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1

High-gain continuous-mode operated gaseous photomultipliers for the visible spectral range  

Energy Technology Data Exchange (ETDEWEB)

We shortly describe recent progress in photon detectors combining bi-alkali photocathodes and cascaded patterned gas-avalanche electron multipliers. It permitted the development and the first feasibility demonstration of high-gain gaseous photomultipliers sensitive in the visible spectral range, operated in continuous-mode with single-photon sensitivity.

Lyashenko, A. [Department of Particle Physics, Weizmann Institute of Science, 76100 Rehovot (Israel)], E-mail: alexey.lyashenko@weizmann.ac.il; Breskin, A.; Chechik, R. [Department of Particle Physics, Weizmann Institute of Science, 76100 Rehovot (Israel); Amaro, F.D. [Physics Department, University of Coimbra, 3004-516 Coimbra (Portugal); Veloso, J.F.C.A. [Physics Department, University of Coimbra, 3004-516 Coimbra (Portugal); Physics Department, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro (Portugal); Santos, J.M.F. dos [Physics Department, University of Coimbra, 3004-516 Coimbra (Portugal)

2009-10-21

2

Spectroscopy of fullerenes, fulleranes and PAHs in the UV, visible and near infrared spectral range  

CERN Document Server

The spectra of fullerenes C60 and C70, higher fullerenes C76, C78 and C84 and hydrogenated fullerenes (fulleranes) were studied in laboratory in the UV and in the visible spectral range and could be used for searching and recognizing these molecules in space. Furthermore, the radical cation spectra of all the mentioned fullerene series and also of a series of large and very large polycyclic aromatic hydrocarbons (PAHs) were generated in laboratory and studied in the near infrared spectral range.

Cataldo, F; Manchado, A; Iglesias-Groth, S

2013-01-01

3

Continuous Spatial Tuning of Laser Emissions in a Full Visible Spectral Range  

Directory of Open Access Journals (Sweden)

Full Text Available In order to achieve a continuous tuning of laser emission, the authors designed and fabricated three types of cholesteric liquid crystal cells with pitch gradient, a wedge cell with positive slope, a wedge cell with negative slope, and a parallel cell. The length of the cholesteric liquid crystal pitch could be elongated up to 10 nm, allowing the lasing behavior of continuous or discontinuous spatial tuning determined by the boundary conditions of the cholesteric liquid crystal cell. In the wedge cell with positive slope, the authors demonstrated a continuous spatial laser tuning in the near full visible spectral range, with a tuning resolution less than 1 nm by pumping with only a single 355 nm laser beam. This continuous tuning behavior is due to the fact that the concentration of pitch gradient matches the fixed helical pitch determined by the cell thickness. This characteristic continuous spatial laser tuning could be confirmed again by pumping with a 532 nm laser beam, over 90 nm in the visible spectral range. The scheme of the spatial laser tuning in the wedge cell bearing a pitch gradient enabled a route to designing small-sized optical devices that allow for a wide tunability of single-mode laser emissions.

Mi-Yun Jeong

2011-03-01

4

MMI-based MOEMS FT spectrometer for visible and IR spectral ranges  

Science.gov (United States)

MEMS spectrometers have very strong potential in future healthcare and environmental monitoring applications, where Michelson interferometers are the core optical engine. Recently, MEMS Michelson interferometers based on using silicon interface as a beam splitter (BS) has been proposed [7, 8]. This allows having a monolithically-integrated on-chip FTIR spectrometer. However silicon BS exhibits high absorption loss in the visible range and high material dispersion in the near infrared (NIR) range. For this reason, we propose in this work a novel MOEMS interferometer allowing operation over wider spectral range covering both the infrared (IR) and the visible ranges. The proposed architecture is based on spatial splitting and combining of optical beams using the imaging properties of Multi-Mode Interference MMI waveguide. The proposed structure includes an optical splitter for spatial splitting an input beam into two beams and a combiner for spatial combining the two interferometer beams. A MEMS moveable mirror is provided to produce an optical path difference between the two beams. The new interferometer is fabricated using DRIE technology on an SOI wafer. The movable mirror is metalized and attached to a comb-drive actuator fabricated in the same lithography step in a self-aligned manner on chip. The novel interferometer is tested as a Fourier transform spectrometer. Red laser, IR laser and absorption spectra of different materials are measured with a resolution of 2.5 nm at 635-nm wavelength. The structure is a very compact one that allows its integration and fabrication on a large scale with very low cost.

Al-Demerdash, Bassem M.; Medhat, Mostafa; Sabry, Yasser M.; Saadany, Bassam; Khalil, Diaa

2014-03-01

5

Detector calibration in the spectral range from vacuum-ultraviolet to visible  

International Nuclear Information System (INIS)

The Electrotechnical Laboratory is responsible for establishing optical units in Japan. Optical units are classified into photometric units which are weighted by human eye responsivity such as candela and radiometric units which are pure physical units such as watt. In this report, the overview of the techniques to determine the radiometric scales for detectors in the spectral region from ultraviolet to visible is described. The characteristics of semiconductor photodiodes as the primary standard detector and rare gas ionization chambers as another example of the primary standard detector are discussed. For characterizing the response of detectors, quantum efficiency or responsivity is used. The definitions of both are given. In order to realize a detector standard, the calibration with a primary standard detector the use of a primary standard radiation source and an efficiency-evaluated monochromatizing component, or the extension of spectral range of an existing detector standard by using a thermal detector is carried out. Noble gas ionization chambers as the primary standard detector in vacuum ultraviolet region, the self-calibration method, and semiconductor photodiodes as the absolute detector are described. (K.I.)

1994-08-01

6

Luminescent properties of the ZnSe:Yb crystals in the visible spectral range  

Energy Technology Data Exchange (ETDEWEB)

Luminescent properties of the ytterbium doped zinc selenide crystals with various concentrations of the doping impurity in 0.03–8 at % range within the temperature interval from 6 K to 300 K were studied. It was shown that ytterbium does not form any proper photoluminescence (PL) bands in the visible spectral range, but it has significant influence on the crystals luminescent properties by changing their defect composition. An attempt to determine ytterbium ion surroundings in the crystal lattice was made based on the obtained experimental results. An assumption about simultaneous compensation of donor and acceptor defects as a result of doping annealing in Zn+X at % Yb melt was made. -- Highlights: • ZnSe:Yb crystals with Yb concentration within 0.03–8 at% range were obtained • Temperature and concentration dependences of ZnSe:Yb PL properties were studied • Ytterbium impurity contribution to formation of the PL bans was determined • A model explaining Yb interaction with native and extrinsic defects was proposed.

Radevici, I., E-mail: ivarad@utu.fi [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Sushkevich, K. [Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Sirkeli, V. [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Huhtinen, H. [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Nedeoglo, D. [Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Paturi, P. [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)

2013-11-15

7

Thermo-optical response of photonic crystal cavities operating in the visible spectral range  

Science.gov (United States)

In this paper we study thermo-optical effects in gallium phosphite photonic crystal cavities in the visible range. By measuring the shift of narrow resonances, we derive the temperature dependency of the local refractive index of gallium phosphide in an attoliter volume over a temperature range between 5 and 300 K at a wavelength of about 605 nm. Additionally, the potential of photonic crystal cavities for thermo-optical switching of visible light is investigated. As an example we demonstrate thermo-optical switching with 13 dB contrast.

Wolters, Janik; Nikolay, Niko; Schoengen, Max; Schell, Andreas W.; Probst, Jürgen; Löchel, Bernd; Benson, Oliver

2013-08-01

8

Investigation of silicon nitride based two-dimensional photonic crystals for the visible spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main topics of this thesis included the fabrication and experimental investigation of silicon nitride based 2D photonic crystals in the visible range of the electromagnetic spectrum. For this purpose, a fabrication process capable of patterning silicon nitride with an ultimate resolution of 25 nm as well as an investigation technique based on non-coherent white light transmission measurements were successfully developed. Using these techniques, photonic crystals with square and hexagonal ...

Kouba, Josef

2008-01-01

9

Optical constants of liquid UO_2 in the visible spectral range obtained from reflectivity measurements  

International Nuclear Information System (INIS)

The optical constants, n,k, of liquid urania were determined from reflectivity measurements with plane-polarized light. Measurements were made with an integrating-sphere laser reflectometer in the wavelength range 450-750 nm at temperatures between 3000 and 4000 K. Consistent results have been obtained for different angles of incidence. The optical constants show little variation with the wavelength and temperature. Liquid urania proves to be opaque to radiation in the whole spectral range studied. Average values of n = 1.7 and k = 0.8 are given for the temperature range 3100-3600 K. From this result it is concluded that internal thermal radiation cannot cause a significant increase in thermal conductivity urania upon melting. (orig.)

1981-01-01

10

Blackbody-based calibration for temperature calculations in the visible and near-IR spectral ranges using a spectrometer  

Energy Technology Data Exchange (ETDEWEB)

This paper presents, the results of a method used to create a blackbody-based referenced calibration curve for a spectrometer in the visible and near-IR range. This method would allow the use of optical temperature measurements in high temperature furnaces when distance, environment, and emissivity effects are not accurately known. A probe containing a lens connected to a fiber-optic cable is inserted into a furnace and aimed toward a hot wall source. Spectral intensity data is fed back to a spectrometer and then to a monitoring computer. Initial data is taken along with another method to measure the source temperature, usually a thermocouple or IR-gun. The spectral data is compared to the blackbody intensities generated from the source temperature to create the calibration curve. This calibration curve is then used to correct intensities for temperature calculations using a spectrometer where furnace conditions are similar to those of the calibration data. This calibration method provides much more accurate temperature measurement results than the common practice of using a halogen reference. The results in the visible range compare favorably with those taken in the near-IR range under the same conditions. 17 refs., 7 figs.

Shahla Keyvan; Rodney Rossow; Carlos Romero [University of Missouri-Columbia, Columbia, MO (United States). Department of Mechanical and Aerospace Engineering, Center for Artificial Intelligence in Engineering and Education

2006-03-15

11

Phase and microstructure investigations of boron nitride thin films by spectroscopic ellipsometry in the visible and infrared spectral range  

International Nuclear Information System (INIS)

Spectroscopic ellipsometry over the spectral range from 700 to 3000 cm-1 and from 1.5 to 3.5 eV is used to simultaneously determine phase and microstructure of polycrystalline hexagonal and cubic boron nitride thin films deposited by magnetron sputtering on (100) silicon. The results are obtained from a single microstructure-dependent model for both infrared and visible-light thin-film anisotropic dielectric functions. The optical behavior of high c-BN content thin films is described by an effective medium approximation. We obtain the amount of h-BN within high c-BN content thin films. A thin oriented nucleation layer between the silicon substrate and the high c-BN content layer is demonstrated. The preferential arrangement of the grain c axes within the h-BN thin films are found to be dependent on the growth parameters. The results from the infrared and visible spectral range ellipsometry model are compared to each other and found to be highly consistent. copyright 1997 American Institute of Physics

1997-09-01

12

Evidence for graphene plasmons in the visible spectral range probed by molecules  

CERN Multimedia

Graphene is considered to be plasmon active only up to the infrared based on combined tight binding model and random phase approximation calculations. Here we show that the optical properties of graphene as measured by ellipsometry and simulated by density functional theory imply the existence of strongly localized graphene plasmons in the visible with a line width of 0.1 eV. Using small emitters that provide the high wavevectors necessary to excite graphene plasmons at optical frequencies we demonstrate graphene plasmon induced excitation enhancement by nearly 3 orders of magnitude.

