dependent density function theory (TD-DFT). The LUMO energy is estimated as −2.856 eV from the HOMO energy and the long-wavelength absorption edge found at 617 nm in the absorption spectrum. The absorption spectrum of IrQ(ppy)2 is calculated by the TD-DFT. Discussion is given on a deviation of the calculated spectrum from the measured spectrum. - Graphical abstract: Display Omitted - Highlights: • IrQ(ppy)2 has red and green emissions of different ratio between film and solution. • Intensity ratio of red to green emissions increases with IrQ(ppy)2 concentration. • Enhancement of red emission is due to energy transfer in two neighboring IrQ(ppy)2. • Lowest-energy absorption band due to the S0 → T1 transition was found at 595 nm. • 5d-Ir orbital and π-obital of quinoline

  17. TDDFT Study of the Electronic Structure, Absorption and Emission Spectra of the Light Emitters of the Amazing Firefly Bioluminescence and Solvation Effects on the Spectra

    REN,Ai-Min; GUO,Jing-Fu; FENG,Ji-Kang; ZOU,Lu-Yi; LI,Zhong-Wei; GODDARD,John,David

    2008-01-01

    The ground and excited state properties of luciferin (LH2) and oxyluciferin (OxyLH2), the bioluminescent chemicals in the firefly, have been characterized using density functional theory (DFT) and time dependent DFT (TDDFT) methods. The effects of solvation on the electronic absorption and emission spectra of luciferin and oxyluciferin were predicted with a self-consistent isodensity polarized continuum model of the solvent using TDDFT.The S0→S1 vertical excitation energies in the gas phase and in water were obtained. Optimizations of the excited state geometries permitted the first predictions of the fluorescence spectra for these biologically important molecules. Shifts in both of the absorption and emission spectra on proceeding from the gas phase to aqueous solution were also predicted.

  18. Comparison of absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissue

    Peresunko, O. P.; Zelinska, N. V.; Prydij, O. G.; Zymnyakov, D. A.; Ushakova, O. V.

    2013-12-01

    We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

  19. Effect of Pressure on Absorption Spectra of Lycopene in n-Hexane and CS2 Solvents

    The absorption spectra of lycopene in n-hexane and CS2 are measured under high pressure and the results are compared with β-carotene. In the lower pressure range, the deviation from the linear dependence on the Bayliss parameter (BP) for β-carotene is more visible than that for lycopene. With the further increase of the solvent BP, the 0–0 bands of lycopene and β-carotene red shift at almost the same rate in n-hexane; however, the 0–0 band of lycopene red shifts slower than that of β-carotene in CS2. The origins of these diversities are discussed taking into account the dispersion interactions and structures of solute and solvent molecules. (atomic and molecular physics)

  20. The stability and absorption spectra of uranium (III) in hydrochloric acid solution

    Uranium(III) solution is obtained eletrolytically by reducing uranyl ion on mercury cathode. The effect of the addition of various aminopolycarboxylic acids (such as EDTA, DTPA, DyDTA and TTHA) and organic water-miscible solvents (such as CH3OH, C2H5OH and CH3COCH) on the stability of uranium(III) in air has been investigated. The absorption spectra of uranium(III) and uranium(IV) in 1 mol/l and 9 mol/l hydrochloric acid solutions are examined. The molar extinction coefficient of uranium(III) is 167 · mol-1 · cm-1 in the HCl concentration range 0.5-4.5 mol/l and uranium (IV) practically does not interfere in the photometric determination of uranium(III) at the wavelength of 521 nm

  1. kspectrum: an open-source code for high-resolution molecular absorption spectra production

    Eymet, V.; Coustet, C.; Piaud, B.

    2016-01-01

    We present the kspectrum, scientific code that produces high-resolution synthetic absorption spectra from public molecular transition parameters databases. This code was originally required by the atmospheric and astrophysics communities, and its evolution is now driven by new scientific projects among the user community. Since it was designed without any optimization that would be specific to any particular application field, its use could also be extended to other domains. kspectrum produces spectral data that can subsequently be used either for high-resolution radiative transfer simulations, or for producing statistic spectral model parameters using additional tools. This is a open project that aims at providing an up-to-date tool that takes advantage of modern computational hardware and recent parallelization libraries. It is currently provided by Méso-Star (http://www.meso-star.com) under the CeCILL license, and benefits from regular updates and improvements.

  2. Absorption Spectra of CuGaSe 2 and CuInSe 2 Semiconducting Nanoclusters

    Mokkath, Junais Habeeb

    2015-10-01

    The structural and optical properties of the chalcopyrite CunGanSe2n and CunInnSe2n nanoclusters (n = 2, 4, 6, and 8) are investigated as a function of the size using a combination of basin-hopping global optimization and time-dependent density functional theory. Although the lowest energy structures are found to show almost random geometries, the band gaps and absorption spectra still are subject to systematic blue shifts for decreasing cluster size in the case of CunGanSe2n, indicating strong electron confinement. The applicability of the nanoclusters in photovoltaics is discussed. © 2015 American Chemical Society.

  3. VARIABILITY OF WATER AND OXYGEN ABSORPTION BANDS IN THE DISK-INTEGRATED SPECTRA OF EARTH

    We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H2O and O2 bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H2O and O2 bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H2O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

  4. Towards Constraints on Dark Energy from Absorption Spectra of Close Quasar Pairs

    Lidz, A; Crotts, A P S; Zaldarriaga, M; Lidz, Adam; Hui, Lam; Crotts, Arlin P.S.; Zaldarriaga, Matias

    2003-01-01

    A comparison between the line of sight power spectrum of absorption in the Lyman-alpha forest and the cross power spectrum between the absorption in neighboring lines of sight offers an evolution-free means to constrain the cosmological constant, or dark energy. Using cosmological simulations, we consider a maximum likelihood method to obtain constraints from this comparison. In our method, measurements of the auto and cross spectra from observations are compared with those from a multi-parameter grid of simulated models of the intergalactic medium. We then marginalize over nuisance parameters to obtain constraints on the cosmological constant. Redshift space distortions due to peculiar velocities and thermal broadening, a potential difficulty in applying this test, are explicitly modeled in our simulations. To illustrate our method, we measure the cross spectrum from a new sample of five close quasar pairs, with separations of 0.5 to 3 arcmin. We attempt to obtain a constraint on Omega_Lambda, but find only ...

  5. Variability of Water and Oxygen Absorption Bands in the Disk-Integrated Spectra of the Earth

    Fujii, Yuka; Suto, Yasushi

    2013-01-01

    We study the variability of major atmospheric absorption features in the disk-integrated spectra of the Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of the Earth provided by the EPOXI mission, and find 5-20% fractional variation of the absorption depths of H2O and O2 bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor ...

  6. Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes

    Standard modeling approaches can produce the most likely values of the formation constants of metal-ligand complexes if a particular set of species containing the metal ion is known or assumed to exist in solution equilibrium with complexing ligands. Identifying the most likely set of species when more than one set is plausible is a more difficult problem to address quantitatively. A Monte Carlo method of data analysis is described that measures the relative abilities of different speciation models to fit optical spectra of open-shell actinide ions. The best model(s) can be identified from among a larger group of models initially judged to be plausible. The method is demonstrated by analyzing the absorption spectra of aqueous Pu(IV) titrated with nitrate ion at constant 2 molal ionic strength in aqueous perchloric acid. The best speciation model supported by the data is shown to include three Pu(IV) species with nitrate coordination numbers 0, 1, and 2. Formation constants are β1=3.2±0.5 and β2=11.2±1.2, where the uncertainties are 95% confidence limits estimated by propagating raw data uncertainties using Monte Carlo methods. Principal component analysis independently indicates three Pu(IV) complexes in equilibrium. (c) 2000 Society for Applied Spectroscopy

  7. Polarized absorption spectra of single crystals of lunar pyroxenes and olivines.

    Burns, R. G.; Huggins, F. E.; Abu-Eid, R. M.

    1972-01-01

    Measurements have been made of the polarized absorption spectra (360-2200 nm) of compositionally zoned pyroxene minerals in rocks 10045, 10047 and 10058 and olivines in rocks 10020 and 10022. The Apollo 11 pyroxenes with relatively high Ti/Fe ratios were chosen initially to investigate the presence of crystal field spectra of Fe(2+) and Ti(3+) ions in the minerals. Broad intense bands at about 1000 and 2100 nm arise from spin-allowed, polarization-dependent transitions in Fe(2+) ions in pyroxenes. Several weak sharp peaks occur in the visible region. Peaks at 402, 425, 505, 550, and 585 nm represent spin-forbidden transitions in Fe(2+) ions, while broader bands at 460-470 nm and 650-660 nm are attributed to Ti(3+) ions. Charge transfer bands, which in terrestrial pyroxenes often extend into the visible region, are displaced to shorter wavelengths in lunar pyroxenes. This feature correlates with the absence of Ti(3+) ions in these minerals.

  8. Source brightness fluctuation correction of solar absorption fourier transform mid infrared spectra

    T. Ridder

    2011-06-01

    Full Text Available The precision and accuracy of trace gas observations using solar absorption Fourier Transform infrared spectrometry depend on the stability of the light source. Fluctuations in the source brightness, however, cannot always be avoided. Current correction schemes, which calculate a corrected interferogram as the ratio of the raw DC interferogram and a smoothed DC interferogram, are applicable only to near infrared measurements. Spectra in the mid infrared spectral region below 2000 cm−1 are generally considered uncorrectable, if they are measured with a MCT detector. Such measurements introduce an unknown offset to MCT interferograms, which prevents the established source brightness fluctuation correction. This problem can be overcome by a determination of the offset using the modulation efficiency of the instrument. With known modulation efficiency the offset can be calculated, and the source brightness correction can be performed on the basis of offset-corrected interferograms. We present a source brightness fluctuation correction method which performs the smoothing of the raw DC interferogram in the interferogram domain by an application of a running mean instead of high-pass filtering the corresponding spectrum after Fourier transformation of the raw DC interferogram. This smoothing can be performed with the onboard software of commercial instruments. The improvement of MCT spectra and subsequent ozone profile and total column retrievals is demonstrated. Application to InSb interferograms in the near infrared spectral region proves the equivalence with the established correction scheme.

  9. Investigation of absorption spectra of Gafchromic EBT2 film's components and their impact on UVR dosimetry

    Aydarous, Abdulkadir

    2016-05-01

    The absorption spectra of the EBT2 film's components were investigated in conjunction with its use for UVA dosimetry. The polyester (topside) and adhesive layers of the EBT2 film have been gently removed. Gafchromic™ EBT2 films with and without the protected layers (polyester and adhesive) were exposed to UVR of 365 nm for different durations. Thereafter, the UV-visible spectra were measured using a UV-visible spectrophotometer (Model Spectro Dual Split Beam, UVS-2700). Films were digitized using a Nikon CanoScan 9000F Mark II flatbed scanner. The dosimetric characteristics including film's uniformity, reproducibility and post-irradiation development were investigated. The color development of EBT2 and new modified EBT2 (EBT2-M) films irradiated with UVA was relatively stable (less than 1%) immediately after exposure. Based on this study, the sensitivity of EBT2 to UVR with wavelength between ~350 nm and ~390 nm can significantly be enhanced if the adhesive layer (~25 μm) is removed. The polyester layer plays almost no part on absorbing UVR with wavelength between ~320 nm and ~390 nm. Furthermore, various sensitivities for the EBT2-M film has been established depending on the wavelength of analysis.

  10. Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations

    Porta A.

    2016-01-01

    Full Text Available Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland using Total Absorption Spectroscopy (TAS. TAS is complementary to techniques based on Germanium detectors. It implies the use of a calorimeter to measure the total gamma intensity de-exciting each level in the daughter nucleus providing a direct measurement of the beta feeding. In these proceedings we present preliminary results for 93Rb, our measured beta feedings for 92Rb and we show the impact of these results on reactor antineutrino spectra and decay heat calculations.

  11. Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations

    Porta, A.; Zakari-Issoufou, A.-A.; Fallot, M.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; Äystö, J.; Bowry, M.; Briz, J. A.; Caballero-Folch, R.; Cano-Ott, D.; Cucouanes, A.; Elomaa, V.-V.; Eronen, T.; Estévez, E.; Farrelly, G. F.; Garcia, A. R.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Karvonen, P.; Kolhinen, V. S.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez-Cerdán, A. B.; Podolyák, Zs.; Penttilä, H.; Regan, P. H.; Reponen, M.; Rissanen, J.; Rubio, B.; Shiba, T.; Sonzogni, A. A.; Weber, C.

    2016-03-01

    Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland) using Total Absorption Spectroscopy (TAS). TAS is complementary to techniques based on Germanium detectors. It implies the use of a calorimeter to measure the total gamma intensity de-exciting each level in the daughter nucleus providing a direct measurement of the beta feeding. In these proceedings we present preliminary results for 93Rb, our measured beta feedings for 92Rb and we show the impact of these results on reactor antineutrino spectra and decay heat calculations.

  12. Influence of surplus negative charge on absorption and fluorescence excitation spectra of asymmetric polymethine dyes

    The combined spectral and quantum-chemical investigations of the vinylog series of the asymmetric anionic polymethine dyes, derivatives of aminocoumarin, as well as the related symmetric dyes, are fulfilled. The charge injection to these types of dyes leads to the essential shifts of electronic levels. The calculations show the inverse character of the first two electron transitions in anionic polymethines and relative cationic polymethines. It is established that going to asymmetric dyes leads to a slight decrease of the spectral effect of the chromophore lengthening. The influence of the asymmetry manifests itself in a positive deviation in the absorption spectra and a negative deviation of the second electron transition manifested visually in the anisotropy of the fluorescence excitation spectra of asymmetric dyes. It is found that the lengthening of the chromophore is accompanied by an increase of the deviation of the first electron transition and, in contrast, by a decrease of the deviation of the second transition. The obtained results may be used in the design of molecular systems with prognosed current-voltage characteristics for nanoelectronics

  13. First principle studies on the electronic structures and absorption spectra in KMgF{sub 3} crystal with fluorine vacancy

    Cheng Fang [College of Science, University of Shanghai for Science and Technology, Shanghai 200093 (China); Liu Tingyu, E-mail: liutyyxj@163.co [College of Science, University of Shanghai for Science and Technology, Shanghai 200093 (China); Zhang Qiren; Qiao Hailin; Zhou Xiuwen [College of Science, University of Shanghai for Science and Technology, Shanghai 200093 (China)

    2010-08-01

    The experiments indicate that the perfect KMgF{sub 3} crystal has no absorption in the visible range, however the electron irradiation induces a complex absorption spectrum. The absorption spectra can be decomposed by five Gaussian bands peaking at 2.5 eV (488 nm), 3.4 eV (359 nm), 4.2 eV (295 nm), 4.6 eV (270 nm) and 5.2 eV (239 nm), respectively. The purpose of this paper is to seek the origins of the absorption bands. The electronic structures and absorption spectra either for the perfect KMgF{sub 3} or for KMgF{sub 3}: V{sub F}{sup +} with electrical neutrality have been studied by using density functional theory code CASTEP with the lattice structure optimized. The calculation results predicate that KMgF{sub 3}: V{sub F}{sup +} also exhibits five absorption bands caused by the existence of the fluorine ion vacancy V{sub F}{sup +} and the five absorption bands well coincide with the experimental results. It is believable that the five absorption bands are related to V{sub F}{sup +} in KMgF{sub 3} crystal produced by the electron irradiation.

  14. First principle studies on the electronic structures and absorption spectra in KMgF 3 crystal with fluorine vacancy

    Cheng, Fang; Liu, Tingyu; Zhang, Qiren; Qiao, Hailin; Zhou, Xiuwen

    2010-08-01

    The experiments indicate that the perfect KMgF 3 crystal has no absorption in the visible range, however the electron irradiation induces a complex absorption spectrum. The absorption spectra can be decomposed by five Gaussian bands peaking at 2.5 eV (488 nm), 3.4 eV (359 nm), 4.2 eV (295 nm), 4.6 eV (270 nm) and 5.2 eV (239 nm), respectively. The purpose of this paper is to seek the origins of the absorption bands. The electronic structures and absorption spectra either for the perfect KMgF 3 or for KMgF 3: VF+ with electrical neutrality have been studied by using density functional theory code CASTEP with the lattice structure optimized. The calculation results predicate that KMgF 3: VF+ also exhibits five absorption bands caused by the existence of the fluorine ion vacancy VF+ and the five absorption bands well coincide with the experimental results. It is believable that the five absorption bands are related to VF+ in KMgF 3 crystal produced by the electron irradiation.

  15. Nucleic acid vibrational circular dichroism, absorption, and linear dichroism spectra. II. A DeVoe theory approach.

    Self, B D; Moore, D S

    1998-01-01

    The DeVoe polarizability theory is used to calculate vibrational circular dichroism (VCD) and infrared (IR) absorption spectra of four polyribonucleotides: poly(rA) x poly(rU), poly(rU) x poly(rA) x poly(rU), poly(rG) x poly(rC), and poly(rC+) x poly(rI) x poly(rC). This is the first report on the use of the DeVoe theory to calculate VCD, oriented VCD, IR absorption, and IR linear dichroism (LD) spectra of double- and triple-stranded polyribonucleotides. Results are reported for DeVoe theory ...

  16. Optical Absorption Spectra and Excitons of Dye-Substrate Interfaces: Catechol on TiO2(110).

    Mowbray, Duncan John; Migani, Annapaola

    2016-06-14

    Optimizing the photovoltaic efficiency of dye-sensitized solar cells (DSSC) based on staggered gap heterojunctions requires a detailed understanding of sub-band gap transitions in the visible from the dye directly to the substrate's conduction band (CB) (type-II DSSCs). Here, we calculate the optical absorption spectra and spatial distribution of bright excitons in the visible region for a prototypical DSSC, catechol on rutile TiO2(110), as a function of coverage and deprotonation of the OH anchoring groups. This is accomplished by solving the Bethe-Salpeter equation (BSE) based on hybrid range-separated exchange and correlation functional (HSE06) density functional theory (DFT) calculations. Such a treatment is necessary to accurately describe the interfacial level alignment and the weakly bound charge transfer transitions that are the dominant absorption mechanism in type-II DSSCs. Our HSE06 BSE spectra agree semiquantitatively with spectra measured for catechol on anatase TiO2 nanoparticles. Our results suggest deprotonation of catechol's OH anchoring groups, while being nearly isoenergetic at high coverages, shifts the onset of the absorption spectra to lower energies, with a concomitant increase in photovoltaic efficiency. Further, the most relevant bright excitons in the visible region are rather intense charge transfer transitions with the electron and hole spatially separated in both the [110] and [001] directions. Such detailed information on the absorption spectra and excitons is only accessible via periodic models of the combined dye-substrate interface. PMID:27183273

  17. Absolute absorption spectra of batho- and photorhodopsins at room temperature. Picosecond laser photolysis of rhodopsin in polyacrylamide.

    Kandori, H; Shichida, Y; Yoshizawa, T

    1989-01-01

    Picosecond laser photolysis of rhodopsin in 15% polyacrylamide gel was performed for estimating absolute absorption spectra of the primary intermediates of cattle rhodopsin (bathorhodopsin and photorhodopsin). Using a rhodopsin digitonin extract embedded in 15% polyacrylamide gel, a precise percentage of bleaching of rhodopsin after excitation of a picosecond laser pulse was measured. Using this value, the absolute absorption spectrum of bathorhodopsin was calculated from the spectral change ...

  18. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  19. Soft X-ray absorption spectra of aqueous salt solutions with highly charged cations in liquid microjets

    Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.

    2010-03-11

    X-ray absorption spectra of 1M aqueous solutions of indium (III) chloride, yttrium (III) bromide, lanthanum (III) chloride, tin (IV) chloride and chromium (III) chloride have been measured at the oxygen K-edge. Relatively minor changes are observed in the spectra compared to that of pure water. SnCl{sub 4} and CrCl{sub 3} exhibit a new onset feature which is attributed to formation of hydroxide or other complex molecules in the solution. At higher energy, only relatively minor, but salt-specific changes in the spectra occur. The small magnitude of the observed spectral changes is ascribed to offsetting perturbations by the cations and anions.

  20. Phonon effects on X-ray absorption and X-ray photoemission spectra

    Highlights: • Some important phonon effects observed in X-ray absorption and X-ray photoemission spectra are discussed on the basis of nonequilibrium Green's function theory. • For the pre-edge structures, the intensity associated with forbidden electric dipole transition is sensitive to temperature compared with allowed electric quadrupole transition. • We also discuss the FC and their interference, which have negligible contribution to pre-edge intensity and energy shift. • The quasi-particle energy is also influenced by the core displacement which can be responsible for the peak shift of the pre-edges. • We also discuss the photoelectron angular distribution caused by the thermal atomic vibration. - Abstract: Some important phonon effects observed in X-ray absorption and X-ray photoemission spectra are discussed on the basis of nonequilibrium Green's function theory. This theoretical framework allows us to incorporate phonon effects, such as Debye–Waller (DW) factors, Franck–Condon (FC) factors and electron–phonon interactions in a natural way. In the case of core level excitations, we can take into account the core–hole effects in lesser Green's function g< and photoelectron propagation in greater Green's function g>. For the core–hole propagation we derive some formulas to describe the thermally displaced core functions: we have p components even for deep core s orbital due to the thermal motion. We should notice that the thermal fluctuation is quite small but it is already in the order of the spread of the core functions. Applying Mermin's theorem, we can calculate the thermal average of the hole propagator g<: here an important ingredient is the Debye–Waller factor used in X-ray and neutron diffraction. For the pre-edge structures, the intensity associated with forbidden electric dipole transition is sensitive to the temperature compared with allowed electric quadrupole transition. We also discuss the FC and

  1. The effects of solvents and structure on the electronic absorption spectra of the isomeric pyridine carboxylic acid N-oxides

    Drmanić Saša Ž.

    2013-01-01

    Full Text Available The ultraviolet absorption spectra of the carboxyl group of three isomeric pyridine carboxylic acids N-oxides (picolinic acid N-oxide, nicotinic acid N-oxide and isonicotinic acid N-oxide were determined in fourteen solvents in the wavelength range from 200 to 400 nm. The position of the absorption maxima (λmax of the examined acids showed that the ultraviolet absorption maximum wavelengths of picolinic acid N-oxide are the shortest, and those of isonicotinic acid N-oxide acid are the longest. In order to analyze the solvent effect on the obtained absorption spectra, the ultraviolet absorption frequencies of the electronic transitions in the carboxylic group of the examined acids were correlated using a total solvatochromic equation of the form max = v0 + sπ + aα+ bβ, where υmax is the absorption frequency (1/λmax, p is a measure of the solvent polarity, β represents the scale of solvent hydrogen bond acceptor basicities and α represent the scale of solvent hydrogen bond donor acidities. The correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The solvent effects on the ultraviolet absorption maximums of the examined acids were discussed.

  2. Comparison of x-ray absorption spectra between water and ice: New ice data with low pre-edge absorption cross-section

    Kaya, Sarp; Sellberg, Jonas A.; Segtnan, Vegard H.; Chen, Chen; Tyliszczak, Tolek; Ogasawara, Hirohito; Nordlund, Dennis; Pettersson, Lars G. M.; Nilsson, Anders

    2014-01-01

    The effect of crystal growth conditions on the O K-edge x-ray absorption spectra of ice is investigated through detailed analysis of the spectral features. The amount of ice defects is found to be minimized on hydrophobic surfaces, such as BaF2(111), with low concentration of nucleation centers. This is manifested through a reduction of the absorption cross-section at 535 eV, which is associated with distorted hydrogen bonds. Furthermore, a connection is made between the observed increase in ...

  3. Effect of heat treatment on the infrared absorption spectra of strontium-sodium-borosilicate glass

    Infrared absorption spectra of the prepared strontium-sodium-borosilicate glass (SiO2 80%-Na2O 12.5%-B2O3 5%-SrO 2.5%) are studied in the frequency range 200-4000 cm-1, where strontium oxide was introduced on partial replacement of soda in sodium-borosilicate glass, to show the effect of divalent metal oxide introduced on the structural units SiO4, BO4, and BO3 within the network structure of strontium-sodium-borosilicate glass, in the temperature range 27-800 degC. The deformation of SiO4 tetrahedra is investigated by using the baseline method, the temperature dependence of the relative integrated intensity, the relaxation time, and rotational energy barrier of this glass proved that the glassy phase is transformed to crystalline phase at 500 degC. A slight shift occurs in the strongest bands of SiO4 tetrahedra to higher frequencies, with temperature increase, which indicates an increase in the force constants between the components of the glass network structure. The increase of the absorbance in the temperature range 600-800 degC indicates strengthening of the SiO4 bonds. (author)

  4. Absorption spectra and sunlight conversion efficiency in fullerene bonded supramolecules on nanostructured ZnO

    Zakhidov, Erkin; Kokhkharov, Abdumutallib; Kuvondikov, Vakhobjon; Nematov, Sherzod; Nusretov, Rafael

    2015-10-01

    The efficiency of solar radiation conversion in a model system of artificial photosynthesis, the porphyrin-fullerene assembly, is analyzed. A study of the optical absorption spectra of the porphyrin and the fullerene molecules, as well as their assembly in organic solutions, made it possible to estimate the energy efficiency of the conversion. Numerical values of the energy efficiency, defined as the fraction of the light quantum energy converted to the chemical potential of separated charges, are calculated for low- and high-concentration solutions of such a supramolecular system. The possibility of the efficient utilization of long-wavelength solar radiation in the high-concentration porphyrin-fullerene assembly solution in toluene and benzene is shown. In the photovoltaic system consisting of such a supramolecular active element, a thin ZnO film with a nanostructured surface may be introduced as a secondary acceptor of electrons from fullerene molecules. An enhancement of the transformation of separated charges of the porphyrin-fullerene assembly into electrical current by means of the ZnO film deposited on the surface of the anode electrode in such a heterogenic photovoltaic unit is proposed.

  5. Effects of excited state mixing on transient absorption spectra in dimers Application to photosynthetic light-harvesting complex II

    Valkunas, L; Trinkunas, G; Müller, M G; Holzwarth, A R

    1999-01-01

    The excited state mixing effect is taken into account considering the difference spectra of dimers. Both the degenerate (homo) dimer as well as the nondegenerate (hetero) dimer are considered. Due to the higher excited state mixing with the two-exciton states in the homodimer, the excited state absorption (or the difference spectrum) can be strongly affected in comparison with the results obtained in the Heitler-London approximation. The difference spectrum of the heterodimer is influenced by two resonance effects (i) mixing of the ground state optical transitions of both monomers in the dimer and (ii) mixing of the excited state absorption of the excited monomer with the ground state optical transition in the nonexcited monomer. These effects have been tested by simulating the difference absorption spectra of the light-harvesting complex of photosystem II (LHC II) experimentally obtained with the 60 fs excitation pulses at zero delay times and various excitation wavelengths. The pairs of coupled chlorophylls...

  6. Study on the electronic structures and absorption spectra for sheelite- and the sheelite-like structures lead tungstate crystal

    The electronic structures and absorption spectra of perfect crystals and crystals containing lead vacancy Vpb2- for both sheelite(PbWO4) and sheelite-like(Pb7.5W8O32) structures have been calculated using density functional theory with the lattice structure optimized. The optical properties of lead tungstate exhibit anisotropy. Numerical calculation shows that the absorption spectra of the sheelite structure crystal containing Vpb2- exhibit additional absorption bands in the visible and near ultra-violet ranges. However, this is not the case for other structures of the PWO crystals such as the sheelite structure crystal without lead vacancy and the sheelite-like structure crystal with or without lead vacancy

  7. Bethe-Salpeter calculation of optical-absorption spectra of In2O3 and Ga2O3

    Varley, Joel B.; Schleife, André

    2015-02-01

    Transparent conducting oxides keep attracting strong scientific interest not only due to their promising potential for ‘transparent electronics’ applications but also due to their intriguing optical absorption characteristics. Materials such as In2O3 and Ga2O3 have complicated unit cells and, consequently, are interesting systems for studying the physics of excitons and anisotropy of optical absorption. Since currently no experimental data is available, for instance, for their dielectric functions across a large photon-energy range, we employ modern first-principles computational approaches based on many-body perturbation theory to provide theoretical-spectroscopy results. Using the Bethe-Salpeter framework, we compute dielectric functions and we compare to spectra computed without excitonic effects. We find that the electron-hole interaction strongly modifies the spectra and we discuss the anisotropy of optical absorption that we find for Ga2O3 in relation to existing theoretical and experimental data.

  8. Bethe–Salpeter calculation of optical-absorption spectra of In2O3 and Ga2O3

    Transparent conducting oxides keep attracting strong scientific interest not only due to their promising potential for ‘transparent electronics’ applications but also due to their intriguing optical absorption characteristics. Materials such as In2O3 and Ga2O3 have complicated unit cells and, consequently, are interesting systems for studying the physics of excitons and anisotropy of optical absorption. Since currently no experimental data is available, for instance, for their dielectric functions across a large photon-energy range, we employ modern first-principles computational approaches based on many-body perturbation theory to provide theoretical-spectroscopy results. Using the Bethe–Salpeter framework, we compute dielectric functions and we compare to spectra computed without excitonic effects. We find that the electron–hole interaction strongly modifies the spectra and we discuss the anisotropy of optical absorption that we find for Ga2O3 in relation to existing theoretical and experimental data. (invited article)

  9. Structure of the absorption spectra of the quasars Q 0420-388 and Q 1101-264

    In the framework of shock-wave model of numerous Ly α absorption lines in spectra of remote quasars, which relate their origin to absorbing areas in the shells of metagalactic shock waves, the recently obtained quasars spectra Q 0420-388 and Q 1101-264 have been analyzed. It is shown that more than 50% of narrow Ly α absorption lines are in ''doublets''-pairs of close (adjacent in the spectrum, as a rule) lines with similar equivalent widths. The fact agrees well with the predictions of the shock-wave model. Line distribution over H I densities in the eyesight ray expected for the model is calculated and agrees with the distribution found by Atwood et al. by the sampling of Ly α unblended lines in the Q 0420-388 and Q 1101-264 spectra

  10. Identifying student and teacher difficulties in interpreting atomic spectra using a quantum model of emission and absorption of radiation

    Savall-Alemany, Francisco; Domènech-Blanco, Josep Lluís; Guisasola, Jenaro; Martínez-Torregrosa, Joaquín

    2016-06-01

    Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two questionnaires, one for teachers and the other for students. By analyzing the responses, we conclude that (i) teachers lack a quantum model for the emission and absorption of electromagnetic radiation capable of explaining the spectra, (ii) teachers and students share the same difficulties, and (iii) these difficulties concern the model of the atom, the model of radiation, and the model of the interaction between them.

  11. Fluorescence and absorption spectra for a multi-photon Jaynes-Cummings in the presence of nonlinearities and stark shift

    Acceptable forms of nonlinearities of both the field and the intensity-dependent atom-field coupling in a generalized Jaynes-Cummings model are considered. The time-dependence of the atom-field system is obtained, by means of which we produce the analytical forms of the fluorescence and absorption spectra produced by an atom in an ideal cavity using the dressed states of the system. We investigate the influences of the mean number of photons, detuning, the nonlinearities and Stark shifts on the spectra, for initial coherent and thermal states. It is shown that features of the fluorescence and absorption spectra are influenced significantly by the kinds of the nonlinearities and the detuning

  12. Electronic absorption spectra of U3+ and U4+ in molten LiCl-RbCl eutectic

    In the non-aqueous reprocessing process of spent nuclear fuels by the pyro-electrochemical method, a spent fuel is dissolved into molten LiCl-KCl and NaCl-CsCl eutectics and dissolved uranium and plutonium are collected as either metal or oxide. However, the binary alkali chloride mixture with the lowest melting point is the LiCl-RbCl eutectic. In this study, electronic absorption spectra of U3+ and U4+ in molten LiCl-RbCl eutectic at various temperatures between 673 and 973 K were measured by the UV/Vis/NIR spectrophotometry. We confirmed that these spectra were similar to those in molten LiCl-KCl and NaCl-CsCl eutectics. The sensitive absorption bands of U4+ in LiCl-RbCl eutectic were found at 22000, 16500, 14900, 8600, and 4950 cm-1. The large absorption bands of U4+ over 25000 cm-1 increased with increasing melt temperature, while absorption peaks at 15500-4000 cm-1 decreased. The large absorption bands of U3+ in LiCl-RbCl eutectic were observed over 14000 cm-1. The sensitive absorption bands of U3+ at Vis/NIR region were found at 13300, 11500-11200, 9800-9400, and 8250 cm-1, and these peaks decreased with increasing temperature.

  13. Electronic absorption spectra of U3+ and U4+ in molten LiCl-RbCl eutectic

    Nagai, T.; Uehara, A.; Fujii, T.; Sato, N.; Yamana, H.

    2010-03-01

    In the non-aqueous reprocessing process of spent nuclear fuels by the pyro-electrochemical method, a spent fuel is dissolved into molten LiCl-KCl and NaCl-CsCl eutectics and dissolved uranium and plutonium are collected as either metal or oxide. However, the binary alkali chloride mixture with the lowest melting point is the LiCl-RbCl eutectic. In this study, electronic absorption spectra of U3+ and U4+ in molten LiCl-RbCl eutectic at various temperatures between 673 and 973 K were measured by the UV/Vis/NIR spectrophotometry. We confirmed that these spectra were similar to those in molten LiCl-KCl and NaCl-CsCl eutectics. The sensitive absorption bands of U4+ in LiCl-RbCl eutectic were found at 22000, 16500, 14900, 8600, and 4950 cm-1. The large absorption bands of U4+ over 25000 cm-1 increased with increasing melt temperature, while absorption peaks at 15500-4000 cm-1 decreased. The large absorption bands of U3+ in LiCl-RbCl eutectic were observed over 14000 cm-1. The sensitive absorption bands of U3+ at Vis/NIR region were found at 13300, 11500-11200, 9800-9400, and 8250 cm-1, and these peaks decreased with increasing temperature.

  14. Comparison of x-ray absorption spectra between water and ice: New ice data with low pre-edge absorption cross-section

    The effect of crystal growth conditions on the O K-edge x-ray absorption spectra of ice is investigated through detailed analysis of the spectral features. The amount of ice defects is found to be minimized on hydrophobic surfaces, such as BaF2(111), with low concentration of nucleation centers. This is manifested through a reduction of the absorption cross-section at 535 eV, which is associated with distorted hydrogen bonds. Furthermore, a connection is made between the observed increase in spectral intensity between 544 and 548 eV and high-symmetry points in the electronic band structure, suggesting a more extended hydrogen-bond network as compared to ices prepared differently. The spectral differences for various ice preparations are compared to the temperature dependence of spectra of liquid water upon supercooling. A double-peak feature in the absorption cross-section between 540 and 543 eV is identified as a characteristic of the crystalline phase. The connection to the interpretation of the liquid phase O K-edge x-ray absorption spectrum is extensively discussed

  15. Computational study of collision-induced dipole moments and absorption spectra of H

    Zheng, Chunguang

    1997-08-01

    H2-H2 collision-induced absorption (CIA) spectra are computed for the first over-tone band at temperatures from 20 to 500 K, and for the rototranslational band at temperatures from 600 to 7,000 K. The theoretical results are based on simple model line shapes. The parameters of the model functions are obtained from the three lowest translational spectral moments, which are computed from the H2-H2 collision-induced dipole moments of Meyer et al. (1) using the sum formulae (2, 3). Ab initio computations of H2-H2 collision- induced dipole moments are performed using the Gaussian 92 program (4). The computations extend the previous work of Meyer et al. (1). Four internuclear distances of H2 molecule 1.111, 1.449, 1.787 and 2.150 a.u., and eleven intermolecular distances of H2-H2 from 2.5 to 9.0 a.u. are included in the computations. The radial transition matrix elements of the collision- induced dipole components are obtained for vibrational transitions /Delta v = (v1' - v1) + (v2' - v2) = 0, 1, 2, 3 and v1,/ v2 = 0, 1, 2. where v1 and v2 are the vibrational quantum numbers of the two interacting H2 molecules, and primes denote final states. The dependences of these matrix elements on the rotational quantum numbers of the two H2 molecules j1j1'j2j2' are obtained for j1j1'j2j2' up to 10. These matrix elements are suitable for high temperature H2-H2 CIA computations. The second overtone band H2-H2 CIA spectra are computed for the first time at temperatures from 20 to 500 K employing the newly developed H2-H2 collision-induced dipole moments. The computations are based on the three lowest translational spectral moments and simple model line shapes.

  16. Solvent dependence of two-photon absorption spectra of the enhanced green fluorescent protein (eGFP) chromophore

    Hosoi, Haruko; Tayama, Ryo; Takeuchi, Satoshi; Tahara, Tahei

    2015-06-01

    Two-photon absorption spectra of 4‧-hydroxybenzylidene-2,3-dimethylimidazolinone, a model chromophore of enhanced green fluorescent protein (eGFP), were measured in various solvents. The two-photon absorption band of its anionic form is markedly blue-shifted from the corresponding one-photon absorption band in all solvents. Moreover, the magnitude of the blue shift varies largely depending on the solvent, which does not accord with the assignment of the two-photon absorption band to the transitions to the vibrationally excited S1 state. Our finding is readily rationalized by considering overlapping contributions of the S1 ← S0 and S2 ← S0 transitions, suggesting the involvement of the S2 state also in two-photon fluorescence of eGFP.

  17. A High Galactic Latitude HI 21 cm-line Absorption Survey using the GMRT: I. Observations and Spectra

    Rekhesh Mohan; K. S. Dwarakanath; G. Srinivasan

    2004-09-01

    We have used the Giant Meterwave Radio Telescope (GMRT) to measure the Galactic HI 21-cm line absorption towards 102 extragalactic radio continuum sources, located at high (|| > 15°) Galactic latitudes. The Declination coverage of the present survey is ≳ -45°. With a mean rms optical depth of ∼ 0.003, this is the most sensitive Galactic HI 21-cm line absorption survey to date. To supplement the absorption data, we have extracted the HI 21-cm line emission profiles towards these 102 lines of sight from the Leiden Dwingeloo Survey of Galactic neutral hydrogen. We have carried out a Gaussian fitting analysis to identify the discrete absorption and emission components in these profiles. In this paper, we present the spectra and the components. A subsequent paper will discuss the interpretation of these results.

  18. Collison-induced rototranslational absorption spectra of H2-He pairs at temperatures from 40 to 3000 K

    Borysow, Jacek; Frommhold, Lothar; Birnbaum, George

    1988-01-01

    The zeroth, first, and second spectral moments of the rototranslational collision-induced absorption (RT CIA) spectra of hydrogen-helium mixtures are calculated from the fundamental theory, for temperatures from 40 to 3000 K. With the help of simple analytical functions of three parameters and the information given, the RT CIA spectra of H2-He pairs can be generated on computers of small capacity, with rms deviations from exact quantum profiles of not more than a few percent. Such representations of the CIA spectra are of interest for work related to the atmospheres of the outer planets and cool stars. The theoretical spectra are in close agreement with existing laboratory measurements at various temperatures from about 77 to 3000 K.

  19. On-the-Fly ab Initio Semiclassical Dynamics of Floppy Molecules: Absorption and Photoelectron Spectra of Ammonia.

    Wehrle, Marius; Oberli, Solène; Vaníček, Jiří

    2015-06-01

    We investigate the performance of on-the-fly ab initio (OTF-AI) semiclassical dynamics combined with the thawed Gaussian approximation (TGA) for computing vibrationally resolved absorption and photoelectron spectra. Ammonia is used as a prototype of floppy molecules, whose potential energy surfaces display strong anharmonicity. We show that despite complications due to the presence of large amplitude motion, the main features of the spectra are captured by the OTF-AI-TGA, which—by definition—does not require any a priori knowledge of the potential energy surface. Moreover, the computed spectra are significantly better than those based on the popular global harmonic approximation. Finally, we probe the limit of the TGA to describe higher-resolution spectra, where long time dynamics is required. PMID:25928833

  20. Interpretation of unexpected behavior of infrared absorption spectra of ScF3 beyond the quasiharmonic approximation

    Piskunov, Sergei; Žguns, Pjotrs A.; Bocharov, Dmitry; Kuzmin, Alexei; Purans, Juris; Kalinko, Aleksandr; Evarestov, Robert A.; Ali, Shehab E.; Rocca, Francesco

    2016-06-01

    Scandium fluoride (ScF3), having cubic ReO3-type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we use the results of diffraction and extended x-ray absorption fine-structure (EXAFS) spectroscopy to interpret the influence of NTE on the temperature dependence of infrared absorption spectra of ScF3. Original infrared absorption and EXAFS experiments in a large temperature range are presented and interpreted using ab initio lattice dynamics simulations within and beyond quasiharmonic approximations. We demonstrate that ab initio electronic structure calculations, based on the linear combination of atomic orbitals method with hybrid functionals, are able to reproduce well the experimental values of lattice parameter a0, band gap Eg, and lattice dynamics in ScF3. However, the simulations performed within quasiharmonic approximation fail to reproduce the temperature dependence of two infrared active bands due to the F-Sc-F bending (at 220 cm-1) and Sc-F stretching (at 520 cm-1) modes present in the infrared absorption spectra. To overcome this problem, an approach beyond the quasiharmonic approximation is proposed: It accounts for the negative thermal expansion of the lattice and for fluorine atom displacements due to strong F vibrational motion perpendicular to the cubic axes and allows us to explain qualitatively the temperature behavior of infrared spectra of ScF3.

  1. Calculation of emission and absorption spectra of LTE plasma by the STA [Super Transition Array] method

    Recent improvements in the Super Transition Array (STA) method for calculating Bound-Bound (BB) and Bound-Free (BF) emission and absorption spectra for LTE plasma are described and illustrated. The method accounts for all possible BB and BF radiative transitions in the plasma. Full detailed first order quantum relativistic treatment is used for calculating transition energies and probabilities. The enormous number of configurations are divided into sets of superconfigurations comprised of a collection of energetically grouped configurations. The contribution of the transition array between two superconfigurations to a specific one-electron transition is then represented by a Gaussian whose moments are calculated accurately using a technique that bypasses the necessity of direct summation over all the levels involved. The calculation of these moments involves the populations of the configurations given by their statistical weights and the Boltzmann factor. For each configuration within the super configuration we use zeroeth order energies in the Boltzmann factor corrected by a super configuration averaged first order term. The structure of the spectrum is increasingly revealed by splitting each STA into a number of smaller STAs. When the spectrum converges it describes the detailed 'UTA' structure, where each configuration-to-configuration array is represented by a separate Gaussian with first order energy in the Boltzmann factor. Convergence is reached with only a few thousand STAs, at most, which makes the calculations practical. It should be pointed out that in this treatment the STA moments are obtained by summing over all level-to-level transitions, rather than configuration-to-configuration average transitions. 4 refs., 9 figs

  2. Observation of π backbonding features appearing in Fe 2p X-ray absorption spectra and Fe 1s-4p-1s resonant X-ray emission spectra of RbMn[Fe(CN)6

    Satellite features by p backbonding (metal-to-ligand charge transfer) were observed in both Fe 2p (L3,2-edge) X-ray absorption spectra and 1s-4p-1s resonant X-ray emission spectra for RbMn[Fe(CN)6], which can be theoretically explained using common parameters. Fe L3,2-edge and Mn L3,2-edge X-ray absorption spectra for low temperature phase are also presented.

  3. Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera.

    Wan, Yuhang; Carlson, John A; Kesler, Benjamin A; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A; Lim, Sung Jun; Smith, Andrew M; Dallesasse, John M; Cunningham, Brian T

    2016-01-01

    A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid's absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics. PMID:27389070

  4. Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera

    Wan, Yuhang; Carlson, John A.; Kesler, Benjamin A.; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A.; Lim, Sung Jun; Smith, Andrew M.; Dallesasse, John M.; Cunningham, Brian T.

    2016-01-01

    A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid’s absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics. PMID:27389070

  5. How Van der Waals Interactions Influence the Absorption Spectra of Pheophorbide a Complexes: A Mixed Quantum-Classical Study.

    Megow, Jörg

    2015-10-01

    The computation of dispersive site energy shifts due to van der Waals interaction (London dispersion forces) was combined with mixed quantum-classical methodology to calculate the linear optical absorption spectra of large pheophorbide a (Pheo) dendrimers. The computed spectra agreed very well with the measurements considering three characteristic optical features occurring with increasing aggregate size: a strong line broadening, a redshift, and a low-energy shoulder. The improved mixed quantum-classical methodology is considered a powerful tool in investigating molecular aggregates. PMID:26275373

  6. First-principles calculation of principal Hugoniot and K-shell X-ray absorption spectra for warm dense KCl

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics (FPMD) method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. It is shown that approximate description of ionization in FPMD has small influence on Hugoniot pressure due to mutual compensation of electronic kinetic pressure and virial pressure. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the 3p electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter

  7. First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

    Zhao, Shijun; Kang, Wei; Li, Zi; Zhang, Ping; He, Xian-Tu

    2015-01-01

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to prevent the deviation of pressure from global accumulation along the Hugoniot. In addition, cancellation between electronic kinetic pressure and virial pressure further reduces the deviation. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the $3p$ electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

  8. First-principles calculation of principal Hugoniot and K-shell X-ray absorption spectra for warm dense KCl

    Zhao, Shijun; Zhang, Shen; Kang, Wei, E-mail: weikang@pku.edu.cn [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); College of Engineering, Peking University, Beijing 100871 (China); Li, Zi [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Zhang, Ping [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); He, Xian-Tu, E-mail: xthe@iapcm.ac.cn [HEDPS, Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); College of Engineering, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

    2015-06-15

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics (FPMD) method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. It is shown that approximate description of ionization in FPMD has small influence on Hugoniot pressure due to mutual compensation of electronic kinetic pressure and virial pressure. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the 3p electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

  9. Fine structures in the optical absorption spectra of photochemical silver in silver halides? A call for further research

    Georgiev, Mladen

    2007-01-01

    A survey is presented of the work done so far to check earlier claims that a fine structure may be observed to occur under certain circumstances in the impurity spectral range of the optical absorption spectra of silver halides following photostimulation in the intrinsic range. This structure, associated with the photochemical formation of silver specks, has been questioned over the years. We now weigh carefully the experimental evidence on the silver halides against a background of similar d...

  10. Interacting He and Ar atoms: Revised theoretical interaction potential, dipole moment, and collision-induced absorption spectra

    Coupled cluster quantum chemical calculations of the potential energy surface and the induced dipole surface are reported for the He–Ar van der Waals collisional complex. Spectroscopic parameters are derived from global analytical fits while an accurate value for the long-range dipole coefficient D7 is obtained by perturbation methods. Collision-induced absorption spectra are computed quantum mechanically and compared with existing measurements

  11. THEORY OF X-RAY-ABSORPTION SPECTRA IN PRO2 AND SOME OTHER RARE-EARTH COMPOUNDS

    OGASAWARA, H; KOTANI, A; OKADA, K; THOLE, BT

    1991-01-01

    We analyze rare-earth 3d-core x-ray-absorption spectra (3d XAS) in PrO2, as well as in CeO2, using the impurity Anderson model. It is shown that the interplay between the atomic multiplet coupling and the solid-state hybridization between rare-earth 4f and oxygen 2p states is essential in determinin

  12. First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

    Zhao, Shijun; Zhang, Shen; Kang, Wei; Li, Zi; Zhang, Ping; He, Xian-Tu

    2015-01-01

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to pr...

  13. Nucleic acid vibrational circular dichroism, absorption, and linear dichroism spectra. I. A DeVoe theory approach.

    Self, B D; Moore, D S

    1997-01-01

    Infrared (IR) vibrational circular dichroism (VCD), absorption, and linear dichroism (LD) spectra of four homopolyribonucleotides, poly(rA), poly(rG), poly(rC), and poly(rU), have been calculated, in the 1750-1550 cm-1 spectral region, using the DeVoe polarizability theory. A newly derived algorithm, which approximates the Hilbert transform of imaginaries to reals, was used in the calculations to obtain real parts of oscillator polarizabilities associated with each normal mode. The calculated...

  14. Research program in nuclear and solid state physics. [including pion absorption spectra and muon spin precession

    1974-01-01

    The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.

  15. Study on the interaction between diphenhydramine and erythrosin by absorption,fluorescence and resonance Rayleigh scattering spectra

    2007-01-01

    In pH 4.5 Britton-Robinson(BR)buffer solution,erythrosin(ET)can react with diphenhydramine(DP)to form a 1:1 ion-association complex,which not only results in the change of the absorption spectra,but also results in the great enhancement of resonance Rayleigh scattering(RRS)and the quenching of fluorescence.Furthermore,a new RRS spectrum will appear,and the maximum RRS wavelength was located at about 580 nm.In this work,the spectral characteristics of the absorption,fluorescence and RRS,the optimum conditions of the reaction and the properties of an analytical chemistry were inves- tigated.A sensitive,simple and new method for the determination of DP by using erythrosin as a probe has been developed.The detection limits for DP were 0.0020μg/mL for RRS method,0.088μg/mL for absorption method and 0.094μg/mL for fluorophotometry.There was a linear relationship between the absorbance,RRS and fluorescence intensities and the drug concentration in the range of 0.0067-2.0, 0.29-6.4 and 0.31-3.2μg/mL,respectively.The effects of the interaction of diphenhydramine and erythrosin on the absorption,fluorescence and resonance Rayleigh scattering spectra were discussed. In light polarization experiment,the polarization of RRS at maximum wavelength was measured to be P =0.9779,and it revealed that the RRS spectrum of DP-ET complex consists mostly of resonance scat- tering and few resonance fluorescence.In this study,enthalpy of formation and mean polarizability were calculated by AM1 quantum chemistry method.In addition,the reaction mechanism and the rea- sons for the enhancement of scattering spectra and the energy transfer between absorption,fluores- cence and RRS were discussed.

  16. pH-Induced changes in electronic absorption and fluorescence spectra of phenazine derivatives

    Ryazanova, O. A.; Voloshin, I. M.; Makitruk, V. L.; Zozulya, V. N.; Karachevtsev, V. A.

    2007-04-01

    The visible electronic absorption and fluorescence spectra as well as fluorescence polarization degrees of imidazo-[4,5-d]-phenazine (F1), 2-methylimidazo-[4,5-d]-phenazine (F2), 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F3), 1,2,3-triazole-[4,5-d]-phenazine (F4) and their glycosides, imidazo-[4,5-d]-phenazine-N1-β- D-ribofuranoside (F1rib), 1,2,3-triazole-[4,5-d]-phenazine-N1-β- D-glucopyranoside (F4gl), were investigated in aqueous buffered solutions over the pH range of 0-12, where the spectral transformations were found to be reversible. The effects of protonation and deprotonation on spectral properties of these dyes were studied. We have determined the ranges of pH, where individual ionic species are predominant. In aqueous buffered solutions the fluorescence was found only for neutral species of F1, F1rib, F2, and F4gl dyes, whereas for the ionic forms of these dyes, as well as for F3 and F4 ones, the fluorescence has not been detected. The concentrational deprotonation p Ka values were evaluated from experimental data. It was shown that donor-acceptor properties of the substituent group in the second position of the pentagonal ring substantially affect the values of the deprotonation constants and the character of protonation for chromophore. The substitution of a hydrogen atom in the NH-group by the sugar residue blocks the formation of the anionic species, and results in enhancement of the dye emission intensity. The steep emission dependence for F1 and F1rib over pH range of 0-7 with intensities ratio of IpH 7/ IpH 1 = 60 allows us to propose them as possible indicator dyes in luminescence based pH sensors for investigation of processes accompanied by acidification, e.g. as gastric pH-sensors. A comparative analysis of the studied dyes has shown that F4gl is the most promising compound to be used as a fluorescent probe for investigation of molecular hybridization of nucleic acids.

  17. Time-dependent radiolytic yields at room temperature and temperature-dependent absorption spectra of the solvated electrons in polyols

    2007-01-01

    The molar extinction coefficients at the absorption maximum of the solvated electron spectrum have been evaluated to be 900, 970, and 1000 mol-1·m2 for 1,2-ethanediol (12ED), 1,2-propanediol (12PD), and 1,3-propanediol (13PD), respectively. These values are two-third or three-fourth of the value usually reported in the published report.Picosecond pulse radiolysis studies have aided in depicting the radiolytic yield of the solvated electron in these solvents as a function of time from picosecond to microsecond. The radiolytic yield in these viscous solvents is found to be strongly different from that of the water solution. The temperature dependent absorption spectra of the solvated electron in 12ED, 12PD, and 13PD have been also investigated. In all the three solvents, the optical spectra shift to the red with increasing temperature. While the shape of the spectra does not change in 13PD, a widening on the blue side of the absorption band is observed in 12ED and 12PD at elevated temperatures.

  18. Ligand and Charge Dependence for Absorption Edge in XANES Spectra of TPP[Fe(Pc)L2]2 Systems

    Takahashi, Kei; Watanabe, Akie; Niki, Kaori; Hanasaki, Noriaki; Kanda, Akinori; Fujikawa, Takashi

    We apply real space full multiple scattering theory to interpret the Fe K-edge XANES spectra of TPP[Fe(Pc)L2]2 (L = CN, Cl and Br) systems, which show the giant magnetoresistance (GMR) at the low temperatures. In the previous paper, we have reported the absorption edge shift of the XANES spectra, whose origin remains unclear, for TPP[Fe(Pc)L2]2 systems. In order to clarify the relation between the charge of the Fe atom, the local structure of the axial ligand and the XANES spectra, we improve the calculation of the XANES spectra by taking into account the wider region including the neighboring Fe(Pc)L2 and TPP molecules. Our multiple scattering analyses suggest that the spectral shape is strongly influenced by the distance between a central Fe and axial ligands L. The number of Fe 3d electrons obtained by density functional theory calculations show weak dependence on the axial ligands L. The EXAFS spectra, the polarization dependence and the temperature dependence of the XANES spectra are also discussed.

  19. Effects of annealing treatment and gamma irradiation on the absorption and fluorescence spectra of Cr:GSGG laser crystal

    Sun, D. L.; Luo, J. Q.; Xiao, J. Z.; Zhang, Q. L.; Jiang, H. H.; Yin, S. T.; Wang, Y. F.; Ge, X. W.

    2008-09-01

    The influence of annealing treatments and gamma-ray irradiation on the absorption and fluorescence spectra of Cr:GSGG crystals grown by the Czochralski method has been investigated. Two absorption bands located near 686 nm and 1050 nm were weakened markedly after the crystal was re-annealed in H2 atmosphere, which is due to the Cr4+ ions being de-oxidized into Cr3+ ions. The other two weak additional absorption bands induced by gamma-ray irradiation appearing near 310 nm and 480 nm are ascribed to the Fe2+ ions and F-type color centers, respectively. In particular, the gamma-ray irradiation with a dose of 100 Mrad has an effect of improving slightly the luminescence properties of Cr:GSGG crystals. The improvement mechanism is analyzed and discussed.

  20. Searching for narrow absorption and emission lines in XMM-Newton spectra of gamma-ray bursts

    Campana, S; D'Avanzo, P; Ghirlanda, G; Melandri, A; Pescalli, A; Salafia, O S; Salvaterra, R; Tagliaferri, G; Vergani, S D

    2016-01-01

    We present the results of a spectroscopic search for narrow emission and absorption features in the X-ray spectra of long gamma-ray burst (GRB) afterglows. Using XMM-Newton data, both EPIC and RGS spectra, of six bright (fluence >10^{-7} erg cm^{-2}) and relatively nearby (z=0.54-1.41) GRBs, we performed a blind search for emission or absorption lines that could be related to a high cloud density or metal-rich gas in the environ close to the GRBs. We detected five emission features in four of the six GRBs with an overall statistical significance, assessed through Monte Carlo simulations, of <3.0 sigma. Most of the lines are detected around the observed energy of the oxygen edge at ~0.5 keV, suggesting that they are not related to the GRB environment but are most likely of Galactic origin. No significant absorption features were detected. A spectral fitting with a free Galactic column density (N_H) testing different models for the Galactic absorption confirms this origin because we found an indication of an...

  1. Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation

    A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters

  2. A Groundbased Imaging Study of Galaxies Causing DLA, subDLA, and LLS Absorption in Quasar Spectra

    Rao, Sandhya M; Turnshek, David A; Monier, Eric M; Nestor, Daniel B; Quider, Anna M

    2011-01-01

    We present results from a search for galaxies that give rise to damped Lyman alpha (DLA), subDLA, and Lyman limit system (LLS) absorption at redshifts 0.1 ~= 0.3 A) whose HI column densities were determined by measuring the Ly-alpha line in HST UV spectra. Photometric redshifts, galaxy colors, and proximity to the quasar sightline, in decreasing order of importance, were used to identify galaxies responsible for the absorption. Our sample includes 80 absorption systems for which the absorbing galaxies have been identified, of which 54 are presented here for the first time. The main results of this study are: (i) the surface density of galaxies falls off exponentially with increasing impact parameter, b, from the quasar sightline relative to a constant background of galaxies, with an e-folding length of ~46 kpc. Galaxies with b >~ 100 kpc calculated at the absorption redshift are statistically consistent with being unrelated to the absorption system. (ii) log N(HI) is inversely correlated with b at the 3.0 sig...

  3. Correlation between Soft X-ray Absorption and Emission Spectra of the Nitrogen Atoms within Imidazolium-Based Ionic Liquids.

    Horikawa, Yuka; Tokushima, Takashi; Takahashi, Osamu; Hoke, Hiroshi; Takamuku, Toshiyuki

    2016-08-01

    Soft X-ray absorption spectroscopy (XAS) has been performed on the N K-edge of two imidazolium-based ionic liquids (ILs), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C2mim][TFSA]) and 1-ethyl-3-methylimidazolium bromide ([C2mim][Br]), to clarify the electronic structures of the ILs. Soft X-ray emission spectroscopy (XES) has also been applied to the ILs by excitation at various X-ray energies according to the XAS spectra. It was possible to fully associate the XAS peaks with the XES peaks. Additionally, both XAS and XES spectra of the ILs were well reproduced by the theoretical spectra for a single-molecule model on [C2mim](+) and [TFSA](-) using density functional theory. The assignments for the XAS and XES peaks of the ILs were accomplished from both experimental and theoretical approaches. The theoretical XAS and XES spectra of [C2mim](+) and [TFSA](-) did not significantly depend on the conformations of the ions. The reproducibility of the theoretical spectra for the single-molecule model suggested that the interactions between the cations and anions are very weak in the ILs, thus scarcely influencing the electronic structures of the nitrogen atoms. PMID:27388151

  4. A Nano-Biosensor for DNA Sequence Detection Using Absorption Spectra of SWNT-DNA Composite

    J. Bansal

    2011-01-01

    Full Text Available A biosensor based on Single Walled Carbon Nanotube (SWNT-Poly (GTn ssDNA hybrid has been developed for medical diagnostics. The absorption spectrum of this assay is determined with the help of a Shimadzu UV-VIS-NIR spectrophotometer. Two distinct bands each containing three peaks corresponding to first and second van Hove singularities in the density of states of the nanotubes were observed in the absorption spectrum. When a single-stranded DNA (ssDNA having a sequence complementary to probic DNA is added to the ssDNA-SWNT conjugates, hybridization takes place, which causes the red shift of absorption spectrum of nanotubes. On the other hand, when the DNA is noncomplementary, no shift in the absorption spectrum occurs since hybridization between the DNA and probe does not take place. The red shifting of the spectrum is considered to be due to change in the dielectric environment around nanotubes.

  5. Sticking to (first) principles: quantum molecular dynamics and Bayesian probabilistic methods to simulate aquatic pollutant absorption spectra.

    Trerayapiwat, Kasidet; Ricke, Nathan; Cohen, Peter; Poblete, Alex; Rudel, Holly; Eustis, Soren N

    2016-08-10

    This work explores the relationship between theoretically predicted excitation energies and experimental molar absorption spectra as they pertain to environmental aquatic photochemistry. An overview of pertinent Quantum Chemical descriptions of sunlight-driven electronic transitions in organic pollutants is presented. Second, a combined molecular dynamics (MD), time-dependent density functional theory (TD-DFT) analysis of the ultraviolet to visible (UV-Vis) absorption spectra of six model organic compounds is presented alongside accurate experimental data. The functional relationship between the experimentally observed molar absorption spectrum and the discrete quantum transitions is examined. A rigorous comparison of the accuracy of the theoretical transition energies (ΔES0→Sn) and oscillator strength (fS0→Sn) is afforded by the probabilistic convolution and deconvolution procedure described. This method of deconvolution of experimental spectra using a Gaussian Mixture Model combined with Bayesian Information Criteria (BIC) to determine the mean (μ) and standard deviation (σ) as well as the number of observed singlet to singlet transition energy state distributions. This procedure allows a direct comparison of the one-electron (quantum) transitions that are the result of quantum chemical calculations and the ensemble of non-adiabatic quantum states that produce the macroscopic effect of a molar absorption spectrum. Poor agreement between the vertical excitation energies produced from TD-DFT calculations with five different functionals (CAM-B3LYP, PBE0, M06-2X, BP86, and LC-BLYP) suggest a failure of the theory to capture the low energy, environmentally important, electronic transitions in our model organic pollutants. However, the method of explicit-solvation of the organic solute using the quantum Effective Fragment Potential (EFP) in a density functional molecular dynamics trajectory simulation shows promise as a robust model of the hydrated organic

  6. The X-ray spectra of optically selected Seyfert 2 galaxies. Are there any Sy2 galaxies with no absorption?

    Pappa, A; Stewart, G C; Zezas, A L

    2001-01-01

    We present an X-ray spectral analysis of a sample of 8 bona-fide Seyfert 2 galaxies, selected on the basis of their high $[OIII]\\lambda5007$ flux, from the Ho et al. (1997) spectroscopic sample of nearby galaxies. We find that, in general, the X-ray spectra of our Seyfert 2 galaxies are complex, with some our objects having spectra different from the 'typical' spectrum of X-ray selected Seyfert 2 galaxies. Two (NGC3147 and NGC4698) show no evidence for intrinsic absorption. We suggest this is due to the fact that when the torus suppresses the intrinsic medium and hard energy flux, underlying emission from the host galaxy, originating in circumnuclear starbursts, and scattering from warm absorbers contributes in these energy bands more significantly. Our asca data alone cannot discriminate whether low absorption objects are Compton-thick AGN with a strong scattered component or lack an obscuring torus. The most striking example of our low absorption Seyfert 2 is NGC4698. Its spectrum could be explained by eith...

  7. Study on the interaction between fluoroquinolones and erythrosine by absorption, fluorescence and resonance Rayleigh scattering spectra and their application

    Wang, Jian; Liu, Zhongfang; Liu, Jiangtao; Liu, Shaopu; Shen, Wei

    2008-03-01

    In pH 4.4-4.5 Britton-Robinson (BR) buffer solution, fluoroquinolone antibiotics (FLQs) including ciprofloxacin (CIP), norfloxacin (NOR), levofloxacin (LEV) and lomefloxacin (LOM) could react with erythrosine (Ery) to form 1:1 ion-association complexes, which not only resulted in the changes of the absorption spectra and the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS). These offered some indications of the determination of fluoroquinolone antibiotics by spectrophotometric, fluorescence and resonance Rayleigh scattering methods. The detection limits for fluoroquinolone antibiotics were in the range of 0.097-0.265 μg/mL for absorption methods, 0.022-0.100 μg/mL for fluorophotometry and 0.014-0.027 μg/mL for RRS method, respectively. Among them, the RRS method had the highest sensitivity. In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions and the properties of the analytical chemistry were investigated. The methods have been successfully applied to determination of some fluoroquinolone antibiotics in human urine samples and tablets. Taking CIP-Ery system as an example, the charge distribution, the enthalpy of formation and the mean polarizability were calculated by density function theory (DFT) method. In addition, the reasons for the enhancement of scattering spectra were discussed.

  8. SYNCHROTRON POLARIZATION AND SYNCHROTRON SELF-ABSORPTION SPECTRA FOR A POWER-LAW PARTICLE DISTRIBUTION WITH FINITE ENERGY RANGE

    We have derived asymptotic forms for the degree of polarization of the optically thin synchrotron and for synchrotron self-absorption (SSA) spectra assuming a power-law particle distribution of the form N(γ) ∼ γ–p with γ1 2, especially for a finite high-energy limit, γ2, in the case of an arbitrary pitch angle. The new results inferred concern more especially the high-frequency range x >> η2 with parameter η = γ2/γ1. The calculated SSA spectra concern instantaneous photon emission where cooling effects are not considered. They have been obtained by also ignoring likely effects such as Comptonization, pair creation and annihilation, as well as magnetic photon splitting. To that aim, in addition to the two usual absorption frequencies, a third possible one has been derived and expressed in terms of the Lambert W function based on the analytical asymptotic form of the absorption coefficient, αν, for the high-frequency range ν >> ν2 (with ν2 the synchrotron frequency corresponding to γ2). We have shown that the latter frequency may not have realistic applications in astrophysics, except in the case of an adequate set of parameters allowing one to neglect Comptonization effects. More detailed calculations and discussions are presented.

  9. Theoretical UV absorption spectra of hydrodynamically escaping O{sub 2}/CO{sub 2}-rich exoplanetary atmospheres

    Gronoff, G.; Mertens, C. J.; Norman, R. B. [NASA LaRC, Hampton, VA (United States); Maggiolo, R. [BIRA-IASB, Avenue Circulaire 3, 1180 Brussels (Belgium); Wedlund, C. Simon [Aalto University School of Electrical Engineering Department of Radio Science and Engineering, P.O. Box 13000, FI-00076 Aalto (Finland); Bell, J. [National Institute of Aerospace, Hampton, VA (United States); Bernard, D. [IPAG, Grenoble (France); Parkinson, C. J. [University of Michigan, MI (United States); Vidal-Madjar, A., E-mail: Guillaume.P.Gronoff@nasa.gov [Observatoire de Paris, Paris (France)

    2014-06-20

    Characterizing Earth- and Venus-like exoplanets' atmospheres to determine if they are habitable and how they are evolving (e.g., equilibrium or strong erosion) is a challenge. For that endeavor, a key element is the retrieval of the exospheric temperature, which is a marker of some of the processes occurring in the lower layers and controls a large part of the atmospheric escape. We describe a method to determine the exospheric temperature of an O{sub 2}- and/or CO{sub 2}-rich transiting exoplanet, and we simulate the respective spectra of such a planet in hydrostatic equilibrium and hydrodynamic escape. The observation of hydrodynamically escaping atmospheres in young planets may help constrain and improve our understanding of the evolution of the solar system's terrestrial planets' atmospheres. We use the dependency of the absorption spectra of the O{sub 2} and CO{sub 2} molecules on the temperature to estimate the temperature independently of the total absorption of the planet. Combining two observables (two parts of the UV spectra that have a different temperature dependency) with the model, we are able to determine the thermospheric density profile and temperature. If the slope of the density profile is inconsistent with the temperature, then we infer the hydrodynamic escape. We address the question of the possible biases in the application of the method to future observations, and we show that the flare activity should be cautiously monitored to avoid large biases.

  10. Absorption and Recurrence Spectra of Sodium Rydberg Atom in a Strong External Magnetic Field

    WANGDe-Hua; LINSheng-Lu

    2004-01-01

    Using core-scattered closed-orbit theory, we calculate the photoabsorption and the scaled recurrence spectra of sodium Rydberg atom in strong magnetic fied below ionization threshoM. The non-Coulombic nature of the ionic core have been modified by a model potential, which includes an attractive Coulomb potential and a short-ranged core potential. A family of core-scattered nonhydrogenic closed orbits have also been discovered. The Fourier transformed spectra of sodium atom have allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The new peaks in the recurrence spectra of sodium atom have been considered as effects caused by the core scattering of returning waves at the ionic core. The results are compared with those of hydrogen case, which show that the core-scattered effects play an important role in alkali-metal atoms.

  11. Absorption and Recurrence Spectra of Sodium Rydberg Atom in a Strong External Magnetic Field

    WANG De-Hua; LIN Sheng-Lu

    2004-01-01

    Using core-scattered closed-orbit theory, we calculate the photoabsorption and the scaled recurrence spectra of sodium Rydberg atom in strong magnetic field below ionization threshold. The non-Coulombic nature of the ionic core have been modified by a model potential, which includes an attractive Coulomb potential and a short-ranged core potential. A family of core-scattered nonhydrogenic closed orbits have also been discovered. The Fourier transformed spectra of sodium atom have allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The new peaks in the recurrence spectra of sodium atom have been considered as effects caused by the core scattering of returning waves at the ionic core. The results are compared with those of hydrogen case, which show that the core-scattered effects play an important role in alkali-metal atoms.

  12. Disentangling vibronic and solvent broadening effects in the absorption spectra of coumarin derivatives for dye sensitized solar cells.

    Cerezo, Javier; Avila Ferrer, Francisco J; Santoro, Fabrizio

    2015-05-01

    We simulate from first-principles the absorption spectra of five structure-related coumarin derivatives utilized in dye sensitized solar cells (DSSCs), investigating the vibronic and solvent contributions to the position and width of the spectra in ethanol. Ground and excited state potential energy surfaces (PESs) are modeled by Density Functional Theory (DFT) and its time-dependent (TD) expression for the excited state (TD-DFT). The solute vibronic structure associated with the spectrum is calculated by a TD formalism, accounting for both Duschinsky and temperature effects, while solvent inhomogeneous broadening is evaluated according to Marcus' theory, computing the solvent reorganization energy by the state-specific implementation of the polarizable continuum model (PCM) within TD-DFT. We adopted both the standard hybrid PBE0 and the range separated CAM-B3LYP functionals showing that the latter performs better both concerning the vibronic and solvent-induced contributions to the absorption lineshape. The different predictions of the two functionals are then rationalized in terms of the charge transfer (CT) character of the transitions showing that, in this class of compounds, it is strongly dependent on the nuclear structure. Such a dependence introduces a bias in the PBE0 PES that has a drastic impact on the vibronic spectra. We show that both the intrinsic vibronic structure and the solvent broadening play a relevant role in differentiating the absorption width of the five dyes. In this sense, our results provide a guide to understand the sources of spectral broadening of this family of dyes, a valuable help for a rational design of new molecules to improve DSSC devices. PMID:25848730

  13. A panchromatic modification of the light absorption spectra of metal-organic frameworks.

    Otal, E H; Kim, M L; Calvo, M E; Karvonen, L; Fabregas, I O; Sierra, C A; Hinestroza, J P

    2016-05-10

    The optical absorption of UiO-66-NH2 MOF was red-shifted using a diazo-coupling reaction. The modifications performed with naphthols and aniline yielded reddish samples, and the modifications with diphenylaniline yielded dark violet ones. The photocatalytic activity of these modified MOFs was assessed for methylene blue degradation, showing a good performance relative to traditional TiO2. The degradation performance was found to correlate with the red shift of the absorption edge. These findings suggest potential applications of these materials in photocatalysis and in dye sensitized solar cells. PMID:27071816

  14. Built-in electric field effect on optical absorption spectra of strained (In,Ga)N–GaN nanostructures

    Based on the effective-mass and the one band parabolic approximations, first order linear, third-order nonlinear and total optical properties related to 1s–1p intra-conduction band transition in wurtzite strained (In,Ga)N–GaN spherical QDs are calculated. The built-in electric field effect, due to the spontaneous and piezoelectric components, is investigated variationally under finite confinement potential. The results reveal that size and internal composition of the dot have a great influence on in-built electric field which affects strongly the optical absorption spectra. It is also found that the modulation of the absorption coefficient, which is suitable for the better performance of optical device applications, can be easily obtained by adjusting geometrical size and internal composition

  15. Communication: X-ray absorption spectra and core-ionization potentials within a core-valence separated coupled cluster framework

    Coriani, Sonia; Koch, Henrik

    2015-11-01

    We present a simple scheme to compute X-ray absorption spectra (e.g., near-edge absorption fine structure) and core ionisation energies within coupled cluster linear response theory. The approach exploits the so-called core-valence separation to effectively reduce the excitation space to processes involving at least one core orbital, and it can be easily implemented within any pre-existing coupled cluster code for low energy states. We further develop a perturbation correction that incorporates the effect of the excluded part of the excitation space. The correction is shown to be highly accurate. Test results are presented for a set of molecular systems for which well converged results in full space could be generated at the coupled cluster singles and doubles level of theory only, but the scheme is straightforwardly generalizable to all members of the coupled cluster hierarchy of approximations, including CC3.

  16. UV absorption spectra and kinetics for alkyl and alkyl peroxy radicals originating from di-tert-butyl ether

    Nielsen, O.J.; Sehested, J.; Langer, S.; Ljungström, E.; Wängberg, I.

    Alkyl, (CH3)(3)COC(CH3)(2)CH2, and alkyl peroxy, (CH3)(3)COC(CH3)(2)CH2O2, radicals from di-tert-butyl ether (DTBE), have been studied in the gas phase at 296 K. A pulse radiolysis UV absorption technique was used to measure the spectra and kinetics. Absorption cross sections were quantified over......) s(-1) was found. The rate constants for the reaction of the alkyl peroxy radicals with NO and NO2 were determined to be (1.8 +/- 0.2) X 10(-12) and (9.9 +/- 1.3) X 10(-12) cm(3) molecule(-1) s(-1), respectively. As a part of the work the rate constants k(F + DTBE) and k(OH + DTBE) were determined to...

  17. The effect of pathological processes on absorption and scattering spectra of samples of bile and pancreatic juice

    Giraev, K. M.; Ashurbekov, N. A.; Magomedov, M. A.; Murtazaeva, A. A.; Medzhidov, R. T.

    2015-07-01

    Spectra of optical transmission coefficients and optical reflectance for bile and pancreatic juice samples were measured experimentally for different forms of pathologies of the pancreas within the range of 250-2500 nm. The absorption and scattering spectra, as well as the spectrum of the anisotropy factor of scattering, were determined based on the results obtained using the reverse Monte Carlo method. The surface morphology for the corresponding samples of the biological media was studied employing electron microscopy. The dynamics of the optical properties of the biological media was determined depending on the stage of the pathology. It has been demonstrated that the results of the study presented are in a good agreement with pathophysiological data and could supplement and broaden the results of conventional methods for diagnostics of the pancreas.

  18. Effects of crossed electric and magnetic fields on the interband optical absorption spectra of variably spaced semiconductor superlattices

    Zuleta, J. N.; Reyes-Gómez, E.

    2016-05-01

    The interband optical absorption spectra of a GaAs-Ga1-xAlxAs variably spaced semiconductor superlattice under crossed in-plane magnetic and growth-direction applied electric fields are theoretically investigated. The electronic structure, transition strengths and interband absorption coefficients are analyzed within the weak and strong magnetic-field regimes. A dramatic quenching of the absorption coefficient is observed, in the weak magnetic-field regime, as the applied electric field is increased, in good agreement with previous experimental measurements performed in a similar system under growth-direction applied electric fields. A decrease of the resonant tunneling in the superlattice is also theoretically obtained in the strong magnetic-field regime. Moreover, in this case, we found an interband absorption coefficient weakly dependent on the applied electric field. Present theoretical results suggest that an in-plane magnetic field may be used to tune the optical properties of variably spaced semiconductor superlattices, with possible future applications in solar cells and magneto-optical devices.

  19. Autler-Townes doublet in the absorption spectra for the transition between excited states of cold cesium atoms

    Liang Qiang-Bing; Yang Bao-Dong; Yang Jian-Feng; Zhang Tian-Cai; Wang Jun-Min

    2010-01-01

    Autler-Townes splitting in absorption spectra of the excited states 6 2P3/2 - 82S1/2 of cold cesium atoms confined in a magneto-optical trap has been observed.Experimental data of the Autler-Townes splitting fit well to the dressedatom theory,by which the fact of the cold atoms dressed by cooling/trapping laser beams is revealed.The results of the theoretical fitting with experiment not only told us the effective Rabi frequency cold atoms experienced,but also could be used for measuring the probability amplitudes of the dressed states.

  20. High resolution infrared absorption spectra, crystal field, and relaxation processes in CsCdBr_3:Pr^3+

    Popova, M. N.; Chukalina, E. P.; Malkin, B. Z.; Iskhakova, A. I.; Antic-Fidancev, E.; P Porcher; Chaminade, J.P.

    2000-01-01

    High resolution low-temperature absorption spectra of 0.2% Pr^3+ doped CsCdBr_3 were measured in the spectral region 2000--7000 cm-1. Positions and widths of the crystal field levels within the 3H5, 3H4, 3F2, and 3F3 multiplets of the Pr^3+ main center have been determined. Hyperfine structure of several spectral lines has been found. Crystal field calculations were carried out in the framework of the semiphenomenological exchange charge model (ECM). Parameters of the ECM were determined by f...

  1. Study of absorption spectra of Er.sup.3+./sup. in KTaO.sub.3./sub. crystals

    Skvortsov, A. P.; Trepakov, Vladimír; Kapphan, S.; Dejneka, Alexandr; Jastrabík, Lubomír

    2009-01-01

    Roč. 51, č. 7 (2009), s. 1470-1472. ISSN 1063-7834. [All-Russia Conference on Physics of Ferroelectrics /18./ (VKS-XVIII). St. Petersburg, 09.06.2008-14.06.2008] R&D Projects: GA ČR GA202/08/1009; GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : KTaO 3 * impurity Er 3+ * absorption spectra Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.721, year: 2009

  2. Vibrational absorption spectra from vibrational coupled cluster damped linear response functions calculated using an asymmetric Lanczos algorithm

    Thomsen, Bo; Hansen, Mikkel Bo; Seidler, Peter;

    2012-01-01

    We report the theory and implementation of vibrational coupled cluster (VCC) damped response functions. From the imaginary part of the damped VCC response function the absorption as function of frequency can be obtained, requiring formally the solution of the now complex VCC response equations. The...... results from the recently reported [P. Seidler, M. B. Hansen, W. Györffy, D. Toffoli, and O. Christiansen, J. Chem. Phys. 132, 164105 (2010)] vibrational configuration interaction damped response function calculated using a symmetric Lanczos algorithm. Calculations of IR spectra of oxazole, cyclopropene...

  3. Experimental and theoretical studies of the VUV emission and absorption spectra of H2, HD and D2 molecules

    The aim of this thesis is to carry out an experimental study of the absorption and emission spectra of the D2 and HD isotopes, with high resolution, in the VUV domain and to supplement it by a theoretical study of the excited electronic states involved in the observed transitions. The emission spectra of HD and D2 are produced by Penning discharge source operating under low pressure and are recorded in the spectral range 78 - 170 nm. The recorded spectra contains more than 20.000 lines. The analysis of the spectrum consists in identifying and assigning the lines to the electronic transitions between energy levels of the molecule. The present analysis is based on our theoretical calculations of the ro-vibrational energy levels of the excited electronic states and the transition probabilities from these states towards the energy levels of the fundamental state. The theoretical results are obtained by resolving the coupled equations between the excited electronic states B1Σu1, B'1Σu1, C1Πu1 and D1Πu1, taking into account the nonadiabatic couplings between these states, and they are obtained in the adiabatic approximation for the excited electronic states B''B-bar1Σu+, D'1Πu1 and D''1Πu1. The equations are resolved using a modern method based on the discretization variables representation method. In addition, we have carried out a study of the absorption spectra of the HD and D2 molecules

  4. Toward the completion of measurement of absorption spectra of 20 amino acids and 5 bases of nuclear acids over wide energy range

    Absorption spectra of biomolecules over wide energy range are very important to study their radiation effects in terms of the optical approximation proposed by Platzman. Using synchrotron radiation we accumulated absorption spectra of amino acids and bases of nuclear acids. Now we will be able to complete the measurement for all 20 amino acids and all 5 bases of nuclear acids within one year. Here we report mainly about basic techniques to obtain precise data. (author)

  5. Temperature effects in the absorption spectra and exciton luminescence in ammonium halides

    Warm-up behavior of the first maximum exciton absorption bands in ammonium halides is explored. Under phase transition occurs offset of bands, bound both with changing a parameter of lattice, and efficient mass of exciton. Warm-up dependency of quantum leaving a luminescence of self-trapped excitons in ammonium halides is measured. (author)

  6. Vibrational absorption spectra, DFT and SCC-DFTB conformational study and analysis of [Leu]enkephalin

    Abdali, Salim; Niehaus, T.A.; Jalkanen, Karl J.;

    2003-01-01

    The endogenous morphine-like pentapeptide, [Leu]enkephalin, which binds to the opiate receptor in the brain, spinal core and gut, is the subject of this study. Vibrational absorption (VA) measurements were carried out on [Leu] enkephalin in non-polar solvent, DMSO-D6 to stabilize the environment...

  7. The Linear Absorption and Pump-Probe Spectra of Cylindrical Molecular Aggregates

    Bednarz, Mariusz; Knoester, Jasper

    2001-01-01

    We study the optical response of Frenkel excitons in molecular J aggregates with a cylindrical geometry. Such aggregates have recently been prepared for a class of cyanine dyes and are akin to the rod- and ring-shaped light-harvesting systems found in certain bacteria. The linear absorption spectrum

  8. Modelling High Resolution Absorption Spectra with ExoMolLine Lists: NH3and CH4

    Barton, E. J.; Yurchenko, S. N.; Tennyson, J.;

    [1]. For this reason, a smart collaboration has been established between Optical Diagnostics Group at DTU and ExoMol, to combine high resolution spectra measured at elevated temperatures and empirically tuned ab initio methods to produce suitable molecular line lists for modelling molecules in...

  9. The SLUGGS survey: Globular cluster stellar population trends from weak absorption lines in stacked spectra

    Usher, Christopher; Brodie, Jean P; Romanowsky, Aaron J; Strader, Jay; Conroy, Charlie; Foster, Caroline; Pastorello, Nicola; Pota, Vincenzo; Arnold, Jacob A

    2014-01-01

    As part of the SLUGGS survey, we stack 1137 Keck DEIMOS spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal to noise ratios of $\\sim 90$ \\AA$^{-1}$. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the H$\\alpha$ and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet--colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour--metallicity relation between galaxies. Two possible explanations for the colour--metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stackin...

  10. Ultraviolet–visible absorption, Raman, vibration spectra of pure silver and Ag–Cu clusters: A density functional theory study

    The UV–visible absorption spectra of Agn and Agn−1Cu1 (n=2–8, 13, 20, 32) clusters were investigated in the framework of TD-DFT using LC-ωPBE (ω=0.40) and the Raman and vibration spectra of Agn and Agn−1Cu1 (n=2–8, 13, 20, 32, 55) clusters were calculated by the DFT/GGA/PBE. The UV–visible absorption, Raman, vibration spectra of pure silver and Ag–Cu clusters are related with their sizes, compositions and structures. Blueshifts are obviously observed as following: from Ag2 to Ag3, from Ag4 to Ag13, from Ag20 to Ag32, from Ag1Cu1 to Ag2Cu1, from Ag3Cu1 to Ag4Cu1, from Ag5Cu1 to Ag12Cu1, from Ag19Cu1 to Ag31Cu1, and from Agn to Agn−1Cu1 (n=2–8, 20, 32); redshifts obviously appear as following changes: from Ag3 to Ag4 and from Ag13 to Ag20, from Ag2Cu1 to Ag3Cu1, from Ag4Cu1 to Ag5Cu1, from Ag13Cu1 to Ag19Cu1, and from Ag13 to Ag12Cu1. On the whole, the wavelengths of the maximum Raman peaks of pure Ag and Ag–Cu clusters lower with increasing cluster size; the intensities of the maximum Raman peaks of pure Ag and Ag–Cu clusters are weakly wavy as clusters change from Ag2 to Ag8, from Ag1Cu1 to Ag7Cu1, then, they (except Ag12Cu1) gradually strengthen with increasing cluster size, however, the intensity of Ag12Cu1 is larger than that of Ag19Cu1. The wavenumbers and intensities of the maximum vibration peaks of pure Ag and Ag–Cu clusters fluctuate with increasing cluster size. The calculated vibrational and Raman spectroscopy of pure Ag and Ag–Cu clusters may be helpful in determining sizes and structures of experimental clusters. - Graphical abstract: The absorption spectra of silver and Ag-Cu clusters are related with their sizes and compositions. Blueshifts and redshifts are observed as sizes and compositions vary.

  11. Treatment of the emission and absorption spectra of a general formalism Λ-type three-level atom driven by a two-mode field with nonlinearities

    An analytical expression of the emission and absorption spectra, for a Λ-type three-level cavity-bound atom interacting with a two-mode cavity field, is given using the dressed states of the system. We take explicitly into account the existence of forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. The characteristics of the emission and absorption spectra for binomial and squeezed coherent states of the modes are exhibited. The effects of the mean number of photons, detuning and the nonlinearity forms on the spectra are analysed

  12. Manifestation of Hubbard and covalent correlations in absorption spectra of YBa2Cu3O6+x films

    The absorption spectra of single-crystal YBa2Cu3O6+x films with various doping levels from x approx 0.35 to x approx 0.9 have been measured in the energy range of 0.3-3eV. The absorption spectral composition is analyzed in terms of intraband and interband transitions as well as local Cu2+ dd-transitions. It is concluded that the dxy → dx2-y2 transition at 1.5 eV reflects the strengthening of covalent of bonding (pd-hybridization) in process of metallization while the spectral peak at approx 1.8 eV provides information about the contribution of electron correlations, since they are sensitive to the opening of the spin gap in the insulator and to antiferromagnetic fluctuations in the metal. The covalent (1.5 eV) and correlation ( approx 1.8 eV) absorption peaks have been found to compete during metallization. However the coexistence of these bands allows one to speak about the validity of the correlation polaron model according to which there exists covalent Cu-O bonding within the polaron moving in the environment of the Hubbard antiferromagnetic fluctuations

  13. XMM-Newton Survey of Local O VII Absorption Lines in the Spectra of Active Galactic Nuclei

    Fang, Taotao; Bullock, James S; Ma, Renyi

    2015-01-01

    Highly ionized, z=0 metal absorption lines detected in the X-ray spectra of background active galactic nuclei (AGNs) provide an effective method to probe the hot ($T\\sim10^6$ K) gas and its metal content in and around the Milky Way. We present an all-sky survey of the $K_{\\alpha}$ transition of the local O VII absorption lines obtained by Voigt-profile fitting archival XMM-Newton observations. A total of 43 AGNs were selected, among which 12 are BL Lac-type AGNs, and the rest are Seyfert 1 galaxies. At above the $3\\sigma$ level the local O VII absorption lines were detected in 21 AGNs, among which 7 were newly discovered in this work. The sky covering fraction, defined as the ratio between the number of detections and the sample size, increases from at about 40% for all targets to 100% for the brightest targets, suggesting a uniform distribution of the O VII absorbers. We correlate the line equivalent width with the Galactic coordinates and do not find any strong correlations between these quantities. Some AG...

  14. Systematic trend of water vapour absorption in red giant atmospheres revealed by high resolution TEXES 12 micron spectra

    Ryde, N; Farzone, M; Richter, M J; Josselin, E; Harper, G M; Eriksson, K; Greathouse, T K

    2014-01-01

    The structures of the outer atmospheres of red giants are very complex. The notion of large optically thick molecular spheres around the stars (MOLspheres) has been invoked in order to explain e.g. spectro-interferometric observations. However, high-resolution spectra in the mid-IR do not easily fit into this picture. They rule out any large sphere of water vapour in LTE surrounding red giants. Our aim here is to investigate high-resolution, mid-infrared spectra for a range of red giants, from early-K to mid M. We have recorded 12 microns spectra of 10 well-studied bright red giants, with TEXES on the IRTF. We find that all giants in our study cooler than 4300 K, spanning a range of effective temperatures, show water absorption lines stronger than expected. The strengths of the lines vary smoothly with spectral type. We identify several spectral features in the wavelength region that undoubtedly are formed in the photosphere. From a study of water-line ratios of the stars, we find that the excitation temperat...