Lange, Philipp; Severin, Nikolai; Benson, Oliver; Rabe, Jürgen P

2014-01-01

13

Analysis of global water vapour trends from satellite measurements in the visible spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME) flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) approach has been used. The combination of the data from both instruments provides...

2008-01-01

14

Optical Characterization of Organic Light-Emitting Thin Films in the Ultraviolet and Visible Spectral Ranges  

CERN Document Server

The spectrophotometric characterization of high efficiency, optically-active samples such as light-emitting organic bulks and thin films can be problematic because their broad-band luminescence is detected together with the monochromatic transmitted and reflected signals, hence perturbing measurements of optical transmittance and reflectance at wavelengths within the photoexcitation band. As a matter of fact, most commercial spectrophotometers apply spectral filtering before the light beam reaches the sample, not after it. In this Report, we introduce and discuss the method we have developed to correct photometric spectra that are perturbed by photoluminescence.

Montereali, R M; Nichelatti, E; Di Pompeo, F; Segreto, E; Canci, N; Cavanna, F

2012-01-01

15

Lasing in the UV, IR and visible spectral ranges in a runaway-electron-preionised diffuse dischrage  

International Nuclear Information System (INIS)

Lasers on the mixtures of inert gases, H2, D2, and nitrogen with NF3 and (or) SF6 are studied under pumping by the volume (diffusive) discharge formed in a nonuniform electric field due to runaway-electron preionisation. Generation in the IR, visible and UV spectral ranges is obtained on atomic transitions of neon (? = 585.3 nm), argon (750.3 nm) and fluorine (712.8 and 731.1 nm), and on molecular transitions of N2 (337.1 nm), XeF * (351 and 353 nm), HF (2.8 – 3.2 ?m) and DF (3.8 – 4.2 ?m). It is shown that in N2 – SF6, H2 – SF6 and D2 – SF6 mixtures the generation efficiency approaches the limiting values. (lasers)

2013-07-31

16

Lasing in the UV, IR and visible spectral ranges in a runaway-electron-preionised diffuse dischrage  

Energy Technology Data Exchange (ETDEWEB)

Lasers on the mixtures of inert gases, H{sub 2}, D{sub 2}, and nitrogen with NF{sub 3} and (or) SF{sub 6} are studied under pumping by the volume (diffusive) discharge formed in a nonuniform electric field due to runaway-electron preionisation. Generation in the IR, visible and UV spectral ranges is obtained on atomic transitions of neon ({lambda} = 585.3 nm), argon (750.3 nm) and fluorine (712.8 and 731.1 nm), and on molecular transitions of N2 (337.1 nm), XeF * (351 and 353 nm), HF (2.8 - 3.2 {mu}m) and DF (3.8 - 4.2 {mu}m). It is shown that in N{sub 2} - SF{sub 6}, H{sub 2} - SF{sub 6} and D{sub 2} - SF{sub 6} mixtures the generation efficiency approaches the limiting values. (lasers)

Vil' tovskii, P O; Lomaev, Mikhail I; Panchenko, Aleksei N; Panchenko, N A; Rybka, D V; Tarasenko, Viktor F [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

2013-07-31

17

Optical properties of native and coagulated lamb brain tissues in vitro in the visible and near-infrared spectral range  

Science.gov (United States)

The aim of this study was to estimate optical properties (?a, ?s, ?t, ?s', ?, ?, g) of native and coagulated (at 45°C, 60°C, 80°C) lamb brain tissues in visible and near-infrared spectral range in vitro. Optical properties of cerebellum, brainstem, cortical (grey matter), and sub-cortical regions (white matter) of frontal lobe tissues of lamb brain were estimated during this study. Diffused transmittance (Td), diffused reflectance (Rd), total reflectance (Rt) and total transmittance (Tt) were measured with single integrating sphere method. Data were processed with software (CAL-g3) developed in Biophotonics Laboratory in the Institute of Biomedical Engineering, Bogazici University. As a result, it was stated that both ?a and ?s values of tissues increased as temperature increases. Also scattering coefficients decreased with the increasing wavelength for all tissue types due to increase in Mie scattering.

Özer, Korhan; Bozkulak, Özgüncem; Tabako?lu, Ha?im Özgür; Kurt, Adnan; Gülsoy, Murat

2006-03-01

18

Analysis of global water vapour trends from satellite measurements in the visible spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data on MetOp.

Using linear and non-linear methods from time series analysis and standard statistics the trends of H2O columns and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes from ?5% per year to +5% per year. These significant trends are distributed over the whole globe. Increasing trends have been calculated for Greenland, East Europe, Siberia and Oceania, whereas decreasing trends have been observed for the northwest USA, Central America, Amazonia, Central Africa and the Arabian Peninsular.

S. Mieruch

2008-02-01

19

Radiative transfer model STORM for full Stokes vector calculations in the visible and near infrared spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available Based on the Matrix-Operator Method the radiative transfer code STORM (STOkes vector Radiative transfer Model is introduced, which was developed in a joint project of DLR and Institut f{ü}r Weltraumwissenschaften-Freie Universität Berlin. STORM calculates the Stokes parameters (I, Q, U, V in a plane parallel, multi layered atmosphere in the visible and near infrared spectral range. The scattering characteristics of aerosols are determined by Mie theory. The surface represents a Lambertian reflector or a wind ruffled water surface described by Cox-Munk model. The results of one calculation are the upward and downward directed Stokes parameters for one wavelength at a desired number of sun incident and viewing angles at varying altitudes in the principal plane and other azimuth angles. STORM is applied for an analysis in view of designing downward looking Earth observing optical remote sensing systems and values of the degree of polarization are presented as generic basis for remote sensing system design and data processing.

U. Böttger

2006-01-01

20

Dispersion control over the ultraviolet-visible-near-infrared spectral range with HfO2/SiO2-chirped dielectric multilayers.  

Science.gov (United States)

We report the first realization, to the best of our knowledge, of a chirped multilayer dielectric mirror providing dispersion control over the spectral range of 300-900 nm and the first use of hafnium oxide in a chirped mirror. The technology opens the door to the reliable and reproducible generation of monocycle laser pulses in the blue-violet spectral range, will benefit the development of optical waveform and frequency-comb synthesizers over the ultraviolet-visible-near-infrared spectral range, and permits the development of ultrabroadband-chirped multilayers for high-power applications. PMID:17410276

Pervak, V; Krausz, F; Apolonski, A

2007-05-01

 
 
 
 
21

The interaction of alcohol radicals with human hemoglobin. Pt. 1. Spectral properties of hemoglobin in the visible range  

International Nuclear Information System (INIS)

Aqueous deoxyhemoglobin solutions (2 mg/ml) were gamma-irradiated by a 60Co source in the presence of methanol, ethanol, 1-butanol and t-butanol under N2O or argon. The effects of the interaction of the particular alcohol radical species with hemoglobin were determined according to the detected spectral alterations in the visible range. The amounts of stable final products in the form of methemoglobin (MetHb) and the sum of hemichromes and cholehemichromes (Hemichr) were estimated in irradiated preparations. For preparations irradiated under N2O, the radiation yield for MetHb formation was three-fold lower in the presence of ethanol and 1-butanol [G(MetHb) = 0.33[ compared with preparations irradiated in the presence of t-butanol or without alcohol [G(MetHb) = 1.00[. The yield of hemichromes and cholehemichromes in preparations irradiated under N2O increased in the order: ethanol (G = 0.38), 1-butanol (B = 0.52), t-butanol (G = 0.59), and in the absence of alcohol (G 0.72). The high effectivity of t-butanol radicals for iron oxidation and Hb destruction is apparently due to their oxidative properties, compared with the other radicals. It was also shown that ethanol radicals reduce MetHb 10 times more effectively [G(Fe(II)) = 2.5[ compared with t-butanol radicals [G(Fe(II)) = 0.24[. For samples irradiated under argon all the observed changes were similar, regardless of the presence of alcohols. This effect can be attributed to reconstruction reactions of Hb molecules in the presence of both oxidizing (OH or t-but.) and reducing agents (e-aq). The following sequence of effectivities of water radiolysis products and secondary alcohol radicals for hemoglobin destruction has been identified: meth., eth. ? 1-but. ? e-aq ? t-but. ? .OH. (orig.)

1994-10-01

22

Radiometric comparison of the primary synchrotron radiation source standard Metrology Light Source with calibrated filter radiometers in the visible and NIR spectral range  

Energy Technology Data Exchange (ETDEWEB)

The Metrology Light Source (MLS), the electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), is operated as a primary radiometric source standard from the near infrared (NIR) to the vacuum ultraviolet spectral region with calculable synchrotron radiation according to electromagnetic theory (Schwinger equation). The operational parameters of the MLS can be varied in a wide range to adjust the spectral distribution and the intensity of the resulting spectrum to the specific measurement requirements. The electron beam energy can be set to values between 105 MeV and 630 MeV, and the electron beam current can be varied from 1 pA (one stored electron) up to 200 mA. Using two calibrated filter radiometers with centre wavelengths of 476 nm and 1595 nm as transfer standards, the calculated spectral radiant power of the MLS into a well-defined aperture was compared with the spectral irradiance responsivity scale of PTB realized by cryogenic radiometers in the visible and NIR spectral range. The measurements were performed with the MLS operated at various electron energies. Good agreement was found within the combined relative uncertainties. (authors)

Klein, R.; Taubert, D.; Thornagel, R.; Hollandt, J.; Ulm, G. [Physikalisch-Technische Bundesanstalt, Berlin (Germany)

2009-06-15

23

Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula  

Science.gov (United States)

A better understanding of the aerosol radiative properties is a crucial challenge for climate change studies. This study aims to provide a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term datasets of aerosol properties from six AERONET stations located in the Iberian Peninsula (Southwestern Europe) are analyzed in term of climatology characterization and trends. Aerosol information is used as input to the libRadtran model in order to determine the aerosol radiative effect at the surface in the ultraviolet (AREUV), visible (AREVIS), near-infrared (ARENIR), and the entire SW range (ARESW) under cloud-free conditions. Over the whole Iberian Peninsula, aerosol radiative effects in the different spectral ranges are: -1.1 AFE), ARE per unit of aerosol optical depth, is also evaluated in the four spectral ranges. AFE exhibits a dependence on single scattering albedo and a weaker one on Ångström exponent. AFE is larger (in absolute value) for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency vary with the aerosol types. Aerosol size determines the fractions of AFEVIS/AFESW and AFENIR/AFESW. VIS range is the dominant region for all types, although non-absorbing large particles cause a more equal contribution of VIS and NIR intervals. The AFEUV / AFESW ratio shows a higher contribution for absorbing fine particles.