  15. Multiple-scattering approach to the x-ray-absorption spectra of perovskite-type compounds

    Kitamura, Michihide; Muramatsu, Shinji; Sugiura, Chikara

    1988-04-01

    The metal K x-ray-absorption near-edge structure has been calculated for the first time from a multiple-scattering formalism for the perovskite-type compounds KMnF3, KFeF3, KCoF3, KNiF3, and KZnF3. The calculation includes the effects of a core hole and of Madelung corrections for crystal potentials. It is shown that the results including the lifetime-broadening effect are in good agreement with the experiment of Shulman et al.

  16. Electronic absorption spectra and nonlinear optical properties of CO2 molecular aggregates: A quantum chemical study

    Tarun K Mandal; Sudipta Dutta; Swapan K Pati

    2009-09-01

    We have investigated the structural aspects of several carbon dioxide molecular aggregates and their spectroscopic and nonlinear optical properties within the quantum chemical theory framework. We find that, although the single carbon dioxide molecule prefers to be in a linear geometry, the puckering of angles occur in oligomers because of the intermolecular interactions. The resulting dipole moments reflect in the electronic excitation spectra of the molecular assemblies. The observation of significant nonlinear optical properties suggests the potential application of the dense carbon dioxide phases in opto-electronic devices.

  17. Emission from water vapor and absorption from other gases at 5-7.5 μm in Spitzer-IRS Spectra Of Protoplanetary Disks

    We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph 5-7.5 μm spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 μm due to the ν2 = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures >500 K, though some of these spectra also show indications of an absorption band, likely from another molecule. This water vapor emission contrasts with the absorption from warm water vapor seen in the spectrum of the FU Orionis star V1057 Cyg. The other 6 of the 13 stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 μm, which for some is consistent with gaseous formaldehyde (H2CO) and for others is consistent with gaseous formic acid (HCOOH). There are indications that some of these six stars may also have weak water vapor emission. Modeling of these stars' spectra suggests these gases are present in the inner few AU of their host disks, consistent with recent studies of infrared spectra showing gas in protoplanetary disks.

  18. A Reverse Monte Carlo study of H+D Lyman alpha absorption from QSO spectra

    Levshakov, S A; Takahara, F

    1997-01-01

    A new method based on a Reverse Monte Carlo [RMC] technique and aimed at the inverse problem in the analysis of interstellar (intergalactic) absorption lines is presented. The line formation process in chaotic media with a finite correlation length $(l > 0)$ of the stochastic velocity field (mesoturbulence) is considered. This generalizes the standard assumption of completely uncorrelated bulk motions $(l \\equiv 0)$ in the microturbulent approximation which is used for the data analysis up-to-now. It is shown that the RMC method allows to estimate from an observed spectrum the proper physical parameters of the absorbing gas and simultaneously an appropriate structure of the velocity field parallel to the line-of-sight. The application to the analysis of the H+D Ly$\\alpha$ profile is demonstrated using Burles & Tytler [B&T] data for QSO 1009+2956 where the DI Ly$\\alpha$ line is seen at $z_a = 2.504$. The results obtained favor a low D/H ratio in this absorption system, although our upper limit for the ...

  19. Light-absorbing aldol condensation products in acidic aerosols: Spectra, kinetics, and contribution to the absorption index

    Nozière, Barbara; Esteve, William

    The radiative properties of aerosols that are transparent to light in the near-UV and visible, such as sulfate aerosols, can be dramatically modified when mixed with absorbing material such as soot. In a previous work we had shown that the aldol condensation of carbonyl compounds produces light-absorbing compounds in sulfuric acid solutions. In this work we report the spectroscopic and kinetic parameters necessary to estimate the effects of these reactions on the absorption index of sulfuric acid aerosols in the atmosphere. The absorption spectra obtained from the reactions of six different carbonyl compounds (acetaldehyde, acetone, propanal, butanal, 2-butanone, and trifluoroacetone) and their mixtures were compared over 190-1100 nm. The results indicated that most carbonyl compounds should be able to undergo aldol condensation. The products are oligomers absorbing light in the 300-500 nm region where few other compounds absorb, making them important for the radiative properties of aerosols. Kinetic experiments in 96-75 wt% H 2SO 4 solutions and between 273 and 314 K gave an activation energy for the rate constant of formation of the aldol products of acetaldehyde of -(70±15) kJ mol -1 in 96 wt% solution and showed that the effect of acid concentration was exponential. A complete expression for this rate constant is proposed where the absolute value in 96 wt% H 2SO 4 and at 298 K is scaled to the Henry's law coefficient for acetaldehyde and the absorption cross-section for the aldol products assumed in this work. The absorption index of stratospheric sulfuric acid aerosols after a 2-year residence time was estimated to 2×10 -4, optically equivalent to a content of 0.5% of soot and potentially significant for the radiative forcing of these aerosols and for satellite observations in channels where the aldol products absorb.

  20. Monte Carlo inversion of hydrogen and metal lines from QSO absorption spectra

    Levshakov, S A; Kegel, W H; Levshakov, Sergei A.; Agafonova, Irina I.; Kegel, Wilhelm H.

    2000-01-01

    A new method, based on the simulated annealing algorithm and aimed at theinverse problem in the analysis of intergalactic (interstellar) complex spectraof hydrogen and metal lines, is presented. We consider the process of lineformation in clumpy stochastic media accounting for fluctuating velocity anddensity fields (mesoturbulence). This approach generalizes our previous ReverseMonte Carlo and Entropy-Regularized Minimization methods which were applied tovelocity fluctuations only. The method allows one to estimate, from an observedsystem of spectral lines, both the physical parameters of the absorbing gas andappropriate structures of the velocity and density distributions along the lineof sight. The validity of the computational procedure is demonstrated using aseries of synthetic spectra that emulate the up-to-date best quality data. HI,CII, SiII, CIV, SiIV, and OVI lines, exhibiting complex profiles, were fittedsimultaneously. The adopted physical parameters have been recovered with asufficiently high accu...

  1. On shape of NMR absorption spectra and cross-relaxation in hetero nuclear spin system

    Zobov, V E; Rodionova, O E

    2001-01-01

    The dynamic theory of the heteronuclear spin systems in solid bodies at high temperatures is developed. The system of the nonlinear integral equations is obtained for the time spin correlation functions in the approximation of the self-consistent fluctuating local field. The corrections, originating due to the fluctuating local fields correlations, existing in the real lattices, are accounted for thereby. The theory is applied to describing available experimental data for the LiF crystal (with two nuclei kinds). The free precession signals for the Li and F nuclei, as well as, the harmonic cross-relaxation spectra, the sup 6 Li isotope cross-polarization and the sup 8 Li isotope depolarization are calculated by the magnetic field orientations along the basic crystallographic axes. Good agreement between theory and experiment is achieved

  2. Theoretical calculations of absorption spectra of GaNAsBi-based MQWs operating at 1.55 μm

    Ben Nasr, A.; Habchi, M.M.; Bilel, C.; Rebey, A., E-mail: ahmed.rebey@fsm.rnu.tn; El Jani, B.

    2015-10-25

    By applying the band anticrossing model combined with the envelope function formalism, a theoretical study of optoelectronic properties of lattice matched GaNAsBi-based multiple quantum wells (MQWs) operating at 1.55 μm was performed. Indeed, the electronic band structure of 4.5 nm GaN{sub .04}As{sub .89}Bi{sub .07}/GaAs double quantum wells (DQWs) was computed for a barrier width (L{sub b}) varying from 1 to 12 nm. We found that the coupling between GaNAsBi wells which occurs for L{sub b} ≤ 8 nm, modifies the confined energies levels and the fundamental interband transition of the coupled GaNAsBi/GaAs DQWs. This produces a slight shift of the wavelength emission from 1.55 μm. We have also discussed the coupling effect on the in-plane carrier effective mass and the optical absorption spectra of these DQWs. Basing on the enhancement of electron mobility and the slight amelioration of absorption peak magnitude brought by the well coupling, we have chosen the GaN{sub .04}As{sub .89}Bi{sub .07}/GaAs DQWs with L{sub b} = 3.5 nm and L{sub w} modified to 4.3 nm as a candidate for optoelectronic devices operating exactly at 1.55 μm. Finally, we are focused on the investigation of the optical properties of 7(GaAs){sub 3.5}6(GaN{sub .04}As{sub .89}Bi{sub .07}){sub 4.1} superlattices (SLs) operating at 1.55 μm especially the absorption coefficient behavior. - Highlights: • Band anticrossing model and envelope function formalism were used in this study. • Coupling between GaNAsBi wells improves the electron mobility of the studied DQWs. • For 4.5 nm GaN{sub .04}As{sub .89}Bi{sub .07}/GaAs DQWs, the coupling effect occurs for L{sub b} ≤ 7 nm. • Optical absorption spectra of GaN{sub .04}As{sub .89}Bi{sub .07}/GaAs DQWs were calculated. • 7(GaAs){sub 3.5} 6(GaN{sub .04}As{sub .89}Bi{sub .07}){sub 4.1} SLs can operate at 1.55 μm at room temperature.

  3. Theoretical calculations of absorption spectra of GaNAsBi-based MQWs operating at 1.55 μm

    By applying the band anticrossing model combined with the envelope function formalism, a theoretical study of optoelectronic properties of lattice matched GaNAsBi-based multiple quantum wells (MQWs) operating at 1.55 μm was performed. Indeed, the electronic band structure of 4.5 nm GaN.04As.89Bi.07/GaAs double quantum wells (DQWs) was computed for a barrier width (Lb) varying from 1 to 12 nm. We found that the coupling between GaNAsBi wells which occurs for Lb ≤ 8 nm, modifies the confined energies levels and the fundamental interband transition of the coupled GaNAsBi/GaAs DQWs. This produces a slight shift of the wavelength emission from 1.55 μm. We have also discussed the coupling effect on the in-plane carrier effective mass and the optical absorption spectra of these DQWs. Basing on the enhancement of electron mobility and the slight amelioration of absorption peak magnitude brought by the well coupling, we have chosen the GaN.04As.89Bi.07/GaAs DQWs with Lb = 3.5 nm and Lw modified to 4.3 nm as a candidate for optoelectronic devices operating exactly at 1.55 μm. Finally, we are focused on the investigation of the optical properties of 7(GaAs)3.56(GaN.04As.89Bi.07)4.1 superlattices (SLs) operating at 1.55 μm especially the absorption coefficient behavior. - Highlights: • Band anticrossing model and envelope function formalism were used in this study. • Coupling between GaNAsBi wells improves the electron mobility of the studied DQWs. • For 4.5 nm GaN.04As.89Bi.07/GaAs DQWs, the coupling effect occurs for Lb ≤ 7 nm. • Optical absorption spectra of GaN.04As.89Bi.07/GaAs DQWs were calculated. • 7(GaAs)3.5 6(GaN.04As.89Bi.07)4.1 SLs can operate at 1.55 μm at room temperature

  4. PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330

    Gatuzz, E.; Mendoza, C. [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); Garcia, J.; Lohfink, A. [Department of Astronomy and Maryland Astronomy Center for Theory and Computation, University of Maryland, College Park, MD 20742 (United States); Kallman, T. R.; Witthoeft, M. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bautista, M. A. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Palmeri, P.; Quinet, P., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@astro.umd.edu, E-mail: alohfink@astro.umd.edu, E-mail: timothy.r.kallman@nasa.gov, E-mail: michael.c.witthoeft@nasa.gov, E-mail: manuel.bautista@wmich.edu, E-mail: palmeri@umons.ac.be, E-mail: quinet@umons.ac.be [Astrophysique et Spectroscopie, Universite de Mons-UMONS, B-7000 Mons (Belgium)

    2013-05-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N{sub H} = 1.38 {+-} 0.01 Multiplication-Sign 10{sup 21} cm{sup -2}; an ionization parameter of log {xi} = -2.70 {+-} 0.023; an oxygen abundance of A{sub O}= 0.689{sup +0.015}{sub -0.010}; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A{sub O}=0.952{sup +0.020}{sub -0.013}, a value close to solar that reinforces the new standard. We identify several atomic absorption lines-K{alpha}, K{beta}, and K{gamma} in O I and O II and K{alpha} in O III, O VI, and O VII-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  5. Fine structures in the optical absorption spectra of photochemical silver in silver halides? A call for further research

    Georgiev, Mladen

    2007-01-01

    A survey is presented of the work done so far to check earlier claims that a fine structure may be observed to occur under certain circumstances in the impurity spectral range of the optical absorption spectra of silver halides following photostimulation in the intrinsic range. This structure, associated with the photochemical formation of silver specks, has been questioned over the years. We now weigh carefully the experimental evidence on the silver halides against a background of similar data on the alkali halides, where competing processes run slower. We come to the conclusion that present day advances in experimental techniques may be quite adequate for providing a solid experimental basis to solve the problem unambiguously.

  6. FTIR spectrometer with 30 m optical cell and its applications to the sensitive measurements of selective and nonselective absorption spectra

    Ponomarev, Yu. N.; Solodov, A. A.; Solodov, A. M.; Petrova, T. M.; Naumenko, O. V.

    2016-07-01

    A description of the spectroscopic complex at V.E. Zuev Institute of Atmospheric Optics, SB RAS, operating in a wide spectral range with high threshold sensitivity to the absorption coefficient is presented. Measurements of weak lines and nonselective spectra of CO2 and H2O were performed based on the built setup. As new application of this setup, positions and intensities of 152 weak lines of H2O were measured between 2400 and 2560 cm-1 with threshold sensitivity of 8.6×10-10 cm-1, and compared with available calculated and experimental data. Essential deviations between the new intensity measurements and calculated data accepted in HITRAN 2012 and GEISA 2015 forthcoming release are found.

  7. Transmittance spectra of the CuGa3Se5 ternary compound near the fundamental absorption edge

    The CuGa3Se5 ternary compound films are produced by laser deposition at the substrate temperatures 480 and 580 K. The composition and structure of the films are studied. It is shown that, similarly to the corresponding crystals, the CuGa3Se5 films crystallize into the imperfect chalcopyrite structure. The transmittance spectra near the fundamental absorption edge are used to establish the energies and nature of optical transitions. The energies of crystal-field splitting (Δcr) and spin-orbit splitting (ΔSO of the valence band of the CuGa3Se5 ternary compound are calculated in the context of the Hopfield quasi-cubic model.

  8. Transmittance spectra of the CuGa{sub 3}Se{sub 5} ternary compound near the fundamental absorption edge

    Bodnar, I. V., E-mail: chemzav@bsuir.by [Belarusian State University of Information and Radio Electronics (Belarus)

    2011-04-15

    The CuGa{sub 3}Se{sub 5} ternary compound films are produced by laser deposition at the substrate temperatures 480 and 580 K. The composition and structure of the films are studied. It is shown that, similarly to the corresponding crystals, the CuGa{sub 3}Se{sub 5} films crystallize into the imperfect chalcopyrite structure. The transmittance spectra near the fundamental absorption edge are used to establish the energies and nature of optical transitions. The energies of crystal-field splitting ({Delta}{sub cr}) and spin-orbit splitting ({Delta}{sub SO} of the valence band of the CuGa{sub 3}Se{sub 5} ternary compound are calculated in the context of the Hopfield quasi-cubic model.

  9. Artificial intelligence applied to the automatic analysis of absorption spectra. Objective measurement of the fine structure constant

    Bainbridge, Matthew B

    2016-01-01

    A new and fully-automated method is presented for the analysis of high-resolution absorption spectra (GVPFIT). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. GVPFIT is also motivated by the importance of obtaining a large statistical sample of measurements of $\\Delta\\alpha/\\alpha$. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. Three numerical methods are unified into one artificial intelligence process: a genetic algorithm that emulates the Darwinian processes of reproduction, mutation and selection, non-linear least-squares with parameter constraints (VPFIT), and Bayesian model averaging. In contrast to previous methodologies, which relied on a particular solution as being the most likely model, GVPFIT plus Bayesian model averaging derives results from a large set of models, and helps overcome systema...

  10. Sensitivity of absorption spectra to surface segregation in InGaN/GaN quantum well structures

    We investigate the influence of the indium surface segregation on absorption spectra in InGaN/GaN quantum well structures having different indium amount. Results of the mathematical modeling show that such influence is more pronounced in quantum well structures with high indium amounts. The origin of this effect is related to the interplay between the indium surface segregation and internal electrostatic fields. Our theoretical analysis is performed using semiconductor Bloch equations within the Hartree-Fock approximation including into consideration excitonic effects. Results of the global sensitivity analysis evidence that the influence of the indium surface segregation is less than one order of magnitude in comparison with the impact of the quantum-well width and indium molar fraction. Also, the influence of the indium surface segregation is not the same for each interface of the quantum well

  11. Electronic absorption spectra and solvatochromic shifts by the vertical excitation model: solvated clusters and molecular dynamics sampling.

    Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G

    2015-01-22

    A physically realistic treatment of solvatochromic shifts in liquid-phase electronic absorption spectra requires a proper account for various short- and long-range equilibrium and nonequilibrium solute-solvent interactions. The present article demonstrates that such a treatment can be accomplished using a mixed discrete-continuum approach based on the two-time-scale self-consistent state-specific vertical excitation model (called VEM) for electronic excitation in solution. We apply this mixed approach in combination with time-dependent density functional theory to compute UV/vis absorption spectra in solution for the n → π* ((1)A2) transition for acetone in methanol and in water, the π → π* ((1)A1) transition for para-nitroaniline (PNA) in methanol and in water, the n → π* ((1)B1) transition for pyridine in water, and the n → π* ((1)B1) transition for pyrimidine in water. Hydrogen bonding and first-solvation-shell-specific complexation are included by means of explicit solvent molecules, and solute-solvent dispersion is included by using the solvation model with state-specific polarizability (SMSSP). Geometries of microsolvated clusters were treated in two different ways, (i) using single liquid-phase global-minimum solute-solvent clusters containing up to two explicit solvent molecules and (ii) using solute-solvent cluster snapshots derived from molecular dynamics (MD) trajectories. The calculations in water involve using VEM/TDDFT excitation energies and oscillator strengths computed over 200 MD-derived solute-solvent clusters and convoluted with Gaussian functions. We also calculate ground- and excited-state dipole moments for interpretation. We find that inclusion of explicit solvent molecules generally improves the agreement with experiment and can be recommended as a way to include the effect of hydrogen bonding in solvatochromic shifts. PMID:25159827

  12. Optical absorption spectra of the uranium (4+) ion in the thorium germanate matrix

    Gajek, Z; Antic-Fidancev, E

    1997-01-01

    Visible and infrared absorption measurements on the U sup 4 sup + ion in tetragonal zircon-type matrix beta-ThGeO sub 4 are reported and analysed in terms of the standard parametrization scheme. The observed 17 main peaks and a number of less intense lines have been assigned and fitted to most of the 32 allowed electric dipole transitions with the root mean square error equal to 65 cm sup - sup 1. The free-ion parameters obtained for the model Hamiltonian, zeta 5f = 1809 cm sup - sup 1 , F sup 2 =43 065 cm sup - sup 1 , F sup 4 =38 977 cm sup - sup 1 and F sup 6 =24 391 cm sup - sup 1 , as well as the corresponding crystal-field parameters, B sub 0 sup 2 =-1790 cm sup - sup 1 , B sub 0 sup 4 =1200 cm sup - sup 1 , B sub 4 sup 4 =3260 cm sup - sup 1 , B sub 0 sup 6 =-3170 cm sup - sup 1 and B sub 4 sup 6 =990 cm sup - sup 1 , agree fairly well with the initial theoretical estimations. The results are discussed in relation to the previous spectroscopic study on the scheelite-type matrix UGeO sub 4. (author)

  13. Revisiting the total ion yield x-ray absorption spectra of liquid water microjets

    Saykally, Richard J; Cappa, Chris D.; Smith, Jared D.; Wilson, Kevin R.; Saykally, Richard J.

    2008-02-16

    Measurements of the total ion yield (TIY) x-ray absorption spectrum (XAS) of liquid water by Wilson et al. (2002 J. Phys.: Condens. Matter 14 L221 and 2001 J. Phys. Chem. B 105 3346) have been revisited in light of new experimental and theoretical efforts by our group. Previously, the TIY spectrum was interpreted as a distinct measure of the electronic structure of the liquid water surface. However, our new results indicate that the previously obtained spectrum may have suffered from as yet unidentified experimental artifacts. Although computational results indicate that the liquid water surface should exhibit a TIY-XAS that is fundamentally distinguishable from the bulk liquid XAS, the new experimental results suggest that the observable TIY-XAS is actually nearly identical in appearance to the total electron yield (TEY-)XAS, which is a bulk probe. This surprising similarity between the observed TIY-XAS and TEY-XAS likely results from large contributions from x-ray induced electron stimulated desorption of ions, and does not necessarily indicate that the electronic structure of the bulk liquid and liquid surface are identical.

  14. Quasar broad absorption line variability measurements using reconstructions of un-absorbed spectra

    Wildy, Conor; Allen, James T

    2013-01-01

    We present a two-epoch SDSS and Gemini/GMOS+WHT/ISIS variability study of 50 broad absorption line quasars of redshift range 1.9 < z < 4.2, containing 38 Si IV and 59 C IV BALs and spanning rest-frame time intervals of approximately 10 months to 3.7 years. We find that 35/50 quasars exhibit one or more variable BALs, with 58% of Si IV and 46% of C IV BALs showing variability across the entire sample. On average, Si IV BALs show larger fractional change in BAL pseudo equivalent width than C IV BALs, as referenced to an unabsorbed continuum+emission-line spectrum constructed using non-negative matrix factorisation. No correlation is found between BAL variability and quasar luminosity, suggesting that ionizing continuum changes do not play a significant role in BAL variability (assuming the gas is in photoionization equilibrium with the ionizing continuum). A subset of 14 quasars have one variable BAL from each of Si IV and C IV with significant overlap in velocity space and for which variations are in the...

  15. Superresolution and other mathematical techniques for quantitative analysis of infrared absorption and emission spectra of gases

    Davies, Nicholas M.; Lettington, Alan H.; Hilton, Moira

    1997-05-01

    Fourier transform IR (FTIR) spectroscopy has become a powerful analytical tool for the detection and measurement of atmospheric pollutant gases. This work describes the application of concentration analysis techniques to data recorded with a versatile FTIR spectroscopy system, developed at the University of Reading PHysics Department. Spectra were recorded at three separate sites, each possessing a distinct source of atmospheric pollution gases. The two sites monitored in the active mode were a traffic congested town center at rush hour and a dairy farm cow shed. The site monitored passively contained three 5 m high methane burners. The analysis techniques have been designed to provide rapid and accurate analysis of the spectrometer data, without the need for high computing power, thus making analysis possible in the field using a laptop PC. In an attempt to enhance the resolution of the spectral data, and therefore resolve overlapping spectral lines, a super- resolution algorithm has been tested on part of the recorded data. The results of applying the algorithm has been tested on part of the recorded data. The results of applying the algorithm, predominantly an image processing technique, are shown and improvements to the algorithm are discussed. Results from the urban and agricultural sites show that CO, CH4, and NH3 can be measured to a ppm level with a maximum uncertainly of 8 percent.

  16. Spectroscopic and DFT study of solvent effects on the electronic absorption spectra of sulfamethoxazole in neat and binary solvent mixtures

    Almandoz, M. C.; Sancho, M. I.; Blanco, S. E.

    2014-01-01

    The solvatochromic behavior of sulfamethoxazole (SMX) was investigated using UV-vis spectroscopy and DFT methods in neat and binary solvent mixtures. The spectral shifts of this solute were correlated with the Kamlet and Taft parameters (α, β and π*). Multiple lineal regression analysis indicates that both specific hydrogen-bond interaction and non specific dipolar interaction play an important role in the position of the absorption maxima in neat solvents. The simulated absorption spectra using TD-DFT methods were in good agreement with the experimental ones. Binary mixtures consist of cyclohexane (Cy)-ethanol (EtOH), acetonitrile (ACN)-dimethylsulfoxide (DMSO), ACN-dimethylformamide (DMF), and aqueous mixtures containing as co-solvents DMSO, ACN, EtOH and MeOH. Index of preferential solvation was calculated as a function of solvent composition and non-ideal characteristics are observed in all binary mixtures. In ACN-DMSO and ACN-DMF mixtures, the results show that the solvents with higher polarity and hydrogen bond donor ability interact preferentially with the solute. In binary mixtures containing water, the SMX molecules are solvated by the organic co-solvent (DMSO or EtOH) over the whole composition range. Synergistic effect is observed in the case of ACN-H2O and MeOH-H2O, indicating that at certain concentrations solvents interact to form association complexes, which should be more polar than the individual solvents of the mixture.

  17. Excited S 1 state dipole moments of nitrobenzene and p-nitroaniline from thermochromic effect on electronic absorption spectra

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-11-01

    The effect of temperature on the absorption spectra of nitrobenzene (NB) and p-nitroaniline (NA) in 1,2-dichloroethane was studied for temperature ranging from 295 K to 378 K and from 296 K to 408 K, respectively. With temperature increase the absorption bands of both compounds are blue shifted, which is caused by the decrease of permittivity ɛ and refractive index n. From the band shifts and by using the Bilot and Kawski theory [ L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621] the dipole moments in the excited singlet state μe = 6.59 D of NB and μe = 13.35 D of NA were determined. The influence of polarizability α, the Onsager cavity radius a and dipole moment in the ground state μg on the determined values of μe are discussed. A comparison of the obtained μe values with those of other authors is given. In the case of p-NA a strong intramolecular charge transfer (ICT) was confirmed.

  18. Physical properties of the interstellar medium using high-resolution Chandra spectra: O K-edge absorption

    Gatuzz, E.; Mendoza, C. [Centro de Física, Instituto Venezolano de Investigaciones Científicas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); García, J. [Harvard-Smithsonian Center for Astrophysics, MS-6, 60 Garden Street, Cambridge, MA 02138 (United States); Kallman, T. R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bautista, M. A.; Gorczyca, T. W., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@head.cfa.harvard.edu, E-mail: manuel.bautista@wmich.edu, E-mail: thomas.gorczyca@wmich.edu, E-mail: timothy.r.kallman@nasa.gov [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States)

    2014-08-01

    Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the accuracy of the atomic data. Hydrogen column densities are derived with a broadband fit that takes into account pileup effects, and in general are in good agreement with previous results. The dominant features in the oxygen-edge region are O I and O II Kα absorption lines whose simultaneous fits lead to average values of the ionization parameter of log ξ = –2.90 and oxygen abundance of A{sub O} = 0.70. The latter is given relative to the standard by Grevesse and Sauval, but rescaling with the revision by Asplund et al. would lead to an average abundance value fairly close to solar. The low average oxygen column density (N{sub O} = 9.2 × 10{sup 17} cm{sup –2}) suggests a correlation with the low ionization parameters, the latter also being in evidence in the column density ratios N(O II)/N(O I) and N(O III)/N(O I) that are estimated to be less than 0.1. We do not find conclusive evidence for absorption by any other compound but atomic oxygen in our oxygen-edge region analysis.

  19. NEW H2 COLLISION-INDUCED ABSORPTION AND NH3 OPACITY AND THE SPECTRA OF THE COOLEST BROWN DWARFS

    We present new cloudy and cloudless model atmospheres for brown dwarfs using recent ab initio calculations of the line list of ammonia (NH3) and of the collision-induced absorption of molecular hydrogen (H2). We compare the new synthetic spectra with models based on an earlier description of the H2 and NH3 opacities. We find a significant improvement in fitting the nearly complete spectral energy distribution of the T7p dwarf Gliese 570D and in near-infrared color-magnitude diagrams of field brown dwarfs. We apply these new models to the identification of NH3 absorption in the H-band peak of very late T dwarfs and the new Y dwarfs and discuss the observed trend in the NH3-H spectral index. The new NH3 line list also allows a detailed study of the medium-resolution spectrum of the T9/T10 dwarf UGPS J072227.51–054031.2 where we identify several specific features caused by NH3.

  20. Indication of single-crystal PuO2 oxidation from O 1s x-ray absorption spectra

    Modin, A.; Yun, Y.; Suzuki, M.-T.; Vegelius, J.; Werme, L.; Nordgren, J.; Oppeneer, P. M.; Butorin, S. M.

    2011-02-01

    The electronic structure of single-crystal PuO2 is studied using O 1s x-ray absorption (XA) and x-ray emission. Interpretation of the experimental data is supported by extensive first-principles calculations on the basis of the densityfunctionaltheory+U approach. The measured XA spectra show a significant difference in intensity for the first two peaks between different spots or areas on the single crystal. Our theoretical simulations show that the first peak, at ~531 eV, can be attributed to O 2p-Pu 5f hybridization, while the second peak, at ~533.4 eV, is due to hybridization of O 2p with Pu d states. The reasons for the observed differences in the O 1s XA spectra are explored by calculating a number of defect structures PuO2±x as well as by simulating the existence of Pu(V) sites. Our results indicate the presence of oxidation states higher than Pu(IV) in some areas of the single crystal. The findings also suggest that plutonium oxide with a Pu fraction in an oxidation state higher than Pu(IV) consists of inequivalent Pu sites with Pu(IV)O2 and Pu(V)O2 rather than representing a system where the Pu oxidation state is constantly fluctuating between Pu(IV) and Pu(V).

  1. Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. I. Full cumulant expansions and system-bath entanglement

    Ma, Jian; Cao, Jianshu, E-mail: jianshu@mit.edu [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-03-07

    We study the Förster resonant energy transfer rate, absorption and emission spectra in multichromophoric systems. The multichromophoric Förster theory (MCFT) is determined from an overlap integral of generalized matrices related to the donor’s emission and acceptor’s absorption spectra, which are obtained via a full 2nd-order cumulant expansion technique developed in this work. We calculate the spectra and MCFT rate for both localized and delocalized systems, and calibrate the analytical 2nd-order cumulant expansion with the exact stochastic path integral method. We present three essential findings: (i) The role of the initial entanglement between the donor and its bath is found to be crucial in both the emission spectrum and the MCFT rate. (ii) The absorption spectra obtained by the cumulant expansion method are nearly identical to the exact spectra for both localized and delocalized systems, even when the system-bath coupling is far from the perturbative regime. (iii) For the emission spectra, the cumulant expansion can give reliable results for localized systems, but fail to provide reliable spectra of the high-lying excited states of a delocalized system, when the system-bath coupling is large and the thermal energy is small. This paper also provides a simple golden-rule derivation of the MCFT, reviews existing methods, and motivates further developments in the subsequent papers.

  2. Local optical absorption spectra of h-BN–MoS2 van der Waals heterostructure revealed by scanning near-field optical microscopy

    Nozaki, Junji; Kobayashi, Yu; Miyata, Yasumitsu; Maniwa, Yutaka; Watanabe, Kenji; Taniguchi, Takashi; Yanagi, Kazuhiro

    2016-06-01

    Van der Waals (vdW) heterostructures, in which different two-dimensional layered materials are stacked, can exhibit unprecedented optical properties. Development of a technique to clarify local optical properties of vdW heterostructures is of great importance for the correct understanding of their backgrounds. Here, we examined local optical absorption spectra of h-BN–MoS2 vdW heterostructures by scanning near-field microscopy measurements with a spatial resolution of 100 nm. In an as-grown sample, there was almost no site dependence of their optical absorption spectra. However, in a degraded sample where defects and deformations were artificially induced, a significant site-dependence of optical absorption spectra was observed.

  3. Monomeric C-phycocyanin at room temperature and 77 K. Resolution of the absorption and fluorescence spectra of the individual chromophores and the energy-transfer rate constants

    Debreczeny, M.P.; Sauer, K. (Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley, CA (United States)); Zhou, J.; Bryant, D.A. (Pennsylvania State Univ., University Park, PA (United States))

    1993-09-23

    At both room temperature (RT) and 77 K, the absorption and fluorescence spectra of the three individual chromophore types ([alpha][sub 84], [beta][sub 84], and [beta][sub 155]) found in monomeric C-phycocyanin ([alpha][sup PC][beta][sup PC]), isolated from the cyanobacterium Synechococcus sp. PCC 7002, were resolved along with the rates of energy transfer between the chromophores. The cpcB/C155S mutant, whose PC is missing the [beta][sub 155] chromophore, was useful in effecting this resolution. At RT, the single broad peak in the visible region of the absorption spectrum of ([alpha][sup PC][beta][sup PC]) was resolved into its three-component spectra by comparing the steady-state absorption spectra of the isolated wild-type [alpha] subunit of PC ([alpha][sup PC]) (containing only the [alpha][sub 84] chromophore) with those of the monomeric PCs isolated from the mutant strain ([alpha][sup PC][beta]*) and the wild-type strain ([alpha][sup PC][beta][sup PC]). At 77 K, the visible region of the absorption spectrum of ([alpha][sup PC][beta][sup PC]) splits into two peaks. This partial resolution at 77 K of the chromophore spectra of ([alpha][sup PC][beta][sup PC]) when compared with the 77 K absorption spectra of [alpha][sup PC], [beta][sup PC], and ([alpha][sup PC][beta]*) provided a confirmation of our RT assignments of the chromophore absorption spectra. 38 refs., 9 figs., 6 tabs.

  4. Analysis of the Damage Site to Oxyleghaemoglobin by H(2)O(2) on the Basis of the Changes in Absorption Spectra.

    Luo, Guang-Hua; Wang, Ai-Guo

    1996-01-01

    Leghaenoglobin (Lb) is a Fe-protein with a high content in the root nodules of soybean (Glycine max). Oxyleghaemoglobin (LbO(2), Fe(2+)-protein) prepared from fresh soybean root nodules in san active form of Lb. LbO(2) displays two distinct absorption bands at 577 nm and 540 nm, which are closely related to the structure of haem (iron-porphyrin). Another absorption band found at 280 nm is related to the configuration of the globin. When LbO(2) was incubated with H(2)O(2), prompt changes in visible-absorption spectra appeared and the UV-absorption spectra was relatively stable. We conclude that the position of damage by H(2)O(2) was located on the Fe(2+)-porphyrin ring rather than in the globin of LbO(2). PMID:12237710

  5. Band intensities in the circular dichroism and absorption spectra and the states of d ions in absorbing media: I. Octahedrally coordinated positions of d ions

    The factors affecting the band intensity in circular dichroism (CD) and absorption spectra (selection rules, point group of structural position, and the electron density of the ground state of octahedrally coordinated d ion in absorbing medium) are considered. The intensities of CD and absorption bands are calculated and compared with the experimental data. It is shown that the differences in the spatial inversion of the electric- and magnetic-dipole moment transformations lead to a more rigorous validity of the symmetry selection rules and increase the resolution of peaks and transparency window of medium absorption in CD spectra (in contrast to absorption ones). Some criteria for estimating the valence and structural states of d ions are formulated.

  6. Emission from Water Vapor and Absorption from Other Gases at 5-7.5 Microns in Spitzer-IRS Spectra of Protoplanetary Disks

    Sargent, B A; Watson, Dan M; Calvet, N; Furlan, E; Kim, K -H; Green, J; Pontoppidan, K; Richter, I; Tayrien, C

    2014-01-01

    We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph (IRS) 5-7.5 micron spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 microns due to the nu_2 = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures > 500 K, though some of these spectra also show indications of an absorption band, likely from another molecule. This water vapor emission contrasts with the absorption from warm water vapor seen in the spectrum of the FU Orionis star V1057 Cyg. The other six of the thirteen stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 microns, which for some is consistent with gaseous formaldehyde (H2CO) and for others is consistent with gaseous formic acid (HCOOH). There are indications that some of these six stars may also have weak water vapor emission....

  7. Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

    Dankowski, S. U.; Streb, D.; M. Ruff; Kiesel, P; Kneissl, M.; Knüpfer, B.; Döhler, G. H.; Keil, Ulrich Dieter Felix; Sørensen, Claus Birger; A.K. Verma

    1996-01-01

    Room temperature absorption spectra of low temperature molecular beam epitaxy grown GaAs (LT-GaAs) and AlGaAs (LT-AlGaAs) are reported. We performed measurements in an extended spectral range from 0.8 eV to photon energies of 2.8 eV far above the band gap. For as-grown LT-materials, the absorption coefficients at the band gap are twice as high as for high temperature grown materials. By annealing the samples, we obtained a drastic reduced absorption coefficient below as well as above the band...

  8. The vacuum thermal treatment effect on the optical absorption spectra of the TiO2 coated by Ni-B nano-clasters photocatalyst powders

    Nadareishvili, M. M.; Kvavadze, K. A.; Mamniashvili, G. I.; Khoperia, T. N.; Zedgenidze, T. I.

    2009-01-01

    The thermal vacuum treatment effect on the optical absorption spectra of the TiO2 nanopowders, both pure and coated by the Ni-B clasters with the original electroless method was investigated. It was observed that the thermal treatment of pure TiO2 nanopowders does not change their optical absorption spectrum while after the coating of these powder particles by the Ni-B clasters the thermal treatment results in the increase of the optical light absorption in the visual region of spectrum. This...

  9. X-ray absorption and infrared spectra of water and ice: A first-principles electronic structure study

    Chen, Wei

    Water is of essential importance for chemistry and biology, yet the physics concerning many of its distinctive properties is not well known. In this thesis we present a theoretical study of the x-ray absorption (XA) and infrared (IR) spectra of water in liquid and solid phase. Our theoretical tools are the density functional theory (DFT), Car-Parrinello (CP) molecular dynamics (MD), and the so-called GW method. Since a systematic review of these ab initio methods is not the task of this thesis, we only briefly recall the main concepts of these methods as needed in the course of our exposition. The focus is, instead, an investigation of what is the important physics necessary for a better description of these excitation processes, in particular, core electron excitations (in XA) that reveal the local electronic structure, and vibrational excitations (in IR) associated to the molecular dynamics. The most interesting question we are trying to answer is: as we include better approximations and more complete physical descriptions of these processes, how do the aforementioned spectra reflect the underlying hydrogen-bonding network of water? The first part of this thesis consists of the first four chapters, which focus on the study of core level excitation of water and ice. The x-ray absorption spectra of water and ice are calculated with a many-body approach for electron-hole excitations. The experimental features, even the small effects of a temperature change in the liquid, are reproduced with quantitative detail using molecular configurations generated by ab initio molecular dynamics. We find that the spectral shape is controlled by two major modifications of the short range order that mark the transition from ice to water. One is associated to dynamic breaking of the hydrogen bonds which leads to a strong enhancement of the pre-edge intensity in the liquid. The other is due to densification, which follows the partial collapse of the hydrogen bond network and is

  10. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-08-01

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5'-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5'-monophosphate, and adenosine 5'-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  11. Structures, vibrational absorption and vibrational circular dichroism spectra of L-alanine in aqueous solution: a density functional theory and RHF study

    Frimand, Kenneth; Bohr, Henrik; Jalkanen, Karl J.; Suhai, S.

    A detailed comparative study of structures, vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra has been carried out for the zwitterionic structure of the amino acid L-alanine. Theoretically determined structures necessary for deriving VA and VCD spectra were calculated...... water molecules and a dielectric media through the Onsager model and only this combination gave excellent comparison to experimental VA and VCD spectra. Two dominant conformers with different backbone configurations are identified, and the inclusion of solvent effects clearly favours one of the...... conformers. The calculated VA and VCD spectra of this conformer are in better agreement with experimentally measured VA and VCD spectra previously reported. (C) 2000 Elsevier Science B.V. All rights reserved....

  12. Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars.

    Srianand, R; Chand, H; Petitjean, P; Aracil, B

    2004-03-26

    We present the results of a detailed many-multiplet analysis performed on a new sample of Mg ii systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in alpha derived from our analysis over the redshift range 0.4quasar absorption line systems. PMID:15089663

  13. Optical absorption spectra and energy levels of Er.sup.3+./sup. ions in KTaO.sub.3./sub. crystals

    Skvortsov, A. P.; Trepakov, V. A.; Krivolapchuk, V.V.; Poletaev, N.K.; Kapphan, S.; Dejneka, Alexandr; Jastrabík, Lubomír

    2009-01-01

    Roč. 354, č. 6 (2009), s. 566-568. ISSN 1063-7850 R&D Projects: GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : optical absorption spectra * energy levels of Er 3+ ions * KTaO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.580, year: 2009

  14. A comparison of fine structures in high-resolution x-ray-absorption spectra of various condensed organic molecules.

    Schoell, A; Zou, Y; Huebner, D; Urquhart, S G; Schmidt, Th; Fink, R; Umbach, E

    2005-07-22

    We report on a high-resolution C-K and O-K near-edge x-ray-absorption fine-structure (NEXAFS) study of large aromatic molecules in condensed thin films, namely, anhydrides 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride, 3,4,9,10-perylene-tetracarboxylic acid dianhydride, benzoperylene-(1,2)-dicarboxylic acid anhydride, and 1,8-naphthalene-dicarboxylic acid anhydride and the quinoic acenaphthenequinone. Due to the high-energy resolution of the third-generation synchrotron source BESSY II we observe large differences in the NEXAFS fine structures even for very similar molecules, resulting in a wealth of new information. The rich fine structure can unambiguously be assigned to the coupling of electronic transitions to vibronic excitations. Backed by ab initio calculations we present a detailed analysis of the spectra that allows the complete interpretation of the near-edge features. It also yields information on the vibronic properties in the electronically excited state as well as on the response of the electronic system upon core excitation. The strong differences in the electron-vibron coupling for different molecules are discussed. PMID:16095371

  15. Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

    Dankowski, S. U.; Streb, D.; Ruff, M.; Kiesel, P.; Kneissl, M.; Knüpfer, B.; Döhler, G. H.; Keil, Ulrich Dieter Felix; Sørensen, Claus Birger; Verma, A. K.

    1996-01-01

    coefficients at the band gap are twice as high as for high temperature grown materials. By annealing the samples, we obtained a drastic reduced absorption coefficient below as well as above the band gap. We observed absorption changes up to 17 000 cm(-1) for LT-GaAs and 9000 cm(-1) for LT-AlGaAs taking place......Room temperature absorption spectra of low temperature molecular beam epitaxy grown GaAs (LT-GaAs) and AlGaAs (LT-AlGaAs) are reported. We performed measurements in an extended spectral range from 0.8 eV to photon energies of 2.8 eV far above the band gap. For as-grown LT-materials, the absorption...

  16. Influence of Duschinsky and Herzberg-Teller effects on S0 → S1 vibrationally resolved absorption spectra of several porphyrin-like compounds

    Yang, Pan; Qi, Dan; You, Guojian; Shen, Wei; Li, Ming; He, Rongxing

    2014-09-01

    The S0 → S1 (Q band) high-resolved absorption spectra of three porphyrin-like compounds, porphycene, magnesium porphyrin, and zinc tetraazaporphyrin, were simulated in the framework of the Franck-Condon approximation including the Duschinsky and Herzberg-Teller (HT) contributions. Substitution of meso-aza on porphyrin macrocycle framework could change severely the absorption energy, vibrational intensity, and spectral profile of Q band. Therefore, we focused attention on the spectral similarities and contrasts among the three compounds based on the density functional theory and its time-dependent extension calculations. The simulated spectra agreed well with the experimental ones and further confirmed that the HT and Duschinsky effects have significant influence on the weakly allowed or forbidden transition of sizable organic molecules. The pure HT and Duschinsky effects were explored separately to clarify their contributions on changing vibrational intensities of different modes. Moreover, we tentatively assigned most of the vibrational modes which appeared in the experimental spectra but corresponding assignments were not given. The present work provided a useful method to simulate and interpret the absorption spectra of porphyrin-like compounds.

  17. Influence of Duschinsky and Herzberg-Teller effects on S₀→ S₁ vibrationally resolved absorption spectra of several porphyrin-like compounds.

    Yang, Pan; Qi, Dan; You, Guojian; Shen, Wei; Li, Ming; He, Rongxing

    2014-09-28

    The S0 → S1 (Q band) high-resolved absorption spectra of three porphyrin-like compounds, porphycene, magnesium porphyrin, and zinc tetraazaporphyrin, were simulated in the framework of the Franck-Condon approximation including the Duschinsky and Herzberg-Teller (HT) contributions. Substitution of meso-aza on porphyrin macrocycle framework could change severely the absorption energy, vibrational intensity, and spectral profile of Q band. Therefore, we focused attention on the spectral similarities and contrasts among the three compounds based on the density functional theory and its time-dependent extension calculations. The simulated spectra agreed well with the experimental ones and further confirmed that the HT and Duschinsky effects have significant influence on the weakly allowed or forbidden transition of sizable organic molecules. The pure HT and Duschinsky effects were explored separately to clarify their contributions on changing vibrational intensities of different modes. Moreover, we tentatively assigned most of the vibrational modes which appeared in the experimental spectra but corresponding assignments were not given. The present work provided a useful method to simulate and interpret the absorption spectra of porphyrin-like compounds. PMID:25273434

  18. XAS spectroelectrochemistry: reliable measurement of X-ray absorption spectra from redox manipulated solutions at room temperature.

    Best, Stephen P; Levina, Aviva; Glover, Chris; Johannessen, Bernt; Kappen, Peter; Lay, Peter A

    2016-05-01

    The design and operation of a low-volume spectroelectrochemical cell for X-ray absorption spectroscopy (XAS) of solutions at room temperature is described. Fluorescence XAS measurements are obtained from samples contained in the void space of a 50 µL reticulated vitreous carbon (sponge) working electrode. Both rapid electrosynthesis and control of the effects of photoreduction are achieved by control over the flow properties of the solution through the working electrode, where a good balance between the rate of consumption of sample and the minimization of decomposition was obtained by pulsing the flow of the solution by 1-2 µL with duty cycle of ∼3 s while maintaining a small net flow rate (26-100 µL h(-1)). The performance of the cell in terms of control of the redox state of the sample and minimization of the effects of photoreduction was demonstrated by XAS measurements of aqueous solutions of the photosensitive Fe(III) species, [Fe(C2O4)3](3-), together with that of the electrogenerated [Fe(C2O4)3](4-) product. The current response from the cell during the collection of XAS spectra provides an independent measure of the stability of the sample of the measurement. The suitability of the approach for the study of small volumes of mM concentrations of protein samples was demonstrated by the measurement of the oxidized and electrochemically reduced forms of cytochrome c. PMID:27140154

  19. S{sub 0} {yields} S{sub n} and S{sub 1} {yields} S{sub n} absorption spectra of thio-distyrylbenzenes

    Baraldi, Ivan [Dipartimento di Chimica, Universita di Modena e Reggio Emilia, 41100 Modena (Italy)], E-mail: baraldi.ivan@unimore.it; Ginocchietti, Gabriella; Mazzucato, Ugo [Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati (CEMIN), Universita di Perugia, 06123 Perugia (Italy); Spalletti, Anna [Dipartimento di Chimica and Centro di Eccellenza Materiali Innovativi Nanostrutturati (CEMIN), Universita di Perugia, 06123 Perugia (Italy)], E-mail: faby@unipg.it

    2007-08-16

    The molecular structures and the S{sub 0} {yields} S{sub n} and S{sub 1} {yields} S{sub n} absorption spectra of 1,4-distyrylbenzene and four thio-analogues, where the side phenyl rings are replaced by 2'-thienyl or 3'-thienyl groups and the central benzene ring is replaced by a 2,5-disubstituted thiophene ring, have been investigated by a combined theoretical and experimental approach. The rotational isomerism of these flexible molecules has been analyzed by ab initio quantum chemistry methodologies. The S{sub 0} {yields} S{sub n} one-photon absorption spectra and the S{sub 1} {yields} S{sub n} transient spectra have been calculated using the CS INDO S-CI and SDT-CI procedures. The calculations on conformational isomers indicate that the stable molecular structures are those where the quasi-single bonds of the vinylene groups have almost planar s-trans configuration. In the 1,4-compounds, there may be an equilibrium between two molecular forms of C{sub 2h} and C{sub 2v} symmetry in the model of planar conformations. As concerns the UV-vis absorption spectra, the importance of the cis band, as probe to investigate the molecular structure of the 2,5-compounds, has been pointed out, and the presence of an equilibrium between two rotamers in the compound bearing side 3'-thienyl groups has been confirmed. The S{sub 1} {yields} S{sub n} absorption spectra are interpretable only with configuration interaction calculations including the multiple excited configurations. In this respect, the role played by the H{sup 2} {yields} L{sup 2} double excitation has been emphasized.

  20. Assignment of near-edge x-ray absorption fine structure spectra of metalloporphyrins by means of time-dependent density-functional calculations

    Schmidt, Norman; Fink, Rainer; Hieringer, Wolfgang

    2010-08-01

    The C 1s and N 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of three prototype tetraphenyl porphyrin (TPP) molecules are discussed in the framework of a combined experimental and theoretical study. We employ time-dependent density-functional theory (TDDFT) to compute the NEXAFS spectra of the open- and closed-shell metalloporphyrins CoTPP and ZnTPP as well as the free-base 2HTPP in realistic nonplanar conformations. Using Becke's well-known half-and-half hybrid functional, the computed core excitation spectra are mostly in good agreement with the experimental data in the low-energy region below the appropriate ionization threshold. To make these calculations feasible, we apply a new, simple scheme based on TDDFT using a modified single-particle input spectrum. This scheme is very easy to implement in standard codes and allows one to compute core excitation spectra at a similar cost as ordinary UV/vis spectra even for larger molecules. We employ these calculations for a detailed assignment of the NEXAFS spectra including subtle shifts in certain peaks of the N 1s spectra, which depend on the central coordination of the TPP ligand. We furthermore assign the observed NEXAFS resonances to the individual molecular subunits of the investigated TPP molecules.

  1. Comment on "Limits on the Time Variation of the Electromagnetic Fine-Structure Constant in the Low Energy Limit from Absorption Lines in the Spectra of Distant Quasars"

    Murphy, Michael T; Flambaum, Victor V

    2007-01-01

    In their Letter [Phys. Rev. Lett. 92, 121302 (2004)] (also [Astron. Astrophys. 417, 853 (2004)]), Srianand et al. analysed optical spectra of heavy-element species in 23 absorption systems along background quasar sight-lines, reporting limits on relative variations in the fine-structure constant: da/a=(-0.06+/-0.06) x 10^{-5}. Here we demonstrate basic flaws in their analysis, using the same data and absorption profile fits, which led to spurious values of da/a and significantly underestimated uncertainties. We conclude that these data and fits offer no stringent test of previous evidence for a varying alpha.

  2. UV-VIS absorption spectra of molten AgCl and AgBr and of their mixtures with group I and II halide salts

    Greening, Giorgio G.W. [Technische Universitaet Darmstadt (Germany). Eduard-Zintl-Institut fuer Anorganische und Physikalische Chemie

    2015-07-01

    The UV-VIS absorption spectra of (Ag{sub 1-X}[Li-Cs, Ba]{sub X})Cl and of (Ag{sub 1-X}[Na, K, Cs]{sub X})Br at 823 K at the concentrations X=0.0, 0.1, 0.2 have been measured. The findings show that on adding the respective halides to molten silver chloride and silver bromide, shifts of the fundamental absorption edge to shorter wavelengths result. A correlation between the observed shifts and the expansion of the silver sub-lattice is found, which is valid for both silver halide systems studied in this work.

  3. Evaluation on radiation features of the KUR deuterium neutron irradiation equipment. Neutron energy spectra and neutron- and gamma-ray absorption dose rate

    The deuterium irradiation equipment at reactor for research in Kyoto University (KUR) was reformed at main aim of upgrading of neutron capture therapy (NCT) from November, 1995 to March, 1996. Neutron energy spectra at reference radiation position evaluated on a partial radiation mode by multiple activated foil method, was introduced. As a result of carrying out a simulation calculation using two dimensional transmission calculation supposing medical radiation using the obtained spectra, experimental results could be followed satisfactorily in total. And, comparison with differential absorption dose rate measured by using twin-type ionization box and semiconductor detector for medical probe was also carried out. (G.K.)

  4. FIRST ULTRAVIOLET REFLECTANCE SPECTRA OF PLUTO AND CHARON BY THE HUBBLE SPACE TELESCOPE COSMIC ORIGINS SPECTROGRAPH: DETECTION OF ABSORPTION FEATURES AND EVIDENCE FOR TEMPORAL CHANGE

    We have observed the mid-UV spectra of both Pluto and its large satellite, Charon, at two rotational epochs using the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) in 2010. These are the first HST/COS measurements of Pluto and Charon. Here we describe the observations and our reduction of them, and present the albedo spectra, average mid-UV albedos, and albedo slopes we derive from these data. These data reveal evidence for a strong absorption feature in the mid-UV spectrum of Pluto; evidence for temporal change in Pluto's spectrum since the 1990s is reported, and indirect evidence for a near-UV spectral absorption on Charon is also reported.

  5. Synthesis and investigation of solvent effects on the ultraviolet absorption spectra of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones

    NATASA V. VALENTIC

    2001-08-01

    Full Text Available A number of 5-substituted-4-methyl-3-cyano-6-hydroxy-2-pyridones from cyanoacetamide and the corresponding alkyl ethyl acetoacetates were synthesized according to modified literature procedures. The alkyl ethyl acetoacetates were obtained by the reaction of C-alkylation of ethyl acetoacetate. An investigation of the reaction conditions for the synthesis of 4-methyl-3-cyano-6-hydroxy-2-pyridone from cyanoacetamide and ethyl acetoacetate in eight different solvents was also performed. The ultraviolet absorption spectra of synthesized pyridones were measured in nine different solvents in the range 200–400 nm. The effects of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of linear solvation energy relationships using a general equation of the form n = n0 + sp* + aa + bb, where p* is a measure of the solvent polarity, a is the scale of the solvent hydrogen bond donor acidities and b is the scale of the solvent hydrogen bond acceptor basicities.

  6. Difference in effect of temperature on absorption and Raman spectra between all-trans-β-carotene and all-trans-retinol

    Qu Guan-Nan; Li Zuo-Wei; Gao Shu-Qin; Li Shuo; Sun Cheng-Lin; Liu Tian-Yuan; Wu Yong-Ling; Sun Shang; Shan Xiao-Ning; Men Zhi-Wei; Chen Wei

    2012-01-01

    Temperature dependencies (81 ℃-18 ℃) of visible absorption and Raman spectra of all-trans-β-carotene and all-trans-retinol extremely diluted in dimethyl sulfoxide are investigated in order to clarify temperature effects on different polyenes.Their absorption spectra are identified to be redshifted with temperature decreasing.Moreover,all-trans-β-carotene is more sensitive to temperature due to the presence of a longer length of conjugated system.The characteristic energy responsible for the conformational changes in all-trans-β-carotene is smaller than that in all-trans-retinol.Both of the Raman scattering cross sections increase with temperature decreasing.The results are explained with electron-phonon coupling theory and coherent weakly damped electron-lattice vibrations model.

  7. Ultraviolet Absorption Spectra, AB Initio Calculations, and Carbonyl Wagging Potential Energy Functions of Cyclobutanone, Cyclopentanone, BICYCLO[3.1.0]HEXAN-3-ONE, and TETRAHYDROFURAN-3-ONE

    Lee, Soono; Dakkouri, Marwan; Choo, Jaebum; Laane, Jaan

    2000-03-01

    The electronic absorption spectra of cyclobutanone, cyclopentanone, bicyclo[3.1.0]hexan-3-one, and tetrahydrofuran-3-one were recorded and analyzed in the 28,000 - 44,000 cm-1 region. Several dozen absorption bands were assigned for each molecule. These arise from combinations of the ring vibrations and the C=O wagging vibrations. Assigned bands were compared with previously recorded jet-cooled fluorescence excitation spectra. Additional C=O out-of-plane wagging bands were found for cyclopentanone and tetrahydrofuran-3-one, and the potential energy functions for this vibration in these molecules were recalculated. These potential energy functions have barriers to inversion reflecting the fact that the carbonyl group is bent out of the ring plane in the S1(n, π*) excited electronic state.

  8. Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

    Jin Zhu; Wenbin Li; Mao Zhu; Wei Zhang; Wencheng Niu; Guohua Liu

    2014-01-01

    The localized surface plasmon resonances (LSPRs) of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3°) crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis) spec...

  9. Absorption spectra of 4f electron transitions of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid and diethylamine systems and its analytical application

    In this paper the absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid and diethylamine have been studied by normal and third-derivative spectrophotometry. Their molar absorptivities are 80 1.mol-1.cm-1 for neodymium and 65 1.mol-1.cm-1 for erbium. Use of the third-derivative spectra, eliminates the interference by other rare earths and increases the sensitivity for Nd and Er. The derivative molar absorptivities are 390 1.mol-1.cm-1 for Nd and 367 1.mol-1.cm-1 for Er. The calibration graphs were linear up to 11.8 μg/ml of Nd and 12.3 μg/ml of Er, respectively. The relative standard deviations evaluated from eleven independent determinations of 7.2 μg/ml (for Nd) and 8.3 μg/ml (for Er) are 1.3% and 1.4%, respectively. The detection limits are 0.2 μg/ml for Nd and 0.3 μg/ml for Er. The method has been developed for determining those two elements in mixture of lanthanides by means of the third-derivative spectra and the analytical results obtained are satisfactory

  10. Low temperature laser absorption spectra of methane in the near-infrared at 1.65 μm for lower state energy determination

    Gao Wei; Chen Wei-Dong; Zhang Wei-Jun; Yuan Yi-Qian; Gao Xiao-Ming

    2012-01-01

    Direct absorption spectra of the 2v3 band of methane (CH4) from 6038 to 6050 cm-1 were studied at different low temperatures using a newly developed cryogenic cell in combination with a distributed feedback (DFB) diode laser.The cryogenic cell can operate at any stabilized temperature ranging from room temperature down to 100 K with temperature fluctuation less than ±l K within 1 hour.In the present work,the CH4 spectra in the range of 6038-6050 cm-1 were recorded at 296,266,248,223,198,and 176 K.The lower state energy E" and the rotational assignment of the angular momentum J were determined by a “2-low-temperature spectra method” using the spectra recorded at 198 and 176 K.The results were compared with the data from the GOSAT and the recently reported results from Campargue and co-workers using two spectra measured at room temperature and 81 K.We demonstrated that the use of a 2-low-temperature spectra method permits one to complete the E" and J values missed in the previous studies.

  11. Low temperature laser absorption spectra of methane in the near-infrared at 1.65 μm for lower state energy determination

    Direct absorption spectra of the 2ν3 band of methane (CH4) from 6038 to 6050 cm−1 were studied at different low temperatures using a newly developed cryogenic cell in combination with a distributed feedback (DFB) diode laser. The cryogenic cell can operate at any stabilized temperature ranging from room temperature down to 100 K with temperature fluctuation less than ±1 K within 1 hour. In the present work, the CH4 spectra in the range of 6038–6050 cm−1 were recorded at 296, 266, 248, 223, 198, and 176 K. The lower state energy E″ and the rotational assignment of the angular momentum J were determined by a “2-low-temperature spectra method” using the spectra recorded at 198 and 176 K. The results were compared with the data from the GOSAT and the recently reported results from Campargue and co-workers using two spectra measured at room temperature and 81 K. We demonstrated that the use of a 2-low-temperature spectra method permits one to complete the E″ and J values missed in the previous studies. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  12. Reflectance, absorptance and transmittance spectra on sunflower (Helianthus annuus L.) as related to their metabolic age and stem position. Pt.2

    The results of a research carried out in order to study the reflectance, absorptance and transmittance spectra of sunflower leaves as related to their stem position are reported. Two sunflower hybrids, which differed for growth habitus (''Monica'', with low size, and ''Hysun-32'' with normal size) were used. Reflectance, absorptance and transmittance spectra were measured in vivo when the plants were in the phases of appearance of inflorescence and anthesis. The measures were taken with a portable spectroradiometer with an external integrating sphere. The radiation over the wavelength range from 400 to 1,100 mm was measured at intervals of 1 mm. Absorptance was calculated. The results have evidenced that leaf position, related to its metabolic age, influence the capacity of reflecting, absorbing and transmitting the radiation in the photosynthetically active region. In the PAR region the variations are different with the spectral band considered. The leaves in medium-high position, as compared to the top and bottom leaves, have lower reflectance and transmittance values and higher absorptance values. No difference emerged in the near infrared region

  13. The mystery of spectral breaks: Lyman continuum absorption by photon-photon pair production in the Fermi GeV spectra of bright blazars

    Stern, Boris E

    2014-01-01

    We reanalyze Fermi/LAT gamma-ray spectra of bright blazars with a higher photon statistics than in previous works and with new Pass 7 data representation. In the spectra of the brightest blazar 3C 454.3 and possibly of 4C +21.35 we detect breaks at 5 GeV (in the rest frame) associated with the photon-photon pair production absorption by He II Lyman continuum (LyC). We also detect confident breaks at 20 GeV associated with hydrogen LyC both in the individual spectra and in the stacked redshift-corrected spectrum of several bright blazars. The detected breaks in the stacked spectra univocally prove that they are associated with atomic ultraviolet emission features of the quasar broad-line region (BLR). The dominance of the absorption by hydrogen Ly complex over He II, rather small detected optical depth, and the break energy consistent with the head-on collisions with LyC photons imply that the gamma-ray emission site is located within the BLR, but most of the BLR emission comes from a flat disk-like structure ...

  14. The mystery of spectral breaks: Lyman continuum absorption by photon-photon pair production in the Fermi GeV spectra of bright blazars

    We re-analyze Fermi/LAT γ-ray spectra of bright blazars using the new Pass 7 version of the detector response files and detect breaks at ∼5 GeV in the rest-frame spectra of 3C 454.3 and possibly also 4C +21.35, associated with the photon-photon pair production absorption by the He II Lyman continuum (LyC). We also detect significant breaks at ∼20 GeV associated with hydrogen LyC in both the individual spectra and the stacked redshift-corrected spectrum of several bright blazars. The detected breaks in the stacked spectra univocally prove that they are associated with atomic ultraviolet emission features of the quasar broad-line region (BLR). The dominance of the absorption by the hydrogen Ly complex over He II, a small detected optical depth, and break energy consistent with head-on collisions with LyC photons imply that the γ-ray emission site is located within the BLR, but most of the BLR emission comes from a flat disk-like structure producing little opacity. Alternatively, the LyC emission region size might be larger than the BLR size measured from reverberation mapping, and/or the γ-ray emitting region is extended. These solutions would resolve the long-standing issue of how the multi-hundred GeV photons can escape from the emission zone without being absorbed by softer photons.

  15. Infrared Measurements of Atmospheric Ethane (C2H6) From Aircraft and Ground-Based Solar Absorption Spectra in the 3000/ cm Region

    Coffey, M. T.; Mankin, W. G.; Goldman, A.; Rinsland, C. P.; Harvey, G. A.; Devi, V. Malathy; Stokes, G. M.

    1985-01-01

    A number or prominent Q-branches or the upsilon(sub 7) band or C2H6 have been identified near 3000/ cm in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The, ground-based spectra yield a column of 9.0 x 10(exp 15) molecules/sq cm above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv.

  16. Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

    Majzlan, Juraj; Alpers, Charles N.; Bender Koch, Christian; McCleskey, R. Blaine; Myneni, Satish B.C.; Neil, John M.

    2011-01-01

    The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and M??ssbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe2O3/FeO): szomolnokite, rozenite, siderotil, halotrichite, r??merite, voltaite, copiapite, monoclinic Fe2(SO4)3, Fe2(SO4)3??5H2O, kornelite, coquimbite, Fe(SO4)(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750-4000cm-1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe3+ octahedra and sulfate tetrahedra. M??ssbauer spectra of selected samples were obtained at room temperature and 80K for ferric minerals jarosite and rhomboclase and mixed ferric-ferrous minerals r??merite, voltaite, and copiapite. Values of Fe2+/[Fe2++Fe3+] determined by M??ssbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases. ?? 2011 Elsevier B.V.

  17. Atomic Transition Frequencies, Isotope Shifts, and Sensitivity to Variation of the Fine Structure Constant for Studies of Quasar Absorption Spectra

    Berengut, J. C.; Dzuba, V. A.; Flambaum, V. V.; King, J. A.; Kozlov, M. G.; Murphy, M. T.; Webb, J. K.

    Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, α = {e}2/hslash c , could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that α varies spatially (61). That is, in one direction on the sky α seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger.

  18. UV-visible and infrared absorption spectra of Bi2O3 in lithium phosphate glasses and effect of gamma irradiation

    Ultraviolet and visible absorption spectra of prepared undoped lithium phosphate glass and samples of the same nominal composition with additional Bi2O3 contents were measured before and after being subjected to gamma doses of 3 and 6 Mrad. The base undoped lithium phosphate glass exhibits strong charge transfer ultraviolet absorption bands, which are related to unavoidable presence of trace iron impurities within the raw materials for the preparation of this glass. Bi2O3-containing glasses show the extension of UV absorption beside the resolution of visible bands at 400, 450, and 700 nm with the increase of Bi2O3 content due the sharing of absorption of Bi3+ ions. Gamma irradiation of the base glass reveals extended induced bands; the UV bands are related to the conversion of some Fe2+ to Fe3+ through photochemical reactions during the irradiation process. The visible induced bands are related to the formation of positive hole centers from the host phosphate glass. Glasses containing Bi2O3 are observed to show some shielding behavior, which is attributed to the presence of heavy weight and large atomic number of Bi3+ ions. Infrared absorption spectral measurements of the base lithium phosphate glass show characteristic vibrational modes which are related to specific phosphate groups. The addition of Bi2O3 in measurable percent produces additional vibrational bands due to the introduction of Bi-O groups such as BiO3 and BiO6. (orig.)

  19. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi [Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo 184-8588 (Japan); Fujii, Kentaro; Yokoya, Akinari [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Fukuda, Yoshihiro; Saitoh, Yuji [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Sayo-gun, Hyougo 679-5148 (Japan)

    2014-08-07

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5{sup ′}-monophosphate, and adenosine 5{sup ′}-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  20. Effects of solvent polarity on the absorption and fluorescence spectra of chlorogenic acid and caffeic acid compounds: determination of the dipole moments.

    Belay, Abebe; Libnedengel, Ermias; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2016-02-01

    The effects of solvent polarity on absorption and fluorescence spectra of biologically active compounds (chlorogenic acid (CGA) and caffeic acids (CA)) have been investigated. In both spectra pronounced solvatochromic effects were observed with shift of emission peaks larger than the corresponding UV-vis electronic absorption spectra. From solvatochromic theory the ground and excited-state dipole moments were determined experimentally and theoretically. The differences between the excited and ground state dipole moment determined by Bakhshiev, Kawski-Chamma-Viallet and Reichardt equations are quite similar. The ground and excited-state dipole moments were determined by theoretical quantum chemical calculation using density function theory (DFT) method (Gaussian 09) and were also similar to the experimental results. The HOMO-LUMO energy band gaps for CGA and CFA were calculated and found to be 4.1119 and 1.8732 eV respectively. The results also indicated the CGA molecule is more stable than that of CFA. It was also observed that in both compounds the excited state possesses a higher dipole moment than that of the ground state. This confirms that the excited state of the hydroxycinnamic compounds is more polarized than that of the ground state and therefore is more sensitive to the solvent. PMID:25991491

  1. Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

    Sun Dunlu [Crystal Lab, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shushanhu Road 350, PO Box 1125, Hefei, Anhui 230031 (China); Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, Aveiro 3810-193 (Portugal)], E-mail: dlsun@aiofm.ac.cn; Luo Jianqiao; Zhang Qingli [Crystal Lab, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shushanhu Road 350, PO Box 1125, Hefei, Anhui 230031 (China); Xiao Jingzhong [Department of Ceramics and Glass Engineering, CICECO, University of Aveiro, Aveiro 3810-193 (Portugal); Xu Jiayue [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Jiang Haihe; Yin Shaotang [Crystal Lab, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shushanhu Road 350, PO Box 1125, Hefei, Anhui 230031 (China)

    2008-12-15

    Laser crystals Nd{sup 3+}:Gd{sub 3}Ga{sub 5}O{sub 12} (Nd:GGG) and Nd{sup 3+}:Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12} (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space.

  2. Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

    Laser crystals Nd3+:Gd3Ga5O12 (Nd:GGG) and Nd3+:Gd3Sc2Ga3O12 (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space

  3. Theoretical calculations of X-ray absorption spectra of a copper mixed ligand complex using computer code FEFF9

    The terms X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) refer, respectively, to the structure in the X-ray absorption spectrum at low and high energies relative to the absorption edge. Routine analysis of EXAFS experiments generally makes use of simplified models and several many-body parameters, e.g. mean free paths, many-body amplitude factors, and Debye-Waller factors, as incorporated in EXAFS analysis software packages like IFEFFIT which includes Artemis. Similar considerations apply to XANES, where the agreement between theory and experiment is often less satisfactory. The recently available computer code FEFF9 uses the real-space Green's function (RSGF) approach to calculate dielectric response over a broad spectrum including the dominant low-energy region. This code includes improved treatments of many-body effects such as inelastic losses, core-hole effects, vibrational amplitudes, and the extension to full spectrum calculations of optical constants including solid state effects. In the present work, using FEFF9, we have calculated the X-ray absorption spectrum at the K-edge of copper in a complex, viz., aqua (diethylenetriamine) (isonicotinato) copper(II), the crystal structure of which is unknown. The theoretical spectrum has been compared with the experimental spectrum, recorded by us at the XAFS beamline 11.1 at ELETTRA synchrotron source, Italy, in both XANES and EXAFS regions.

  4. Investigation of Lyman-limit absorption in QSO spectra - indirect evidence for evolution of the multicomponent nature of the absorbers

    This paper reexamines the redshift distribution of the class of QSO absorption-line systems that are optically-thick to Lyman continuum radiation (i.e., the Lyman-limit systems LLS), using a sample of 129 QSOs for which suitable data are available. It was found that the LLSs are uniformly distributed in velocity, relative to the background QSOs, and that the rate of incidence of the systems does not strongly evolve with redshift; the observed redshift distribution is consistent with nonevolving absorbers in a standard Friedmann cosmology with the deceleration parameter equal to 0.5. The reason for the discrepancy of this finding with data published on systems selected on the basis of Mg II absorption is discussed. It is suggested that the number of separate velocity components comprising the Mg II absorption lines decreases with time. 63 references

  5. Investigation of Lyman-limit absorption in QSO spectra - indirect evidence for evolution of the multicomponent nature of the absorbers

    Lanzetta, K.M.

    1988-09-01

    This paper reexamines the redshift distribution of the class of QSO absorption-line systems that are optically-thick to Lyman continuum radiation (i.e., the Lyman-limit systems LLS), using a sample of 129 QSOs for which suitable data are available. It was found that the LLSs are uniformly distributed in velocity, relative to the background QSOs, and that the rate of incidence of the systems does not strongly evolve with redshift; the observed redshift distribution is consistent with nonevolving absorbers in a standard Friedmann cosmology with the deceleration parameter equal to 0.5. The reason for the discrepancy of this finding with data published on systems selected on the basis of Mg II absorption is discussed. It is suggested that the number of separate velocity components comprising the Mg II absorption lines decreases with time. 63 references.

  6. Detected CFCs: UV Absorption Spectra, Atmospheric Lifetimes, Global Warming and Ozone Depletion Potentials for CFC-112, CFC-112a, CFC-113a and CFC-114a

    Bernard, F.; Davis, M. E.; McGillen, M.; Fleming, E. L.; Burkholder, J. B.

    2015-12-01

    Chlorofluorocarbons (CFCs) are ozone depleting substances (ODSs) and potent greenhouse gases. Measurements have observed CFC-112 (CFCl2CFCl2), CFC-112a (CF2ClCCl3), and CFC-113a (CCl3CF3) in the atmosphere (Laube et al., 2014). The current atmospheric abundances of CFC-112 and CFC-112a are ~0.4 and ~0.06 ppt, respectively, with decreasing abundance since 1995. In contrast, CFC-113a was found to show continuous growth over the past 50 years with a current atmospheric abundance of ~0.5 ppt. The major atmospheric removal process for these compounds is expected to be UV photolysis in the stratosphere. To date there is, however, no UV absorption spectra for these compounds available in the literature. To better determine the atmospheric lifetimes and environmental impact of these CFCs, laboratory measurements of the UV absorption spectra of CFC-112, CFC-112a, CFC-113a, and CFC-114a (Cl2FCF3) between 195 and 235 nm and over the temperature range 207 to 323 K were performed. Spectrum parametrizations were developed for use in atmospheric models. Atmospheric lifetimes and ozone depletion potentials (ODPs) were calculated using the Goddard Space Flight Center 2-D atmospheric chemistry model. Infrared absorption spectra of these compounds were also measured and used to calculate their global warming potentials. The results of the laboratory measurements and model calculations will be presented. J. C. Laube et al., Newly detected ozone-depleting substances in the atmosphere, Nature Geoscience, 7, 266-269, 2014

  7. Two-stage laser burning of stable holes in absorption spectra of organic molecules. 2. Perylene in boric acid

    Frequency-selective two-stage hole burning in the absorption spectrum of perylene in boric acid is detected and investigated at helium temperatures. A pulsed dye laser whose radiation frequency corresponded to the frequency of the 0--0 transition of perylene was used to achieve two-stage excitation by the singlet level system. The photochemical reaction responsible for the burning effect is two-quantum photoionization. The absorption spectrum of the photochemical product---the perylene cation-radical---was recorded. The photochemical reaction is irreversible. According to estimates the quantum efficiency of the burning process in the second excitation stage is ∼0.1--1

  8. X-ray Absorption Spectra Analysis for the Investigation of the Retardation Mechanism of Iodine Migration by the Silver Ion Added to Bentonite

    Most of iodine was captured by the block when NaI solution flowed through a bentonite block sorbed silver to retard the migration of iodine released from high-level radioactive wastes. In order to understand in detail the mechanism for the retardation of the iodine by the silver ion, X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra of the silver sorbed bentonite before and after the contact with iodide were compared with those of AgO, Ag2O and AgI as references. This examination suggests that the silver ion sorbed on the bentonite is desorbed, and then it retards the migration of iodine by forming the cluster of AgI precipitate

  9. Absorption spectra of CsNd(MoO4)2 and CsGd(MoO4)2-Nd3+ crystals in strong magnetic fields

    The comparison of the electronic structure of Nd3+ in CsNd(MoO4)2 and CsGd(MoO4)2 - Nd3+ crystals is made. It is established that in these crystals the activator centers, mainly, of the certain type with the symmetry of the local environment C2 are formed. The absorption spectra of self-activated CsNd(MoO4)2 crystal differ from spectra of CsGd(MoO4)2 - Nd3+ by the presence of the vibrating structure. The Stark splittings of energy levels of Nd3+ in the investigated crystalline matrices are more sensitive to the environment effect than the Zeeman ones. The ground state of Nd3+ ion in CsNd(MoO4)2 and CsGd(MoO4)2 molybdates is characterized by the similar values of g-factors

  10. A reflectance spectra model of heavy metal stressed leaves: advances in the PROSPECT model adding specific absorption coefficients of heavy metal ion

    This article aims to investigate the reflectance model of heavy metal copper stressed crop. Forty-six groups of copper-treated leaves were measured during a laboratory experiment in order to obtain the leaf biochemical component information and its corresponding scanning electron microscopy image. Then a new reflectance spectral model was developed on the basis of the classical broadleaf radiative transfer model-PROSPECT. Comparing with the PROSPECT model, new models mainly consider adding specific absorption coefficient of copper ion. The scattering process is described by a refractive index (n) and a leaf structure parameter (N). Absorption is modeled using pigment concentration, water content, dry matter content, copper ion contamination and the corresponding specific spectral absorption coefficients (Kab, Kw, Kd, KCu). Thus, reflectance spectral modeling is an inversion procedure to calculate the above 6 parameters accurately. To validate the model 16 leaves were tested in laboratory experiment. This experiment showed that the inversion values of KCu had very strong agreement with the published absorption spectra of Cupric Chloride. The linear regression analysis between simulated and measured reflectance provides a correlation coefficient of 0.93 and a root mean squares of 0.067

  11. Excited state dipole moments of chloroanilines and chlorophenols from solvatochromic shifts in electronic absorption spectra: Support for the concept of excited state group moments

    Prabhumirashi, L. S.; Satpute, R. S.

    The dipole moments of isomeric o-, m- and p-chloroanilines and chlorophenols in electronically excited L a and L b states are estimated from solvent induced polarization shifts in electronic absorption spectra. It is observed that μ e( L a) > μ e( L b) > μ g, which is consistent with the general theory of polarization red shift. The μ es are found to be approximately co-linear with the corresponding μ gs. The concept of group moments is extended to aromatic molecules in excited states. This approach is found to be useful in understanding correlations among the excited states of mono- and disubstituted benzenes.

  12. Thermal bleaching of optical absorption and photoluminescence spectra of γ-irradiated CaF_2:Dy:Pb:Na single crystals

    S.M.; Moses; Kennedy

    2010-01-01

    The variation of the optical absorption (OA) and photoluminescence (PL) spectra with temperature was studied on γ-irradiated CaF2:Dy:Pb:Na single crystals. The OA spectrum showed bands around 2.05, 3.20, 3.82 and 6.20 eV which could be attributed to different sodium associated (SA) colour centres (CCs) such as MNa and RA+ . Heating the crystal indicated the annihilation and formation of different SACCs. The excitation spectrum for the characteristic Dy3+ emission at 2.14 eV immediately after irradiation was...

  13. Modification of the gamma-ray spectra by internal absorption in OVV blazars: The example cases of 3C 273 and 3C 279

    Sitarek, J.; Bednarek, W.

    2008-01-01

    Recent observations with the low threshold Cherenkov telescopes proved that sub-TeV gamma-rays are able to arrive from active galaxies at relatively large distances in spite of expected severe absorption in the extragalactic background light (EBL). We calculate the gamma-ray spectra at TeV energies from two example OVV quasars, 3C 273 and 3C 279, assuming that gamma-rays are injected in the inner parts of the jets launched by the accretion disks. It is assumed that gamma-rays in the broad ene...

  14. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies.

    El-Shishtawy, Reda M; Elroby, Shaaban A; Asiri, Abdullah M; Müllen, Klaus

    2016-01-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1-SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (-4.26 eV) of the conduction band of TiO₂ nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO₂ in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices. PMID:27043556

  15. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies

    Reda M. El-Shishtawy

    2016-04-01

    Full Text Available The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1–SQD4 were investigated using density functional theory (DFT and time-dependent (TD-DFT density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0, and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (−4.26 eV of the conduction band of TiO2 nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO2 in dye-sensitized solar cells (DSSCs. Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices.

  16. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI−)), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI− although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm−1 agrees well with the experimental measurement

  17. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach

    Ma, HuiLi; Zhao, Yi; Liang, WanZhen

    2014-03-01

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI-)), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI- although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm-1 agrees well with the experimental measurement.

  18. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach

    Ma, HuiLi [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Institute of Fujian Provincial Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Zhao, Yi; Liang, WanZhen, E-mail: liangwz@xmu.edu.cn [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Institute of Fujian Provincial Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)

    2014-03-07

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI{sup −})), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI{sup −} although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm{sup −1} agrees well with the experimental measurement.

  19. Collision-Induced Absorption Spectra of Binary Mixtures of Molecular Hydrogen with Molecular Deuterium and Argon and of Pure Hydrogen, D

    Hsieh, Chang-Tsang William

    In the present research project a systematic study of the collision-induced infrared absorption (CIA) spectra of the binary mixtures of H_2 - D_2 in the region of the double fundamental vibrations of H_2 and D_2, and H_2 - Ar in the fundamental band of H_2, and of pure HD in its fundamental and first overtone regions was undertaken. The experiments were carried out with a 2.0 m high-pressure low-temperature transmission-type absorption cell at 77, 201 and 296 K at total gas densities up to 550 amagat. Infrared prism and grating spectrometers equipped with a microprocessor -controlled stepping motor were used to record the spectra. All the experimental results obtained represent first-time observations in collision-induced absorption. Collision-induced infrared absorption spectra of the double transitions of H_2(v=1>=ts 0) and D_2(v=1>=ts 0) have been observed at 77 and 201 K in the spectral region 7000-8000 cm^{-1} for total gas densities up to 550 amagat with a partial gas density ratio of 1:1 of H_2 and D_2. The observed spectra are interpreted in terms of the transitions, Q_1(J) of H_2+Q_1(J) of D _2, Q_1(J) of H_2+S _1(J) of D_2, S_1(J) of H_2 + Q_1(J) of D_2, and S_1(J) of H_2 + S_1(J) of D_2 for J = 0 and 1 for H _2 and J = 0, 1, and 2 for D_2. Analysis of the experimental absorption profiles was carried out using appropriate lineshape functions. The absorption coefficients, lineshape parameters, etc., are obtained from the analysis. Collision-induced enhancement absorption spectra of the fundamental band of H_2 in H_2 - Ar mixtures were recorded at room temperature for a base density of 72 amagat of H_2 for several partial densities of Ar up to 440 amagat. Hexadecapole-induced U transitions, U_1(1), U_1(2), Q_1(0)+U _0(1), and Q_1(1) + U_0(1) have been identified in the spectral region 5400 -6200 cm^{-1}. A "cage" model has been proposed to account for the double transitions of H_2 - H_2 in the H _2 - Ar enhancement spectra. From the analysis of the

  20. Excitations, optical absorption spectra, and optical excitonic gaps of heterofullerenes: I. C60, C59N+ and C48N12

    Xie, R; Bryant, G W; Sun, G; C.Nicklaus, M; Heringer, D; Frauenheim, T; Manaa, M R; Smith, Jr., V H; Araki, Y; Ito, O

    2003-10-02

    Low-energy excitations and optical absorption spectrum of C{sub 60} are computed by using time-dependent (TD) Hartree-Fock (HF), TD-density functional theory (TD-DFT), TD-DFT-based tight-binding (TD-DFT-TB) and a semiempirical ZINDO method. A detailed comparison of experiment and theory for the excitation energies, optical gap and absorption spectrum of C{sub 60} is presented. It is found that electron correlations and collective effects of exciton pairs play important roles in assigning accurately the spectral features of C{sub 60} and the TD-DFT method with non-hybrid functionals or a local spin density approximation leads to more accurate excitation energies than with hybrid functionals. The level of agreement between theory and experiment for C{sub 60} justifies similar calculations of the excitations and optical absorption spectrum of a monomeric azafullerene cation C{sub 59}N{sup +} exhibits distinguishing spectral features different from C{sub 60}: (1) the first singlet is dipole-allowed and the optical gap is redshifted by 1.44 eV; (2) several weaker absorption maxima occur in the visible region; (3) the transient triplet-triplet absorption at 1.60 eV (775 nm) is much broader and the decay of the triplet state is much faster. The calculated spectra of C{sub 59}N{sup +} characterize and explain well our measured ultraviolet-visible (UV-vis) and transient absorption spectra of the carborane anion salt [C{sub 59}N][Ag(CB{sub 11}H{sub 6}Cl{sub 6}){sub 2}]. For the most stable isomer of C{sub 48}N{sub 12}, we predict that the first singlet is dipole-allowed, the optical gap is redshifted by 1.22 eV relative to that of C{sub 60}, and optical absorption maxima occur at 585, 528, 443, 363, 340, 314 and 303 nm. We point out that the characterization of the UV-vis and transient absorption spectra of C{sub 48}N{sub 12} isomers is helpful in distinguishing the isomer structures required for applications in molecular electronics. For C{sub 59}N{sup +} and C{sub 48}N

  1. Absorption-line ''forest'' in quasar spectra, and the structure of the universe

    Doroshkevich, A.G.; Muket, J.P.

    1985-05-01

    The ''forest'' of absorption lines observed in the spectrum of distant quasars is interpreted in light of the adiabatic (pancake) theory for the origin and evolution of structure in the universe. The hidden mass might reside in neutrino-like particles (perhaps unstable) having a rest mass of about 60--100 eV. Opportunities for testing the hypothesis observationally are discussed.

  2. N_2O weak lines observed between 3900 and 4050 cm^-1 from long path absorption spectra

    Herbin, H; Guelachvili, G; Sorokin, E; Sorokina, I T; Herbin, Herv\\'{e}; Picqu\\'{e}, Nathalie; Guelachvili, Guy; Sorokin, Evgeni; Sorokina, Irina T.

    2006-01-01

    Previously unobserved nitrous oxide transitions around 2.5 $\\mu$m are measured by intracavity laser absorption spectroscopy (ICLAS) analyzed by time-resolved Fourier transform (TRFT) spectrometer. With an accuracy of the order of 10^-3 cm^-1, measured positions of 1637 assigned weak transitions are provided. They belong to 42 vibrational transitions, among which 33 are observed for the first time. These data are believed to be useful in particular to monitoring atmosphere purposes.

  3. Atomic transition frequencies, isotope shifts, and sensitivity to variation of the fine structure constant for studies of quasar absorption spectra

    Berengut, J C; Flambaum, V V; King, J A; Kozlov, M G; Murphy, M T; Webb, J K

    2010-01-01

    Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that alpha varies spatially. That is, in one direction on the sky alpha seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger. To continue this study we need accurate laboratory measurements of atomic transition frequencies. The aim of this paper is to provide a compilation of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 A, and require an accuracy of better than 10^{-4} A. We discuss isotope shift measurements that are...

  4. Tailored pump-probe transient spectroscopy with time-dependent density-functional theory: controlling absorption spectra

    Walkenhorst, Jessica; De Giovannini, Umberto; Castro, Alberto; Rubio, Angel

    2016-05-01

    Recent advances in laser technology allow us to follow electronic motion at its natural time-scale with ultra-fast time resolution, leading the way towards attosecond physics experiments of extreme precision. In this work, we assess the use of tailored pumps in order to enhance (or reduce) some given features of the probe absorption (for example, absorption in the visible range of otherwise transparent samples). This type of manipulation of the system response could be helpful for its full characterization, since it would allow us to visualize transitions that are dark when using unshaped pulses. In order to investigate these possibilities, we perform first a theoretical analysis of the non-equilibrium response function in this context, aided by one simple numerical model of the hydrogen atom. Then, we proceed to investigate the feasibility of using time-dependent density-functional theory as a means to implement, theoretically, this absorption-optimization idea, for more complex atoms or molecules. We conclude that the proposed idea could in principle be brought to the laboratory: tailored pump pulses can excite systems into light-absorbing states. However, we also highlight the severe numerical and theoretical difficulties posed by the problem: large-scale non-equilibrium quantum dynamics are cumbersome, even with TDDFT, and the shortcomings of state-of-the-art TDDFT functionals may still be serious for these out-of-equilibrium situations.

  5. First-principles calculations of K-shell X-ray absorption spectra for warm dense nitrogen

    Li, Zi; Zhang, Shen; Wang, Cong; Kang, Wei; Zhang, Ping

    2016-05-01

    X-ray absorption spectrum is a powerful tool for atomic structure detection on warm dense matter. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations on warm dense nitrogen along a Hugoniot curve. From the molecular dynamics trajectory, the detailed atomic structures are examined for each thermodynamical condition. The K-shell X-ray absorption spectrum is calculated, and its changes with temperature and pressure along the Hugoniot curve are discussed. The warm dense nitrogen systems may contain isolated nitrogen atoms, N2 molecules, and nitrogen clusters, which show quite different contributions to the total X-ray spectrum due to their different electron density of states. The changes of X-ray spectrum along the Hugoniot curve are caused by the different nitrogen structures induced by the temperature and the pressure. Some clear signatures on X-ray spectrum for different thermodynamical conditions are pointed out, which may provide useful data for future X-ray experiments.