Mateos, D.; Antón, M.; Toledano, C.; Cachorro, V. E.; Alados-Arboledas, L.; Sorribas, M.; Costa, M. J.; Baldasano, J. M.

2014-04-01

24

Ion-induced effects in GEM & GEM/MHSP gaseous photomultipliers for the UV and the visible spectral range  

CERN Document Server

We report on the progress in the study of cascaded GEM and GEM/MHSP gas avalanche photomultipliers operating at atmospheric pressure, with CsI and bialkali photocathodes. They have single-photon sensitivity, ns time resolution and good localization properties. We summarize operational aspects and results, with the highlight of a high-gain stable gated operation of a visible-light device. Of particular importance are the results of a recent ion-backflow reduction study in different cascaded multipliers, affecting the detector's stability and the photocathode's liftime. We report on the significant progress in ion-blocking and provide first results on bialkali-photocathode aging under gas multiplication.

Breskin, Amos; Lyashenko, A; Chechik, R; Amaro, F D; Maia, J M; Veloso, J F C; Dos Santos, J M F

2005-01-01

25

Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula  

Directory of Open Access Journals (Sweden)

Full Text Available A better understanding of the aerosol radiative properties is a crucial challenge for climate change studies. This study aims to provide a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW solar spectrum. For this purpose, long-term datasets of aerosol properties from six AERONET stations located in the Iberian Peninsula (Southwestern Europe are analyzed in term of climatology characterization and trends. Aerosol information is used as input to the libRadtran model in order to determine the aerosol radiative effect at the surface in the ultraviolet (AREUV, visible (AREVIS, near-infrared (ARENIR, and the entire SW range (ARESW under cloud-free conditions. Over the whole Iberian Peninsula, aerosol radiative effects in the different spectral ranges are: ?1.1 UV ?2, ?5.7 VIS ?2, ?2.8 NIR ?2, and ?9.5 SW ?2. The four variables showed positive statistically significant trends between 2004 and 2012, e.g., ARESW increased +3.6 W m?2 per decade. This fact is linked to the decrease in the aerosol load, which presents a trend of ?0.04 per unit of aerosol optical depth at 500 nm per decade, hence a reduction of aerosol effect on solar radiation at the surface is seen. Monthly means of ARE show a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE, ARE per unit of aerosol optical depth, is also evaluated in the four spectral ranges. AFE exhibits a dependence on single scattering albedo and a weaker one on Ångström exponent. AFE is larger (in absolute value for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency vary with the aerosol types. Aerosol size determines the fractions of AFEVIS/AFESW and AFENIR/AFESW. VIS range is the dominant region for all types, although non-absorbing large particles cause a more equal contribution of VIS and NIR intervals. The AFEUV / AFESW ratio shows a higher contribution for absorbing fine particles.

D. Mateos

2014-04-01

26

Sensitivity of spectral reflectance to aerosol optical properties in UV and visible wavelength range: Preparatory study for aerosol retrieval from Geostationary Environmental Monitoring Spectrometer (GEMS)  

Science.gov (United States)

Asia, with its rapid increase in industrialization and population, has been receiving great attention as one of important source regions of pollutants including aerosols and trace gases. Since the spatio-temporal distribution of the pollutants varies rapidly, demands to monitor air quality in a geostationary satellite have increased recently. In these perspectives, the Ministry of Environment of Korea initiated a geostationary satellite mission to launch the Geostationary Environmental Monitoring Spectrometer (GEMS) onboard the GEO-KOMPSAT in 2017-2018 timeframe. From the Ozone Monitoring Instrument (OMI) measurements, it has been found that the low surface reflectance and strong interaction between aerosol absorption and molecular scattering in UV wavelength range can be advantageous in retrieving aerosol optical properties, such as aerosol optical thickness (AOT) and optical type (or single scattering albedo), over the source regions as well as ocean areas. In addition, GEMS is expected to have finer spatial resolution compared to OMI (13 x 24 km2 at nadir), thereby less affected by sub-pixel clouds. In this study, we present sensitivity of spectral reflectance to aerosol optical properties in ultraviolet (UV) and visible wavelength range for a purpose to retrieve aerosol optical properties from GEMS. The so called UV-VIS algorithm plans to use spectral reflectance in 350-650 nm. The algorithm retrieves AOT and aerosol type using an inversion method, which adopts pre-calculated lookup table (LUT) for a set of assumed aerosol models. For the aerosol models optimized in Asia areas, the inversion data of Aerosol Robotic Network (AERONET) located in the target areas are selectively used to archive aerosol optical properties. As a result, major aerosol types representing dust, polluted dust, and absorbing/non-absorbing anthropogenic aerosols are constructed and used for the LUT calculations. We analyze the effect of cloud contamination on the retrieved AOT by comparing the results from different spatial resolutions (7.5 x 7.5 km2, 5 x 5 km2, 2.5 x 7.5 km2, 1.25 x 3.75 km2). In addition, improved methodology to obtain aerosol products using hyper-spectral UV-VIS measurements is discussed.

KIM, M.; Kim, J.; Lee, J.

2011-12-01

27

Comparison of the usability of different spectral ranges within the near ultraviolet, visible and near infrared ranges (UV-VIS-NIR) region for the determination of the content of scab-damaged component in blended samples of ground wheat.  

Science.gov (United States)

Soft wheat grain samples of the same variety were obtained from a plot where the crop grew under natural conditions (control material) and from a plot where the crop was inoculated with Fusarium culmorum. The grain was ground and sieved with the finest fraction (a particle size less than 0.18 mm) of both materials being used for the preparation of samples in which the content of damaged constituent varied from zero to approximately 84%. Diffuse reflectance spectra of the absorbance from the blended samples were recorded in the 200-2500 nm spectral range and multivariate calibration PLS (Partial Least Squares) models were built within three spectral ranges: 200-2500, 200-1400 and 1400-2500 nm. Before modelling, several variants for spectra pre-processing were tried: multiple scatter correction, single and double differentiation, in all cases with and without centring. Single differentiation followed by centring was found to be the best method for spectra pre-processing in all spectral ranges. Very good calibration models were obtained for the whole and shorter wavelengths spectral ranges, allowing the detection of 1.50 and 0.76% of the content of scab-damaged constituent, respectively. Two-dimensional correlation spectroscopy applied to the set of spectra enabled the assignment of spectral bands and an analysis of changes in the chemical composition caused by scab damage. It was found that the content of protein and lipids increased with an increase of the scab-damaged constituent, whereas the content of moisture and starch decreased. PMID:17071523

Siuda, R; Balcerowska, G; Sadowski, C

2006-11-01

28

Spectral absorption studies of visible materials  

Science.gov (United States)

Results of studies of optical absorption in twelve thin-film optical coatings at 482 nm wavelength, surface and bulk absorption in sapphire throughout the visible and near IR, and initial measurements in KDP are described. Laser calorimetry was carried out at room temperature, using an unfocused laser beam at normal incidence. All thin-film absorption data yielded values of P(sub abs)/P(sub inc) in the range 3 x 10 to the -4 to 3 x 10 to the -3 power at a wavelength of 482 nm. Sapphire absorption showed Urbach-tail behavior at 350 nm to 1300 nm. The range of absorption, being far lower than usual, extends the range of application of Urbach's rule. Finally, KDP measurements were attempted, but surface degradation due to the hydroscopic nature of the samples resulted in excessive light scatter.

Bass, M.; Swimm, R. T.

29

Electromagnetic cloaking in the visible frequency range  

CERN Multimedia

Electromagnetic metamaterials provide unprecedented freedom and flexibility to introduce new devices, which control electromagnetic wave propagation in very unusual ways. Very recently theoretical design of an "invisibility cloak" has been suggested, which has been realized at microwave frequencies in a two-dimensional cylindrical geometry. In this communication we report on the experimental realization of the dielectric permittivity distribution required for non-magnetic cloaking in the visible frequency range.

Smolyaninov, I I; Davis, C C

2007-01-01

30

Globally integrated measurements of the Earth's visible spectral albedo  

CERN Multimedia

We report spectroscopic observations of the earthshine reflected from the Moon. By applying our photometry methodology to spectroscopy, we were able to precisely determine the Earth's reflectance, and its variation as a function of wavelength through a single night as the Earth rotates. These data imply that planned regular monitoring of earthshine spectra will yield valuable, new inputs for climate models, which would be complementary to those from the more standard broadband measurements of satellite platforms. The mean spectroscopic albedo over the visible is consistent with simultaneous broadband photometric measurements. We found no evidence for an appreciable "red" or "vegetation edge" in the Earth's spectral albedo, and no evidence for changes in this spectral region (700 -740 nm) over the 40 degrees of Earth's rotation covered by our observations.

Montanes-Rodriguez, P; Goode, P R; Hickey, J; Koonin, S E

2005-01-01

31

Visibility analysis of point cloud in close range photogrammetry  

Science.gov (United States)

The ongoing development of advanced techniques in photogrammetry, computer vision (CV), robotics and laser scanning to efficiently acquire three dimensional geometric data offer new possibilities for many applications. The output of these techniques in the digital form is often a sparse or dense point cloud describing the 3D shape of an object. Viewing these point clouds in a computerized digital environment holds a difficulty in displaying the visible points of the object from a given viewpoint rather than the hidden points. This visibility problem is a major computer graphics topic and has been solved previously by using different mathematical techniques. However, to our knowledge, there is no study of presenting the different visibility analysis methods of point clouds from a photogrammetric viewpoint. The visibility approaches, which are surface based or voxel based, and the hidden point removal (HPR) will be presented. Three different problems in close range photogrammetry are presented: camera network design, guidance with synthetic images and the gap detection in a point cloud. The latter one introduces also a new concept of gap classification. Every problem utilizes a different visibility technique to show the valuable effect of visibility analysis on the final solution.

Alsadik, B.; Gerke, M.; Vosselman, G.

2014-05-01

32

Large-area transparent in visible range silicon carbide photodiode  

Science.gov (United States)

This paper describes the construction, fabrication and properties of large-area ultra violet detector that is transparent in the visible range. The device was made on n-type 4H SiC substrate with a double epitaxial layer in which aluminum was implanted to form a p-n junction close to the surface, and a SiO2 layer was formed for passivation, without a guard ring. The design of the top and bottom electrodes of 4mm diameter UV sensitive area allows not less than 20% visible range transmission. This transmission was measured across sensitive area of examined devices and was only 5% lower than that of the substrate before implantation and electrodes deposition.

Borecki, M.; Kociubi?ski, A.; Duk, M.; Kwietniewski, N.; Korwin-Pawlowski, M. L.; Doroz, P.; Szmidt, J.

2013-10-01

33

Towards isotropic negative magnetics in the visible range  

CERN Multimedia

The idea of isotropic resonant magnetism in the visible range of frequencies known from precedent publications is developed having in mind achievements of the modern chemistry. Plasmonic colloidal nanoparticles covering a silica core form a cluster with resonant and isotropic magnetic response. Two approximate models giving the qualitative mutual agreement are used to evaluate the magnetic polarizability of the cluster. It is shown that the electrostatic interaction of nanocolloids decreases the resonant frequency of an individual complex magnetic scatterer (nanocluster) compared to the previously studied variant of a planar circular nanocluster with same size. This means the reduction of the optical size of nanoclusters that presumably allows one to avoid strong spatial dispersion within the frequency range of the negative permeability.

Simovski, C R

2008-01-01

34

Polarization of AGN in UV Spectral Range  

CERN Multimedia

We present the review of some new problems in cosmology and physics of stars in connection with future launching of WSO. We discuss three problems. UV observations of distant z > 6 quasars allow to obtain information on the soft < 1 KeV X-ray radiation of the accretion disk around a supermassive black hole because of its cosmological redshift. Really the region of X-ray radiation is insufficiently investigated because of high galactic absorption. In a result one will get important information on the reionization zone of the Universe. Astronomers from ESO revealed the effect of alignment of electric vectors of polarized QSOs. One of the probable mechanism of such alignment is the conversion of QSO radiation into low mass pseudoscalar particles (axions) in the extragalactic magnetic field. These boson like particles have been predicted by new SUSY particle physics theory. Since the probability of such conversion is increasing namely in UV spectral range one can expect the strong correlation between UV spectr...

Gnedin, Yu N; Natsvlishvili, T M

2011-01-01

35

Ultraviolet and visible range plasmonics of a topological insulator  

CERN Document Server

The development of metamaterials, data processing circuits and sensors for the visible and UV parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations and drives the intense search for plasmonic materials beyond noble metals. By studying plasmonic nanostructures fabricated on the surface of topological insulator $\\mbox{Bi}_{1.5}\\mbox{Sb}_{0.5}\\mbox{Te}_{1.8}\\mbox{Se}_{1.2}$ we found that it is orders of magnitude better plasmonic material than gold and silver in the blue-UV range. Metamaterial fabricated from $\\mbox{Bi}_{1.5}\\mbox{Sb}_{0.5}\\mbox{Te}_{1.8}\\mbox{Se}_{1.2}$ show plasmonic resonances from 350 nm to 550 nm while surface gratings exhibit cathodoluminescent peaks from 230 nm to 1050 nm. The negative permittivity underpinning plasmonic response is attributed to the combination of bulk interband transitions and surface contribution of the topologically protected states. The importance of our result is in the identification of new mechanisms of negative permittiv...

Ou, Jun-Yu; Adamo, Giorgio; Sulaev, Azat; Wang, Lan; Zheludev, Nikolay I

2014-01-01

36

Investigation into the ways of tuning parametric oscillators of visible and IR ranges  

International Nuclear Information System (INIS)

Different versions of optical parametric oscillator (OPO) schemes were experimentally realised and investigated, which utilise AgGaS2, LiNbO3 and HgGa2S4 single crystals as well as an Hg1-xCdxGa2S4 solid solution. The OPOs generate radiation in the 1.2-5.7-?m range and make use of different ways of output wavelength tuning, including fast wavelength tuning (in a time shorter than 0.1 ms) with the help of an acoustooptical deflector. The output spectral line was narrowed by means of an intracavity acoustooptical filter. An OPO for the visible range with an electrodynamic tuning to an arbitrary wavelength in this range in a time of 5ms was implemented employing a BBO single crystal. (invited paper)

2010-06-23

37

Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example...

Aube?, Martin; Roby, Johanne; Kocifaj, Miroslav

2013-01-01

38

Forensic inspection of document using visible and near-infrared spectral imaging  

Science.gov (United States)

In this study, the potential of visible and near-infrared spectral imaging as a technique of document inspection was examined. Doubtful documents are often found in economic cases, distinguished between original and added strokes and detected blurry characters are very useful for judgment. Burned, covered and rinsed documents in which the characters can't be identified with naked eyes were experimentally studied with a visible spectral imaging technique. Meanwhile, the same color inks were detected by both visible and near-infrared imaging spectrometers. Classification of spectral images was carried out in specialist spectral imaging software packager Misystem provided by Institute of Forensic Science. The technique significantly improved the detection of many documents, especially those that might be considered of poor quality or borderline characters. The visible spectral imaging was successful in detecting the burnt Chinese characters produced using pencils. It was possible to form spectral images showing the strokes even covered by Chinese ink by means of imaging at characteristic frequencies. As inks have very different spectral from the clothes, contribution and contrast of the rinsed lines and illegible seal words on clothes were clearly enhanced. By examining the spectral images from the inks, it was possible to determine whether the same color inks were written by the different pens. The results also show that the near-infrared spectrometer is better than visible one in distinguishing the same inks. In blind testing, spectral imaging was shown to achieve an average 85.1% chance of success. The results reveal the wide applications of spectral imaging in document evidence analysis. The potential of this technique in forensic science will be more apparent along with the further and deeper studies.

Huang, Wei; Wang, Guiqiang; Xu, Xiaojing; Yu, Tao; Yang, Zhicheng

2010-11-01

39

Spectral Aging Model Applied to Meteosat First Generation Visible Band  

Directory of Open Access Journals (Sweden)

Full Text Available The Meteosat satellites have been operational since the early eighties, creating so far a continuous time period of observations of more than 30 years. In order to use this data for climate data records, a consistent calibration is necessary between the consecutive instruments. Studies have shown that the Meteosat First Generation (MFG satellites (1982–2006 suffer from in-flight degradation which is spectral of nature and is not corrected by the official calibration of EUMETSAT. Continuing on previous published work by the same authors, this paper applies the spectral aging model to a set of clear-sky and cloudy targets, and derives the model parameters for all six MFG satellites (Meteosat-2 to -7. Several problems have been encountered, both due to the instrument and due to geophysical occurrences, and these are discussed and illustrated here in detail. The paper shows how the spectral aging model is an improvement compared to the EUMETSAT calibration method with a stability of 1%–2% for Meteosat-4 to -7, which increases up to 6% for ocean sites using the full MFG time period.

Ilse Decoster

2014-03-01

40

Refined approximations for the distortion visibility function and mu-type spectral distortions  

CERN Document Server

The physical processes affecting the thermalization of cosmic microwave background spectral distortions are very simple and well understood. This allows us to make precise predictions for the distortions signals caused by various energy release scenarios, where the theoretical uncertainty is largely dominated by the physical ingredients that are used for the calculation. Here, we revisit various approximations for the distortion visibility function -- defined using the fraction of the released energy that does not thermalize -- and early $\\mu$-type distortions. Our approach is based on a perturbative expansion, which allows us to identify and clarify the origin of different improvements over earlier approximations. It provides a better than ~0.1%-1% description of our numerical results over a wide range of parameters. In particular, we are able to capture the high-frequency part of the mu-distortion, which directly depends on the time-derivative of the electron temperature. We also include lowest order double...

Chluba, Jens

2013-01-01

 
 
 
 
41

Linear refractive index and absorption measurements of nonlinear optical liquids in the visible and near-infrared spectral region  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Liquid-filled photonic crystal fibers and optofluidic devices require infiltration with a variety of liquids whose linear optical properties are still not well known over a broad spectral range, particularly in the near infrared. Hence, dispersion and absorption properties in the visible and near-infrared wavelength region have been determined for distilled water, heavy water, chloroform, carbon tetrachloride, toluene, ethanol, carbon disulfide, and nitrobenzene at a temperature of 20 °C. Fo...

2012-01-01

42

Passive ranging of dynamic rocket plumes using infrared and visible oxygen attenuation  

Science.gov (United States)

Atmospheric oxygen absorption bands in observed spectra of boost phase missiles can be used to accurately estimate range from sensor to target. One method is to compare observed values of band averaged absorption to radiative transfer models. This is most effective using bands where there is a single absorbing species. This work compares spectral attenuation of two oxygen absorption bands in the near-infrared (NIR) and visible (Vis) spectrum, centered at 762 nm and 690 nm, to passively determine range. Spectra were observed from a static test of a full-scale solid rocket motor at a 900m range. The NIR O2 band provided range estimates accurate to within 3%, while the Vis O2 band had a range error of 15%. A Falcon 9 rocket launch at an initial range of 13km was also tracked and observed for 90 seconds after ignition. The NIR O2 band provided in-flight range estimates accurate to within 2% error for the first 30 seconds of tracked observation. The Vis O2 band also provided accurate range estimates with an error of approximately 4%. Rocket plumes are expected to be significantly brighter at longer wavelengths, but absorption in the NIR band is nearly ten times stronger than the Vis band, causing saturation at shorter path lengths. An atmospheric band is considered saturated when all the in-band frequencies emitted from the rocket plume are absorbed before reaching the sensor.

Vincent, R. Anthony; Hawks, Michael R.

2011-05-01

43

A Wide Spectral Range Reflectance and Luminescence Imaging System  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we introduce a wide spectral range (200–2500 nm imaging system with a 250 ?m minimum spatial resolution, which can be freely modified for a wide range of resolutions and measurement geometries. The system has been tested for reflectance and luminescence measurements, but can also be customized for transmittance measurements. This study includes the performance results of the developed system, as well as examples of spectral images. Discussion of the system relates it to existing systems and methods. The wide range spectral imaging system that has been developed is however highly customizable and has great potential in many practical applications.

Tapani Hirvonen

2013-10-01

44

A Wide Spectral Range Reflectance and Luminescence Imaging System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study, we introduce a wide spectral range (200–2500 nm) imaging system with a 250 ?m minimum spatial resolution, which can be freely modified for a wide range of resolutions and measurement geometries. The system has been tested for reflectance and luminescence measurements, but can also be customized for transmittance measurements. This study includes the performance results of the developed system, as well as examples of spectral images. Discussion of the system relates it to exi...

Tapani Hirvonen; Niko Penttinen; Markku Hauta–Kasari; Mika Sorjonen; Kai–Erik Peiponen

2013-01-01

45

Spectral broadening and self-compression of negatively chirped visible femtosecond pulses in fused silica  

Energy Technology Data Exchange (ETDEWEB)

This paper describes a new effect: spectral broadening and self-compression of negatively chirped visible femtosecond pulses as a result of nonlinear interaction of large-aperture beams with fused silica. We assume that the likely mechanism of the observed spectral broadening is the combined effect of self-phase modulation and four-wave mixing. (special issue devoted to the 90th anniversary of n.g. basov)

Aristov, A I; Grudtsyn, Ya V; Mikheev, L D; Polivin, A V; Stepanov, S G; Trofimov, V A; Yalovoi, V I

2012-12-31

46

Aurones: small molecule visible range fluorescent probes suitable for biomacromolecules.  