  6. Ab initio calculation of UV-absorption spectra of chlorophyll a: Comparison study between RHF/CIS, TDDFT, and semi-empirical methods

    Suendo, Veinardi

    2011-01-01

    Chlorophyll a is one the most abundant pigment on Earth, which is responsible for trapping the light energy to perform the photosynthesis process in green plants. This molecule is a metal-complex compound that consists of a porphyrins ring with high symmetry that acts as ligands with magnesium as the central ion. Chlorophyll a has been studied for many years from different point of views for both experimental and theoretical interests. In this study, the restricted Hartree-Fock configuration interaction single (RHF/CIS), time-dependent density functional theory (TDDFT) and some semi-empirical methods (CNDO/s and ZINDO) calculations were carried out and compared to reconstruct the UV-Vis absorption spectra of chlorophyll a. In some extend, the calculation results based on a single molecule calculation were succeeded to reconstruct the absorption spectra but required to be scaling and broaden to match the experimental one. Different computational methods (ab initio and semi-empirical) exhibits the differences i...

  7. Photoionization modeling of oxygen K absorption in the interstellar medium:the Chandra grating spectra of XTE J1817-330

    Gatuzz, E; Mendoza, C; Kallman, T R; Witthoeft, M; Lohfink, A; Bautista, M A; Palmeri, P; Quinet, P

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(H)=1.38+/-0.01\\times 10^21 cm^-2; ionization parameter of log(xi)=-2.70+/-0.023; oxygen abundance of A(O)= 0.689^{+0.015}_{-0.010}; and ionization fractions of OI/O = 0.911, OII/O = 0.077, and OIII/O = 0.012 that are in good agreement with previous ...

  8. Ab initio calculation of UV-absorption spectra of chlorophyll a: Comparison study between RHF/CIS, TDDFT, and semi-empirical methods

    Veinardi Suendo

    2012-07-01

    Full Text Available Chlorophyll a is one the most abundant pigment on Earth that responsible for trapping the light energy to perform photosynthesis in green plants. This molecule has been studied for many years from different point of views in both experimental and theoretical interests. In this study, the restricted Hartree-Fock configuration interaction single (RHF/CIS, time-dependent density functional theory (TDDFT and several semi-empirical methods (CNDO/s and ZINDO calculations were carried out to reconstruct the UV-Vis absorption spectra of chlorophyll a. In some extend, the calculation results based on single molecule approach were succeeded to reconstruct the absorption spectra but required to be rescaled to fit the experimental one. In general, the semi-empirical methods provide better energy scaling factor that closer to unity. However, they lack of vertical transition fine features with respect to the spectrum obtained experimentally. Here, the ab initio calculations provide more complete features, especially the TDDFT at high level of basis sets that also has a good accuracy in the transition energies. The contribution of ground states and excited states orbitals in the main vertical transitions is discussed based on delocalization nature of the wavefunctions and the presence of solvent through polarizable continuum model (PCM.

  9. Influence of Gamma-Ray Irradiation on Absorption and Fluorescent Spectra of Nd:YAG and Yb:YAG Laser Crystals

    We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd3+:Y3A15O12 (Nd:YAG) and Yb3+:Y3A15O12 (Yb:YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340 nm. The former is contributed due to Fe3+ impurity, the latter is due to Fe2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100Mrad gamma-ray In contrast, the same dose irradiation does not impair the fluorescent properties of Yb:YAG crystal. These results indicate that Yb:YAG crystal possesses the advantage over Nd:YAG crystal that has better reliability for applications in harsh radiant environment. (fundamental areas of phenomenology (including applications))

  10. Method of Gaussian quadrature in the calculation of optical absorption and magnetic circular dichroism spectra of s2 ions in alkali halide crystals: application to KBr:In+

    The problem of calculating the lineshape functon for optical absorption and magnetic circular dichroism due to ionic impurities with the ns2 outer electron configuraton, incorporated substitutionally in alkali halide crystals, has been reformulated. The complete energy matrix has been diagonalized directly. Integration over the interaction mode coordinates of E sub(g) and T sub(2g) symmetry has been carried out numerically using Gaussian quadrature formulae; the interaction with the A sub(1g) mode has been taken into account by the usual convolution procedure. The method has been applied to KBr:In+. The calculated lineshape functions for optical absorption at temperatures ranging from 4 to 300 K and, for MCD at 5 K, are in good agreement with the experimentally determined lineshapes. Moreover, the theory accounts very well for the observed variation of the effective g tensor for the A band with temperature. The calculated values for the moments of the absorption and MCD lineshape functions are in reasonably satisfactory agreement with those deduced from the observed spectra. (author)

  11. Modeling of pressure-induced far-infrared absorption spectra Molecular hydrogen pairs. [in outer planets atmospheres

    Borysow, J.; Trafton, L.; Frommhold, L.; Birnbaum, G.

    1985-01-01

    Meyer et al. (1985) have calculated the accurate induced dipole moment function of H2-H2 from first principles, using highly correlated wave functions for the first time in such work. The present paper is concerned with the collision-induced translational-rotational absorption coefficient for molecular hydrogen pairs, taking into account computations on the basis of the fundamental theory considered by Meyer et al. Data have been obtained for temperatures in the range from 40 to 300 K. Criteria are developed for choosing among various model line shapes. It is found that certain models are capable of approximating the quantum profiles closely, with rms errors of only a few percent.

  12. Weak-probe absorption and dispersion spectra in a two-level system driven by a strong trichromatic field

    A. V. Alekseev; Davydov, A. V.; Sushilov, N.V.; Zinin, Yu. A.

    1990-01-01

    With the help of a probe-field method the time-behaviour of a two-level system subjected to a strong trichromatic near-resonant field is studied. The suitable Bloch equations are solved by a matrix exponent method which allows us to do without the continued fractions. It is shown that, when the Rabi frequency is sufficiently large, the profile of the weak-probe field absorption resembles a dispersion profile. The existence of a new type of parametric resonances not connected with the Rabi res...

  13. Thermal diffusivity of Zn1-xBexSe crystals and it's correlation with electrical conductivity and optical absorption spectra

    Bodzenta, J.; Firszt, F.; Kaźmierczak-Bałata, A.; Pyka, M.; Szperlich, P.; Szydłowski, M.; Zakrzewski, J.

    2008-01-01

    This article presents results obtained for mixed crystal of Zn{1-x}Be{x}Se. Samples with different Be contents were examined to determine their thermal, optical and electrical properties. The influence of composition of investigated mixed crystals on the value of thermal diffusivity, electrical resistivity and energy gap was checked. An interesting problem is a correlation between thermal properties and other physical parameters. In this work possible correlations between the thermal diffusivity and either the optical band gap determined from photothermal spectra or electrical conductivity are studied. The current investigation is a part of research projects: BK-269/RMF-1/2006 and 1 P03B 092 27.

  14. Optical absorption and photoluminescence spectra of the ordered defect compound CuIn{sub 3}Te{sub 5}

    Rincon, C [Centro de Estudios de Semiconductores, Departamento de Fisica Facultad de Ciencias, Universidad de Los Andes, Apartado, Postal No 1, La Hechicera Merida 5101 (Venezuela); Wasim, S M [Centro de Estudios de Semiconductores, Departamento de Fisica Facultad de Ciencias, Universidad de Los Andes, Apartado, Postal No 1, La Hechicera Merida 5101 (Venezuela); Marin, G [Centro de Estudios de Semiconductores, Departamento de Fisica Facultad de Ciencias, Universidad de Los Andes, Apartado, Postal No 1, La Hechicera Merida 5101 (Venezuela); Delgado, J M [Centro Nacional de Difraccion de Rayos-X, Facultad de Ciencias, Universidad de Los Andes, Apartado, Postal No 40, La Hechicera, Merida 5101 (Venezuela); Petroff, P M [Materials Department, University of California, Santa Barbara, CA 93106 (United States)

    2003-05-21

    The optical properties of the ordered defect compound CuIn{sub 3}Te{sub 5} which crystallizes in a chalcopyrite-related structure have been studied by absorption and photoluminescence (PL) techniques. Optical absorption measurements show that the band gap energy E{sub G} varies from 1.078 to 1.040 eV between 10 and 300 K. It is found that the variation of E{sub G} with temperature is mainly due to the contribution of optical phonons with a characteristic energy of about 16 meV. The PL measurements, carried out between 4 and 100 K with laser excitation intensities in the range from 1 to 400 mW, reveal that the main PL band is due to a donor-acceptor recombination between donor and acceptor defect levels that have activation energies of 60 and 30 meV, respectively. These donor and acceptor states are tentatively assigned as originating from indium atoms on copper sites and copper vacancies, respectively.

  15. Comparative analysis of the vibrational structure of the absorption spectra of acrolein in the excited ( S 1) electronic state

    Koroleva, L. A.; Tyulin, V. I.; Matveev, V. K.; Pentin, Yu. A.

    2012-04-01

    The assignments of absorption bands of the vibrational structure of the UV spectrum are compared with the assignments of bands obtained by the CRDS method in a supersonic jet from the time of laser radiation damping for the trans isomer of acrolein in the excited ( S 1) electronic state. The ν00 trans = 25861 cm-1 values and fundamental frequencies, including torsional vibration frequency, obtained by the two methods were found to coincide in the excited electronic state ( S 1) for this isomer. The assignments of several absorption bands of the vibrational structure of the spectrum obtained by the CRDS method were changed. Changes in the assignment of (0-v') transition bands of the torsional vibration of the trans isomer in the Deslandres table from the ν00 trans trans origin allowed the table to be extended to high quantum numbers v'. The torsional vibration frequencies up to v' = 5 were found to be close to the frequencies found by analyzing the vibrational structure of the UV spectrum and calculated quantum-mechanically. The coincidence of the barrier to internal rotation (the cis-trans transition) in the one-dimensional model with that calculated quantum-mechanically using the two-dimensional model corresponds to a planar structure of the acrolein molecule in the excited ( S 1) electronic state.

  16. HCFC-133a (CF3CH2Cl): OH rate coefficient, UV and infrared absorption spectra, and atmospheric implications

    McGillen, Max R.; Bernard, François; Fleming, Eric L.; Burkholder, James B.

    2015-07-01

    HCFC-133a (CF3CH2Cl), an ozone-depleting substance, is primarily removed from the atmosphere by gas-phase reaction with OH radicals and by UV photolysis. The rate coefficient, k, for the OH + HCFC-133a reaction was measured between 233 and 379 K and is given by k(T) = (9.32 ± 0.8) × 10-13 exp(-(1296 ± 28)/T), where k(296 K) was measured to be (1.10 ± 0.02) × 10-14 (cm3 molecule-1 s-1) (2σ precision uncertainty). The HCFC-133a UV absorption spectrum was measured between 184.95 and 240 nm at 213-323 K, and a spectrum parameterization is presented. The HCFC-133a atmospheric loss processes, lifetime, ozone depletion potential, and uncertainties were evaluated using a 2-D atmospheric model. The global annually averaged steady state lifetime and ozone depletion potential (ODP) were determined to be 4.45 (4.04-4.90) years and 0.017 (±0.001), respectively, where the ranges are based solely on the 2σ uncertainty in the kinetic and photochemical parameters. The infrared absorption spectrum of HCFC-133a was measured, and its global warming potential was determined to be 380 on the 100 year time horizon.

  17. Modelling the Emission And/or Absorption Features in the High Resolution Spectra of the Southern Binary System: HH Car

    Koseoglu, Dogan; Bakış, Hicran

    2016-07-01

    High-resolution spectra (R=48000) of the southern close binary system, HH Car, has been analyzed with modern analysis techniques. Precise absolute parameters were derived from the simultaneous solution of the radial velocity, produced in this study and the light curves, published. According to the results of these analyses, the primary component is an O9 type main sequence star while the secondary component is a giant/subgiant star with a spectral type of B0. Hα emissions can be seen explicitly in the spectra of HH Car. These features were modelled using the absolute parameters of the components. Since components of HH Car are massive early-type stars, mass loss through stellar winds can be expected. This study revealed that the components of HH Car have stellar winds and the secondary component loses mass to the primary. Stellar winds and the gas stream between the components were modelled as a hot shell around the system. It is determined that the interaction between the winds and the gas stream leads to formation of a high temperature impact region.

  18. The optical spectra of matrix-isolated palladium-nitrogen complexes: An investigation by absorption, emission, and photoelectron spectroscopy

    Schrittenlacher, W.; Schroeder, W.; Rotermund, H. H.; Wiggenhauser, H.; Grinter, R.; Kolb, D. M.

    1986-08-01

    The optical spectra of palladium in neon and argon matrices containing up to 100% dinitrogen have been studied. Beside the known bands of isolated Pd atoms new strong bands assigned to weakly bonded Pd(N2)m (m=1, 2) complexes appear. The bands are attributed to three different types of transition. The dominant lines are essentially due to transitions localized at the Pd atom but strongly perturbed by a ``crystal field'' due to the weakly bonded N2 molecules. Secondly, a vibrational progression at lower energies is assigned to a Pd to N2 charge transfer transition and thirdly, at high energies, a vibrational progression assigned to a locally excited state of an N2 molecule perturbed by weak bonding to Pd is observed. No evidence has been found for the presence of Pd(N2)3. Photoelectron spectra of the Pd(N2)m complexes in neon have been observed. The Pd 4d photoemission peak is shifted with respect to the Pd atom in Ne by ˜1.1 eV to higher binding energies.

  19. Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: The peculiarity of Z-cinnamics.

    Salum, María L; Arroyo Mañez, Pau; Luque, F Javier; Erra-Balsells, Rosa

    2015-07-01

    Cinnamic acids are present in all kinds of plant tissues and hence in herbs and derived medicines, cosmetics and foods. The interest in their role in plants and their therapeutic applications has grown exponentially. Because of their molecular structure they can exist in E- and Z-forms, which are both found in plants. However, since only the E-forms are commercially available, very few in vitro and in vivo studies of the Z-form have been reported. In this work the physico-chemical properties of Z-cinnamic acids in solution have been examined by means of UV-absorption spectroscopy and high-level quantum mechanical computations. For each isomer similar absorption spectra were obtained in methanol and acetonitrile. However, distinct trends were found for Z- and E forms of cinnamic acids in water, where a higher hypsochromic shift of the Z-isomer relative to the E-form was observed. In general the wavelength of maximal absorption of the Z-form is dramatically blue shifted (-30 to -40 nm) to λ<280 nm, while a slightly blue shift of the absorption maxima for the corresponding E-form (+3 to -4 nm) was observed. This difference is associated with the non-planar, largely distorted, Z-structure and to the almost complete flat structure of the E-form. The results provide a basis for the study of functional and biotechnological roles of cinnamic acids and for the analysis of samples containing mixture of both geometric isomers. PMID:25911983

  20. Theoretical study of finite temperature spectroscopy in van der Waals clusters. II Time-dependent absorption spectra

    Calvo, F; Wales, D J

    2002-01-01

    Using approximate partition functions and a master equation approach, we investigate the statistical relaxation toward equilibrium in selected CaAr$_n$ clusters. The Gaussian theory of absorption (previous article) is employed to calculate the average photoabsorption intensity associated with the 4s^2-> 4s^14p^1 transition of calcium as a function of time during relaxation. In CaAr_6 and CaAr_10 simple relaxation is observed with a single time scale. CaAr_13 exhibits much slower dynamics and the relaxation occurs over two distinct time scales. CaAr_37 shows much slower relaxation with multiple transients, reminiscent of glassy behavior due to competition between different low-energy structures. We interpret these results in terms of the underlying potential energy surfaces for these clusters.

  1. Absorption and fluorescence spectra of C60 fullerene concentrated solutions in hexane and polystyrene at 77-300 K

    The locations of the 000-bands for S1 #60 solutions in hexane. It is shown that the profile of the S1 #00-band in the forbidden 11T1g #1Ag transition is explained by symmetry reduction in the C60+environment system due to the interaction of electrons with local phonons. The temperature coefficients of the red shift for the 256,3- and 328,3-nm bands of allowed 1T1u #1Ag transitions for C60 in hexane are equal to -1.45 and -0.46 cm-1@K-1, respectively. The peak and half-width values of the 337,2-nm band for C60 in polystyrene remain unchanged on cooling to 77 K. Absorption in the 700-800-nm region for concentrated hexane solutions of fullerene at 292 K results from the production of (C60)n-clusters. (authors)

  2. Frequency dispersed transient absorption spectra of dissolved perylene: A case study using the density matrix version of the MCTDH method

    A theoretical scheme is presented to calculate non-linear optical spectra of molecules in solution. Starting with electronic structure calculations of the ground and excited state, a subset of vibrational coordinates exhibiting the largest Huang-Rhys factors is assigned. It is used to set up a model Hamiltonian for density matrix multi configurational time-dependent Hartree (MCTDH) calculations. The expression derived for the dissipative part of the equation of motion goes beyond the earlier used Lindblad-form. In order to calculate the non-linear response the electric field strength is introduced into the density matrix equations used to directly determine the polarization. The whole scheme is applied to perylene as a reference case

  3. Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method.

    Guo, Meiyuan; Sørensen, Lasse Kragh; Delcey, Mickaël G; Pinjari, Rahul V; Lundberg, Marcus

    2016-01-28

    The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)6](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems. PMID:26742851

  4. Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars

    We present the results of a detailed many-multiplet analysis performed on a new sample of Mg ii systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in α derived from our analysis over the redshift range 0.4≤z≤2.3 is Δα/α=(-0.06±0.06)x10-5. The median redshift of our sample (z≅1.55) corresponds to a look-back time of 9.7 Gyr in the most favored cosmological model today. This gives a 3σ limit, -2.5x10-16≤(Δα/αΔt)≤+1.2x10-16 yr-1, for the time variation of α, that forms the strongest constraint obtained based on high redshift quasar absorption line systems

  5. Ab-initio multiplet calculations of Fe-L2,3 X-ray absorption spectra in LiFePO4 and FePO4

    Soft X-ray absorption near-edge structures (XANES) at the L2,3-edges of transition metal has been widely used for investigating the chemical reactions during charge-discharge cycles in the cathode materials of lithium ion batteries. In order to extract the information about the electronic structures from the experimental results, however, a theoretical tool that can deal with the strong electronic correlations between 2p and 3d electrons is necessary. In this study, the ab-initio multiplet method based on the relativistic configuration interaction (CI) method has been applied to the calculations of Fe-L2,3 XANES of LiFePO4 and FePO4. Experimental XANES spectra were quantitatively reproduced by this method. The effects of local symmetries around Fe ions to the spectral shapes were also discussed. (author)

  6. Effects of excess oxygen on the 4.5-6.3 eV absorption spectra of oxygen-rich high purity silica

    Magruder, R. H.; Robinson, S. J.

    2016-05-01

    Type III silica samples were implanted with O using a multi-energy process that produced a layer of constant concentration to within ±5% beginning ∼80 nm from the surface and extending to ∼640 nm below the surfaces of the samples. The concentrations of excess oxygen in the layer ranged from 0.035 to ∼2.1at.%. In these samples we show that E‧ centers and NBOHCs, as well as the normal cadre of ODC (II) centers, were suppressed, and the optical absorption from 4.7 to 6.4 eV was primarily due to oxygen excess defects. Using Gaussian fitting techniques to examine the optical difference spectra, we have been able to identify four defect centers that are related to excess oxygen defect bands at 4.76 eV, 5.42 eV, 5.75 eV and 6.25 eV.

  7. THE VERY YOUNG TYPE Ia SUPERNOVA 2013dy: DISCOVERY, AND STRONG CARBON ABSORPTION IN EARLY-TIME SPECTRA

    Zheng, WeiKang; Filippenko, Alexei V.; Nugent, Peter E.; Graham, Melissa; Kelly, Patrick L.; Fox, Ori D.; Shivvers, Isaac; Clubb, Kelsey I.; Li, Weidong [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Silverman, Jeffrey M.; Howie Marion, G. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Kasen, Daniel [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Wang, Xiaofeng [Department of Physics, Tsinghua University, Beijing 100084 (China); Valenti, Stefano; Howell, D. Andrew [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Santa Barbara, CA 93117 (United States); Ciabattari, Fabrizio [Monte Agliale Observatory, Borgo a Mozzano, Lucca, I-55023 Italy (Italy); Cenko, S. Bradley [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Balam, Dave [Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Hsiao, Eric [Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile); Sand, David, E-mail: zwk@astro.berkeley.edu [Physics Department, Texas Tech University, Lubbock, TX 79409 (United States); and others

    2013-11-20

    The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ≈ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 ± 0.05 days (2.4 ± 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R {sub 0} ≲ 0.25 R {sub ☉}, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 days after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of M{sub B} = –18.72 ± 0.03 mag ∼17.7 days after first light.

  8. UV absorption spectra, kinetics and mechanism for alkyl and alkyl peroxy radicals originating from t-butyl alcohol

    Langer, S.; Ljungström, E.; Sehested, J.;

    1994-01-01

    the self-reaction of HOC(CH3)2CH2. and HOC(CH3)2CH2O2. radicals were found to be (3.0 +/ -0.5) x 10(-11) and (7.8 +/- 1.5) X 10(-12) cm3 molecule-1 s-1, respectively. For the reaction of the alkyl radical with O2 in 1 atm SF6 a rate constant of (1.8 +/- 0.2) x 10(-12) cm3 molecule-1 s-1 was found. k......) to identify and quantify the reaction products. Absorption cross sections were quantified over the wavelength range 220-320 nm. At 240 nm, sigma(HOC(CH3)2CH2) = (2.4 +/- 0.3) x 10(-18) and sigma(HOC(CH3)2CH2O2) = (3.4 +/- 0.5) X 10(-18) cm2 molecule-1 have been obtained. Observed rate constants for......(HOC(CH3)2CH2O2. + NO) and k(HOC(CH3)2CH2O2. + NO2) were determined to be (4.9 +/- 0.9) X 10(-12) and (6.7 +/- 0.9) x 10(-12) cm3 molecule-1 s-1, respectively. In the FTIR experiments products were studied using chlorine-initiated oxidation in TBA/N2/Cl2 and TBA/N2/O2/Cl2 mixtures....

  9. THE VERY YOUNG TYPE Ia SUPERNOVA 2013dy: DISCOVERY, AND STRONG CARBON ABSORPTION IN EARLY-TIME SPECTRA

    The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ≈ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 ± 0.05 days (2.4 ± 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R 0 ≲ 0.25 R ☉, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 days after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of MB = –18.72 ± 0.03 mag ∼17.7 days after first light

  10. Errarum: Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655-40

    Ueda, Y.; Inoue, H.; Tanaka, Y.; Ebisawa, K.; Nagase, F.; Kotani, T.; Gehrels, N.

    1998-06-01

    In the paper ``Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655-40'' by Y. Ueda, H. Inoue, Y. Tanaka, K. Ebisawa, F. Nagase, T. Kotani, and N. Gehrels (ApJ, 492, 782 [1998]), there is an error in the curve of growth for the Kα absorption line (Fig. 4). The revised version of Figure 4 given here replaces Figure 4 in the paper. Several numbers derived from the figure should be corrected accordingly, but the conclusion of the paper is not affected. In the third paragraph of the discussion section (page 786), the iron column density of the plasma should be 1019-1020 cm-2, which corresponds to a hydrogen column density of 3 × 1023-3 × 1024 cm-2. The final limit on the hydrogen column density of the line-absorbing plasma should be changed to 3 × 1023 cm-2 < NH < 1024 cm-2.

  11. Lowest excited states and optical absorption spectra of donor–acceptor copolymers for organic photovoltaics: a new picture emerging from tuned long-range corrected density functionals

    Pandey, Laxman

    2012-01-01

    Polymers with low optical gaps are of importance to the organic photovoltaics community due to their potential for harnessing a large portion of the solar energy spectrum. The combination along their backbones of electron-rich and electron-deficient fragments contributes to the presence of low-lying excited states that are expected to display significant charge-transfer character. While conventional hybrid functionals are known to provide unsatisfactory results for charge-transfer excitations at the time-dependent DFT level, long-range corrected (LRC) functionals have been reported to give improved descriptions in a number of systems. Here, we use such LRC functionals, considering both tuned and default range-separation parameters, to characterize the absorption spectra of low-optical-gap systems of interest. Our results indicate that tuned LRC functionals lead to simulated optical-absorption properties in good agreement with experimental data. Importantly, the lowest-lying excited states (excitons) are shown to present a much more localized nature than initially anticipated. © 2012 the Owner Societies.

  12. Study on the absorption and fluorescence and resonance Rayleigh scattering spectra of Cu (Ⅱ)-fluoroquinolone chelates with erythrosine and their applications

    2008-01-01

    In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (Ⅱ) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultaneously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fading reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg·L-1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70-3.10 μg·L-1 for RRS method. Among the above three methods, the RRS method has the highest sensitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addition, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods.

  13. Infrared, Raman, and ultraviolet absorption spectra and theoretical calculations and structure of 2,3,5,6-tetrafluoropyridine in its ground and excited electronic states

    Highlights: • The structures of 2,3,5,6-tetrafluoropyridine for its S0 and S1(π, π∗) states have been calculated. • TFPy is rigidly planar in its ground electronic state, but is quasi-planar and floppy in S1. • The barrier to planarity is 30 cm−1 in the excited state. • The observed vibrational frequencies for both states agree well with the computations. • A ring-bending potential energy function for the S1(π, π∗) state was proposed. - Abstract: Infrared and Raman spectra of 2,3,5,6-tetrafluoropyridine (TFPy) were recorded and vibrational frequencies were assigned for its S0 electronic ground states. Ab initio and density functional theory (DFT) calculations were used to complement the experimental work. The lowest electronic excited state of this molecule was investigated with ultraviolet absorption spectroscopy and theoretical CASSCF calculations. The band origin was found to be at 35,704.6 cm−1 in the ultraviolet absorption spectrum. A slightly puckered structure with a barrier to planarity of 30 cm−1 was predicted by CASSCF calculations for the S1(π, π∗) state. Lower frequencies for the out-of-plane ring bending vibrations for the electronic excited state result from the weaker π bonding within the pyridine ring

  14. Infrared, Raman, and ultraviolet absorption spectra and theoretical calculations and structure of 2,3,5,6-tetrafluoropyridine in its ground and excited electronic states

    Sheu, Hong-Li; Boopalachandran, Praveenkumar [Department of Chemistry, Texas A& M University, College Station, TX 77843-3255 (United States); Kim, Sunghwan [National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, 8600 Rockville Pike, Bethesda, MD 20894 (United States); Laane, Jaan, E-mail: laane@chem.tamu.edu [Department of Chemistry, Texas A& M University, College Station, TX 77843-3255 (United States)

    2015-07-29

    Highlights: • The structures of 2,3,5,6-tetrafluoropyridine for its S{sub 0} and S{sub 1}(π, π{sup ∗}) states have been calculated. • TFPy is rigidly planar in its ground electronic state, but is quasi-planar and floppy in S{sub 1}. • The barrier to planarity is 30 cm{sup −1} in the excited state. • The observed vibrational frequencies for both states agree well with the computations. • A ring-bending potential energy function for the S{sub 1}(π, π{sup ∗}) state was proposed. - Abstract: Infrared and Raman spectra of 2,3,5,6-tetrafluoropyridine (TFPy) were recorded and vibrational frequencies were assigned for its S{sub 0} electronic ground states. Ab initio and density functional theory (DFT) calculations were used to complement the experimental work. The lowest electronic excited state of this molecule was investigated with ultraviolet absorption spectroscopy and theoretical CASSCF calculations. The band origin was found to be at 35,704.6 cm{sup −1} in the ultraviolet absorption spectrum. A slightly puckered structure with a barrier to planarity of 30 cm{sup −1} was predicted by CASSCF calculations for the S{sub 1}(π, π{sup ∗}) state. Lower frequencies for the out-of-plane ring bending vibrations for the electronic excited state result from the weaker π bonding within the pyridine ring.

  15. Dense Sampling and Large Volume: The Structure of the Intergalactic Medium from 50,000 SDSS3 BOSS Quasar Absorption Spectra

    Croft, Rupert A.; Arnau, E.; Aubourg, E.; Bailey, S.; Bechtold, J.; Bhardwaj, V.; Bolton, A.; Borde, A.; Brinkmann, J.; Busca, N.; Carithers, W.; Cen, R.; Charlassier, R.; Cortes, M.; Dall'Aglio, A.; Cristiani, S.; Dawson, K.; Delubac, T.; Font-Ribera, A.; Hamilton, J.; Ho, S.; Lee, K.; LeGoff, J.; Kirkby, D.; Lundgren, B.; Menard, B.; Miralda-Escude, J.; Palanque-Delabrouille, N.; Myers, A.; Paris, I.; Peirani, S.; Petitjean, P.; Pieri, M.; Rich, J.; Rollinde, E.; Ross, N.; Schlegel, D.; Skibba, R.; Slosar, A.; Suzuki, N.; Trac, H.; Vikas, S.; Viel, M.; Wake, D.; Weinberg, D.; White, M.; Yeche, C.

    2012-01-01

    The BOSS quasar spectra analyzed so far contain over a quarter billion pixels of information on the intervening intergalactic medium. The statistical power of BOSS has previously enabled 10% of the eventual full dataset to yield the first measurements of three dimensional large-scale structure in the Lya forest (Slosar et al 2011). Here we present results from a sample several times larger, covering several topics in cosmology and intergalactic medium science which are qualitatively transformed by the dense sampling (20 quasars per square degree) and enormous sky area. These include new constraints on cosmology and the neutrino mass from a Lya forest power spectrum measurement using 20 times more spectra than the largest previously published analysis (from SDSS), a new catalog of metal absorbers and a stacking analysis which has uncovered many metal species never before seen in the intergalactic medium. Cross-correlations of quasars, galaxies, metal lines and Lyman series absorption provide us with a wide variety of probes, including of cosmology, quasar host masses, lifetimes, and absorber galaxy masses. We show several of these results. We also show through correlation function analysis that the prime task, of making a BAO detection from Lya forest clustering, (the first BAO constraint between z=1 and the CMB) is well on the way to completion.

  16. Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars

    Srianand, R; Petitjean, P; Aracil, B; Srianand, Raghunathan; Chand, Hum; Petitjean, Patrick; Aracil, Bastien

    2004-01-01

    Most of the successful physical theories rely on the constancy of few fundamental quantities (such as the speed of light, $c$, the fine-structure constant, \\alpha, the proton to electron mass ratio, \\mu, etc), and constraining the possible time variations of these fundamental quantities is an important step toward a complete physical theory. Time variation of \\alpha can be accurately probed using absorption lines seen in the spectra of distant quasars. Here, we present the results of a detailed many-multiplet analysis performed on a new sample of Mg II systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in \\alpha derived from our analysis over the redshift range 0.4

  17. Resonance Raman and electronic absorption spectra of O3- ions in γ-irradiated KC1O3 and NaC1O3

    Resonance Raman and electronic absorption spectra have been measured for the ozonide ion, O-3, produced in single crystals of KClO3 and NaClO3 by irradiation with γ rays. The O-3 ions are oriented in four to six symmetrically nonequivalent positions in KClO3 and appear to be oriented in two nonequivalent positions in NaClO3. Differences between the nonequivalent orientations affect both the ground and excited electronic states of O-3 as well as its ground vibrational states. The progressions of ν1 observed in the electronic spectra show that the vibrational spacing of ν1 in the excited electronic state is about 857 cm/sup -1/ as compared with the ground state spacing of about 1020 cm/sup -1/. Measurements of relative Raman intensities obtained with different exciting lines indicate that excitation near the center of a vibronic transition (0--n') produces extra enhancement of the intensity of the nν1 vibrational transition

  18. Fluorescence excitation and ultraviolet absorption spectra and theoretical calculations for benzocyclobutane: Vibrations and structure of its excited S{sub 1}(π,π{sup *}) electronic state

    Shin, Hee Won; Ocola, Esther J.; Laane, Jaan, E-mail: laane@mail.chem.tamu.edu [Department of Chemistry, Texas A and M University, College Station, Texas 77843-3255 (United States); Kim, Sunghwan [National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Department of Health and Human Services, 8600 Rockville Pike, Bethesda, Maryland 20894 (United States)

    2014-01-21

    The fluorescence excitation spectra of jet-cooled benzocyclobutane have been recorded and together with its ultraviolet absorption spectra have been used to assign the vibrational frequencies for this molecule in its S{sub 1}(π,π{sup *}) electronic excited state. Theoretical calculations at the CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to compute the structure of the molecule in its excited state. The calculated structure was compared to that of the molecule in its electronic ground state as well as to the structures of related molecules in their S{sub 0} and S{sub 1}(π,π{sup *}) electronic states. In each case the decreased π bonding in the electronic excited states results in longer carbon-carbon bonds in the benzene ring. The skeletal vibrational frequencies in the electronic excited state were readily assigned and these were compared to the ground state and to the frequencies of five similar molecules. The vibrational levels in both S{sub 0} and S{sub 1}(π,π{sup *}) states were remarkably harmonic in contrast to the other bicyclic molecules. The decreases in the frequencies of the out-of-plane skeletal modes reflect the increased floppiness of these bicyclic molecules in their S{sub 1}(π,π{sup *}) excited state.

  19. Polarized X-ray absorption spectra and electronic structure of molybdenite (2H-MoS2)

    Li, Dien; Bancroft, G. M.; Kasrai, M.; Fleet, M. E.; Feng, X. H.; Tan, K. H.

    1995-03-01

    Polarized S K- and L-edge, Mo L3- and L2-edge x-ray absorption near-edge structure (XANES) of natural molybdenite (2H-MoS2) have been measured with synchrotron radiation. These results are qualitatively interpreted using the energy band model of molybdenite and provide important information on the unoccupied states of molybdenite. The valence band (VB) maximum of molybdenite is characterized by fully occupied Mo 4dz 2, and the conduction band (CB) minimum of molybdenite is characterized by unoccupied Mo 4d states. The unoccupied Mo 4d band is split into two sub-bands, designated as t{2g/-}/t{2g/+}and e{g/-}/e{g/+}sets. Although the relative energy of these two sets are difficult to be evaluated, probably the former has the lower energy than the latter, both two sets have the combination wave functions of the other unoccupied Mo 4d components, rather than the simple 4dx 2 — y2 and 4dxy states. The unoccupied Mo 4d sub-bands contain significant DOS of both S 3 p- and 3 s-like states, indicating strong hybridization with S 3s and 3 p states. In the lower energy sub-band, the DOS of the S pz- and px,y-like states are very similar. However, in the higher energy sub-band, the DOS of the S 3 px,y-like state is lower than that of the S 3pz state. Polarized S K-edge XANES also reveal the features of antibonding S pz- and px,y-like states in molybdenite. The feature assigned to the S 3 pz-like states is stronger and sharper, and shifts to lower energy by about 2 eV relative to that for the S 3 px,y-like states.

  20. Electronic structure, bonding, charge distribution, and x-ray absorption spectra of the (001) surfaces of fluorapatite and hydroxyapatite from first principles

    Rulis, Paul; Yao, Hongzhi; Ouyang, Lizhi; Ching, W. Y.

    2007-12-01

    Fluorapatite (FAP) and hydroxyapatite (HAP) are two very important bioceramic crystals. The (001) surfaces of FAP and HAP crystals are studied by ab initio density functional calculations using a supercell slab geometry. It is shown that in both crystals, the O-terminated (001) surface is more stable with calculated surface energies of 0.865 and 0.871J/m2 for FAP and HAP, respectively. In FAP, the two surfaces are symmetric. In HAP, the orientation of the OH group along the c axis reduces the symmetry such that the top and bottom surfaces are no longer symmetric. It is revealed that the atoms near the surface and subsurface are significantly relaxed especially in the case of HAP. The largest relaxations occurred via the lateral movements of the O ions at the subsurface level. The electronic structures of the surface models in the form of layer-by-layer resolved partial density of states for all the atoms show systematic variation from the surface region toward the bulk region. The calculated Mulliken effective charge on each type of atom and the bond order values between cations (Ca, P) and anions (O, F) show different charge transfers and bond strength variations from the bulk crystal values. Electron charge density calculations show that the surfaces of both FAP and HAP crystals are mostly positively charged due to the presence of Ca ions at the surface. The positively charged surfaces have implications for the absorption on apatite surfaces of water and other organic molecules in an aqueous environment which are an important part of its bioactivity. The x-ray absorption near-edge structure (XANES) spectra ( Ca-K , O-K , F-K , P-K , and P-L3 edges) of both the surface models and the bulk crystals are calculated and compared. The calculations use a supercell approach which takes into account the electron-core-hole interaction. It is shown that the site-specific XANES spectra show significant differences between atoms near the surface and in the bulk and are very

  1. First-Principles Studies on Electronic Structures and Absorption Spectra of PbWO4 Crystals with Defect [VP2-Pb-V2+O-VP2-Pb]2-

    LIU Ting-Yu; ZHANG Qi-Ren; ZHUANG Song-Lin

    2007-01-01

    @@ Electronic structures and absorption spectra for perfect PbWO4 (PWO) crystals and the crystal containing aggregated defect [VP2-Pb-V2+O -VP2-Pb]2- have been calculated using density functional theory code CASTEP with the lattice structure optimized. The calculated absorption spectra of the PWO crystal containing the aggregated defect [VP2-Pb-V2+O -VP2-Pb]2- exhibit two absorption bands peaking at 1.90eV (650nm) and 3.02eV (410 nm). It is predicted that the 420 and 680 nm absorption bands are related to the existence of the aggregated defect [VP2-Pb-V2+O -VP2-Pb]2- in the PWO crystal.

  2. A ground-based imaging study of galaxies causing damped Lyman α (DLA), sub-DLA and Lyman limit system absorption in quasar spectra

    Rao, Sandhya M.; Belfort-Mihalyi, Michèle; Turnshek, David A.; Monier, Eric M.; Nestor, Daniel B.; Quider, Anna

    2011-09-01

    We present results from a search for galaxies that give rise to damped Lyman α (DLA), sub-DLA and Lyman limit system (LLS) absorption at redshifts 0.1 ≲z≲ 1 in the spectra of background quasars. The sample was formed from a larger sample of strong Mg II absorbers (Wλ27960≥ 0.3 Å) whose H I column densities were determined by measuring the Lyα line in Hubble Space Telescope ultraviolet spectra. Photometric redshifts, galaxy colours and proximity to the quasar sightline, in decreasing order of importance, were used to identify galaxies responsible for the absorption. Our sample includes 80 absorption systems for which the absorbing galaxies have been identified, of which 54 are presented here for the first time. In some cases a reasonable identification for the absorbing galaxy could not be made. The main results of this study are (i) the surface density of galaxies falls off exponentially with increasing impact parameter, b, from the quasar sightline relative to a constant background of galaxies, with an e-folding length of ≈46 kpc. Galaxies with b≳ 100 kpc calculated at the absorption redshift are statistically consistent with being unrelated to the absorption system, and are either background or foreground galaxies. (ii) ? is inversely correlated with b at the 3.0σ level of significance. DLA galaxies are found systematically closer to the quasar sightline, by a factor of 2, than are galaxies which give rise to sub-DLAs or LLSs. The median impact parameter is 17.4 kpc for the DLA galaxy sample, 33.3 kpc for the sub-DLA sample and 36.4 kpc for the LLS sample. We also find that the decline in ? with b can be roughly described by an exponential with an e-folding length of 12 kpc that occurs at ?. (iii) Absorber galaxy luminosity relative to L*, L/L*, is not significantly correlated with Wλ27960, ? or b. (iv) DLA, sub-DLA and LLS galaxies comprise a mix of spectral types, but are inferred to be predominantly late-type galaxies based on their spectral

  3. Study on the absorption and fluorescence and resonance Rayleigh scattering spectra of Cu (II)-fluoroquinolone chelates with erythrosine and their applications

    2008-01-01

    In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (II) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultane- ously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fad- ing reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg·L?1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70 -3.10 μg·L?1 for RRS method. Among the above three methods, the RRS method has the highest sen- sitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addi- tion, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods.

  4. Effect of [Li]/[Nb] ratios on the absorption and up-conversion emission spectra in In:Yb:Ho:LiNbO3 crystal

    Highlights: • In:Yb:Ho:LiNbO3 crystals were grown with various [Li]/[Nb] ratios. • The influence of [Li]/[Nb] ratios on the UV–VIS–NIR is investigated. • This UC process is three-photon process. • In:Yb:Ho:LiNbO3 crystals (Li/Nb = 1.38) is a promising material for 2 μm wavelength radiation. - Abstract: In:Yb:Ho:LiNbO3 crystals with high optical quality were grown by the Czochralski method with various ratios of [Li]/[Nb], that is 0.94, 1.05, 1.20 and 1.38 in the melt. The UV–VIS–NIR absorption spectra of In:Yb:Ho:LiNbO3 crystals were measured. The transition intensity parameters Ωt (t = 2, 4 and 6), spectroscopic quality factor (X) and the lifetimes of Ho3+ in In:Yb:Ho:LiNbO3 crystals were all evaluated by the Judd–Ofelt theory. The spectroscopic quality factor Ω4/Ω6 of In:Yb:Ho:LiNbO3 crystals with the [Li]/[Nb] ratio of 1.38 was found to be 1.69, which is comparable with those found in widely used Ho3+ doped crystals. Furthermore, up-conversion emission spectra were determined and analyzed under 980 nm LD excitation in the In:Yb:Ho:LiNbO3 crystals. The results revealed that In:Yb:Ho:LiNbO3 crystal with the [Li]/[Nb] ratio of 1.38 is a promising material for 2 μm wavelength radiation

  5. Evaluation of Compton attenuation and photoelectric absorption coefficients by convolution of scattering and primary functions and counts ratio on energy spectra

    Estimation of Compton attenuation and the photoelectric absorption coefficients were explored at various depths. A new method was proposed for estimating the depth based on the convolution of two exponential functions, namely convolution of scattering and primary functions (CSPF), which the convolved result will conform to the photopeak region of energy spectrum with the variable energy-window widths (EWWs) and a theory on the scattering cross-section. The triple energy-windows (TEW) and extended triple energy-windows scatter correction (ETEW) methods were used to estimate the scattered and primary photons according to the energy spectra at various depths due to a better performance than the other methods in nuclear medicine. For this purpose, the energy spectra were employed, and a distinct phantom along with a technetium-99 m source was simulated by Monte Carlo method. The simulated results indicate that the EWW, used to calculate the scattered and primary counts in terms of the integral operators on the functions, was proportional to the depth as an exponential function. The depth will be calculated by the combination of either TEW or ETEW and proposed method resulting in the distinct energy-window. The EWWs for primary photons were in good agreement with those of scattered photons at the same as depths. The average errors between these windows for both methods TEW, and ETEW were 7.25% and 6.03% at different depths, respectively. The EWW value for functions of scattered and primary photons was reduced by increasing the depth in the CSPF method. This coefficient may be an index for the scattering cross-section

  6. Vibrational absorption and vibrational circular dichroism spectra of leucine in water under different pH conditions: Hydrogen-bonding interactions with water

    Poopari, Mohammad Reza; Zhu, Peiyan; Dezhahang, Zahra; Xu, Yunjie

    2012-11-01

    Vibrational absorption (VA) and vibrational circular dichroism (VCD) spectroscopy have been used to study leucine, a flexible branched-chain amino acid, in aqueous solution. The VA spectra in the range of 1800-1250 cm-1 of leucine in D2O under three representative pHs from strongly acidic (pH = 1), near neutral (pH = 6), to strongly basic (pH = 13), have been measured. The related VCD spectrum has been obtained under near neutral condition. Searches have been carried out to identify the most stable conformers of the Zwitterionic, protonated, and deprotonated forms of leucine in water. The geometry optimization, harmonic frequency calculations, and VA and VCD intensities have been computed at the B3LYP/6-311++G(d,p) level with the implicit polarizable continuum solvation model. While the observed VA spectra under three pHs can be well interpreted with the inclusion of the implicit solvation model, both implicit and explicit solvation models have been found to be crucial for the adequate interpretation of the complex VCD features observed. Molecular dynamics simulations and radial distribution functions have been used to aid the modeling of the leucine-(water)N clusters. It has been recognized that the insertion of a water molecule between the COO- and NH3+ functional groups in the explicit solvated clusters is critical to reproduce the VCD signatures observed. Furthermore, the inclusion of the implicit bulk water environment has been found to be essential to lock water molecules, which are directly hydrogen bonded to leucine, into the positions expected in solution. The application of the explicit and implicit solvation models simultaneously allows new insights into the hydrogen bonding network surrounding leucine in aqueous solution and the role of the surrounding bulk water in stabilizing such hydrogen-bonding network.