Science.gov (United States)

Aurones, derivatives of 2-benylidenebenzofuran-3(2H)-one, are natural products that serve as plant pigments. There have been reports that some of these substances fluoresce, but little information about their optical properties is in the literature. In this report, series of aurone derivatives were synthesized as possible fluorescent probes that can be excited by visible light. We found that an amine substituent shifted the lowest energy absorption band from the near-UV to the visible region of the electromagnetic spectrum. Four amine-substituted aurone derivatives were synthesized to explore the effect of this substituent on the absorption and emission properties of the aurone chromophore. The emission maxima and intensities of the molecules are strongly dependent on the nature of the substituent and the solvent polarity. Overall, the emission intensity increases and the maximum wavelength decreases in less polar solvents; thus, the aurones may be useful probes for hydrophobic sites on biological molecules. A limited investigation with model protein, nucleic acid and fixed cells supports this idea. It is known that the sulfur analog of aurone can undergo photo-induced E/Z isomerization. This possibility was investigated for one of the aminoaurones, which was observed to reversible photoisomerize. The two isomers have similar absorption spectra, but the emission properties are distinct. We conclude that appropriately substituted aurones are potentially useful as biological probes and photoswitches. PMID:21748237

Shanker, Natasha; Dilek, Ozlem; Mukherjee, Kamalika; McGee, Dennis W; Bane, Susan L

2011-11-01

47

Application of spectral derivative data in visible and near-infrared spectroscopy  

International Nuclear Information System (INIS)

The use of the spectral derivative method in visible and near-infrared optical spectroscopy is presented, whereby instead of using discrete measurements around several wavelengths, the difference between nearest neighbouring spectral measurements is utilized. The proposed technique is shown to be insensitive to the unknown tissue and fibre contact coupling coefficients providing substantially increased accuracy as compared to more conventional techniques. The self-calibrating nature of the spectral derivative techniques increases its robustness for both clinical and industrial applications, as is demonstrated based on simulated results as well as experimental data.

2010-06-21

48

Sb2O3 nanobelt networks for excellent visible-light-range photodetectors  

International Nuclear Information System (INIS)

Excellent photoconductive properties have been found in Sb2O3 nanobelts synthesized by a surfactant-assisted solvothermal method. Visible-light photodetectors have been designed from Sb2O3 nanobelt networks using micrometer-wide gold wires as masks. Photodetectors show high sensitivity to visible light, high stability, and reproducibility. Fast response and decay times (2O3 nanobelt networks can indeed serve as high-performance photodetectors in the visible light range.

2011-04-22

49

Lunar resources using moderate spectral resolution visible and near-infrared spectroscopy: Al/Si and soil maturity  

Science.gov (United States)

Modern visible and near-infrared detectors are critically important for the accurate identification and relative abundance measurement of lunar minerals; however, even a very small number of well-placed visible and near-infrared bandpass channels provide a significant amount of general information about crucial lunar resources. The Galileo Solid State Imaging system (SSI) multispectral data are an important example of this. Al/Si and soil maturity will be discussed as examples of significant general lunar resource information that can be gleaned from moderate spectral resolution visible and near-infrared data with relative ease. Because quantitative-albedo data are necessary for these kinds of analyses, data such as those obtained by Galileo SSI are critical. SSI obtained synoptic digital multispectral image data for both the nearside and farside of the Moon during the first Galileo Earth-Moon encounter in December 1990. The data consist of images through seven filters with bandpasses ranging from 0.40 microns in the ultraviolet to 0.99 microns in the near-infrared. Although these data are of moderate spectral resolution, they still provide information for the following lunar resources: (1) titanium content of mature mare soils based upon the 0.40/0.56-micron (UV/VIS) ratio; (2) mafic mineral abundance based upon the 0.76/0.99-micron ratio; and (3) the maturity or exposure age of the soils based upon the 0.56-0.76-micron continuum and the 0.76/0.99-micron ratio. Within constraints, these moderate spectral resolution visible and near-infrared reflectance data can also provide elemental information such as Al/Si for mature highland soils.

Fischer, Erich M.; Pieters, Carle M.; Head, James W.

1992-01-01

50

Dependence of cloud properties derived from spectrally resolved visible satellite observations on surface temperature  

Directory of Open Access Journals (Sweden)

Full Text Available Cloud climate feedback constitutes the most important uncertainty in climate modelling, and currently even its sign is still unknown. In the recently published report of the intergovernmental panel on climate change (IPCC, 6 out of 20 climate models showed a positive and 14 a negative cloud radiative feedback in a doubled CO2 scenario. The radiative budget of clouds has also been investigated by experimental methods, especially by studying the relation of satellite observed broad band shortwave and longwave radiation to sea surface temperature. Here we present a new method for the investigation of the dependence of cloud properties on temperature changes, derived from spectrally resolved satellite observations in the visible spectral range. Our study differs from previous investigations in three important ways: first, we directly extract cloud properties (effective cloud fraction and effective cloud top height and relate them to surface temperature. Second, we retrieve the cloud altitude from the atmospheric O2 absorption instead from thermal IR radiation. Third, our correlation analysis is performed using 7.5 years of global monthly anomalies (with respect to the average of the same month for all years. For most parts of the globe (except the tropics we find a negative correlation of effective cloud fraction versus surface-near temperature. In contrast, for the effective cloud top height a positive correlation is found for almost the whole globe. Both findings might serve as an indicator for an overall positive cloud radiative feedback. Another peculiarity of our study is that the cloud-temperature relationships are determined for fixed locations (instead to spatial variations over selected areas and are based on the "natural" variability over several years (instead the anomaly for a strong El-Nino event. From a detailed comparison to cloud properties from the International Satellite Cloud Climatology Project (ISCCP, in general good agreement is found. However, also systematic differences occurred indicating that our results provide independent and complementary information on cloud properties. Climate models should thus aim to reproduce our findings. Recommendations for the development of a "processor" to convert model results into the cloud sensitive quantities observed by the satellite are given.

T. Wagner

2008-05-01

51

Full-range spectral domain Doppler optical coherence tomography  

Science.gov (United States)

Spectral domain optical coherence tomography (SD-OCT) systems achieve higher sensitivities compared to time domain OCT systems. However, one of the main challenges in SD-OCT is the obscuring object structure called "ghost image" or "mirror image" that arises from the Fourier transform of a real function. We have designed and developed a phaseshifting- based full-range SD-OCT system that we refer to as the dual detection full range SD-OCT. The proposed technique simultaneously obtains the quadrature components of a complex spectral interference. Therefore, the technique enables full range imaging without any loss of speed and is intrinsically less sensitive to movements of the subject. In this paper, we demonstrate that the dual detection technique can be applied to Doppler imaging without loss in the velocity dynamic range since the phase information of the acquired spectra is preserved. The dual detection full range SD-OCT provides a superior signal-to-noise ratio over a conventional SD-OCT since the most sensitive region around the zero path delay is usable. This capability improves the image quality of not only the structural image but also the Doppler image.

Meemon, P.; Lee, K. S.; Rolland, J. P.

2010-02-01

52

Exploring the Full Range of Properties of Quasar Spectral Distributions  

Science.gov (United States)

The aim of this work is to support our ISO, far-infrared (IR) observing program of quasars and active galaxies. We have obtained, as far as possible, complete spectral energy distributions (radio-X-ray) of the ISO sample in order to fully delineate the continuum shapes and to allow detailed modelling of that continuum. This includes: ground-based optical, near-IR and mm data, the spectral ranges closest to the ISO data, within 1-2 years of the ISO observations themselves. ISO was launched in Nov 1995 and is currently observing routinely. It has an estimated lifetime is 2 years. All near-IR and optical imaging and spectroscopy are now in hand and in the process of being reduced, mm data collection and proposal writing continues.

Wilkes, B.

1998-01-01

53

Stark widths and shifts of Ar II spectral lines in visible part of spectrum  

International Nuclear Information System (INIS)

Stark widths and shifts of 13 Ar II spectral lines in the visible part of spectrum were measured. Spectral lines were emitted from pulsed wall stabilized Ar arc plasma under atmospheric pressure. Profiles were recorded at plasma electron densities of 1.3×1023 m?3 and 1.6×1023 m?3 and plasma electron temperatures of 13,400 K and 14,200 K respectively. Obtained results are compared with other experimental results as well as with theoretical values. The analysis of the experimental and theoretical data is given as well. -- Highlights: •Precise and reliable measurements of Stark parameters. •The use of these data for plasma diagnostic purposes. •Comparisons of obtained data with available experimental and theoretical values

2013-09-01

54

Free spectral range adjustment of a silicon rib racetrack resonator  

International Nuclear Information System (INIS)

One of the most important parameters that describe the quality of photonic components and devices is the free spectral range (FSR). In this paper, the measured outgoing power of a silicon rib racetrack resonator was compared with calculated transfer functions derived by coupled mode theory. The influence of geometric parameters on the FSR and resonant wavelength has been investigated. By altering the values of the coupling length and racetrack radius, derived transfer functions were adjusted to match experimental data. This procedure gives the possibility of estimating the FSR and resonant wavelength for different geometric parameters and predicting resonator functionality.

2012-05-01

55

Experimental demonstration of a broadband array of invisibility cloaks in the visible frequency range  

CERN Multimedia

Very recently Farhat et al. [1] have suggested that arrays of invisibility cloaks may find important applications in low-interference communication, noninvasive probing, sensing and communication networks, etc. We report on the first experimental realization of such an array of broadband invisibility cloaks, which operates in the visible frequency range. Wavelength and angular dependencies of the cloak array performance have been studied.

Smolyaninova, V N; Ermer, H K

2012-01-01

56

The Ch asteroids: Connecting a Visible Taxonomic Class to a 3-µm spectral shape  

Science.gov (United States)

The Ch-class asteroids in the Bus and Bus-DeMeo classifications are characterized by an absorption near 0.7-µm, first described in a series of papers by Vilas and her co-workers, and associated with phyllosilicates. We have known for some time that the presence of this band is correlated with the presence of the 3-µm absorption band diagnostic for OH/H2O in asteroids and meteorites (Howell, Vilas et al.). In the meteorite collection, the 0.7-µm band seems to be limited to a particular subset of carbonaceous chondrites, the CM group (Cloutis et al.). The difference in 3-µm band shape between Ceres and Pallas has been recognized since the 1980s from work by Lebofsky, Feierberg et al.. Several surveys in this spectral region have established that on the order of 3-4 different spectral shapes exist in the asteroid population (Takir et al., Rivkin et al.). One group, the largest member of which is Pallas, has spectral shapes similar to what is seen in the carbonaceous chondrite meteorites. At this writing, the L-band Mainbelt/NEO Observing Program (LMNOP) has obtained spectra for 25 asteroids classified as Ch by the SMASS surveys. Of the 20 objects that can be unambiguously assigned a 3-µm spectral type, all 20 have a Pallas-type spectral shape. An additional 6 objects in the LMNOP without SMASS classifications are classified as Ch by the S3OS2 survey. Only one of these 6 objects is not obviously Pallas-like, 791 Ani, and inspection of the S3OS2 spectrum leads to doubt that it is actually a Ch-class object. The assignment of at least 80% and perhaps 100% of Ch-class asteroids to the Pallas 3-µm type (depending on how ambiguous objects are treated) serves as evidence for a specific tie between the visible-region and infrared spectral regions, and that the 0.7-µm band can be used not only as a proxy for the presence of a 3-µm band but for a specific band shape and mineralogy. We will present our spectral results and analysis.

Rivkin, Andrew S.; Howell, E. S.; Emery, J. P.; Volquardsen, E. L.

2013-10-01

57

Imitrines. I. A new class of laser dyes in the visible range  

Energy Technology Data Exchange (ETDEWEB)

Laser action has been achieved in solutions of imidazotriazine (imitrine) dyes excited by the third (355 nm) and fourth (266 nm) harmonics of a neodymium laser. The widths of the free-lasing spectra of the dyes were 40 to 50 nm and covered the 475 to 580 nm range. The threshold pump intensity and lasing efficiency were measured. The prospects for using imitrines in lasers in the visible range are discussed.

Kruglenko, V.P.; Logunov, O.A.; Startsev, A.V.; Stoilov, Y.Y.; Povstyanoi, M.V.

1980-10-01

58

Solar Spectral Irradiance Variability in the Visible and Infrared During the SORCE Mission  

Science.gov (United States)

The Spectral Irradiance Monitor (SIM) is a dual prism spectrometer onboard the SORCE (Solar Irradiance and Climate Experiment) satellite that was launched in January 2003. SIM covers the wavelength region 200- 2700 nm with a spectral resolution varying from 0.25 to 34 nm over this range. The primary detector for this instrument is an electrical substitution radiometer (ESR), and three additional photodiode detectors complement the ESR measurement and span the spectral range from 308 to 1600 nm; these photodiodes provide the bulk of the data used to study solar variability. The ESR calibrates the radiant sensitivities of the photodiodes in flight, and pre-flight measurements of the prism transmission and the spectral response function give the absolute calibration of the instrument. The SIM solar spectrum is in good agreement with other standard solar spectra such as the SOLSPEC spectrum (Thuillier et al. Metrologia, 35, 689, 1998) and the Davos World Radiation Center Reference Spectrum (Wehrli, C., World Radiation Center (WRC) Publication No. 615, Davos-Dorf, Switzerland, July 1985). SIM is able to detect short-term spectral irradiance variability of about 0.1% in the of 27-day solar rotation period induced by the appearance and varying intensity of solar structural features (such as sun spots and plage) relative to the quiet sun. A comparative study of the SIM solar spectrum relative to other standard spectra and an analysis of short-term solar variability as measured by SIM will be presented.

Harder, J. W.; Fontenla, J.; Smiley, B.; Rottman, G.; Lawrence, G.; Woods, T.

2003-12-01

59

An Approach for Identifying of Fusarium Infected Maize Grains by Spectral Analysis in the Visible and Near Infrared Region, SIMCA Models, Parametric and Neural Classifiers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An approach for identifying of Fusarium infected single maize grains based on diffuse reflectance in visible and near infrared region is proposed in the paper. Spectral characteristics were collected in the range 400-2500 nm in steps of 2 nm. Soft independent modeling of class analogy (SIMCA) is used for data processing. Maize grains classification is based on SIMCA classifier and Probabilistic neural network (PNN). Recognition accuracy which is achieved for both classes of grains is respecti...

Tsvetelina Draganova; Plamen Daskalov; Rusin Tsonev

2010-01-01

60

Method for detection and imaging over a broad spectral range  

Science.gov (United States)

A method of controlling the coordinate sensitivity in a superconducting microbolometer employs localized light, heating or magnetic field effects to form normal or mixed state regions on a superconducting film and to control the spatial location. Electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y--Ba--Cu--O films. Two different sensor designs were tested: (i) a 3 millimeter long and 40 micrometer wide stripe and (ii) a 1.25 millimeters long, and 50 micron wide meandering-like structure. Scanning the laser beam along the stripe leads to physical displacement of the sensitive area, and, therefore, may be used as a basis for imaging over a broad spectral range. Forming the superconducting film as a meandering structure provides the equivalent of a two-dimensional detector array. Advantages of this approach are simplicity of detector fabrication, and simplicity of the read-out process requiring only two electrical terminals.

Yefremenko, Volodymyr (Westmont, IL); Gordiyenko, Eduard (Westmont, IL); Pishko, legal representative, Olga (Kharkov, UA); Novosad, Valentyn (Chicago, IL); Pishko, deceased; Vitalii (Westmont, IL)

2007-09-25

 
 
 
 
61

On mimicking diffuse reflectance spectra in the visible and near-infrared ranges for tissue-like phantom design  

Science.gov (United States)

A novel methodology is presented to mimic diffuse reflectance spectra of arbitrary biological tissues in the visible and near-infrared ranges. The prerequisite for this method is that the spectral information of basic components is sufficient to mimic an arbitrary tissue. Using a sterile disposable fiber optic probe the diffuse reflectance spectrum of a tissue (either in vivo or ex vivo) is measured, which forms the target spectrum. With the same type of fiber probe, a wide variety of basic components (ingredients) has been previously measured and all together forms a spectral database. A "recipe" for the optimal mixture of ingredients can then be derived using an algorithm that fits the absorption and scattering behavior of the target spectrum using the spectra of the basic components in the database. The spectral mimicking accuracy refines by adding more ingredients to the database. The validity of the principle is demonstrated by mimicking an arbitrary mixture of components. The method can be applied with different kinds of materials, e.g. gelatins, waxes and silicones, thus providing the possibility of mimicking the mechanical properties of target tissues as well. The algorithm can be extended from single point contact spectral measurement to contactless multi- and hyper-spectral camera acquisition. It can be applied to produce portable and durable tissue-like phantoms that provides consistent results over time for calibration, demonstration, comparison of instruments or other such tasks. They are also more readily available than living tissue or a cadaver and are not so limited by ease of handling and legislation; hence they are highly useful when developing new devices.

Debernardi, N.; Dunias, P.; van El, B.; Statham, A. E.

2014-03-01

62

Blackbody radiation sources for the IR spectral range  

Science.gov (United States)

Metrological radiometric facilities for optoelectronic instruments calibration utilize in terms of standards as radiation detectors in a form of cryogenic radiometers (CR), so as radiation sources. However in practice, there are no CR working within IR spectral range. An alternative way of radiometric calibration in middle and far IR ranges is to develop a parametric series of standard radiation sources - blackbody (BB) models. The paper describes some of BBs developed at VNIIOFI for the last time [1] from cryogenic (80 K to 200 K), to low (about 200 K to 400 K) and medium (400 K to 700 K) temperature regions for calibration of the IR instruments under cryogenic-vacuum conditions. These BBs are presented by models of both types: variable-temperature and based on fixed points of Ga or In. BBs are characterized with high temperature uniformity and stability. Copper and aluminum alloys are used as the radiation cavity materials. The required value of emissivity ?? is achieved by using different black coatings. Low-temperature and cryogenic BBs are based on the principles of indirect multi-zone electric heating (with heat isolation from LN2 cooling loop, or by using an external liquid thermostat with circulating heat-transfer agent. The principles of operation, design and test results of BBs are described.

Ogarev, S. A.; Morozova, S. P.; Katysheva, A. A.; Lisiansky, B. E.; Samoylov, M. L.

2013-09-01

63

Blackbody radiation sources for the IR spectral range  

Energy Technology Data Exchange (ETDEWEB)

Metrological radiometric facilities for optoelectronic instruments calibration utilize in terms of standards as radiation detectors in a form of cryogenic radiometers (CR), so as radiation sources. However in practice, there are no CR working within IR spectral range. An alternative way of radiometric calibration in middle and far IR ranges is to develop a parametric series of standard radiation sources - blackbody (BB) models. The paper describes some of BBs developed at VNIIOFI for the last time [1] from cryogenic (80 K to 200 K), to low (about 200 K to 400 K) and medium (400 K to 700 K) temperature regions for calibration of the IR instruments under cryogenic-vacuum conditions. These BBs are presented by models of both types: variable-temperature and based on fixed points of Ga or In. BBs are characterized with high temperature uniformity and stability. Copper and aluminum alloys are used as the radiation cavity materials. The required value of emissivity ?{sub ?} is achieved by using different black coatings. Low-temperature and cryogenic BBs are based on the principles of indirect multi-zone electric heating (with heat isolation from LN2 cooling loop, or by using an external liquid thermostat with circulating heat-transfer agent. The principles of operation, design and test results of BBs are described.

Ogarev, S. A.; Morozova, S. P.; Katysheva, A. A.; Lisiansky, B. E.; Samoylov, M. L. [All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI), Moscow (Russian Federation)

2013-09-11

64

Experimental demonstration of a broadband array of invisibility cloaks in the visible frequency range  

Science.gov (United States)

Very recently Farhat et al (2011, Phys. Rev. B 84 235105) suggested that arrays of invisibility cloaks may find important applications in low-interference communication, noninvasive probing, sensing and communication networks and so on. We report on the first experimental realization of such an array of broadband invisibility cloaks that operates in the visible frequency range. The wavelength and angular dependences of the cloak array performance have been studied.

Smolyaninova, V. N.; Smolyaninov, I. I.; Ermer, H. K.

2012-05-01

65

Experimental demonstration of a broadband array of invisibility cloaks in the visible frequency range  

International Nuclear Information System (INIS)

Very recently Farhat et al (2011, Phys. Rev. B 84 235105) suggested that arrays of invisibility cloaks may find important applications in low-interference communication, noninvasive probing, sensing and communication networks and so on. We report on the first experimental realization of such an array of broadband invisibility cloaks that operates in the visible frequency range. The wavelength and angular dependences of the cloak array performance have been studied. (paper)

2012-05-01

66

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Directory of Open Access Journals (Sweden)

Full Text Available Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3, and NO2, the measured solar spectra are compared with previous observations. Our solar irradiance is +1.6% larger than the re-calibrated Kurucz et al. (1984 solar spectrum (Fontenla et al., 1999, called MODTRAN 3.5 in the visible spectral range (435–650 nm, +1.5% larger in the (370–415 nm wavelength interval, but ?4% smaller in the UV spectral range (316.7–370 nm, when the Kurucz spectrum is convolved to the spectral resolution of our instrument. The same comparison with the SOLSPEC solar spectrum (Thuillier et al., 1997, 1998a, b confirms the somewhat larger solar irradiance (+1.7% measured by the balloon instrument from 435–500 nm, but not from 500–650 nm, where the SOLSPEC is ?1.3% lower than MODTRAN 3.5. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (– re-calibrated by the University of Bremen – with MODTRAN 3.5 indicates an agreement of +0.2% in the visible spectral range (435–585 nm. With this calibration, the SCIAMACHY solar spectrum is congruent with the balloon observations (?1% in the 316.7–370 nm wavelength range, but both are up to ?5%/?3% smaller than MODTRAN 3.5 and SOLSPEC, respectively. In agreement with findings of Skupin et al. (2002 our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

W. Gurlit

2004-12-01

67

From the infrared to the visible range: Spectroscopic studies of ytterbium doped oxyborates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The spectroscopic study of yttrium oxyborates doped with trivalent ytterbium is conducted in the UV-Visible and infrared range. The multiplicity of the ytterbium environments in the studied compounds leads to complex emission spectra in the infrared and excitation spectra in the ultraviolet. Different 2F5/2 and 2F7/2 transitions have been pointed out. The emission extends up to 1090 nm for one compound. A correlation was evidenced between position and de-excitation mode of a charge transfer b...