  7. Effect of [Li]/[Nb] ratios on the absorption and up-conversion emission spectra in In:Yb:Ho:LiNbO{sub 3} crystal

    Dai, Li, E-mail: daili198108@126.com [Applied Science College, Harbin University of Science and Technology, Harbin 150080 (China); State Key Laboratory of Crystal Material, Shandong University, Jinan 250100 (China); Yan, Zhehua; Jiao, Shanshan [Applied Science College, Harbin University of Science and Technology, Harbin 150080 (China); Xu, Chao; Xu, Yuheng [Department of the Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)

    2015-09-25

    Highlights: • In:Yb:Ho:LiNbO{sub 3} crystals were grown with various [Li]/[Nb] ratios. • The influence of [Li]/[Nb] ratios on the UV–VIS–NIR is investigated. • This UC process is three-photon process. • In:Yb:Ho:LiNbO{sub 3} crystals (Li/Nb = 1.38) is a promising material for 2 μm wavelength radiation. - Abstract: In:Yb:Ho:LiNbO{sub 3} crystals with high optical quality were grown by the Czochralski method with various ratios of [Li]/[Nb], that is 0.94, 1.05, 1.20 and 1.38 in the melt. The UV–VIS–NIR absorption spectra of In:Yb:Ho:LiNbO{sub 3} crystals were measured. The transition intensity parameters Ω{sub t} (t = 2, 4 and 6), spectroscopic quality factor (X) and the lifetimes of Ho{sup 3+} in In:Yb:Ho:LiNbO{sub 3} crystals were all evaluated by the Judd–Ofelt theory. The spectroscopic quality factor Ω{sub 4}/Ω{sub 6} of In:Yb:Ho:LiNbO{sub 3} crystals with the [Li]/[Nb] ratio of 1.38 was found to be 1.69, which is comparable with those found in widely used Ho{sup 3+} doped crystals. Furthermore, up-conversion emission spectra were determined and analyzed under 980 nm LD excitation in the In:Yb:Ho:LiNbO{sub 3} crystals. The results revealed that In:Yb:Ho:LiNbO{sub 3} crystal with the [Li]/[Nb] ratio of 1.38 is a promising material for 2 μm wavelength radiation.

  8. Four-Component Damped Density Functional Response Theory Study of UV/Vis Absorption Spectra and Phosphorescence Parameters of Group 12 Metal-Substituted Porphyrins.

    Fransson, Thomas; Saue, Trond; Norman, Patrick

    2016-05-10

    The influences of group 12 (Zn, Cd, Hg) metal-substitution on the valence spectra and phosphorescence parameters of porphyrins (P) have been investigated in a relativistic setting. In order to obtain valence spectra, this study reports the first application of the damped linear response function, or complex polarization propagator, in the four-component density functional theory framework [as formulated in Villaume et al. J. Chem. Phys. 2010 , 133 , 064105 ]. It is shown that the steep increase in the density of states as due to the inclusion of spin-orbit coupling yields only minor changes in overall computational costs involved with the solution of the set of linear response equations. Comparing single-frequency to multifrequency spectral calculations, it is noted that the number of iterations in the iterative linear equation solver per frequency grid-point decreases monotonously from 30 to 0.74 as the number of frequency points goes from one to 19. The main heavy-atom effect on the UV/vis-absorption spectra is indirect and attributed to the change of point group symmetry due to metal-substitution, and it is noted that substitutions using heavier atoms yield small red-shifts of the intense Soret-band. Concerning phosphorescence parameters, the adoption of a four-component relativistic setting enables the calculation of such properties at a linear order of response theory, and any higher-order response functions do not need to be considered-a real, conventional, form of linear response theory has been used for the calculation of these parameters. For the substituted porphyrins, electronic coupling between the lowest triplet states is strong and results in theoretical estimates of lifetimes that are sensitive to the wave function and electron density parametrization. With this in mind, we report our best estimates of the phosphorescence lifetimes to be 460, 13.8, 11.2, and 0.00155 s for H2P, ZnP, CdP, and HgP, respectively, with the corresponding transition

  9. Franck-Condon factors perturbed by damped harmonic oscillators: Solvent enhanced X {sup 1}A{sub g} ↔ A{sup 1}B{sub 1u} absorption and fluorescence spectra of perylene

    Wang, Chen-Wen; Zhu, Chaoyuan, E-mail: cyzhu@mail.nctu.edu.tw; Lin, Sheng-Hsien [Institute of Molecular Science, Department of Applied Chemistry and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30050, Taiwan (China); Yang, Ling [Institute of Molecular Science, Department of Applied Chemistry and Center for Interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 30050, Taiwan (China); Institute of Theoretical and Simulation Chemistry, Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150080 (China); Yu, Jian-Guo [Department of Chemistry, Beijing Normal University, Beijing 100875 (China)

    2014-08-28

    Damped harmonic oscillators are utilized to calculate Franck-Condon factors within displaced harmonic oscillator approximation. This is practically done by scaling unperturbed Hessian matrix that represents local modes of force constants for molecule in gaseous phase, and then by diagonalizing perturbed Hessian matrix it results in direct modification of Huang–Rhys factors which represent normal modes of solute molecule perturbed by solvent environment. Scaling parameters are empirically introduced for simulating absorption and fluorescence spectra of an isolated solute molecule in solution. The present method is especially useful for simulating vibronic spectra of polycyclic aromatic hydrocarbon molecules in which hydrogen atom vibrations in solution can be scaled equally, namely the same scaling factor being applied to all hydrogen atoms in polycyclic aromatic hydrocarbons. The present method is demonstrated in simulating solvent enhanced X {sup 1}A{sub g} ↔ A{sup 1}B{sub 1u} absorption and fluorescence spectra of perylene (medium-sized polycyclic aromatic hydrocarbon) in benzene solution. It is found that one of six active normal modes v{sub 10} is actually responsible to the solvent enhancement of spectra observed in experiment. Simulations from all functionals (TD) B3LYP, (TD) B3LYP35, (TD) B3LYP50, and (TD) B3LYP100 draw the same conclusion. Hence, the present method is able to adequately reproduce experimental absorption and fluorescence spectra in both gas and solution phases.

  10. Infrared Absorption Spectra, Radiative Efficiencies, and Global Warming Potentials of Newly-Detected Halogenated Compounds: CFC-113a, CFC-112 and HCFC-133a

    Maryam Etminan

    2014-07-01

    Full Text Available CFC-113a (CF3CCl3, CFC-112 (CFCl2CFCl2 and HCFC-133a (CF3CH2Cl are three newly detected molecules in the atmosphere that are almost certainly emitted as a result of human activity. It is important to characterise the possible contribution of these gases to radiative forcing of climate change and also to provide information on the CO2-equivalence of their emissions. We report new laboratory measurements of absorption cross-sections of these three compounds at a resolution of 0.01 cm−1 for two temperatures 250 K and 295 K in the spectral range of 600–1730 cm−1. These spectra are then used to calculate the radiative efficiencies and global warming potentials (GWP. The radiative efficiencies are found to be between 0.15 and 0.3 W∙m−2∙ppbv−1. The GWP for a 100 year time horizon, relative to carbon dioxide, ranges from 340 for the relatively short-lived HCFC-133a to 3840 for the longer-lived CFC-112. At current (2012 concentrations, these gases make a trivial contribution to total radiative forcing; however, the concentrations of CFC-113a and HCFC-133a are continuing to increase. The 2012 CO2-equivalent emissions, using the GWP (100, are estimated to be about 4% of the current global CO2-equivalent emissions of HFC-134a.

  11. Temperature dependent ozone absorption cross section spectra measured with the GOME-2 FM3 spectrometer and first application in satellite retrievals

    W. Chehade

    2012-10-01

    Full Text Available The Global Ozone Monitoring Experiment (GOME-2 Flight Model (FM absorption cross section spectra of ozone were measured under representative atmospheric conditions in the laboratory setup at temperatures between 203 K and 293 K in the wavelength range of 230–790 nm at a medium spectral resolution of 0.24 to 0.54 nm. Since the exact ozone amounts were unknown in the gas flow system used, the measured ozone cross sections were required to be scaled to absolute cross section units using published literature data. The Hartley, Huggins and Chappuis bands were recorded simultaneously and their temperature dependence is in good agreement with previous studies (strong temperature effect in the Huggins band and weak in the Hartley and Chappuis bands. The overall agreement of the GOME-2 FM cross sections with the literature data is well within 3%. The total ozone column retrieved from the GOME-2/MetOp-A satellite using the new cross section data is within 1% compared to the ozone amounts retrieved routinely from GOME-2.

  12. Electromeric effect of substitution at 6th position in 2-(Furan-2-yl)-3-hydroxy-4 H-chromen-4-one (FHC) on the absorption and emission spectra

    Manisha Bansal; Ranbir Kaur

    2015-03-01

    Five 3-Hydroxychromones (3HCs), namely, 2-(furan-2-yl)-3-hydroxy-4H-chromen-4-one (FHC) and its four derivatives by substitution of -CH3, -OH, -NO2 and -Cl at 6th position were synthesized from their corresponding 2’-hydroxyacetophenone and furan-2-carboxaldehyde. Various spectral transitions of all these 3-hydroxychromones (3-HCs) have been assigned by interpreting their absorption spectra in cyclohexane, acetonitrile and methanol. It has been shown that the electromeric effects of substitution at 2nd and 6th positions on the 2–3 double bond in `C’ ring are similar but the effect on the double bond of 4-carbonyl group is opposite. It has been found that the substitution at 2nd position changes mainly the electron density directly at the 4-carbonyl group and substitution at 6th position changes the electron density of the `C’ ring, changing the overall dipole moment of the molecule, which in turn changes the electron density at the 4-carbonyl group. Emission spectral studies showed that the increase and decrease in dipole moment by substitution at 6th position with electron withdrawing group like NO2 and electron donating group like -CH3 and -OH, stabilizes and destabilizes the N* state in the polar solvents respectively

  13. Structures of Plutonium(IV) and Uranium(VI) with N,N-Dialkyl Amides from Crystallography, X-ray Absorption Spectra, and Theoretical Calculations.

    Acher, Eléonor; Hacene Cherkaski, Yanis; Dumas, Thomas; Tamain, Christelle; Guillaumont, Dominique; Boubals, Nathalie; Javierre, Guilhem; Hennig, Christoph; Solari, Pier Lorenzo; Charbonnel, Marie-Christine

    2016-06-01

    The structures of plutonium(IV) and uranium(VI) ions with a series of N,N-dialkyl amides ligands with linear and branched alkyl chains were elucidated from single-crystal X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and theoretical calculations. In the field of nuclear fuel reprocessing, N,N-dialkyl amides are alternative organic ligands to achieve the separation of uranium(VI) and plutonium(IV) from highly concentrated nitric acid solution. EXAFS analysis combined with XRD shows that the coordination structure of U(VI) is identical in the solution and in the solid state and is independent of the alkyl chain: two amide ligands and four bidentate nitrate ions coordinate the uranyl ion. With linear alkyl chain amides, Pu(IV) also adopt identical structures in the solid state and in solution with two amides and four bidentate nitrate ions. With branched alkyl chain amides, the coordination structure of Pu(IV) was more difficult to establish unambiguously from EXAFS. Density functional theory (DFT) calculations were consequently performed on a series of structures with different coordination modes. Structural parameters and Debye-Waller factors derived from the DFT calculations were used to compute EXAFS spectra without using fitting parameters. By using this methodology, it was possible to show that the branched alkyl chain amides form partly outer-sphere complexes with protonated ligands hydrogen bonded to nitrate ions. PMID:27171842

  14. Temperature and polarization dependence of Fe L{sub 3}-edge X-ray absorption spectra of LuFe{sub 2}O{sub 4}

    Agui, A., E-mail: agui@spring8.or.jp [Japan Atomic Energy Agency, SPring-8, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Mizumaki, M. [Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Kuroda, T.; Kawai, M.; Nagata, T.; Ikeda, N. [Graduate School of Natural Science and Technology, Okayama University, Kita-ku, Okayama 700-8530 (Japan); Uozumi, T. [Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan)

    2014-12-15

    Highlights: • We have measured the Fe L{sub 2,3} XAS were measured at the temperature range of 7–573 K. • We found the polarization dependence of XAS revealed that the energy level of (d{sub xy}, d{sub x2–y2}) was lower than that of (d{sub yz}, d{sub zx}). • We observed the Fe{sup 2+} and Fe{sup 3+} are kept even at higher temperatures. - Abstract: The charge ordering of Fe{sup 2+} and Fe{sup 3+} ions in LuFe{sub 2}O{sub 4} induces ferroelectricity below 330 K. In this study, the X-ray absorption spectra (XAS) at the Fe L{sub 2,3}-edge are investigated to study charge ordered- and disordered-states. The polarization dependence of XAS revealed that the energy level of (d{sub xy}, d{sub x2–y2}) is lower than that of (d{sub yz}, d{sub zx}). In the charge-ordered state, the Fe L{sub 3}-XAS shows a double-peak structure, which is a characteristic of Fe{sup 2+} and Fe{sup 3+} ions. In the high-temperature region, the double-peak structure becomes a broad single peak, because of overlap with the thermally excited state.

  15. Superposition model analysis from polarized electronic absorption spectra of Co2+ in trigonally distorted octahedra in brucite-type Co(OH)2

    Polarized electronic absorption spectra of Co2+ in trigonally compressed octahedra in brucite-type Co(OH)2 have been measured at 290 and 90 K by microscope-spectrometric techniques and analysed in terms of the superposition model (SM) of crystal fields. The resulting SM and interelectronic repulsion parameters are B-bar4=5260, B-bar2=4920, Racah B = 825, Racah C = 3550 cm-1 at 290 K and B-bar4=5320, B-bar2=3900, Racah B = 830, Racah C = 3500 cm-1 at 90 K (R0 = 2.1115 A; fixed exponential and spin-orbit parameters t4=5, t2=3, ζ = 500 cm-1). Together with a recent SM analysis of Li2Co3(SeO3)4, the B-bark refined for Co(OH)2 further confine the magnitude of the hitherto unknown 'correct' SM parameters of Co2+ for future application to structurally and/or chemically less well defined systems. (author)

  16. Technical Note: Recipe for monitoring of total ozone with a precision of around 1 DU applying mid-infrared solar absorption spectra

    M. Schneider

    2008-01-01

    Full Text Available Mid-infrared solar absorption spectra recorded by a state-of-the-art ground-based FTIR system have the potential to provide precise total O3 amounts. The currently best-performing retrieval approaches use a combination of small and broad spectral O3 windows between 780 and 1015 cm−1. We show that for these approaches the uncertainties of the temperature profile are by far the major error sources. We demonstrate that a joint optimal estimation of temperature and O3 profiles widely eliminates this error. The improvements are documented by an extensive theoretical error estimation. Our results suggest that mid-infrared FTIR measurements can provide total O3 amounts with a precision of around 1 DU, placing this method among the most precise ground-based O3 monitoring techniques. We recapitulate the requirements on the instrumental hardware and on the retrieval that are needed to achieve this high precision.

  17. Recipe for continuous monitoring of total ozone with a precision of around 1 DU applying mid-infrared solar absorption spectra

    M. Schneider

    2007-06-01

    Full Text Available Mid-infrared solar absorption spectra recorded by a state-of-the-art ground-based FTIR system have the potential to provide precise total O3 amounts. The currently best-performing retrieval approaches use a combination of small and broad spectral O3 windows between 780 and 1015 cm−1. We show that for these approaches uncertainties in the temperature profile are by far the major error sources. We demonstrate that a joint optimal estimation of temperature and O3 profiles widely eliminates this error. The improvements are documented by an extensive theoretical error estimation. Our results suggest that mid-infrared FTIR measurements can provide total O3 amounts with a precision of around 1 DU, placing this method among the most precise ground-based O3 monitoring techniques. We recapitulate the requirements on instrumental hardware and retrieval necessary to achieve this high precision.

  18. Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

    Jin Zhu

    2014-03-01

    Full Text Available The localized surface plasmon resonances (LSPRs of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3° crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis spectroscopy, and atomic force microscopy (AFM. The results showed that the gold particle coverage decreases with increasing pH value of the gold colloid solution. This phenomenon demonstrates that self-assembled gold surfaces were formed via the electrostatic adsorption of gold particles on the positively charged, ionized amino groups on the crystal plates in the acidic solution. The spectrum of gold nanoparticles with different coverage degree on the crystal plates showed that the LSPR properties are highly dependent on pH.

  19. Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

    The localized surface plasmon resonances (LSPRs) of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3°) crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis) spectroscopy, and atomic force microscopy (AFM). The results showed that the gold particle coverage decreases with increasing pH value of the gold colloid solution. This phenomenon demonstrates that self-assembled gold surfaces were formed via the electrostatic adsorption of gold particles on the positively charged, ionized amino groups on the crystal plates in the acidic solution. The spectrum of gold nanoparticles with different coverage degree on the crystal plates showed that the LSPR properties are highly dependent on pH

  20. Effects of ionic liquid [bmim][PF6] on absorption spectra and reaction kinetics of the duroquinone triplet state in acetonitrile.

    Zhu, Guanglai; Wu, Guozhong; Sha, Maolin; Long, Dewu; Yao, Side

    2008-04-10

    The transient absorption spectra and photoinduced electron-transfer process of duroquinone (DQ) in mixed binary solutions of ionic liquid (IL) [bmim][PF6] and acetonitrile (MeCN) have been investigated by laser photolysis at an excitation wavelength of 355 nm. A spectral blue shift of 3DQ* was observed in the IL/MeCN mixtures compared to MeCN. At lower VIL(volume fraction of IL), the interaction between DQ and the solvent is dominant, and the decay rate constant (kobs) of 3DQ* increases steadily with the increasing of VIL; to the contrary, at higher VIL, the network structures due to the hydrogen bond and viscosity are dominant, and the decay rate constant decreases obviously with increasing VIL. A critical point (turnover) was observed at VIL = approximately 0.30. The dependence of the observed growth rate (kgr) of the photoinduced electron-transfer (PET) products on VIL is complex and shows a special change; kgr first decreases with increasing VIL, then increases, and finally decreases slowly with further increasing of VIL. It is speculated that the PET process in the mixture can be affected by factors including the local structure and the reorganization energy of the solvent and salt and cage effects. The change of local structure of [bmim][PF6]/MeCN is supported by following the steady-state fluorescence behavior of the mixture, in combination with the molecular dynamics simulation of the thermodynamic property. The results revealed that the degree of self-aggregation of monomeric cations (bmim+) to associated forms increases with increasing VIL. This is in good agreement with the laser photolysis results for the same solutions. PMID:18331005

  1. Electronic Absorption Spectra of Neutral Perylene (C20H12), Terrylene (C30H16), and Quaterrylene (C40H20) and their Positive and Negative Ions: Ne Matrix-Isolation Spectroscopy and Time Dependent Density Functional Theory Calculations

    Halasinski, Thomas M.; Weisman, Jennifer L.; Lee, Timothy J.; Salama, Farid; Head-Gordon, Martin; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We present a full experimental and theoretical study of an interesting series of polycyclic aromatic hydrocarbons, the oligorylenes. The absorption spectra of perylene, terrylene and quaterrylene in neutral, cationic and anionic charge states are obtained by matrix-isolation spectroscopy in Ne. The experimental spectra are dominated by a bright state that red shifts with growing molecular size. Excitation energies and state symmetry assignments are supported by calculations using time dependent density functional theory methods. These calculations also provide new insight into the observed trends in oscillator strength and excitation energy for the bright states: the oscillator strength per unit mass of carbon increases along the series.

  2. A search for HI absorption in the radio spectra of the quasi-stellar objects 4C 05.34 and PKS 0237-23

    In an attempt to learn more about the nature of the intergalactic medium, a search was undertaken for an absorption line at a frequency corresponding to the HI 21 cm line at the red shift of an optical absorption line system. Detection of a red shift 21 cm absorption would verify that the optical absorption line system was not a chance identification, and would help to establish the intergalactic origin of the absorbing clouds. The objects chosen for investigation were 4C 05.34 and PKS 0237-23. (R.L.)

  3. Quenching of singlet oxygen by natural and synthetic antioxidants and assessment of electronic UV/Visible absorption spectra for alleviating or enhancing the efficacy of photodynamic therapy

    Kaneez Fatima

    2016-02-01

    Full Text Available Photodynamic therapy (PDT is one of the methods involved in cancer therapy exploiting singlet oxygen as a weapon to kill cancer cells. Singlet oxygen, a bizarre reactive oxygen species as it is not related to electron transfer to O2 but it is one of the most active intermediate involved in biochemical reactions as it directly reacts with all the major macromolecules like DNA, protein, lipids etc, various photosensitized oxidations and in the photodegradation of dyes and polymers. Recent studies about the usage of antioxidant along with the photo-sensitizer involved in photodynamic therapy have shown concentration- dependent dual behavior like usually it retards the efficacy of PDT but at a higher dose mostly, it actually enhances the damaging effect of PDT. The natural and synthetic antioxidants are being used in our day to day life in order to increase the shelf life of various food ingredients and processed foods. In this paper, we have compared natural and synthetic antioxidants along with the known singlet oxygen quencher (DABCO in order to understand the quenching potential of singlet oxygen (1O2 which is lowest electronically excited state of molecular oxygen. The singlet oxygen can be artificially generated through various methods such as sunlight, phosphate, ozonides, NaOCl and H2O2 etc. We have studied the mechanisms of the few antioxidant effects on the bleaching of RNO linked with the energy decay of 1O2 produced by the Mallet reaction (H2O2+HOCl and #8200; and #8594; and #8200;HCl+H2O+1O2. beta-Carotene, and #945;-Tocopherol, Ascorbic acid and Quercetin exhibited best dose-dependent singlet quenching ranging from 92.3 to 56.5 % at 100 and #956;M among others. Overall singlet oxygen is a major concern of light-related properties so we have analyzed the theoretical aspect of electronic UV/visible absorption spectra of the antioxidants studied through ZINDO CI semi-empirical Hamiltonian method. We have compared only the first singlet

  4. Direct deconvolution of two-state pump-probe x-ray absorption spectra and the structural changes in a 100 ps transient of Ni(II)-tetramesitylporphyrin.

    Della-Longa, S.; Chen, L. X.; Frank, P.; Hayakawa, K.; Hatada, K.; Benfatto, M.; Chemical Sciences and Engineering Division; Univ. dell' Aquila; Lab. Nazionali di Frascati; Northwestern Univ.; Stanford Univ.; Museo storico della Fisica e Centro Studi e Ricerche

    2009-05-04

    Full multiple scattering (FMS) Minuit XANES (MXAN) has been combined with laser pump-probe K-edge X-ray absorption spectroscopy (XAS) to determine the structure of photoexcited Ni(II)tetramesitylporphyrin, Ni(II)TMP, in dilute toluene solution. It is shown that an excellent simulation of the XANES spectrum is obtained, excluding the lowest-energy bound-state transitions. In ground-state Ni(II)TMP, the first-shell and second-shell distances are, respectively, d(Ni-N) = (1.93 {+-} 0.02) {angstrom} and d(Ni-C) = (2.94 {+-} 0.03) {angstrom}, in agreement with a previous EXAFS result. The time-resolved XANES difference spectrum was obtained from the spectra of Ni(II)TMP in its photoexcited T{sub 1} state and its ground state, S{sub 0}. The XANES difference spectrum has been analyzed to obtain both the structure and the fraction of the T{sub 1} state. If the T{sub 1} fraction is kept fixed at the value (0.37 {+-} 0.10) determined by optical transient spectroscopy, a 0.07 {angstrom} elongation of the Ni-N and Ni-C distances [d(Ni-N) and d(Ni-C)] is found, in agreement with the EXAFS result. However, an evaluation of both the distance elongation and the T{sub 1} fraction can also be obtained using XANES data only. According to experimental evidence, and MXAN simulations, the T{sub 1} fraction is (0.60 {+-} 0.15) with d(Ni-N) = (1.98 {+-} 0.03) {angstrom} (0.05 {angstrom} elongation). The overall uncertainty of these results depends on the statistical correlation between the distances and T{sub 1} fraction, and the chemical shift of the ionization energy because of subtle changes of metal charge between the T{sub 1} and S{sub 0} states. The T{sub 1} excited-state structure results, independently obtained without the excited-state fraction from optical transient spectroscopy, are still in agreement with previous EXAFS investigations. Thus, full multiple scattering theory applied through the MXAN formalism can be used to provide structural information, not only on the ground

  5. Optical-absorption spectra, crystal-field energy levels, and transition line strengths of holmium in trigonal Na3[Ho(C4H4O5)3].2NaClO4.6H2O

    Moran, D. M.; de Piante, Anne; Richardson, F. S.

    1990-08-01

    Locations and assignments of 105 crystal-field levels are reported for Ho3+ in the trigonal Na3[Ho(oxydiacetate)3].2NaClO4.6H2O system. These levels were located and assigned from transitions observed in axial and σ- and π-polarized orthoaxial absorption spectra obtained on single-crystal samples at temperatures between 5 and 295 K. The absorption measurements spanned the 8000-37 000-cm-1 spectral region, and the assigned energy levels derive from 23 different [SL]J multiplet manifolds of the 4f10 electronic configuration of Ho3+, with principal SL parentages derived from nine different Russell-Saunders terms (5I, 5F, 5S, 3K, 5G,3H, 3L, 3M, and 5D). The empirical energy-level data are analyzed in terms of a parametrized model Hamiltonian for the 4f10 electronic configuration, assumed to be perturbed by a crystal field of trigonal dihedral (D3) symmetry. Parametric fits of calculated-to-empirical energy-level data yield a rms deviation of ~9 cm-1 (between calculated and observed energies). The Hamiltonian parameter values obtained from these energy-level analyses are compared with results obtained from similar analyses of Ho3+ in other crystals and of other lanthanide (M3+) ions in the Na3[M(oxydiacetate)3].2NaClO4.6H2O system. In addition to energy-level locations and assignments, quantitatively determined line strengths are reported for 42 transitions observed in the axial absorption spectra at 10 K, and for 19 transitions observed in the π-polarized orthoaxial absorption spectra at 10 K. Fifty of these transitions originate from the ground crystal-field level of the 5I8 (ground) multiplet, and eleven originate from the second crystal-field level (located 14 cm-1 above ground) of 5I8.

  6. Optical absorption spectra, crystal-field analysis, and electric dipole intensity parameters for europium in Na 3[En(ODA) 3]-2NaClO 4·6H 2O

    Berry, Mary T.; Schwieters, Charles; Richardson, F. S.

    1988-05-01

    Locations and assignments of 61 crystal-field levels are reported for Eu 3+ in the trigonal Na 3[Eu(oxydiacetate) 3]· 2NaClO 46H 2O system. These energy levels span the 0-37400 cm - energy region, and they were located and assigned from optical emission spectra and from axial and orthoaxial (σ and π-polarized) absorption measurements on single crystals. The assigned crystal-field levels span 22 different multiplet manifolds, with principal parentages derived from seven different f 6 Russell-Saunders terms ( 2F, 5D, 5L, 5H, 5F, 5I, and 5K). The assigned levels are analyzed in terms of a 26-parameter electronic Hamiltonian in which six of the parameters are defined to represent the 4f-electron/crystal-field interactions for Eu 3+ ions located at sites with trigonal dihedral (D 3) symmetry. Quantitative line intensities are reported for 39 individual 4f→4f (crystal-field) transitions observed in the low-temperature (10 K) absorption spectra, and these intensity data are analyzed in terms of a general parametric model for 4f→4f transition intensities in lanthanide systems. The energy and intensity parameterizations provide a basis for calculating the 4f→4f absorption spectra of Eu 3+ in Na 3[Eu(oxydiacetate) 3]· 2NaClO 4·6H 2O over a wide spectral range and excellent agreement between calculated and experimentally measured spectra is obtained. Several of the intensity parameters determined to be important in this study carry information of particular significance to understanding the structural and mechanisticbases of lanthanid

  7. Spectra of alkali atoms

    Emission spectra of alkali atoms has been determined by using spectrometer at the ultraviolet to infra red waves range. The spectra emission can be obtained by absorption spectrophotometric analysis. Comparative evaluations between experimental data and data handbook obtained by spark method were also presented. (author tr.)

  8. Contribution of magnetic-dipole transitions in the magnetic circular anisotropy of the absorption spectra of Eu3Ga5O12

    The optical absorption and magnetic circular dichroism of Eu3Ga5O12 has been investigated in the wavelength range 526 - 527 nm at 85 K. The comparison between theoretical and experimental investigations show that the appearance of the MCD feature observed at absorption line near 526.6 nm may be well explained by the contribution of Van-Vleck 'mixing' between the Stark singlet states from the 7F0 and 7F1 multiplet manifolds of Eu3Ga5O12. (authors)

  9. Preliminary optical design of a varied line-space spectrograph for the multi-channel detection of near-edge X-ray absorption fine structure (NEXAFS) spectra in the 280-550 eV energy range

    Wheeler, B.S.; McKinney, W.R.; Hussain, Z.; Padmore, H.

    1996-07-01

    The optical design of a varied line-space spectrograph for the multi-channel recording of NEXAFS spectra in a single {open_quotes}snapshot{close_quotes} is proposed. The spectrograph is to be used with a bending magnet source on beamline 7.3.2 at the Advanced Light Source (ALS). Approximately 20 volts of spectra are simultaneously imaged across a small square of material sample at each respective K absorption edge of carbon, nitrogen, and oxygen. Photoelectrons emitted from the material sample will be collected by an electron imaging microscope, the view field of which determines the sampling size. The sample also forms the exit slit of the optical system. This dispersive method of NEXAFS data acquisition is three to four orders of magnitude faster than the conventional method of taking data point-to-point using scanning of the grating. The proposed design is presented along with the design method and supporting SHADOW raytrace analysis.

  10. Gamma ray interaction, crystallization and infrared absorption spectra of some glasses and glass-ceramics from the system Li2O.B2O3.Al2O3

    The infrared absorption spectra of some selected ternary glasses and their glass-ceramic derivatives from the system Li2OB2O3Al2O3 have been measured in the spectral range 200-4000 cm-1 before and after successive gamma rays irradiation. Vibrational and crystallization techniques are employed to investigate the structure and phases which are found in this system by controlled crystallization. The role of Al2O3 in the structure and the crystallization behaviour of the system has been discussed. The effect of gamma rays on the surface of the glasses and glass-ceramics as revealed from infrared spectroscopy is discussed. (author)

  11. First-principles calculations of X-ray absorption spectra at the K-edge of 3d transition metals: an electronic structure analysis of the pre-edge

    Cabaret, Delphine; Bordage, Amélie; Juhin, Amélie; Arfaoui, M.; Gaudry, Emilie

    2010-01-01

    We first present an extended introduction of the various methods used to extract electronic and structural information from the K pre-edge X-ray absorption spectra of 3d transition metal ions. The K pre-edge structure is then modelled for a selection of 3d transition metal compounds and analyzed using first-principles calculations based on the density functional theory (DFT) in the local density approximation (LDA). The selected compounds under study are presented in an ascending order of ele...

  12. Hypersensitivity in the 4f-4f absorption spectra of tris (acetylacetonato) neodymium(III) complexes with imidazole and pyrazole in non-aqueous solutions. Effect of environment on hypersensitive transitions

    Ansari, Anees A.; Ilmi, Rashid [Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India); Iftikhar, K., E-mail: kiftikhar.ch@jmi.ac.in [Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India)

    2012-01-15

    The optical absorption spectra of [Nd(acac){sub 3}(H{sub 2}O){sub 2}].H{sub 2}O, [Nd(acac){sub 3}(im){sub 2}] and [Nd(acac){sub 3}(pz){sub 2}] (where acac is the anion of acetylacetone, im is imidazole and pz is pyrazole) complexes in the visible region have been analyzed. The transition {sup 4}G{sub 5/2} <- {sup 4}I{sub 9/2} located near the middle of the visible region (17,500 cm{sup -1}) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f-4f transitions. It is overlapped by a less intense transition {sup 2}G{sub 7/2} <- {sup 4}I{sub 9/2}. The band shapes of the hypersensitive transition show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of changes in the environment about the Nd(III) ion in the various solutions and suggests coordination of a solvent molecules. Pyridine has been found especially effective in promoting 4f-4f electric-dipole intensity. The DMSO invades the complexes and replaces the water molecules and heterocyclic amines from the coordination sphere. Two DMSO molecules coordinate and the complexes acquire similar structure, [Nd(acac){sub 3}(DMSO){sub 2}] in solution. The oscillator strength and the band shape of the hypersensitive transition of all the complexes remains the same in this solvent. The IR spectra and the NMR spectra of the complexes have also discussed. - Highlights: > Structurally similar eight-coordinate complexes of neodymium are synthesized. > The 4f-4f absorption spectra are investigated in non-aqueous solvents. > Methanol, isopropanol and acetonitrile are coordinating solvents. > Pyridine and DMSO are coordinating solvents by replacing the ancillary ligands. > Pyridine is most effective in promoting the 4f-4f intensity.

  13. Hypersensitivity in the 4f-4f absorption spectra of tris (acetylacetonato) neodymium(III) complexes with imidazole and pyrazole in non-aqueous solutions. Effect of environment on hypersensitive transitions

    The optical absorption spectra of [Nd(acac)3(H2O)2].H2O, [Nd(acac)3(im)2] and [Nd(acac)3(pz)2] (where acac is the anion of acetylacetone, im is imidazole and pz is pyrazole) complexes in the visible region have been analyzed. The transition 4G5/2 4I9/2 located near the middle of the visible region (17,500 cm-1) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f-4f transitions. It is overlapped by a less intense transition 2G7/2 4I9/2. The band shapes of the hypersensitive transition show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of changes in the environment about the Nd(III) ion in the various solutions and suggests coordination of a solvent molecules. Pyridine has been found especially effective in promoting 4f-4f electric-dipole intensity. The DMSO invades the complexes and replaces the water molecules and heterocyclic amines from the coordination sphere. Two DMSO molecules coordinate and the complexes acquire similar structure, [Nd(acac)3(DMSO)2] in solution. The oscillator strength and the band shape of the hypersensitive transition of all the complexes remains the same in this solvent. The IR spectra and the NMR spectra of the complexes have also discussed. - Highlights: → Structurally similar eight-coordinate complexes of neodymium are synthesized. → The 4f-4f absorption spectra are investigated in non-aqueous solvents. → Methanol, isopropanol and acetonitrile are coordinating solvents. → Pyridine and DMSO are coordinating solvents by replacing the ancillary ligands. → Pyridine is most effective in promoting the 4f-4f intensity.

  14. A Novel Observation of 'a Sharp Absorption Line' Using Much More Broad Laser Lights: Quantum Interference in the Autoionization Spectra of Sc

    The most accurate measurements in physical sciences will be precision spectroscopic experiments which are based on the usage of most narrow lines in cooperation with interference phenomena. We present a novel experimental observation of 'a sharp absorption resonance line' with much more broad laser lights. The mechanism of such a novel phenomenon will be elucidated and its implications will be discussed

  15. Limits on the temporal variation of the fine structure constant, quark masses and strong interaction from quasar absorption spectra and atomic clock experiments

    Flambaum, V V; Thomas, A W; Young, R D

    2004-01-01

    We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of $(m_q/\\Lambda_{QCD})$ from recent measurements of hydrogen hyperfine (21 cm) and molecular rotational transitions in quasar absorption systems, atomic clock experiments with hyperfine transitions in H, Rb, Cs, Yb$^+$, Hg$^+$ and optical transition in Hg$^+$. Experiments with Cd$^+$, deuterium/hydrogen, molecular SF$_6$ and Zeeman transitions in $^3$He/Xe are also discussed.

  16. Effect of gamma rays absorbed doses and heat treatment on the optical absorption spectra of silver ion-exchanged silicate glass

    Farah, Khaled; Hosni, Faouzi; Mejri, Arbi; Boizot, Bruno; Hafedh, Ben; Hamzaoui, Ahmed Hichem

    2014-01-01

    International audience Samples of a commercial silicate glass have been subjected to ion exchange at 320 °C in a molten mixture of AgNO 3 and NaNO 3 with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1–250 kGy and heating at the temperature of 550 °C for different time periods ranging from 10 to 582 min. The spectral absorption in UV–Vis range of the Ag–Na ion exchanged glass was measured and used to determine the s...

  17. Vibrational analysis of various irotopes of L-alanyl-L-alanine in aqueous solution: Vibrational Absorption (VA), Vibrational Circular Dichroism (VCD), Raman and Raman Optical Activity (ROA) Spectra

    Jalkanen, Karl J.; Nieminen, R.M.; Knapp-Mohammady, M.;

    2003-01-01

    dipole-magnetic dipole polarizability derivatives (EDMDPD) and the electric dipole-electric cluadrapole polarizability derivatives (EDEQPD) have been calculated at the RHF/6-31G* level of theory, The VA, VCD, Raman, and ROA spectral simulations for the various isotoporners are compared with the....... DFT Becke3LYP/6-31G* theory has been used to determine the geometry, Hessian, atomic polar tensors (APT), and atomic axial tensors (AAT), and the electric dipole-electric dipole polarizability derivatives (EDEDPD), which are required for us to simulate the VA, VCD, and Raman spectra. The electric...

  18. Experimental and theoretical correlations between vanadium K-edge X-ray absorption and K[Formula: see text] emission spectra.

    Rees, Julian A; Wandzilak, Aleksandra; Maganas, Dimitrios; Wurster, Nicole I C; Hugenbruch, Stefan; Kowalska, Joanna K; Pollock, Christopher J; Lima, Frederico A; Finkelstein, Kenneth D; DeBeer, Serena

    2016-09-01

    A series of vanadium compounds was studied by K-edge X-ray absorption (XAS) and K[Formula: see text] X-ray emission spectroscopies (XES). Qualitative trends within the datasets, as well as comparisons between the XAS and XES data, illustrate the information content of both methods. The complementary nature of the chemical insight highlights the success of this dual-technique approach in characterizing both the structural and electronic properties of vanadium sites. In particular, and in contrast to XAS or extended X-ray absorption fine structure (EXAFS), we demonstrate that valence-to-core XES is capable of differentiating between ligating atoms with the same identity but different bonding character. Finally, density functional theory (DFT) and time-dependent DFT calculations enable a more detailed, quantitative interpretation of the data. We also establish correction factors for the computational protocols through calibration to experiment. These hard X-ray methods can probe vanadium ions in any oxidation or spin state, and can readily be applied to sample environments ranging from solid-phase catalysts to biological samples in frozen solution. Thus, the combined XAS and XES approach, coupled with DFT calculations, provides a robust tool for the study of vanadium atoms in bioinorganic chemistry. PMID:27251139

  19. X-ray absorption spectra of nucleotides (AMP, GMP, and CMP) in liquid water solutions near the nitrogen K-edge

    Ukai, Masatoshi; Yokoya, Akinari; Fujii, Kentaro; Saitoh, Yuji

    2010-07-01

    The X-ray absorption of nucleotides (adenosine-5'-monophosphate, guanosine 5'-monophosphate, and cytidine 5'-monophosphate) are measured in both water solutions and thin solid films at X-ray energies near the nitrogen K-edge in the 'water-window' region. Each spectrum corresponds to the selective excitation of a nucleobase site in a nucleotide, and thus has features similar to the spectrum of the corresponding nucleobase. An additional new peak in the energy region of the nitrogen 1s → π* resonance is observed for each nucleotide. No significant difference between the water solutions and thin solid films is found, which might be attributable to the hydrophobic properties of a nucleobase in a nucleotide.

  20. Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: explicit treatment of the vibronic transitions.

    D'Abramo, Marco; Aschi, Massimiliano; Amadei, Andrea

    2014-04-28

    Here, we extend a recently introduced theoretical-computational procedure [M. D'Alessandro, M. Aschi, C. Mazzuca, A. Palleschi, and A. Amadei, J. Chem. Phys. 139, 114102 (2013)] to include quantum vibrational transitions in modelling electronic spectra of atomic molecular systems in condensed phase. The method is based on the combination of Molecular Dynamics simulations and quantum chemical calculations within the Perturbed Matrix Method approach. The main aim of the presented approach is to reproduce as much as possible the spectral line shape which results from a subtle combination of environmental and intrinsic (chromophore) mechanical-dynamical features. As a case study, we were able to model the low energy UV-vis transitions of pyrene in liquid acetonitrile in good agreement with the experimental data. PMID:24784250

  1. Effect of gamma rays absorbed doses and heat treatment on the optical absorption spectra of silver ion-exchanged silicate glass

    Farah, Khaled, E-mail: kafarah@gmail.com [Unité de recherche: Maîtrise et développement des techniques nucléaires à caractère pacifique, Centre National des Sciences et Technologie Nucléaires, 2020 Sidi-Thabet (Tunisia); ISTLS, University of Sousse (Tunisia); Hosni, Faouzi [Unité de recherche: Maîtrise et développement des techniques nucléaires à caractère pacifique, Centre National des Sciences et Technologie Nucléaires, 2020 Sidi-Thabet (Tunisia); Academie Militaire de Fondouk Jedid, 8012 Nabeul (Tunisia); Mejri, Arbi [Unité de recherche: Maîtrise et développement des techniques nucléaires à caractère pacifique, Centre National des Sciences et Technologie Nucléaires, 2020 Sidi-Thabet (Tunisia); Boizot, Bruno [Laboratoire des Solides Irradiés, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Hamzaoui, Ahmed Hichem [Centre National de Recherche en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Ben Ouada, Hafedh [Laboratoire des Interfaces et Matériaux Avancés, Faculté des Sciences, University of Monastir, Avenue de l’environnement, 5019 Monastir (Tunisia)

    2014-03-15

    Samples of a commercial silicate glass have been subjected to ion exchange at 320 °C in a molten mixture of AgNO{sub 3} and NaNO{sub 3} with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1–250 kGy and heating at the temperature of 550 °C for different time periods ranging from 10 to 582 min. The spectral absorption in UV–Vis range of the Ag–Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 °C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy.

  2. Thermal annealing and UV irradiation effects on structure, morphology, photoluminescence and optical absorption spectra of EDTA-capped ZnS nanoparticles

    Osman, M. A.; Othman, A. A.; El-Said, Waleed A.; Abd-Elrahim, A. G.; Abu-sehly, A. A.

    2016-02-01

    Monodispersed ZnS nanoparticles (NPs) were prepared by the chemical precipitation method. Thermally induced structural, morphological and optical changes have been investigated using x-ray diffraction, high-resolution transmission electron microscopy, optical absorption, photoluminescence (PL), and Fourier transform infrared and Raman spectroscopy. It was found that D increases with increasing annealing temperature (T a). The onset of the ZnS phase transition from cubic to hexagonal structure takes place at 400 °C, while cubic ZnS transforms into hexagonal ZnO via thermal oxidation in air at 600 °C. It is also noted that increasing T a results in the red shift of the optical band gap (E\\text{g}\\text{opt} ) and the thermal bleaching of exciton absorption. The PL spectrum of as-prepared ZnS nanopowder shows UV emission bands at 363 and 395 nm and blue and green emission at 438 and 515 nm, respectively. With increasing T a up to 500 °C, these bands were quenched and red-shifted. In addition, the UV irradiation effects on colloidal ZnS NPs were investigated. UV irradiation at a dose  photopolymerization, the formation of a ZnSO4 passivation layer, as well as the reduction of D by photocorrosion. At a UV irradiation dose  <13 J cm-2 both E\\text{g}\\text{opt} and D did not change and PL intensity was quenched, which were caused by the creation of nonradiative surface states by the photodegradation of the capping agent and photopassivated layer. The mechanism of the PL emission process in ZnS NPs was discussed and an energy band diagram was proposed.