Jubera, Ve?ronique; Sablayrolles, Jean; Guillen, Franc?ois; Decourt, Rodolphe; Couzi, Michel; Garcia, Alain

2009-01-01

68

Subwavelength imaging in the visible range using a metal coated carbon nanotube forest.  

Science.gov (United States)

We demonstrate subwavelength imaging in the visible range by using a metal coated carbon nanotube forest. Under 532 nm illumination, a 160 nm separated double slit is resolved. This corresponds to the resolution of 0.3 wavelength. By controlling the growing conditions and with the help of the microtoming technique, we made a dense carbon nanotube forest layer of 400 nm thickness. The metal coated carbon nanotube forest, acting as a wire medium nanolens, delivers imaging information including details in the evanescent fields near the objects. PMID:24777238

Choe, Jong-Ho; Choi, Muhan; Lee, Won Jun; Kang, Byungsoo; Kim, Jinhyung; Seo, Min-Kyo; Min, Bumki; Kim, Sang Ouk; Choi, Choon-Gi

2014-06-01

69

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Science.gov (United States)

Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3 and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance spectrum perfectly agrees within +0.03% with the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.7) in the visible spectral range (415-650 nm), but it is +2.1% larger in the (370-415 nm) wavelength interval, and -4% smaller in the UV-A spectral range (316.7-370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. Similar comparisons of the SOLSPEC (Thuillier et al., 1997, 1998a, b) and SORCE/SIM (Harder et al., 2000) solar spectra with MODTRAN 3.7 confirms our findings with the values being -0.5%, +2%, and -1.4% for SOLSPEC -0.33%, -0.47%, and -6.2% for SORCE/SIM, respectively. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (- re-calibrated by the University of Bremen -) with MODTRAN 3.7 indicates an agreement within -0.4% in the visible spectral range (415-585 nm), -1.6% within the 370-415 nm, and -5.7% within 325-370 nm wavelength interval, in agreement with the results of the other sensors. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

Gurlit, W.; Bösch, H.; Bovensmann, H.; Burrows, J. P.; Butz, A.; Camy-Peyret, C.; Dorf, M.; Gerilowski, K.; Lindner, A.; Noël, S.; Platt, U.; Weidner, F.; Pfeilsticker, K.

2005-07-01

70

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Directory of Open Access Journals (Sweden)

Full Text Available Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3 and NO2, the measured solar spectra are compared with previous observations. Our solar irradiance spectrum perfectly agrees within +0.03% with the re-calibrated Kurucz et al. (1984 solar spectrum (Fontenla et al., 1999, called MODTRAN 3.7 in the visible spectral range (415-650 nm, but it is +2.1% larger in the (370-415 nm wavelength interval, and -4% smaller in the UV-A spectral range (316.7-370 nm, when the Kurucz spectrum is convolved to the spectral resolution of our instrument. Similar comparisons of the SOLSPEC (Thuillier et al., 1997, 1998a, b and SORCE/SIM (Harder et al., 2000 solar spectra with MODTRAN 3.7 confirms our findings with the values being -0.5%, +2%, and -1.4% for SOLSPEC -0.33%, -0.47%, and -6.2% for SORCE/SIM, respectively. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (- re-calibrated by the University of Bremen - with MODTRAN 3.7 indicates an agreement within -0.4% in the visible spectral range (415-585 nm, -1.6% within the 370-415 nm, and -5.7% within 325-370 nm wavelength interval, in agreement with the results of the other sensors. In agreement with findings of Skupin et al. (2002 our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

W. Gurlit

2005-01-01

71

Using Visible Spectral Information to Predict Long-Wave Infrared Spectral Emissivity: A Case Study over the Sokolov Area of the Czech Republic with an Airborne Hyperspectral Scanner Sensor  

Directory of Open Access Journals (Sweden)

Full Text Available Remote-sensing platforms are often comprised of a cluster of different spectral range detectors or sensors to benefit from the spectral identification capabilities of each range. Missing data from these platforms, caused by problematic weather conditions, such as clouds, sensor failure, low temporal coverage or a narrow field of view (FOV, is one of the problems preventing proper monitoring of the Earth. One of the possible solutions is predicting a detector or sensor’s missing data using another detector/sensor. In this paper, we propose a new method of predicting spectral emissivity in the long-wave infrared (LWIR spectral region using the visible (VIS spectral region. The proposed method is suitable for two main scenarios of missing data: sensor malfunctions and narrow FOV. We demonstrate the usefulness and limitations of this prediction scheme using the airborne hyperspectral scanner (AHS sensor, which consists of both VIS and LWIR spectral regions, in a case study over the Sokolov area, Czech Republic.

Gila Notesco

2013-11-01

72

Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols  

Directory of Open Access Journals (Sweden)

Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

C. E. Lund Myhre

2004-01-01

73

Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols  

Directory of Open Access Journals (Sweden)

Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

C. E. Lund Myhre

2004-06-01

74

Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$  

CERN Document Server

For the first time the fine structure of rovibronic spectral lines in visible part of emission spectra of $D_2$ molecule has been observed. Observed splitting in visible doublets is about 0.2 cm$^{-1}$ in good accordance with previous observations in the infrared part of the spectrum ($a^3\\Sigma_g^+ \\to c^3\\Pi_u$ electronic transition) by means of FTIR and laser spectroscopy. Relative intensities of the fine structure components are in agreement with our calculations of adiabatic line strengths for Hund's case "b" coupling scheme.

Lavrov, B P; Zhukov, A S

2011-01-01

75

Generation of pulsed light in the visible spectral region based on non-linear cavity dumping  

DEFF Research Database (Denmark)

We propose a novel generic approach for generation of pulsed light in the visible spectrum based on sum-frequency generation between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser. For demonstration, we used a CW 1342 nm laser mixed with a passively Q-switched 1064 nm laser to generate pulsed light at 593 nm. Light sources in the yellow spectral region have several applications, e.g. dermatology, laser displays and flow cytometry. Traditionally, copper-vapor lasers at 578 nm and dye lasers are used in this spectral region. These are however bulky, inefficient and contain highly toxic gasses and liquids. Different approaches to replace these are: frequency-doubled semiconductor lasers1, sum-frequency generation between solid-state lasers in both in CW2 and Q-switched3 operation and Raman lasers4. An intra-cavity 1342 nm Nd:YVO4 laser acted as the CW light source, using a folded cavity to achieve tight focussing in the non-linear crystal which was a 11 mm long PPKTP. The pulsed light source was a Nd:YVO4 laser emitting at 1064 nm using Cr:YAG as a passive saturable absorber, resulting in a pulse length of 100 ns and a repetition frequency of 215 kHz. Both lasers were pumped with 808 nm laser diodes delivering 4 W of output power. The circulating power of the 1342 nm laser was 57 W and the peak power of the 1064 nm laser reaching the PPKTP crystal was 17 W. A peak power of approximately 4 W at 593 nm was measured. Accounting for the Fresnel losses for the outcoupling mirror, this would correspond to 5.3 W of generated 593 nm power. The pulsed yellow-orange light follows exactly the 1064 nm pulses in terms of repetition frequency and pulse width. By matching the pulse length of the passively Q-switched laser to the round-trip time of the CW intra-cavity laser, the circulating power could be more efficiently depleted. Calculations give that yellow peak powers in the order of 50 W could be reached.

Johansson, Sandra; Andersen, Martin

76

Dose dependence of visible range diffuse reflectivity for Si+ and C+ ion implanted polymers  

Science.gov (United States)

Detailed insight into the near-surface area of the ion beam modified polymer is supplied by the measured diffuse reflectivity spectra. The near-surface layer (50÷150 nm) of bulk polymer samples have been implanted with silicon (Si+) and carbon (C+) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 5.1012-2.1017 cm+2). The polymer materials studied were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-propylene (PP), and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra Rd = f(?) of the implanted samples have been measured in the visible range (? = 400÷830 nm). In this paper the dose dependences of the size and sign of the diffuse reflectivity changes ?Rd = f(D) have been analyzed.

Balabanov, S.; Tsvetkova, T.; Borisova, E.; Avramov, L.; Bischoff, L.

2008-05-01

77

Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator  

International Nuclear Information System (INIS)

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624–672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

2013-05-01

78

Low-Loss Optical Waveguides for the Near Ultra-Violet and Visible Spectral Regions with Al2O3 Thin Films from Atomic Layer Deposition  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work, we report low-loss single-mode integrated optical waveguides in the near ultra-violet and visible spectral regions with aluminum oxide (Al2O3) films using an atomic layer deposition (ALD) process. Alumina films were deposited on glass and fused silica substrates by the ALD process at substrate/chamber temperatures of 200 °C and 300 °C. Transmission spectra and waveguide measurements were performed in our alumina films with thicknesses in the range of 210 – 380 nm for the opt...

2010-01-01

79

SCIAMACHY solar irradiance observation in the spectral range from 240 to 2380nm  

Science.gov (United States)

SCIAMACHY (SCanning Imaging Absorption Spectrometer for Atmospheric CHartographY) is part of the payload of ESA's Environmental Satellite ENVISAT which was launched into a sun-synchronous polar orbit on 2002-03-01. It is the first spaceborne instrument covering a wavelength range from 240 to 2380 nm thus including ultraviolet, visible and near infrared spectral regions. The main purpose of the instrument is to determine the amount and distribution of various trace gases and aerosol as well as cloud cover and cloud top height in Earth's atmosphere by measuring the atmospheric radiance in limb and nadir geometry. In addition several solar observations are performed with daily or orbital frequency that offer the possibility to monitor solar variations on a dense time grid. The presented results will cover the following topics:(a) Comparison of the solar irradiance measured by SCIAMACHY with other in-orbit instruments like SOLSTICE and SOLSPEC. (b) Comparison of the SCIAMACHY solar Mg II index with GOME and NOAA instruments. (c) Correlation of SCIAMACHY solar irradiance with the sun spot index. Together with the European ozone monitoring experiments GOME (launched 1995) and GOME2 (to be launched 2005) SCIAMACHY completes a triple of similar instruments ensuring a continuous record of solar and atmospheric observations starting in 1995 and ranging into the second decade of the 21st century.