  3. Effect of gamma rays absorbed doses and heat treatment on the optical absorption spectra of silver ion-exchanged silicate glass

    Samples of a commercial silicate glass have been subjected to ion exchange at 320 °C in a molten mixture of AgNO3 and NaNO3 with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1–250 kGy and heating at the temperature of 550 °C for different time periods ranging from 10 to 582 min. The spectral absorption in UV–Vis range of the Ag–Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 °C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy

  4. Experimental and theoretical studies of the VUV emission and absorption spectra of H{sub 2}, HD and D{sub 2} molecules; Etude experimentale et theorique des spectres d'emission et d'absorption VUV des molecules H{sub 2}, D{sub 2} et HD

    Roudjane, M

    2007-12-15

    The aim of this thesis is to carry out an experimental study of the absorption and emission spectra of the D{sub 2} and HD isotopes, with high resolution, in the VUV domain and to supplement it by a theoretical study of the excited electronic states involved in the observed transitions. The emission spectra of HD and D{sub 2} are produced by Penning discharge source operating under low pressure and are recorded in the spectral range 78 - 170 nm. The recorded spectra contains more than 20.000 lines. The analysis of the spectrum consists in identifying and assigning the lines to the electronic transitions between energy levels of the molecule. The present analysis is based on our theoretical calculations of the ro-vibrational energy levels of the excited electronic states and the transition probabilities from these states towards the energy levels of the fundamental state. The theoretical results are obtained by resolving the coupled equations between the excited electronic states B{sup 1}{sigma}{sub u}{sup 1}, B'{sup 1}{sigma}{sub u}{sup 1}, C{sup 1}{pi}{sub u}{sup 1} and D{sup 1}{pi}{sub u}{sup 1}, taking into account the nonadiabatic couplings between these states, and they are obtained in the adiabatic approximation for the excited electronic states B''B-bar{sup 1}{sigma}{sub u}{sup +}, D'{sup 1}{pi}{sub u}{sup 1} and D''{sup 1}{pi}{sub u}{sup 1}. The equations are resolved using a modern method based on the discretization variables representation method. In addition, we have carried out a study of the absorption spectra of the HD and D{sub 2} molecules.

  5. Power and polarization dependences of ultra-narrow electromagnetically induced absorption (EIA) spectra of 85 Rb atoms in degenerate two-level system

    Qureshi, Muhammad Mohsin; Rehman, Hafeez Ur; Noh, Heung-Ryoul; Kim, Jin-Tae

    2016-05-01

    We have investigated ultra-narrow EIA spectral features with respect to variations of polarizations and powers of pump laser beam in a degenerate two-level system of the transition of 85 Rb D2 transition line. Polarizations of the probe laser beam in two separate experiments were fixed at right circular and horizontal linear polarizations, respectively while the polarizations of the pump lasers were varied from initial polarizations same as the probe laser beams to orthogonal to probe polarizations. One homemade laser combined with AOMs was used to the pump and probe laser beams instead of two different lasers to overcome broad linewidths of the homemade lasers. Theoretically, probe absorption coefficients have been calculated from optical Bloch equations of the degenerate two level system prepared by a pump laser beam. In the case of the circular polarization, EIA signal was obtained as expected theoretically although both pump and probe beams have same polarization. The EIA signal become smaller as power increases and polarizations of the pump and probe beams were same. When the polarization of the pump beam was linear polarization, maximum EIA signal was obtained theoretically and experimentally. Experimental EIA spectral shapes with respect to variations of the pump beam polarization shows similar trends as the theoretical results.

  6. Efficient simultaneous reverse Monte Carlo modeling of pair-distribution functions and extended x-ray-absorption fine structure spectra of crystalline disordered materials

    Németh, Károly; Chapman, Karena W.; Balasubramanian, Mahalingam; Shyam, Badri; Chupas, Peter J.; Heald, Steve M.; Newville, Matt; Klingler, Robert J.; Winans, Randall E.; Almer, Jonathan D.; Sandi, Giselle; Srajer, George

    2012-02-01

    An efficient implementation of simultaneous reverse Monte Carlo (RMC) modeling of pair distribution function (PDF) and EXAFS spectra is reported. This implementation is an extension of the technique established by Krayzman et al. [J. Appl. Cryst. 42, 867 (2009)] in the sense that it enables simultaneous real-space fitting of x-ray PDF with accurate treatment of Q-dependence of the scattering cross-sections and EXAFS with multiple photoelectron scattering included. The extension also allows for atom swaps during EXAFS fits thereby enabling modeling the effects of chemical disorder, such as migrating atoms and vacancies. Significant acceleration of EXAFS computation is achieved via discretization of effective path lengths and subsequent reduction of operation counts. The validity and accuracy of the approach is illustrated on small atomic clusters and on 5500-9000 atom models of bcc-Fe and α-Fe2O3. The accuracy gains of combined simultaneous EXAFS and PDF fits are pointed out against PDF-only and EXAFS-only RMC fits. Our modeling approach may be widely used in PDF and EXAFS based investigations of disordered materials.

  7. Ab initio calculations on SnCl2 and Franck-Condon factor simulations of its ÖX˜ and B˜-X˜ absorption and single-vibronic-level emission spectra

    Lee, Edmond P. F.; Dyke, John M.; Mok, Daniel K. W.; Chow, Wan-ki; Chau, Foo-tim

    2007-07-01

    Minimum-energy geometries, harmonic vibrational frequencies, and relative electronic energies of some low-lying singlet and triplet electronic states of stannous dichloride, SnCl2, have been computed employing the complete-active-space self-consistent-field/multireference configuration interaction (CASSCF/MRCI) and/or restricted-spin coupled-cluster single-double plus perturbative triple excitations [RCCSD(T)] methods. The small core relativistic effective core potential, ECP28MDF, was used for Sn in these calculations, together with valence basis sets of up to augmented correlation-consistent polarized-valence quintuple-zeta (aug-cc-pV5Z) quality. Effects of outer core electron correlation on computed geometrical parameters have been investigated, and contributions of off-diagonal spin-orbit interaction to relative electronic energies have been calculated. In addition, RCCSD(T) or CASSCF/MRCI potential energy functions of the X˜A11, ãB13, and B˜B11 states of SnCl2 have been computed and used to calculate anharmonic vibrational wave functions of these three electronic states. Franck-Condon factors between the X˜A11 state, and the ãB13 and B˜B11 states of SnCl2, which include anharmonicity and Duschinsky rotation, were then computed, and used to simulate the ÖX˜ and B˜-X˜ absorption and corresponding single-vibronic-level emission spectra of SnCl2 which are yet to be recorded. It is anticipated that these simulated spectra will assist spectroscopic identification of gaseous SnCl2 in the laboratory and/or will be valuable in in situ monitoring of SnCl2 in the chemical vapor deposition of SnO2 thin films in the semiconductor gas sensor industry by laser induced fluorescence and/or ultraviolet absorption spectroscopy, when a chloride-containing tin compound, such as tin dichloride or dimethyldichlorotin, is used as the tin precursor.

  8. 1H NMR, electronic-absorption and resonance-Raman spectra of isomeric okenone as compared with those of isomeric β-carotene, canthaxanthin, β-apo-8'-carotenal and spheroidene

    Fujii, Ritsuko; Chen, Chun-Hai; Mizoguchi, Tadashi; Koyama, Yasushi

    1998-05-01

    Eleven cis- trans isomers of okenone were isolated by means of HPLC using a silica-gel column from an isomeric mixture which was obtained by iodine-sensitized photo-isomerization of the all- trans isomer. The configurations of eight isomers among them were determined by NMR spectroscopy using the isomerization shifts of the olefinic 1Hs and the 1H- 1H NOE correlations to be all- trans, 7- cis, 7- cis,8-s- cis, 9- cis, 9'- cis, 13- cis, 13'- cis and 9,9'-di- cis, and their electronic-absorption and resonance-Raman spectra were recorded. Based on the results: (1) the chemical shifts of the olefinic 1Hs in NMR; (2) the wavelength of the A g-→B u+ transition; and (3) the relative intensity of the A g-→A g+ versus the A g-→B u+ transition in electronic absorption; (4) the CC stretching frequency; and (5) the relative intensity of the C10-C11 (C10'-C11') versus the C14-C15 (C14'-C15') stretching vibration in resonance Raman were compared among the all- trans, 7- cis, 9- cis (9'- cis) and 13- cis (13'- cis) isomers of β-carotene, canthaxanthin, β-apo-8'-carotenal, neurosporene, spheroidene and okenone. Relevance of the systematic changes in the above five different parameters originally found in β-carotene was examined in the rest of the carotenoids, and the effects of the peripheral groups on them were explained in terms of the length and asymmetry of the conjugated system consisting of the CC and CO bonds.

  9. 太阳光谱对高分辨吸收光谱反演大气CO2浓度影响的研究%Study on the Effect of Solar Spectra on the Retrieval of Atmospheric CO2 Concentration Using High Resolution Absorption Spectra

    胡振华; 黄腾; 王颖萍; 丁蕾; 郑海洋; 方黎

    2011-01-01

    以太阳光为辐射源的近红外波段高分辨率吸收光谱广泛应用于大气参数遥测.以CO2浓度反演为例,研究了太阳光谱分辨率的影响.利用美国AER公司编制的太阳光谱计算程序得到大气上界的理论计算太阳光谱作为辐射源,结合自行编制的高分辨率大气透过率模拟软件HRATS对大气中CO2平均浓度进行模拟反演.数值模拟计算结果表明,太阳光谱的准确度对浓度反演非常重要,特别是在超分辨光谱反演中异常重要,虽然反演浓度的偏差与观测分辨率没有明显的线性变化规律,但有趋势:观测分辨率的降低对太阳光谱分辨率的要求也降低,为了精确反演大气中CO2浓度,因此需要充分利用大气层顶的高分辨太阳辐射光谱数据.%Taking solar source as radiation in the near-infrared high-resolution absorption spectrum is widely used in remote sensing of atmospheric parameters. The present paper will take retrieval of the concentration of CO2 for example, and study the effect of solar spectra resolution. Retrieving concentrations of CO2 by using high resolution absorption spectra, a method which uses the program provided by AER to calculate the solar spectra at the top of atmosphere as radiation and combine with the HRATS (high resolution atmospheric transmission simulation) to simulate retrieving concentration of CO2. Numerical simulation shows that the accuracy of solar spectrum is important to retrieval, especially in the hyper-resolution spectral retrieavl, and the error of retrieval concentration has poor linear relation with the resolution of observation, but there is a tendency that the decrease in the resolution requires low resolution of solar spectrum. In order to retrieve the concentration of CO2 of atmosphere, the authors' should take full advantage of high-resolution solar spectrum at the top of atmosphere

  10. Modelling the light absorption properties of particulate matter forming organic particles suspended in seawater.Part 1. Model description, classification of organic particles, and example spectra of the light absorption coefficient and the imaginary part of the refractive index of particulate matter for phytoplankton cells and phytoplankton-like particles

    Bogdan Woźniak

    2005-06-01

    Full Text Available Data on organic substances in the sea are applied to distinguish hypothetical chemical classes and physical types of suspended particulate organic matter (POM in seawater. Spectra of the light absorption coefficients of particulate matter apm(λ and the imaginary refractive index n'p(λ, are assessed for some of these classes and types of POM in seawater, that is, for live phytoplankton cells and phytoplankton-like particles. The spectral characteristics of these coefficients are established and the probable ranges of variability of their absolute magnitudes defined on the basis of the mass-specific coefficients of light absorption by the various organic substances forming the particles. Also presented are mathematical relationships linking the coefficients apm(λ and n'p(λ for the various chemical classes of POM with their physical parameters, such as the relative contents of organic matter, water, air or some other gas. This article is part of a bio-optical study undertaken by the authors, the objective of which is to implement remote sensing techniques in the investigation of Baltic ecosystems (Woźniak et al. 2004.

  11. 一种基于香豆素的迈克尔加成型硫醇比色探针%Synthesis and Absorption Spectra of a New Cumarin,derivative as a Colorimetric Probe for Thiols

    周先树; 苗利强; 刘滇生

    2012-01-01

    A colorimetric probe for thiols was developed by using an cumarin derivative based on the Michael addition of thiol to α,β-unsaturated double bond. The Michael addition of a thiol group to Michael acceptor of 1 blocked the intramolecular charge transfer (ICT) from the electron-rich diethylaminocoumarin group to the electron-poor Michael acceptor,leading to a blue shift in the absorption spectra with an evident color change from blueviolet to colorless. The probe exhibited higher selectivity toward thiols (Cys, Hey and GSH) than other amino acids.%基于硫醇对α,β-不饱和双键的亲核加成,设计合成了一种香豆素-3-氧代-2,3-二氢苯并[b]噻吩加合物的比色硫醇探针.硫醇与探针发生迈克尔加成,打断了分子内的共轭体系,阻止了香豆素向缺电子的3-氧代-2,3-二氢苯并[b]噻吩基团的分子内电荷转移,引起了吸收光谱上的蓝移和溶液颜色的变化.

  12. Espectro de gotas e idade de trifólios na taxa de absorção e efeito residual de fungicidas em soja Drops spectra and leaflets age on the fungicides absorption rate and residual effect in soybean

    Giuvan Lenz

    2011-10-01

    Full Text Available O objetivo do presente trabalho foi avaliar o efeito de espectros de gotas (grossas, médias e finas na velocidade de absorção de fungicidas, para trifólios de diferentes idades através de medida indireta expressa pelo residual de controle de ferrugem asiática da soja (Phakopsora pachyrhizi. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições, em arranjo fatorial (3x3x5x4, cujos fatores foram compostos por: três categorias de gotas (grossas, médias e finas; três diferentes posições de avaliação na planta (1°, 3° e 5° trifólios; quatro períodos de tempo entre a aplicação de fungicidas e aplicação de chuva simulada (0, 30, 60 e 120min, mais uma testemunha sem chuva; testemunha sem aplicação, mais os fungicidas azoxistrobina + ciproconazol (60+24g i.a. ha-1 + óleo mineral 0,6L ha-1, azoxistrobina (50g i.a. ha-1 + óleo mineral 0,6L ha-1 e ciproconazol (30g i.a. ha-1. Avaliou-se a densidade de gotas por centímetro quadrado, diâmetro mediano volumétrico, diâmetro mediano numérico e amplitude relativa, além do número de dias para o aparecimento da primeira pústula. Verificou-se que gotas de menor DMV proporcionam maior velocidade de absorção de fungicidas. Trifólios mais novos absorvem os fungicidas mais rapidamente. A utilização de azoxistrobina + ciproconazol + óleo mineral proporcionou o maior número de dias até o aparecimento da primeira pústula.This research aimed to evaluate the effect of large, medium and fine droplets spectra and its interaction with the fungicide absorption rate and leaflets age through indirect measurement expressed by the residual control of Asian soybean rust (Phakopsora pachyrhizi. The experimental design was completely randomized with four replications in a factorial scheme (3x3x5x4, which factors were composed of: three drops spectra (large, medium and fine; three different positions in the plant evaluated (1st, 3rd and 5th leaflets, four

  13. Study on Chemical Compositions and Infrared Absorption Spectra of Natural and Synthetic Emeralds%天然祖母绿与合成祖母绿的成分及红外吸收光谱研究

    申柯娅

    2011-01-01

    祖母绿是一种高档名贵的宝石,其矿物学名称为绿柱石,化学成分为铍铝硅酸盐.鉴别天然祖母绿和人工合成祖母绿,已成为祖母绿宝石鉴定中的一个重要课题.文章采用常规宝石学研究方法、激光剥蚀-电感耦合等离子体质谱法和红外光谱技术对天然祖母绿(包括哥伦比亚祖母绿和巴西祖母绿)、合成祖母绿(包括助熔剂法合成祖母绿和水热法合成祖母绿)样品进行了系统的分析和研究.结果表明,天然祖母绿与合成祖母绿的主要致色微量元素Cr的含量越高,祖母绿的绿色越浓艳;天然祖母绿与合成祖母绿的红外吸收光谱特征具有明显的差异;根据祖母绿中是否含水、水的赋存状态以及氯的吸收峰,可作为准确鉴别天然祖母绿和合成祖母绿的重要依据.等离子体质谱法化学成分分析不能确定祖母绿是天然形成还是人工合成,需在常规宝石学检测的基础上,综合研究祖母绿的红外吸收光谱特征及内含物特征,才能准确地鉴别天然祖母绿、水热法合成祖母绿和助熔剂法合成祖母绿.%As a top-grade and rare gemstone, emerald is a variety of the mineral beryl with the chemical composition Be3 Al2 (SiO3) 6. It is a significant research project to identify natural emerald as opposed to synthetic emerald. The routine gemological methods, laser ablation-inductively coupled plasma mass spectrometry ( LA-ICP-MS) and Fourier Transform Infrared Spectroscopy (FTIR) absorption techniques were used to study natural emeralds from Colombia and Brazil and synthetic emeralds made by flux-grown and hydrothermal synthetic methods. The green color of emerald was closely related to the concentration of the trace element Cr( Ⅲ). The infrared absorption spectra characteristics indicated obvious differences between natural and synthetic emeralds. This technique can provide important information for identifying natural and synthetic emeralds, combined

  14. Action spectra again?

    Coohill, T P

    1991-11-01

    Action spectroscopy has a long history and is of central importance to photobiological studies. Action spectra were among the first assays to point to chlorophyll as the molecule most responsible for plant growth and to DNA as the genetic material. It is useful to construct action spectra early in the investigation of new areas of photobiological research in an attempt to determine the wavelength limits of the radiation region causing the studied response. But due to the severe absorption of ultraviolet (UV) radiation by biological samples, UV action spectra were first limited to small cells (bacteria and fungi). Advances in techniques (e.g. single cell culture) and analysis allowed accurate action spectra to be reported even for mammalian cells. But precise analytical action spectra are often difficult to obtain when large, pigmented, or groups of cells are investigated. Here some action spectra are limited in interpretation and merely supply a wavelength vs effect curve. When polychromatic sources are employed, the interpretation of action spectra is even more complex and formidable. But such polychromatic action spectra can be more directly related to ambient responses. Since precise action spectra usually require the completion of a relatively large number of careful experiments using somewhat sophisticated equipment over a range of at least six wavelengths, they are often not pursued. But they remain central to the elucidation of the effect being studied. The worldwide community has agreed that stratospheric ozone is depleting, with the possibility of a consequent rise in the amount of UV-B (290-320 nm) reaching the earth's surface. It is therefore essential that new action spectra be completed for UV-B effects on a large variety of responses of human, animal, and aquatic plant systems. Combining these action spectra with the known amounts of UV-B reaching the biosphere can give rise to solar UV effectiveness spectra that, in turn, can give rise to estimates

  15. MS-Xα calculation of the elastic electron scattering cross sections and x-ray absorption spectra of CX4 and SiX4 (X = H,F,Cl)

    Multiple scattering Xα bound state and continuum calculations are used to study low energy elastic electron scattering cross sections and pre-edge features in the x-ray absorption spectra (XAS) of (C,Si)X4, X = H,F,Cl. Maxima in the electron scattering cross section are predicted to occur at energies below 4 eV in the t2 channel for CF4, CCl4, SiH4, and SiCl4. These maxima can be assigned to final state orbitals which are bound in XAS and well localized in space and a quantitative correspondence of such scattering ''resonance'' energies and XAS energies may be obtained using the transition state approach. For CH4 and SiF4 even those bound state orbitals giving the greatest XAS intensity are very diffuse, being essentially of Rydberg character. Broad electron scattering maxima are found at energies above 4 eV in these molecules which cannot be directly associated with the bound state orbitals dominating the XAS. The results thus establish that low energy electron scattering resonances and pre-edge XAS are closely related only for orbitals bound and reasonably well localized in XAS. The MS-Xα results almost always reproduce experimental trends along the molecular series but quantitative discrepancies from experiment are sometimes substantial, particularly for the broad high energy scattering maxima in CH4. The narrow t2 resonance calculated for CF4 is found to vary greatly in position and intensity as the C--F distance is varied by small amounts but the stronger, broader t2 resonance in SiH4 is little affected by bond distance variation

  16. BETA SPECTRA. I. Negatrons spectra

    Using the Fermi theory of beta decay, the beta spectra for 62 negatrons emitters have been computed introducing a correction factor for unique forbidden transitions. These spectra are plotted vs. energy, once normal i sed, and tabulated with the related Fermi functions. The average and median energies are calculated. (Author)

  17. 样品的激光诱导击穿光谱及谱线的自吸收现象%Laser Induced Breakdown Spectra of Coal Sample and Self-Absorption of the Spectral Line

    张贵银; 季慧; 靳一东

    2014-01-01

    以脉冲Nd∶AG激光器的二倍频输出为激发源,获得了一种家庭用煤的激光诱导击穿光谱(laser induced breakdown spectrum ,LIBS)。通过对谱线的归属,发现该煤种除包含文献报道的C ,Si ,Mg ,Fe , Al ,Ca ,Ti ,Na ,K元素外,还包含Cd ,Co ,Hf ,Ir ,Li ,Mn ,Ni ,Rb ,Sr ,V ,W ,Zn ,Zr等微量元素,谱图中没有出现对应H和O元素的谱线,把该现象归因于H和O原子的跃迁概率较小,而灵敏谱线对应跃迁的上能级能量较大。同时发现随激光脉冲能量的增加,等离子体发射谱线的强度增大,增加到一定程度,K原子766.493和769.921 nm谱线会出现自吸收现象,自吸收的程度随激光能量的增加而增强,出现明显的双峰结构,把自吸收现象归因于原子大的跃迁概率及激光强度增加引起等离子体中粒子数密度的增大。%The LIBS of one kind of household fuel coal was obtained with the first harmonic output 532 nm of an Nd・YAG laser as radiation source .With the assignment of the spectral lines ,it was found that besides the elements C ,Si ,Mg ,Fe ,Al ,Ca , Ti ,Na and K ,which are reported to be contained in coal ,the presented sample also contains trace elements ,such as Cd ,Co , Hf ,Ir ,Li ,Mn ,Ni ,Rb ,Sr ,V ,W ,Zn ,Zr etc ,but the spectral lines corresponding to O and H elements did not appear in the spectra .This is owing to the facts that the transition probability of H and O atoms is small and the energy of the upper level for transition is higher .The results of measurement also show that the intensity of spectral line increases with the laser pulse energy and self-absorption of the spectral lines K766.493 nm and K769.921 nm will appear to some extent .Increasing laser energy fur-ther will make self-absorption more obvious .The presence of self-absorption can be attributed to two factors .One is the higher transition rate of K atoms ,and the other is that the increase

  18. UV and infrared absorption spectra, atmospheric lifetimes, and ozone depletion and global warming potentials for CCl2FCCl2F (CFC-112), CCl3CClF2 (CFC-112a), CCl3CF3 (CFC-113a), and CCl2FCF3 (CFC-114a)

    Davis, Maxine E.; Bernard, François; McGillen, Max R.; Fleming, Eric L.; Burkholder, James B.

    2016-07-01

    The potential impact of CCl2FCF3 (CFC-114a) and the recently observed CCl2FCCl2F (CFC-112), CCl3CClF2 (CFC-112a), and CCl3CF3 (CFC-113a) chlorofluorocarbons (CFCs) on stratospheric ozone and climate is presently not well characterized. In this study, the UV absorption spectra of these CFCs were measured between 192.5 and 235 nm over the temperature range 207-323 K. Precise parameterizations of the UV absorption spectra are presented. A 2-D atmospheric model was used to evaluate the CFC atmospheric loss processes, lifetimes, ozone depletion potentials (ODPs), and the associated uncertainty ranges in these metrics due to the kinetic and photochemical uncertainty. The CFCs are primarily removed in the stratosphere by short-wavelength UV photolysis with calculated global annually averaged steady-state lifetimes (years) of 63.6 (61.9-64.7), 51.5 (50.0-52.6), 55.4 (54.3-56.3), and 105.3 (102.9-107.4) for CFC-112, CFC-112a, CFC-113a, and CFC-114a, respectively. The range of lifetimes given in parentheses is due to the 2σ uncertainty in the UV absorption spectra and O(1D) rate coefficients included in the model calculations. The 2-D model was also used to calculate the CFC ozone depletion potentials (ODPs) with values of 0.98, 0.86, 0.73, and 0.72 obtained for CFC-112, CFC-112a, CFC-113a, and CFC-114a, respectively. Using the infrared absorption spectra and lifetimes determined in this work, the CFC global warming potentials (GWPs) were estimated to be 4260 (CFC-112), 3330 (CFC-112a), 3650 (CFC-113a), and 6510 (CFC-114a) for the 100-year time horizon.

  19. Study of optical absorption, visible emission and NIR–vis luminescence spectra of Tm3+/Yb3+, Ho3+/Yb3+ and Tm3+/Ho3+/Yb3+ doped tellurite glasses

    Tm3+/Yb3+, Ho3+/Yb3+ co-doped and Tm3+/Ho3+/Yb3+ triply doped TeO2–Bi2O3–ZnO–Li2O–Nb2O5 (TBZLN) tellurite glasses were prepared by melt quenching method. Judd–Ofelt intensity parameters (Ωλ, λ=2, 4 and 6), radiative transition probabilities, branching ratios and radiative lifetimes of Tm3+, Ho3+ ions in co-doped TBZLN glasses were calculated from the optical absorption spectra. Excitation, visible luminescence and decay lifetimes in visible region were also investigated. The stimulated emission and gain cross-sections for the Tm3+:3F4→3H6 (1700 nm) and Ho3+:5I7→5I8 (1956 nm) transitions in co-doped TBZLN glasses have been analyzed and compared with those of other reported glasses. Up-conversion luminescence was observed in TBZLN glasses under 980 nm laser excitation and energy transfer mechanisms have been discussed. Finally, CIE color co-ordinates were calculated and it is observed that the color co-ordinates fall in blue and green regions for Tm3+/Yb3+ and Ho3+/Yb3+ co-doped TBZLN glasses, respectively. A subsequent shift in color co-ordinates from green to greenish-yellow region has been observed with an increase in the concentration (0.1, 0.5 and 1.0 mol%) of Tm3+ ions in Tm3+/Ho3+/Yb3+ triply doped TBZLN glasses. - Highlights: • High degree of covalecy of RE–O bond in co-doped TBZLN glasses was observed. • Tm3+:1D2→3F4 and Ho3+:5F4(5S2)→5I8 transitions show high emission cross-section. • Visible and strong 793 nm emission was observed when pumped by 980 nm diode laser. • Triply doped glasses exhibits tunable emission intensity by increasing Tm3+ ions

  20. FTIR spectra

    Machovič, Vladimír; Novák, František; Madronová, L.; Novák, J.

    New York : Nova Science Publisher, 2011 - (Madronová, L.), s. 21-33 ISBN 978-1-61668-965-0. - ( Chemistry Research and Applications) Institutional research plan: CEZ:AV0Z30460519; CEZ:AV0Z60660521 Keywords : FTIR spectra * humic acids * soil Subject RIV: DB - Geology ; Mineralogy

  1. Quasar Absorption Studies

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  2. X-ray Absorption Spectroscopy

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  3. Molecular absorption in transition region spectral lines

    Schmit, Donald; Ayres, Thomas; Peter, Hardi; Curdt, Werner; Jaeggli, Sarah

    2014-01-01

    Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra. Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence. Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary . The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales...

  4. Absorption studies

    Absorption studies were once quite popular but hardly anyone does them these days. It is easier to estimate the blood level of the nutrient directly by radioimmunoassay (RIA). However, the information obtained by estimating the blood levels of the nutrients is not the same that can be obtained from the absorption studies. Absorption studies are primarily done to find out whether some of the essential nutrients are absorbed from the gut or not and if they are absorbed, to determine how much is being absorbed. In the advanced countries, these tests were mostly done to detect pernicious anaemia where vitamin B12 is not absorbed because of the lack of the intrinsic factor in the stomach. In the tropical countries, ''malabsorption syndrome'' is quire common. In this condition, several nutrients like fat, folic acid and vitamin B12 are not absorbed. It is possible to study absorption of these nutrients by radioisotopic absorption studies

  5. AVIRIS spectra of California wetlands

    Gross, Michael F.; Ustin, Susan L.; Klemas, Vytautas

    1988-01-01

    Spectral data gathered by the AVIRIS from wetlands in the Suisun Bay area of California on 13 October 1987 were analyzed. Spectra representing stands of numerous vegetation types (including Sesuvium verrucosum, Scirpus acutus and Scirpus californicus, Xanthium strumarium, Cynadon dactylon, and Distichlis spicata) and soil were isolated. Despite some defects in the data, it was possible to detect vegetation features such as differences in the location of the chlorophyll red absorption maximum. Also, differences in cover type spectra were evident in other spectral regions. It was not possible to determine if the observed features represent noise, variability in canopy architecture, or chemical constituents of leaves.

  6. Pion absorption processes

    Proton and deuteron production from low-energy pion absorption in light nuclei leading to discrete and continuum states were measured. The LEP beam line at LAMPF was used with a stack of 8 intrinsic germanium crystals. The proton energy spectra are in general characterized by a broad bump at an energy approximately corresponding to π+d → pp reaction kinematics, suggestive of pion absorption on 2 nucleons. The energy-integrated cross-section for production of deuterons has an angular distribution similar to that for production of protons. The dependence of the total pion absorption cross-section on A is explained using a semi-classical model for pion transport in nuclei. The (π+,p) as well as (π+,d) reactions generally favor transitions involving larger angular momentum transfer to the residual nucleus when states of similar nuclear structure are considered. The low-energy excitation spectra from the (π+,p) reaction are similar to the spectra from (p,d) reaction on 12C and 13C. However, a calculation of the (π+,p) cross-section using the measured (p,d) reaction with the formulation of Wilkin to relate the two reactions is in moderate disagreement with the measured (π+,p) cross-sections. The excitation spectra from the (π+,p) reaction indicte the importance of two-step processes for the reaction. The (π+,d) reaction leading to the ground state of -- residual nucleus has been seen for 7Li, 12C, and 13C targets. The measured cross section for the 12C(π+,d)10C reaction to the 2+ state is much higher than that for the ground state. For the case of 18O, no counts were seen for excitation energy of +,d) reaction

  7. Crystal-field analysis for RE3+ ions in laser materials: II. Absorption spectra and energy levels calculations for Nd3+ ions doped into SrLaGa3O7 and BaLaGa3O7 crystals and Tm3+ ions in SrGdGa3O7

    Graphical abstract: In this paper we report a detailed analysis of spectroscopic data obtained from low temperature absorption spectra, which enabled assignment of energy levels, and subsequently their analysis in terms of the free-ion and crystal field (CF) parameters. Highlights: → Polarized absorption spectra measured for Nd3+ and Tm3+ ions in ABC3O7 crystals. → Energy levels analyzed in terms of the free-ion and crystal-field (CF) parameters. → The combined ADS/SPM procedure have been successfully applied. → The B-bark parameters and the power law exponents tk of SPM model are determined. → The energies of levels are important for evaluation of the emission cross-section. - Abstract: Low temperature polarized absorption spectra are analyzed to achieve assignments of energy levels for Nd3+ and Tm3+ ions at monoclinic Cs site symmetry in ABC3O7 crystals. Based on the concept of average optical center, the experimental energy levels for single crystals of SrLaGa3O7:Nd3+ (SLG:Nd), BaLaGa3O7:Nd3+ (BLG:Nd), and SrGdGa3O7:Tm3+ (SGG:Tm) were analyzed in terms of the free-ion parameters and the crystal field (CF) ones, Bkq. Assignments of the energy levels resolved in the spectra were done in stages applying the ascent/descent in symmetry method in CF analysis. The actual monoclinic Cs site symmetry at the metal centers in ABC3O7 crystals and the approximated orthorhombic C2v and tetragonal C4v symmetry were considered. The starting values of Bkq's for SLG:Nd and BLG:Nd crystals were obtained from superposition model (SPM) analysis. The final fitted crystal field parameters show high compatibility with the existing data for structurally similar ion-host systems. The obtained values of the intrinsic parameters provide basis for SPM analysis of CF parameters for rare earth ions in other similar systems, especially those exhibiting low-symmetry sites. The SPM parameters derived for SLG:Nd are used for simulation and assignment of the energy levels involved in the

  8. Evaluation of Transient Absorption Spectra of N, N, N′, N′- Tetra - ( p -methylphenyl ) - 4, 4′- diamino - 1, 1′- diphenyl Ether ( TPDAE ) for Electron Transfer from TPDAE to Fullerenes ( C60 / C70 ) by Laser Flash Photolysis

    2002-01-01

    Photoinduced electron transfer processes between fullerenes (C60 / C70) and N, N, N′, N′- tetra - ( p-methylphenyl ) - 4, 4′- diamino - 1, 1′- diphenyl ether ( TPDAE ) have been studied by nanosecond laser flash photolysis. Quantum yields and rate constants of electron transfer from TPDAE to excited triplet state of fullerenes (C60 / C70 ) in benzonitrile have been evaluated by observing the transient absorption bands in the near-IR region where the excited triplet state, radical anion of fullerenes ( C60 / C70 ) and radical cations of TPDAE appear.

  9. VAPID: Voigt Absorption-Profile [Interstellar] Dabbler

    Howarth, Ian D.

    2015-06-01

    VAPID (Voigt Absorption Profile [Interstellar] Dabbler) models interstellar absorption lines. It predicts profiles and optimizes model parameters by least-squares fitting to observed spectra. VAPID allows cloud parameters to be optimized with respect to several different data set simultaneously; those data sets may include observations of different transitions of a given species, and may have different S/N ratios and resolutions.

  10. Correction method for self-absorption effects of fluorescence x-ray absorption near-edge structure on multilayer samples

    It is well known that fluorescence x-ray absorption spectroscopy suffers from the self-absorption effects for thick and concentrated samples. In this study, a simple correction method is provided for correcting the self-absorption effects of fluorescence x-ray absorption near edge structure (XANES) spectrum for multilayer samples. This method is validated by application on fluorescence XANES spectra for a Cr/C multilayer measured at different incidence angles. The errors produced by the self-absorption effects for the measured fluorescence x-ray absorption spectra without corrections are also estimated and discussed. (paper)

  11. Photothermal Absorption Spectroscopy of Individual Semiconductor Nanocrystals

    Berciaud, Stéphane; Cognet, Laurent; Lounis, Brahim

    2007-01-01

    Photothermal heterodyne detection is used to record the first room-temperature absorption spectra of single CdSe/ZnS semiconductor nanocrystals. These spectra are recorded in the high cw excitation regime, and the observed bands are assigned to transitions involving biexciton and trion states. Comparison with the single nanocrystals photoluminescence spectra leads to the measurement of spectral Stokes shifts free from ensemble averaging.

  12. Determination of the dynamical structure of galaxies using optical spectra

    De Rijcke, S.; Dejonghe, H.

    1998-01-01

    Galaxy spectra are a rich source of kinematical information since the shapes of the absorption lines reflect the movement of stars along the line-of-sight. We present a technique to directly build a dynamical model for a galaxy by fitting model spectra, calculated from a dynamical model, to the observed galaxy spectra. Using synthetic spectra from a known galaxy model we demonstrate that this technique indeed recovers the essential dynamical characteristics of the galaxy model. Moreover, the ...

  13. QSO Absorption Lines from QSOs

    Bowen, D V; Ménard, B; Chelouche, D; Inada, N; Oguri, M; Richards, G T; Strauss, M A; Vanden Berk, Daniel E; York, D G; Bowen, David V.; Hennawi, Joseph F.; Menard, Brice; Chelouche, Doron; Inada, Naohisa; Oguri, Masamune; Richards, Gordon T.; Strauss, Michael A.; Berk, Daniel E. Vanden; York, Donald G.

    2006-01-01

    We present the results of a search for metal absorption lines in the spectra of background QSOs whose sightlines pass close to foreground QSOs. We detect MgII(2796,2803) absorption in Sloan Digital Sky Survey (SDSS) spectra of four z>1.5 QSOs whose lines of sight pass within 26-98 kpc of lower redshift (z~0.5-1.5) QSOs. The 100% [4/4 pairs] detection of MgII in the background QSOs is clearly at odds with the incidence of associated (z_abs ~ z_em) systems -- absorbers which exist towards only a few percent of QSOs. Although the quality of our foreground QSO spectra is not as high as the SDSS data, absorption seen towards one of the background QSOs clearly does not show up at the same strength in the spectrum of the corresponding foreground QSO. This implies that the absorbing gas is distributed inhomogeneously around the QSO, presumably as a direct consequence of the anisotropic emission from the central AGN. We discuss possible origins for the MgII lines, including: absorption by gas from the foreground QSO h...

  14. Photochemical properties of trans-1-chloro-3,3,3-trifluoropropene (trans-CHCl═CHCF3): OH reaction rate constant, UV and IR absorption spectra, global warming potential, and ozone depletion potential.

    Orkin, Vladimir L; Martynova, Larissa E; Kurylo, Michael J

    2014-07-17

    Measurements of the rate constant for the gas-phase reactions of OH radicals with trans-1-chloro-3,3,3-trifluoropropene (trans-CHCl═CHCF3) were performed using a flash photolysis resonance-fluorescence technique over the temperature range 220-370 K. The reaction rate constant exhibits a noticeable curvature of the temperature dependence in the Arrhenius plot, which can be represented by the following expression: kt-CFP (220-370 K) = 1.025 × 10(-13) × (T/298)(2.29) exp(+384/T) cm(3 )molecule(-1) s(-1). The room-temperature rate constant was determined to be kt-CFP (298 K) = (3.29 ± 0.10) × 10(-13) cm(3) molecule(-1) s(-1), where the uncertainty includes both two standard errors (statistical) and the estimated systematic error. For atmospheric modeling purposes, the rate constant below room temperature can be represented by the following expression: kt-CFP (220-298 K) = (7.20 ± 0.46) × 10(-13) exp[-(237 ± 16)/T] cm(3) molecule(-1) s(-1). There was no difference observed between the rate constants determined at 4 kPa (30 Torr) and 40 kPa (300 Torr) at both 298 and 370 K. The UV and IR absorption cross sections of this compound were measured at room temperature. The atmospheric lifetime, global warming potential, and ozone depletion potential of trans-CHCl═CHCF3 were estimated. PMID:24955760

  15. Estimation of the CO2 Concentration From the Measurements of Solar Absorption Spectra at an Altitude of 800 Meters by Using the FTS (GOSAT-BBM) in SWIR Region

    Yoshida, Y.; Oguma, H.; Morino, I.; Suto, H.; Yokota, T.; Inoue, G.; Kuze, A.

    2006-12-01

    The Greenhouse gases Observing SATellite (GOSAT) is scheduled to be launched in 2008 to observe tropospheric CO2 and CH4 from space. We developed a retrieval algorithm, which simultaneously estimates the CO2 column concentration and the surface albedo from a spectrum of surface scattered solar radiation at 1.6 μm region measured by Fourier Transform Spectrometer (FTS) with some assumptions on the aerosol parameters. To validate and to improve the retrieval algorithm, a field experiment was conducted from 10:30 to 14:30 JST of November 17, 2005 using a bread board model (BBM) of the FTS. The surface scattered and the direct transmitted solar spectra were measured by BBM, which was installed at the terminal station of the ropeway near the summit of Mt. Tsukuba (an altitude of about 800 m). In-situ CO2 concentration was measured continuously at the surface target point and near the BBM. There seemed to exist visible aerosols within the atmospheric boundary layer; however, no measurements of aerosol parameters were made. We have tried to retrieve the CO2 concentrations with the assumptions of no aerosol and the boundary layer aerosol, respectively. Although the absolute values of the retrieved CO2 concentrations are different between these two analyses, the relative patterns of temporal variation of the retrieved column concentrations are similar. Also, there existed the lag correlation between the retrieved CO2 column concentration and the in-situ observed CO2 concentration at the surface target point. This suggests that our algorithm can at least detect the variation of the CO2 concentration. To retrieve more accurate absolute concentration of CO2, effects of aerosol should be considered properly.

  16. Aerosol Effects on the Estimation of the Carbon Dioxide Concentration From the Measurements of Solar Absorption Spectra at an Altitude of 800 Meters by Using the FTS (GOSAT-BBM) in SWIR Region

    Yoshida, Y.; Tanaka, T.; Saito, R.; Oguma, H.; Morino, I.; Aoki, K.; Machida, T.; Yokota, T.

    2007-12-01

    The Greenhouse gases Observing SATellite (GOSAT) is scheduled to be launched in 2008 to observe tropospheric CO2 and CH4 from space. We developed a retrieval algorithm, which simultaneously estimates the CO2 column concentration and the surface albedo from a spectrum of surface scattered solar radiation at 1.6 μm region measured by Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer (TANSO-FTS) aboard GOSAT. To validate and improve the retrieval algorithm, a field experiment was conducted from 1st to 18th December, 2006 using a bread board model (BBM) of the FTS. The surface scattered solar spectra were measured by BBM, which was installed at the terminal station of the cable car near the summit of Mt. Tsukuba (at an altitude of about 800 m). In-situ CO2 censors (NDIR) and skyradiometers were set up at the surface target point and near the BBM for the continuous measurements. Also, CO2 profile was observed in-situ by Cessna aircraft near the surface up to altitude of 3km. Data obtained with no cloud condition were analyzed. The CO2 column concentrations (CCO2) were retrieved with the assumption of with and without the boundary layer aerosol. Optical properties of aerosol were estimated from the skyradiometer measurements. The difference between the CCO2 with and without aerosol had good correlation with the aerosol optical thickness at 1.6 μm, and -0.1 to 0.6 % change in the CCO2 occurred due to aerosol. Most of the CCO2 agreed with in-situ observation within 1.0 % but the maximum difference reached up to 3.0 %.

  17. Rotational structure in molecular infrared spectra

    di Lauro, Carlo

    2013-01-01

    Recent advances in infrared molecular spectroscopy have resulted in sophisticated theoretical and laboratory methods that are difficult to grasp without a solid understanding of the basic principles and underlying theory of vibration-rotation absorption spectroscopy. Rotational Structure in Molecular Infrared Spectra fills the gap between these recent, complex topics and the most elementary methods in the field of rotational structure in the infrared spectra of gaseous molecules. There is an increasing need for people with the skills and knowledge to interpret vibration-rotation spectra in ma

  18. Vibrational Spectra of a Mechanosensitive Channel

    Liang, Chungwen; Louhivuori, Martti; Marrink, Siewert J.; Jansen, Thomas L.C.; Knoester, Jasper

    2013-01-01

    We report the simulated vibrational spectra of a mechanosensitive membrane channel in different gating states. Our results show that while linear absorption is insensitive to structural differences, linear dichroism and sum-frequency generation spectroscopies are sensitive to the orientation of the

  19. Theoretical calculation of spectra of dibutyl phthalate and dioctyl phthalate

    Du, Jian-Bin; Tang, Yan-Lin; Long, Zheng-Wen; Hu, Shuang-Hui; Li, Tao

    2014-05-01

    Dibutyl phthalate DBP and dioctyl phthalate DOP are the main components of the plasticizers. In order to investigate their molecular structure, chemical bond and spectrum, the geometrical parameters of the ground state and infrared (IR) spectrum are calculated using the density functional theory B3LYP method at the level of 6-311++G( d, p). On this basis, the first twenty-six excited states and the UV-Vis absorption spectra of DBP and DOP are studied using the time-dependent density functional theory (TDDFT) in the same fundamental group and compared with the ultraviolet absorption peak of the molecules measured with UNICO UV-Vis spectrophotometer. The two kinds of molecular spectra are then classified and compared with that in reference. The results show that the strong absorption of IR spectra of DOP and DBP are produced by C-H bending in-plane vibration and C=O telescopic vibration producing. The most absorption of UV-Vis absorption spectra appears in the end absorption belt from n to σ* transition, and the stronger absorption in the E belt of benzene electronic transition from π to π*. There are blue shift for DOP end absorption belt from n to σ* transition and red shift for DOP E absorption belt from π to π* transition relative to that of DBP. This calculation results are better in accord with the spectral data measured by UNICO ultraviolet and visible spectrophotometer.

  20. Atmospheric CO2 retrieved from ground-based solar spectra

    Yang, Z.; Toon, G. C.; Margolis, J. S.; Wennberg, P. O.

    2002-01-01

    The column-averaged volume mixing ration of CO2 over Kitt Peak, Arizona, has been retrieved from high-resolution solar absorption spectra obtained with the fourier transform spectrometer on the McMath telescope.

  1. Online Spectral Fit Tool for Analyzing Reflectance Spectra

    Penttilä, A.; Kohout, T.

    2015-11-01

    The Online Spectral Fit Tool is developed for analyzing Vis-NIR spectral behavior of asteroids and meteorites. Implementation is done using JavaScript/HTML. Fitted spectra consist of spline continuum and gamma distributions for absorption bands.

  2. Beta spectra. II-Positron spectra

    Using the Fermi theory of beta decay, the beta spectra for 30 positron emitters have been computed, introducing a correction factor for unique forbidden transitions. The spectra are ploted vs. energy, once normalised, and tabulated with the related Fermi functions. The average and median energies are calculated. (author)

  3. Crystal field spectra of lunar pyroxenes.

    Burns, R. G.; Abu-Eid, R. M.; Huggins, F. E.

    1972-01-01

    Absorption spectra in the visible and near infrared regions have been obtained for pyroxene single crystals in rocks from the Apollo 11, 12, 14, and 15 missions. The polarized spectra are compared with those obtained from terrestrial calcic clinopyroxenes, subcalcic augites, pigeonites, and orthopyroxenes. The lunar pyroxenes contain several broad, intense absorption bands in the near infrared, the positions of which are related to bulk composition, Fe(2+) site occupancy and structure type of the pyroxene. The visible spectra contain several sharp, weak peaks mainly due to spin-forbidden transitions in Fe(2+). Additional weak bands in this region in Apollo 11 pyroxenes are attributed to Ti(3+) ions. Spectral features from Fe(3+), Mn(2+), Cr(3+), and Cr(2+) were not observed.

  4. The HI absorption 'Zoo'

    Gereb, K; Morganti, R; Oosterloo, T A

    2014-01-01

    We present an analysis of the HI absorption in a sample of 101 flux-selected radio AGN (S_1.4 GHz > 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). HI absorption is detected in 32 galaxies, showing a broad variety of widths, shapes and kinematical properties. We characterize the HI spectra of the individual detections using the busy function (Westmeier et al. 2014). With the goal of identifying different morphological structures of HI, we study the kinematical and radio source properties of the detections as function of their width. Narrow lines (FWHM = 500 km/s). These detections are good candidates for being HI outflows. The detection rate of HI outflows is 5 percent in the total radio AGN sample. This fraction represents a lower limit, however it could suggests that, if outflows are a characteristic phenomenon of all radio sources, they would have a short depletion timescale compared to the lifetime of the AGN. Blueshifted and broad/asymmetric lines are more often present among young...

  5. Vibrationally high-resolved electronic spectra of MCl2 (M=C, Si, Ge, Sn, Pb) and photoelectron spectra of MCl2(.).

    Ran, Yibin; Pang, Min; Shen, Wei; Li, Ming; He, Rongxing

    2016-10-01

    We systematically studied the vibrational-resolved electronic spectra of group IV dichlorides using the Franck-Condon approximation combined with the Duschinsky and Herzberg-Teller effects in harmonic and anharmonic frameworks (only the simulation of absorption spectra includes the anharmonicity). Calculated results showed that the band shapes of simulated spectra are in accordance with those of the corresponding experimental or theoretical ones. We found that the symmetric bend mode in progression of absorption is the most active one, whereas the main contributor in photoelectron spectra is the symmetric stretching mode. Moreover, the Duschinsky and anharmonic effects exert weak influence on the absorption spectra, except for PbCl2 molecule. The theoretical insights presented in this work are significant in understanding the photophysical properties of MCl2 (M=C, Si, Ge, Sn, Pb) and studying the Herzberg-Teller and the anharmonic effects on the absorption spectra of new dichlorides of this main group. PMID:27280730

  6. Far-IR and THz Absorption Spectra Studies of Metronidazole, Tinidazole and Ornidazole%甲硝唑、替硝唑和奥硝唑药品的远红外与太赫兹吸收光谱研究

    张振伟; 左剑; 张存林

    2012-01-01

    Metronidazole, tinidazole and ornidazole are 5-nitro-imidazole medicines used particularly for anaerobic bacteria and protozoa infections. The present paper reports that terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infra-red spectroscopy (Far-FTIR) were used to measure the fingerprint spectra of metronidazole, tinidazole and ornidazole in the frequency range of 0. 9-19. 5 THz under the room temperature. In addition, THz-TDS was also used to measure the absorption spectra of pure tinidazole and tinidazole tablets from different manufactures between 0. 2 and 2. 2 THz. In parallel with the experimental study, the cross correlation analysis was applied to compare the array of correlation coefficients between pure tinidazole and different tinidazole tablets. Results show that the method is rapid, simple and accurate to identify their effective chemical compositions and stability when the FTIR and THz spectra data combine with the array of correlation coefficient. Our research provides a visual approach to the standardization and modernization of the quality control in the production and sale of such drugs.%甲硝唑、替硝唑和奥硝唑为5'-硝基咪唑类化合物,常用于抗厌氧菌和抗滴虫治疗.运用太赫兹时域光谱技术(THz-TDS)和傅里叶变换红外光谱(FTIR)技术在室温环境中测量了三种药品在0.9~19.5THz波段的光谱特性,得到其指纹谱.另外,通过探测替硝唑参照品和不同厂家、不同批次替硝唑药片在太赫兹波段的光谱信息,结合相关系数法、阵列相关系数法等信息处理技术对光谱信号进行数据挖掘;最终建立了一种能够快速、有效、系统地鉴定替硝唑片活性成分和稳定性的分析方法.研究结果为此类药品生产和销售质量的规范化和现代化提供了可视化途径.

  7. Reactor Neutrino Spectra

    Hayes, A C

    2016-01-01

    We present a review of the antineutrino spectra emitted from reactors. Knowledge of these and their associated uncertainties are crucial for neutrino oscillation studies. The spectra used to-date have been determined by either conversion of measured electron spectra to antineutrino spectra or by summing over all of the thousands of transitions that makeup the spectra using modern databases as input. The uncertainties in the subdominant corrections to beta-decay plague both methods, and we provide estimates of these uncertainties. Improving on current knowledge of the antineutrino spectra from reactors will require new experiments. Such experiments would also address the so-called reactor neutrino anomaly and the possible origin of the shoulder observed in the antineutrino spectra measured in recent high-statistics reactor neutrino experiments.

  8. Influence of ultrafast carrier dynamics on semiconductor absorption spectra

    Ouerdane, H

    2001-01-01

    set of coupled rate equations. We obtained a good qualitative agreement with experiments and further insight into the interplay between the various dynamical processes by varying the phenomenological parameters entering the rate equations. In particular we found that the carrier spin-flip occurs on a relatively long time scale (several tens of picoseconds) compared to the carrier distributions relaxation and thermalization (a picosecond or less). We also could monitor the time evolution of the plasma density, energy, temperature and screening. In this thesis, we also studied the photoluminescence in II-VI quantum wells at room temperature. We built a mathematical model to account for Coulomb correlations that are expected to strongly influence the spontaneous emission rate in these materials. We assumed the 1s exciton-free electron scattering to be the main process leading an exciton to the photon line before recombination. The excitonic wavefunctions in a 2D screened Coulomb potential were calculated using t...

  9. Optical spectra of distant radio loud quasars. I. Data: spectra of 67 quasars

    We present spectra of 67 radio-loud quasars (1.5 em < 3.8) covering the wavelength range 3380 - 7780A at a resolution of about 5 A. Accurate redshifts, emission line strengths, widths and positions are given. A total of 1198 absorption lines were found, including 138 metal line systems, of which 68 show CIV and 60 MgII

  10. A cylindrical furnace for absorption spectral studies

    R Venkatasubramanian

    2001-06-01

    A cylindrical furnace with three heating zones, capable of providing a temperature of 1100°C, has been fabricated to enable recording of absorption spectra of high temperature species. The temperature of the furnace can be controlled to ± 1°C of the set temperature. The salient feature of this furnace is that the material being heated can be prevented from depositing on the windows of the absorption cell by maintaining a higher temperature at both the ends of the absorption cell.

  11. THz induced nonlinear absorption in ZnTe

    Pedersen, Pernille Klarskov; Jepsen, Peter Uhd

    2015-01-01

    Absorption spectra of ZnTe during strong-field THz interaction are investigated. Bleaching of the difference phonon modes below the fundamental TO mode is observed when field strengths higher than 4 MV/cm are applied....

  12. The HI absorption "Zoo"

    Geréb, K.; Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.

    2015-03-01

    We present an analysis of the H I 21 cm absorption in a sample of 101 flux-selected radio AGN (S1.4 GHz> 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). We detect H I absorption in 32 objects (30% of the sample). In a previous paper, we performed a spectral stacking analysis on the radio sources, while here we characterize the absorption spectra of the individual detections using the recently presented busy function. The H I absorption spectra show a broad variety of widths, shapes, and kinematical properties. The full width half maximum (FWHM) of the busy function fits of the detected H I lines lies in the range 32 km s-1 200 km s-1). We study the kinematical and radio source properties of each group, with the goal of identifying different morphological structures of H I. Narrow lines mostly lie at the systemic velocity and are likely produced by regularly rotating H I disks or gas clouds. More H I disks can be present among galaxies with lines of intermediate widths; however, the H I in these sources is more unsettled. We study the asymmetry parameter and blueshift/redshift distribution of the lines as a function of their width. We find a trend for which narrow profiles are also symmetric, while broad lines are the most asymmetric. Among the broadest lines, more lines appear blueshifted than redshifted, similarly to what was found by previous studies. Interestingly, symmetric broad lines are absent from the sample. We argue that if a profile is broad, it is also asymmetric and shifted relative to the systemic velocity because it is tracing unsettled H I gas. In particular, besides three of the broadest (up to FW20 = 825 km s-1) detections, which are associated with gas-rich mergers, we find three new cases of profiles with blueshifted broad wings (with FW20 ≳ 500 km s-1) in high radio power AGN. These detections are good candidates for being HI outflows. Together with the known cases of outflows already included in the sample (3C 293 and

  13. Atomic spectra in a helium bubble

    Nakatsukasa, Takashi; Yabana, Kazuhiro; Bertsch, George F.

    2002-01-01

    Density functional theory (DFT) is applied to atomic spectra under perturbations of superfluid liquid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and D2 absorption lines are quite well reproduced by theory, suggesting that the DFT may be useful for describing spectral perturb...

  14. Reflectance spectra of subarctic lichens

    Lichens constitute a major portion of the ground cover of high latitude environments, but little has been reported concerning their in situ solar spectral reflectance properties. Knowledge of these properties is important for the interpretation of remotely sensed observations from high latitude regions, as well as in studies of high latitude ecology and energy balance climatology. The spectral reflectance of common boreal vascular plants is similar to that of vascular plants of the mid latitudes. The dominant lichens, in contrast, display variable reflectance patterns in visible wavelengths. The relative reflectance peak at 0.55 μm, common to green vegetation, is absent or indistinct in spectra of pervasive boreal forest and tundra lichens, despite the presence of chlorophyll in the inner algal cells. Lichens of the dominant genus, Cladina, display strong absorption of ultraviolet energy and short-wavelength blue light relative to their absorption in other visible wavelengths. Since the Cladinae dominate both the surface vegetation in open woodlands of the boreal forest and the low arctic tundra, their unusual spectral reflectance patterns will enable accurate monitoring of the boreal forest-tundra ecotone and detection of its vigor and movement in the future. (author)

  15. Optical absorption of boron nitride nanomaterials

    Optical absorption spectra have been measured for hexagonal boron nitride (h-BN), rhombohedral BN(rh-BN), and material obtained by laser vaporization of BN target under a nitrogen atmosphere and contained single-wall BN-nanotubes. Band gap of the BN materials was found to have a value of 6.0-6.3 eV. The spectra of h -BN and vaporized material exhibited a peak at ∝5.5 eV, moreover, the latter sample showed an absorption band around 4.5 eV. The vaporized material has been fractionated to the BN-platelets and single-wall BN-nanotubes. Absorption peaks, located bellow the bottom of the conductance band, were found to be characteristics of thin BN-platelets and they could be attributed to defects in BN network. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Aerosol Absorption Measurements in MILAGRO.

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    to carbonyl- and nitro- functional groups on conjugated and aromatic organic structures (e.g. PAH, and terpene derived products). Using 12-hour fine (0.1-1.0 micron) aerosol samples collected in the field on quartz filters, uv/vis and infrared spectra were obtained in the laboratory using integrating spheres and diffuse reflectance spectroscopy, respectively. An inter-comparison of the "real-time" measurements made by the photo-acoustic, aethalometer and MAAP techniques have been described. In addition, the in situ aethalometer (seven-channel) results are compared with continuous integrating sphere uv-visible spectra to examine the angstrom absorption coefficient variance. These results will be briefly overviewed and the specific posters detailing these results will be highlighted highlighted. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City under the support of the Atmospheric Science Program. "This researchwas supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-07ER64329.

  17. Statistical method for predicting protein absorption peaks in terahertz region

    Terahertz vibrational spectroscopy has recently been demonstrated as a novel noninvasive technique for the characterization of biological molecules. But the interpretation of the experimentally measured terahertz absorption bands requires robust computational method. In this paper, we present a statistical method for predicting the absorption peak positions of a macromolecule in the terahertz region. The essence of this method is to calculate the absorption spectra of a biological molecule based on multiple short scale molecular dynamics trajectories instead of using a long time scale trajectory. The method was employed to calculate the absorption peak positions of the protein, thioredoxin from Escherichia coli (E.coli), in the range of 10-25 cm-1 to verify the reliability of this statistical method. The predicted absorption peak positions of thioredoxin show good correlation with measured results demonstrating that the proposed method is effective in terahertz absorption spectra modeling. Such approach can be applied to predict characteristic spectral features of biomolecules in the terahertz region. (authors)

  18. Absorption Complex between Porphyrin and Phenothiazine in Reverse Micelles

    2002-01-01

    The interaction between amphiphilic porphyrin and phenothiazine in AOT/isooctane/ water reverse micelle was investigated by UV-Vis spectra. A new absorption complex between the two species is formed in such circumstances, which is ascribed to the enrichment of the components by the reverse micelle. The fluorescence quenching of CHTTP by PTH becomes more efficient after the formation of the absorption complex.

  19. Blackbody absorption efficiencies for six lamp pumped Nd laser materials

    Cross, Patricia L.; Barnes, Norman P.; Skolaut, Milton W., Jr.; Storm, Mark E.

    1990-01-01

    Utilizing high resolution spectra, the absorption efficiencies for six Nd laser materials were calculated as functions of the effective blackbody temperature of the lamp and laser crystal size. The six materials were Nd:YAG, Nd:YLF, Nd:Q-98 Glass, Nd:YVO4, Nd:BEL, and Nd:Cr:GSGG. Under the guidelines of this study, Nd:Cr:GSGG's absorption efficiency is twice the absorption efficiency of any of the other laser materials.

  20. Spectra for commutative algebraists

    Greenlees, J. P. C.

    2006-01-01

    The article is designed to explain to commutative algebraists what spectra (in the sense of algebraic topology) are, why they were originally defined, and how they can be useful for commutative algebra.

  1. Microscopic Theory and Simulation of Quantum-Well Intersubband Absorption

    Li, Jianzhong; Ning, C. Z.

    2004-01-01

    We study the linear intersubband absorption spectra of a 15 nm InAs quantum well using the intersubband semiconductor Bloch equations with a three-subband model and a constant dephasing rate. We demonstrate the evolution of intersubband absorption spectral line shape as a function of temperature and electron density. Through a detailed examination of various contributions, such as the phase space filling effects, the Coulomb many-body effects and the non-parabolicity effect, we illuminate the underlying physics that shapes the spectra. Keywords: Intersubband transition, linear absorption, semiconductor heterostructure, InAs quantum well

  2. Relativistic Effects Around Black Holes: Smearing Absorption Edges

    Zhang, X. L.; Feng, Y. X.; Zhang, S. N.; Yao, Y.

    2002-01-01

    Broad iron absorption structures have been observed in the X-ray spectra of both AGNs and black hole X-ray binaries (BHXBs). A correctly modeled absorption structure can reveal the physical condition of the source, help to determine the continuum spectra and thus help to estimate other spectral lifes more accurately. The absorption structures are usually thought to be caused by the reflection of X-rays by the accretion disks around the central black holes, and the broadening can be a ttributed to the ionization states of the disk and relativistic effects.

  3. On the nature of absorption features toward nearby stars

    Kohl, S.; Czesla, S.; Schmitt, J. H. M. M.

    2016-06-01

    Context. Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in τ Boo. Aims: We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars τ Boo, HD 33608, and α CrB. Methods: We focus our analysis on a strong DIB located at 5780.61 Å and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, τ Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of τ Boo, HD 33608, and α CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles. Results: The intercomparison between τ Boo and HD 33608 reveals that the difference in the line depth is 6.85 ± 1.48 mÅ at the DIB location which is, however, unlikely to be caused by DIB absorption. The comparison between PHOENIX models and observed spectra yields an upper limit of 34.0 ± 0.3 mÅ for any additional interstellar absorption in τ Boo; similar results are obtained for HD 33608 and α CrB. For all objects we derive unrealistically large values for the radial velocity of any presumed interstellar clouds. In τ Boo we find Na D absorption with an equivalent width of 0.65 ± 0.07 mÅ and 2.3 ± 0.1 mÅ in the D2 and D1 lines. For the other Na, absorption of the same magnitude could only be detected in the D2 line. Our comparisons between model and data show that the interstellar absorption toward τ Boo is not abnormally high. Conclusions: We find no significant DIB absorption in any of our target stars. Any differences between modeled and

  4. Study of optical absorption, visible emission and NIR–vis luminescence spectra of Tm{sup 3+}/Yb{sup 3+}, Ho{sup 3+}/Yb{sup 3+} and Tm{sup 3+}/Ho{sup 3+}/Yb{sup 3+} doped tellurite glasses

    Seshadri, M., E-mail: seshumeruva@gmail.com [Institute of Physics, University of Campinas, UNICAMP, P.O. Box 6165, Campinas 13083-970 (Brazil); Barbosa, L.C.; Cordeiro, C.M.B.; Radha, M. [Institute of Physics, University of Campinas, UNICAMP, P.O. Box 6165, Campinas 13083-970 (Brazil); Sigoli, F.A. [Institute of Chemistry, University of Campinas, UNICAMP, P.O. Box 6154, Campinas 13083-970 (Brazil); Ratnakaram, Y.C. [Department of Physics, Sri Venkateswara University, SVU, Tirupat 517502 (India)

    2015-10-15

    Tm{sup 3+}/Yb{sup 3+}, Ho{sup 3+}/Yb{sup 3+} co-doped and Tm{sup 3+}/Ho{sup 3+}/Yb{sup 3+} triply doped TeO{sub 2}–Bi{sub 2}O{sub 3}–ZnO–Li{sub 2}O–Nb{sub 2}O{sub 5} (TBZLN) tellurite glasses were prepared by melt quenching method. Judd–Ofelt intensity parameters (Ω{sub λ}, λ=2, 4 and 6), radiative transition probabilities, branching ratios and radiative lifetimes of Tm{sup 3+}, Ho{sup 3+} ions in co-doped TBZLN glasses were calculated from the optical absorption spectra. Excitation, visible luminescence and decay lifetimes in visible region were also investigated. The stimulated emission and gain cross-sections for the Tm{sup 3+}:{sup 3}F{sub 4}→{sup 3}H{sub 6} (1700 nm) and Ho{sup 3+}:{sup 5}I{sub 7}→{sup 5}I{sub 8} (1956 nm) transitions in co-doped TBZLN glasses have been analyzed and compared with those of other reported glasses. Up-conversion luminescence was observed in TBZLN glasses under 980 nm laser excitation and energy transfer mechanisms have been discussed. Finally, CIE color co-ordinates were calculated and it is observed that the color co-ordinates fall in blue and green regions for Tm{sup 3+}/Yb{sup 3+} and Ho{sup 3+}/Yb{sup 3+} co-doped TBZLN glasses, respectively. A subsequent shift in color co-ordinates from green to greenish-yellow region has been observed with an increase in the concentration (0.1, 0.5 and 1.0 mol%) of Tm{sup 3+} ions in Tm{sup 3+}/Ho{sup 3+}/Yb{sup 3+} triply doped TBZLN glasses. - Highlights: • High degree of covalecy of RE–O bond in co-doped TBZLN glasses was observed. • Tm{sup 3+}:{sup 1}D{sub 2}→{sup 3}F{sub 4} and Ho{sup 3+}:{sup 5}F{sub 4}({sup 5}S{sub 2})→{sup 5}I{sub 8} transitions show high emission cross-section. • Visible and strong 793 nm emission was observed when pumped by 980 nm diode laser. • Triply doped glasses exhibits tunable emission intensity by increasing Tm{sup 3+} ions.

  5. Collecting, analyzing and archiving of ground based infrared solar spectra obtained from several locations

    Murcray, David G.; Murcray, Frank J.; Goldman, Aaron; Mcelroy, Charles T.; Chu, William P.; Rinsland, Curtis P.; Woods, Peter; Matthews, W. A.; Johnston, P. V.

    1990-01-01

    The infrared solar spectrum as observed from the ground under high resolution contains thousands of absorption lines. The majority of these lines are due to compounds that are present in the Earth's atmosphere. Ground based infrared solar spectra contain information concerning the composition of the atmosphere at the time the spectra were obtained. The objective of this program is to record solar spectra from various ground locations, and to analyze and archive these spectra. The analysis consists of determining, for as many of the absorption lines as possible, the molecular species responsible for the absorption, and to verify that current models of infrared transmission match the observed spectra. Archiving is an important part of the program, since a number of the features in the spectra have not been identified. At some later time, when the features are identified, it will be possible to determine the amount of that compound that was present in the atmosphere at the time the spectrum was taken.

  6. A model for partitioning particulate absorption into phytoplanktonic and detrital components

    Cleveland, J. S.; Perry, M. J.

    1994-01-01

    A model for partitioning total particulate absorption, measured on glass fiber filters, into phytoplanktonic and detrital components is developed. The model reconstructs absorption spectra for living phytoplankton using total particulate absorption at the red absorption maxima for chlorophylls a and b, concentrations of chlorophyll a and pheopigment, and mean normalized absorption spectra for laboratory-grown algal cultures. The model was developed in stages for two types of phytoplankton assemblages. Section A of the model applies to waters dominated by eukaryotic algae and is based on absorption spectra for chromophytic (phytoplankton containing chlorophyll c) and chlorophytic (containing chlorophyll b) species. Section B of the model, allowing more variability in spectral shape, was developed for algal communities with more diverse pigmentation. All spectra are processed through Section A, with an internal evaluation determining whether processing continues through Section B. Detrital spectra, generated as the difference between total particulate and modelled phytoplanktonic spectra, included pheopigment absorption and had high blue absorption. Blind tests on samples of known composition predicted absorption within 8-10% at 436 nm and 1-13% when averaged from 400 to 700 nm, which is within the expected accuracy of the glass fiber filter method. No true measure of phytoplankton absorption in field samples is available for testing the model, but results from methanol-extractions were used for comparison despite inclusion of pheopigment absorption as "phytoplankton". For samples collected from coastal waters of Washington State, the Sargasso Sea and coastal waters of Norway, modelled absorption (averaged over 400-700 nm) ranged from 25% lower to 0.5% higher than the methanol-extraction results; pheopigment absorption inappropriately included in the phytoplankton component accounts for the higher phytoplanktonic absorption estimated by the methanol technique

  7. D-xylose absorption

    D-xylose absorption is a laboratory test to determine how well the intestines absorb a simple sugar (D-xylose). The test ... test is primarily used to determine if nutrient absorption problems are due to a disease of the ...

  8. D-xylose absorption

    ... this page: //medlineplus.gov/ency/article/003606.htm D-xylose absorption To use the sharing features on this page, please enable JavaScript. D-xylose absorption is a laboratory test to determine ...

  9. Molecular hydrogen absorption systems in SDSS

    Balashev, S A; Ivanchik, A V; Varshalovich, D A; Petitjean, P; Noterdaeme, P

    2014-01-01

    We present a systematic search for molecular hydrogen absorption systems at high redshift in quasar spectra from the Sloan Digital Sky Survey (SDSS) II Data Release 7 and SDSS-III Data Release 9. We have selected candidates using a modified profile fitting technique taking into account that the Ly$\\alpha$ forest can effectively mimic H$_2$ absorption systems at the resolution of SDSS data. To estimate the confidence level of the detections, we use two methods: a Monte-Carlo sampling and an analysis of control samples. The analysis of control samples allows us to define regions of the spectral quality parameter space where H$_2$ absorption systems can be confidently identified. We find that H$_2$ absorption systems with column densities $\\log {\\rm N_{H_2}} > 19$ can be detected in only less than 3% of SDSS quasar spectra. We estimate the upper limit on the detection rate of saturated H$_2$ absorption systems ($\\log {\\rm N_{H_2}} > 19$) in Damped Ly-$\\alpha$ (DLA) systems to be about 7%. We provide a sample of ...

  10. Nutrition and magnesium absorption.

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true magnesium absorption was neither affected by soybean protein in the diet nor by supplemental phytate. The inhibitory influence of soybean protein and phytate on apparent magnesium absorption was found to be cau...

  11. Study of self-absorption in laser induced breakdown spectroscopy

    We present a simple analytical expression for self-absorption correction of a spectrum recorded in the image mode of a CCD camera. It is assumed that two spectra are available, F2 recorded with a back mirror and F1 recorded without. The corrected spectrum F0, free of self-absorption, is given by the following simple expression F0=(2F1)/(1+(F2−F1)/(GF1) ) . We discuss the influence of noise on subsequent inverse Abel transform. An example, illustrating proposed method for self-absorption correction and Abel inversion is given in details. - Highlights: • We present a simple expression for self-absorption correction in LIBS plasma. • Method needs two spectra recorded in the image mode of the CCD. • Abel transform is not necessary for self-absorption correction

  12. A transient absorption study of allophycocyanin

    Y J Shiu; J M Zhang; M Hayashi; V Gulbinas; C M Yang; S H Lin

    2002-12-01

    Transient dynamics of allophycocyanin trimers and monomers are observed by using the pump-probe, transient absorption technique. The origin of spectral components of the transient absorption spectra is discussed in terms of both kinetics and spectroscopy. We find that the energy gap between the ground and excited states of the unexcited subunit of allophycocyanin monomer decreases via an interaction with another excited subunit. For allophycocyanin trimer, we find that the fast dynamics results from the fast internal conversion and the first excited state is the only one electronic state which can trap the final population.

  13. Computer Processing Of Tunable-Diode-Laser Spectra

    May, Randy D.

    1991-01-01

    Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.

  14. Calculation of Vibrational Energy-Spectra of α-Helical Protein Molecules and Its Properties

    PANG XiaoFeng; CHEN XiangRong

    2002-01-01

    The quantum vibrational energy-spectra of amide-Is in alpha-protein molecules are calculated by using the discretely nonlinear Schrodinger equation and physical parameters appropriate to the systems on the basis of theory of bio-energy transport. The numerical results for the energy-spectra are basically consistent with the experimental values obtained by the infrared absorption and Raman scattering and emission-spectra of infrared lights of person's hand-fingers. Utilizing the energy-spectra we explain the laser-Raman spectrum from metabolically active E. Coli. and give some features of the infrared absorption of the protein molecules.

  15. Atomic Spectra Database (ASD)

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  16. Function spectra and continuous G-spectra

    Davis, Daniel

    2011-01-01

    Let G be a profinite group, {X_alpha}_alpha a cofiltered diagram of discrete G-spectra, and Z a spectrum with trivial G-action. We show how to define the homotopy fixed point spectrum F(Z, holim_alpha X_alpha)^{hG} and that when G has finite virtual cohomological dimension (vcd), it is equivalent to F(Z, holim_alpha (X_alpha)^{hG}). With these tools, we show that the K(n)-local Spanier-Whitehead dual is always a homotopy fixed point spectrum, a well-known Adams-type spectral sequence is actually a descent spectral sequence, and, for a sufficiently nice k-local profinite G-Galois extension E, with K a closed normal subgroup of G, the equivalence (E^{h_kK})^{h_kG/K} \\simeq E^{h_kG} (due to Behrens and the author), where (-)^{h_k(-)} denotes k-local homotopy fixed points, can be upgraded to an equivalence that just uses ordinary (non-local) homotopy fixed points, when G/K has finite vcd.

  17. Calcium absorption and achlorhydria

    Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

  18. Infrared Spectra of High Pressure Carbon Monoxide

    Evans, W J; Lipp, M J; Lorenzana, H E

    2001-09-21

    We report infrared (IR) spectroscopic measurements of carbon monoxide (CO) at high pressures. Although CO is one of the simplest heteronuclear diatomic molecules, it displays surprisingly complex behavior at high pressures and has been the subject of several studies [1-5]. IR spectroscopic studies of high pressures phases of CO provide data complementing results from previous studies and elucidating the nature of these phases. Though a well-known and widely utilized diagnostic of molecular systems, IR spectroscopy presents several experimental challenges to high pressure diamond anvil cell research. We present measurements of the IR absorption bands of CO at high pressures and experimentally illustrate the crucial importance of accurate normalization of IR spectra specially within regions of strong absorptions in diamond.

  19. Silicon Carbide: The Problem with Laboratory Spectra

    Speck, A. K.; Hofmeister, A. M.; Barlow, M. J.

    2000-03-01

    The interpretation of astronomical observations of infrared (IR) silicon carbide (SiC) features in the spectra of carbon stars have revealed discrepancies between the work of astronomers and that of meteoriticists. The silicon carbide observed around carbon stars has been attributed to one type of SiC (α) while meteoritic samples believed to have formed around such stars are of another type of SiC (β). The key to solving this problem has been to understand the sources of laboratory data used by astronomers in order to interpret the IR spectra. Through comparison of thin film IR absorption spectra and spectra taken using finely ground samples dispersed in potassium bromide (KBr) pellets we show that the previously invoked ``KBr matrix-correction'' is unnecessary for powder dispersions obtained from very fine grain sizes of SiC. Comparison of our data and previous measurements show that dust around carbon stars is β-SiC, consistent with laboratory studies of presolar grains in meteorites. The implications of these findings affect twenty years of work. The IR spectroscopic laboratory data used by astronomers to identify dust species in space must be carefully scrutinized to ensure that the KBr correction is not responsible for further misattributions of minerals in astronomical dust features.

  20. Light absorption by organic carbon from wood combustion

    Y. Chen

    2010-02-01

    Full Text Available Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While black carbon (BC is highly absorbing, some organic carbon (OC also has significant absorption, especially at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to positive direct aerosol radiative forcing. Quantification of that absorption is necessary so that radiative-transfer models can evaluate the net radiative effect of OC.

    In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble OC contributes to light absorption at both ultraviolet and visible wavelengths. However, a larger portion of the absorption comes from OC that is extractable only by methanol. Absorption spectra of water-soluble OC are similar to literature reports. We compare spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating OC with higher absorption; changing wood temperature from a devolatilizing state of 210 °C to a near-flaming state of 360 °C causes about a factor of four increase in mass-normalized absorption at visible wavelengths. A clear-sky radiative transfer model suggests that, despite the absorption, both high-temperature and low-temperature OC result in negative top-of-atmosphere radiative forcing over a surface with an albedo of 0.19 and positive radiative forcing over bright surfaces. Unless absorption by real ambient aerosol is higher than that measured here, it probably affects global average clear-sky forcing very little, but could be important in energy balances over bright

  1. Online spectral fit tool (OSFT) for analyzing reflectance spectra

    Penttilä, A.; Kohout, T.; Muinonen, K.

    2015-10-01

    We present an algorithm and its implementation for fitting continuum and absorption bands to UV/VIS/NIR reflectance spectra. The implementation is done completely in JavaScript and HTML, and will run in any modern web browser without requiring external libraries to be installed.

  2. Far-infrared spectra of lanthanide complexes with 8-hydroxyquinoline

    Vibrational spectra of lanthanide oxines have been measured in the far-infrared region. In addition, the similar yttrium complex was investigated for further experimental evidence for the proposed band assignments. The most important metal-oxygen and metal-nitrogen bond vibrations have been attributed to absorptions between 390-350cm-1 and 210-170cm-1, respectively. (Author)

  3. Variability of calcium absorption

    Variability in calcium absorption was estimated in three groups of normal subjects in whom Ca absorption was measured by standard isotopic-tracer methods at interstudy intervals ranging from 1 to 4 mo. Fifty absorption tests were performed in 22 subjects. Each was done in the morning after an overnight fast with an identical standard breakfast containing a Ca load of approximately 250 mg. Individual fractional absorption values were normalized to permit pooling of the data. The coefficient of variation (CVs) for absorption for the three groups ranged from 10.57 to 12.79% with the size of the CV increasing with interstudy duration. One other published study presenting replicate absorption values was analyzed in a similar fashion and was found to have a CV of absorption of 9.78%. From these data we estimate that when the standard double-isotope method is used to measure Ca absorption there is approximately 10% variability around any given absorption value within an individual human subject and that roughly two-thirds of this represents real biological variability in absorption

  4. Spectral Absorption Properties of Atmospheric Aerosols

    Bergstrom, R. W.; Pilewskie, P.; Russell, P. B.; Redemann, J.; Bond, T. C.; Quinn, P. K.; Sierau, B.

    2007-01-01

    We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We combined airborne measurements of the solar net radiant flux density and the aerosol optical depth with a detailed radiative transfer model for all but one of the cases. The field programs (SAFARI 2000, ACE Asia, PRIDE, TARFOX, INTEX-A) contained aerosols representing the major absorbing aerosol types: pollution, biomass burning, desert dust and mixtures. In all cases the spectral absorption optical depth decreases with wavelength and can be approximated with a power-law wavelength dependence (Absorption Angstrom Exponent or AAE). We compare our results with other recent spectral absorption measurements and attempt to briefly summarize the state of knowledge of aerosol absorption spectra in the atmosphere. We discuss the limitations in using the AAE for calculating the solar absorption. We also discuss the resulting spectral single scattering albedo for these cases.

  5. Light absorption by organic carbon from wood combustion

    Y. Chen

    2009-09-01

    Full Text Available Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While BC is highly absorbing, some organic compounds also have significant absorption, which is greater at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to direct aerosol radiative forcing.

    In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble organic carbon contributed to light absorption at both ultraviolet and visible wavelengths. However, a larger portion came from organic carbon that is extractable only by methanol. The spectra of water-soluble organic carbon are similar to others in the literature. We compared spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating organic aerosol with higher absorption, causing about a factor of four increase in mass-normalized absorption at visible wavelengths. A simple model suggests that, despite the absorption, both high-temperature and low-temperature carbon have negative climate forcing over a surface with average albedo.

  6. Absorption and fluorescence spectroscopy on a smartphone

    Hossain, Md. Arafat; Canning, John; Cook, Kevin; Ast, Sandra; Rutledge, Peter J.; Jamalipour, Abbas

    2015-07-01

    A self-powered smartphone-based field-portable "dual" spectrometer has been developed for both absorption and fluorescence measurements. The smartphone's existing flash LED has sufficient optical irradiance to undertake absorption measurements within a 3D-printed case containing a low cost nano-imprinted polymer diffraction grating. A UV (λex ~ 370 nm) and VIS (λex ~ 450 nm) LED are wired into the circuit of the flash LED to provide an excitation source for fluorescence measurements. Using a customized app on the smartphone, measurements of absorption and fluorescence spectra are demonstrated using pH-sensitive and Zn2+-responsive probes. Detection over a 300 nm span with 0.42 nm/pixel spectral resolution is demonstrated. Despite the low cost and small size of the portable spectrometer, the results compare well with bench top instruments.

  7. Evidence for Partial Melting in Reflectance Spectra of 433 Eros

    McFadden, L. A.; Goldman, Noah; Gaffey, M. J.; Izenberg, N. R.

    2005-01-01

    The NEAR Shoemaker spacecraft returned near-IR spectra of asteroid 433 Eros at spatial resolutions ranging from 2.5 to 100's km during its year-long orbital mission in 2000. Assuming modified Gaussian absorption bands represent the reflectance spectrum between 0.8-2.5 m we fit the average of all geometrically corrected spectra acquired by the near-IR spectrometer (NIS) with seven absorption bands. Interpretation of the absorption bands in terms of olivine and pyroxene minerals indicates that the surface of Eros contains olivine and two pyroxenes with compositions that are indicative of a partially melted assemblage. This partial melting must have occurred when the asteroid was part of a larger minor planet, prior to break up into its current elongated and irregular shape.

  8. Laser- and gamma-induced transformations of optical spectra of indium-doped sodium borate glass

    Kopyshinsky, O V; Zelensky, S E; Danilchenko, B A; Shakhov, O P

    2003-01-01

    The optical absorption and luminescence properties of indium-doped sodium borate glass irradiated by gamma-rays and by powerful UV lasers within the impurity-related absorption band are investigated experimentally. It is demonstrated that both the laser- and gamma-irradiation cause similar transformations of optical spectra in the UV and visible regions. The changes of the spectra observed are described with the use of a model which includes three types of impurity centres formed by differently charged indium ions.

  9. Atmospheric absorption of terahertz radiation and water vapor continuum effects

    The water vapor continuum absorption spectrum was investigated using Fourier Transform Spectroscopy. The transmission of broadband terahertz radiation from 0.300 to 1.500 THz was recorded for multiple path lengths and relative humidity levels. The absorption coefficient as a function of frequency was determined and compared with theoretical predictions and available water vapor absorption data. The prediction code is able to separately model the different parts of atmospheric absorption for a range of experimental conditions. A variety of conditions were accurately modeled using this code including both self and foreign gas broadening for low and high water vapor pressures for many different measurement techniques. The intensity and location of the observed absorption lines were also in good agreement with spectral databases. However, there was a discrepancy between the resonant line spectrum simulation and the observed absorption spectrum in the atmospheric transmission windows caused by the continuum absorption. A small discrepancy remained even after using the best available data from the literature to account for the continuum absorption. From the experimental and resonant line simulation spectra the air-broadening continuum parameter was calculated and compared with values available in the literature. -- Highlights: •Broadband absorption measurements of water vapor were performed at 300–1500 GHz. •The absorption coefficient of water vapor was modeled and compared with data. •The air-broadened continuum coefficient for water vapor was determined. •The modeled absorption coefficient is presented for 10–90% humidity at 0–3 THz

  10. H-modulated microwave absorption and superconducting transition in YBCO and BSCCO powders in fields up to 10 KOe

    In this paper H-modulated non-resonant microwave absorption spectra (X-band) are given for YBCO and BSCCO powders, recorded in decreasing temperature down to 68 K at various constant fields in the range 20 Oe - KOe. The effect of the applied magnetic field on the spectra is discussed in the hypothesis of proportionality between the microwave absorption and the resistivity

  11. Optical absorption and thermoluminescence of x-irradiated KDP

    Optical absorption and thermoluminescence spectra of nominally pure x-irradiated KDP have been obtained between 13 K and room temperature. Absorption spectra and their associated thermal bleaching curves exhibit a strong dichroism. Two glow peaks are observed at 73 K and 123 K which correlate well with main decay steps on the bleaching curve. From these data the existence of two different centres with activation energies of approximately 0.042 eV and approximately 0.22 eV is concluded. Different possibilities for the structure of these centres are discussed. (author)

  12. Transient x-ray absorption spectroscopy of hydrated halogen atom

    Elles, Christopher G; Crowell, Robert A; Arms, Dohn A; Landahl, Eric C

    2007-01-01

    Time-resolved x-ray absorption spectroscopy monitors the transient species generated by one-photon detachment of an electron from aqueous bromide. Hydrated bromine atoms with a lifetime of ca. 17 ns were observed, nearly half of which react with excess Br- to form Br2-. The K-edge spectra of the Br atom and Br2- anion exhibit distinctive resonant transitions that are absent for the Br- precursor. The absorption spectra indicate that the solvent shell around a Br0 atom is defined primarily by hydrophobic interactions, in agreement with a Monte Carlo simulation of the solvent structure.

  13. Zeeman atomic absorption spectroscopy

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  14. Nutrition and magnesium absorption.

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true magnesium abs

  15. Absorption and emission spectroscopic characterisation of 8-amino-riboflavin

    Tyagi, A.; Zirak, P.; Penzkofer, A.; Mathes, T.; Hegemann, P.; Mack, M.; Ghisla, S.

    2009-10-01

    The flavin dye 8-amino-8-demethyl- D-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2-5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.

  16. Absorption and emission spectroscopic characterisation of 8-amino-riboflavin

    Tyagi, A.; Zirak, P. [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Penzkofer, A., E-mail: alfons.penzkofer@physik.uni-regensburg.de [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Mathes, T.; Hegemann, P. [Institut fuer Biologie/Experimentelle Biophysik, Humboldt Universitaet zu Berlin, Invalidenstrasse 42, D-10115 Berlin (Germany); Mack, M. [Institut fuer Technische Mikrobiologie, Hochschule Mannheim, Paul-Wittsack-Str. 10, D-68163 Mannheim (Germany); Ghisla, S. [Universitaet Konstanz, Fakultaet fuer Biologie, P.O. Box 5560-M644, D-78457 Konstanz (Germany)

    2009-10-16

    The flavin dye 8-amino-8-demethyl-D-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2-5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.

  17. Deconvolution of Positrons' Lifetime spectra

    In this paper, we explain the iterative method previously develop for the deconvolution of Doppler broadening spectra using the mathematical optimization theory. Also, we start the adaptation and application of this method to the deconvolution of positrons' lifetime annihilation spectra

  18. Effect of γ-radiation on the IR spectra of lanthanide 8-hydroxyquinoline complexes

    IR absorption spectra of eight lanthanide elements chelated with 8-hydroxyquinoline were measured before and after gamma irradiation with different doses (25-850 MR). It was found that the rate of decrease K of M-O and C-O absorption bands depend on the chelated cation. A mechanism based on the target theory is proposed. (author)

  19. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    We have applied a Learning Vector Quantization (LVQ) algorithm to SDSS DR5 quasar spectra in order to create a large catalogue of broad absorption line quasars (BALQSOs). We first discuss the problems with BALQSO catalogues constructed using the conventional balnicity and/or absorption indices (BI and AI), and then describe the supervised LVQ network we have trained to recognise BALQSOs. The resulting BALQSO catalogue should be substantially more robust and complete than BI-or AI-based ones.

  20. Multiple scattering approach to X-ray absorption spectroscopy

    2003-01-01

    In this paper we present the state of the art of the theoretical background needed for analyzing X-ray absorption spectra in the whole energy range. The multiple-scattering (MS) theory is presented in detail with some applications on real systems. We also describe recent progress in performing geometrical fitting of the XANES (X-ray absorption near-edge structure) energy region and beyond using a full multiple-scattering approach.