Skupin, J.; Noël, S.; Wuttke, M. W.; Gottwald, M.; Bovensmann, H.; Weber, M.; Burrows, J. P.

80

Exploring the Full Range of Properties of Quasar Spectral Distribution  

Science.gov (United States)

The aim of this work is to obtain multi-wavelength supporting data for the sample of quasars and active galaxies observed in the far-infrared (IR) by ISO as part of our Key Project on quasars and active galaxies. This dataset then provides complete spectral energy distributions (radio-X-ray) of the ISO sample in order to fully delineate the continuum shapes and to allow detailed modeling of that continuum. The report is made up of a short project summary, and a bibliography of published papers, proceedings and presentations.

Wilkes, B.

1999-01-01

 
 
 
 
81

Spectral Variability among Rocks in Visible and Near Infrared Multispectral Pancam Data Collected at Gusev Crater: Examinations using Spectral Mixture Analysis and Related Techniques  

Science.gov (United States)

Visible and Near Infrared (VNIR) multispectral observations of rocks made by the Mars Exploration Rover Spirit s Panoramic camera (Pancam) have been analysed using a spectral mixture analysis (SMA) methodology. Scenes have been examined from the Gusev crater plains into the Columbia Hills. Most scenes on the plains and in the Columbia Hills could be modeled as three endmember mixtures of a bright material, rock, and shade. Scenes of rocks disturbed by the rover s Rock Abrasion Tool (RAT) required additional endmembers. In the Columbia Hills there were a number of scenes in which additional rock endmembers were required. The SMA methodology identified relatively dust-free areas on undisturbed rock surfaces, as well as spectrally unique areas on RAT abraded rocks. Spectral parameters from these areas were examined and six spectral classes were identified. These classes are named after a type rock or area and are: Adirondack, Lower West Spur, Clovis, Wishstone, Peace, and Watchtower. These classes are discriminable based, primarily, on near-infrared (NIR) spectral parameters. Clovis and Watchtower class rocks appear more oxidized than Wishstone class rocks and Adirondack basalts based on their having higher 535 nm band depths. Comparison of the spectral parameters of these Gusev crater rocks to parameters of glass-dominated basaltic tuffs indicates correspondence between measurements of Clovis and Watchtower classes, but divergence for the Wishstone class rocks which appear to have a higher fraction of crystalline ferrous iron bearing phases. Despite a high sulfur content, the rock Peace has NIR properties resembling plains basalts.

Farrand, W. H.; Bell, J. F., III; Johnson, J. R.; Squyres, S. W.; Soderblom, J.; Ming, D. W.

2006-01-01

82

Tailoring Metallodielectric Structures for Super Resolution and Superguiding Applications in the Visible and Near IR Ranges  

CERN Document Server

We discuss propagation effects in realistic, transparent, metallo-dielectric photonic band gap structures in the context of negative refraction and super-resolution in the visible and near infrared ranges. In the resonance tunneling regime, we find that for transverse-magnetic incident polarization, field localization effects contribute to a waveguiding phenomenon that makes it possible for the light to remain confined within a small fraction of a wavelength, without any transverse boundaries, due to the suppression of diffraction. This effect is related to negative refraction of the Poynting vector inside each metal layer, balanced by normal refraction inside the adjacent dielectric layer: The degree of field localization and material dispersion together determine the total momentum that resides within any given layer, and thus the direction of energy flow. We find that the transport of evanescent wave vectors is mediated by the excitation of quasi-stationary, low group velocity surface waves responsible for...

De Ceglia, D; Cappeddu, M G; Centini, M; Akozbek, N; DOrazio, A; Haus, J W; Bloemer, M J; Scalora, M

2008-01-01

83

Spectral irradiance measurement in the visible-ultraviolet region using synchrotron radiation  

International Nuclear Information System (INIS)

Spectral irradiances of a quartz-bromine lamp calibrated against the currently maintained ETL standard were compared with those of synchrotron radiation from TERAS in order to reconfirm the magnitude of standard unit, especially, in the ultraviolet region. The spectral irradiance unit at the wavelength of 500 nm was taken to be equal to each other. It was concluded that the magnitude of spectral irradiance unit currently used at ETL should be increased at the short wavelengths by maximum 7%. (author)

1991-01-01

84

Spectral irradiance measurement in the visible-ultraviolet region using synchrotron radiation  

Energy Technology Data Exchange (ETDEWEB)

Spectral irradiances of a quartz-bromine lamp calibrated against the currently maintained ETL standard were compared with those of synchrotron radiation from TERAS in order to reconfirm the magnitude of standard unit, especially, in the ultraviolet region. The spectral irradiance unit at the wavelength of 500 nm was taken to be equal to each other. It was concluded that the magnitude of spectral irradiance unit currently used at ETL should be increased at the short wavelengths by maximum 7%. (author).

Saito, Terubumi; Habu, Mitsuhiro; Katori, Kanji; Nishi, Morotake; Nagasaka, Takehiko; Onuki, Hideo (Electrotechnical Lab., Tsukuba, Ibaraki (Japan))

1991-06-01

85

Solid state image sensors in visual spectral range. Kashiko kotai satsuzo soshi  

Energy Technology Data Exchange (ETDEWEB)

This paper describes configurations and operations of solid state image sensors in visible spectral range, and structure and characteristics of the charge coupled device (CCD), a representative solid state image sensor. It also mentions research trends in latest solid state image sensors. A solid state image sensor is a light sensor that utilizes a photoelectric effect of a semiconductor. It spreads unit cells called picture elements two-dimensionally to form an image sensor. The number of picture elements is about 300,000 elements in a standard television mode, and two million elements in the high definition television (HDTV) set under development. A high definition monochrome camera that uses the developed HDTVCCD shows such superior values as sensitivity of 400 Lux (F4) and S/N ratio of 56 dB. Development trends of solid state image sensors are represented by size reduction and improvement in resolution and sensitivity of the elements, and signal processing functions performed on chips. A multi-element CCD image sensor with 26.2 million picture elements has been reported. The picture element used mainly for astronomic observation has a picture element size of 12 [mu]m and a light receiving area of 6.1 cm square. 17 refs., 10 figs., 3 tabs.

Matsumoto, K. (Olympus Optical Co. Ltd., Tokyo (Japan))

1994-02-25

86

Optical properties of human brain tissue, meninges, and brain tumors in the spectral range of 200 to 900 nm.  

Science.gov (United States)

Considering the increasing use of lasers in neurosurgery and the increasing number of wavelengths of laser light becoming available, we evaluated optical properties between 200 and 900 nm of meninges, normal human brain tissue, and brain tumors. We used a two-beam spectral photometer with an integrating sphere as the measuring instrument. The material consisted of 13 brains and 1 specimen each of dura mater, falx, and arachnoid obtained at autopsy and 30 samples of brain tumors removed during operation. In tissue samples more than 5 mm thick, the relative levels of absorption and scattering were estimated from the relative level of reflection measured according to the Kubelka-Munk theory. In thin tissue slices, penetration depth was calculated according to Beer's law from measurements of reflection and transmission. Generally, in all tissues there was an increase of reflection, scattering, and penetration depth and a decrease of absorption from the ultraviolet up to the near infrared spectral range interrupted by the absorption bands of hemoglobin. Within the ultraviolet spectral range, no major differences of optical properties were observed. Within the visible and near infrared spectral range, white matter reflected most of the incident power and showed the lowest level of absorption and the shortest penetration depth. Low grade gliomas revealed optical properties similar to those of gray matter. In comparison with normal brain tissue, meningiomas and glioblastomas showed significantly higher levels of absorption calculated according to the Kubelka-Munk theory from reflection measurements in thick tissue samples, but also deeper penetration obtained from measurements of reflection and transmission in thin slices, especially within the near infrared spectral range. PMID:3683777

Eggert, H R; Blazek, V

1987-10-01

87

Detection of wavelengths in the visible range using fiber optic sensors  

Science.gov (United States)

This paper shows the design and implementation of a fiber optic sensor for detecting and identifying wavelengths in the visible range. The system consists of a diffuse optical fiber, a conventional laser diode 650nm, 2.5mW of power, an ambient light sensor LX1972, a PIC 18F2550 and LCD screen for viewing. The principle used in the detection of the lambda is based on specular reflection and absorption. The optoelectronic device designed and built used the absorption and reflection properties of the material under study, having as active optical medium a bifurcated optical fiber, which is optically coupled to an ambient light sensor, which makes the conversion of light signals to electricas, procedure performed by a microcontroller, which acquires and processes the signal. To verify correct operation of the assembly were utilized the color cards of sewing thread and nail polish as samples for analysis. This optoelectronic device can be used in many applications such as quality control of industrial processes, classification of corks or bottle caps, color quality of textiles, sugar solutions, polymers and food among others.

Díaz, Leonardo; Morales, Yailteh; Mattos, Lorenzo; Torres, Cesar O.

2013-11-01

88

Accuracy of the spectral and radiometric laboratory calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)  

Science.gov (United States)

The laboratory procedures, algorithms, measurements, and uncertainties associated with generation of the spectral and radiometric calibration of data acquired by AVIRIS are described. AVIRIS is an airborne sensor that obtains high-spatial-resolution image data of the earth in 224 spectral channels in four spectrometers covering the range from 400 to 2450 nm. The spectral calibration of AVIRIS agrees with the in-flight data to within two nanometers, and the absolute radiometric calibration is consistent with the in-flight verification to 10 percent over the spectral range. In-flight radiometric stability as measured by five consecutive passes over the surface calibration site is reported to be between three and five percent.

Chrien, Thomas G.; Green, Robert O.; Eastwood, Michael L.

1990-01-01

89

External quantum efficiency of Pt/n-GaN Schottky diodes in the spectral range 5-500nm  

International Nuclear Information System (INIS)

The external quantum efficiency in the spectral wavelength range 5-500nm of a large active area Pt/n-type GaN Schottky photodiode that exhibits low reverse bias leakage current, is reported. The Schottky photodiodes were fabricated from n-/n+ epitaxial layers grown by low pressure metalorganic vapour phase epitaxy on single crystal c-plane sapphire. The current-voltage (I-V) characteristics of several 0.25cm2 devices are presented together with the capacitance-voltage (C-V) characteristics of one of these devices. A leakage current as low as 14 pA at 0.5V reverse bias is reported, for a 0.25cm2 diode. The ultraviolet quantum efficiency measurements show that the diodes can be used as radiation hard detectors for the 5-365nm spectral range without the use of visible blocking filters. A peak responsivity of 77.5mA/W at 320nm is reported for one of the fabricated devices, corresponding to a spectral detectivity, D*=1.5x1014cmHz1/2W-1. The average detectivity between 250 and 350nm, for the same device, is reported to be D-bar*=1.3x1014cmHz1/2W-1. The spatial responsivity uniformity variation was established, using H2 Lyman-? radiation, to be +/-3% across the surface of a typical 0.25cm2 diode

2005-02-21

90

Comparison of Plasma Visible Spectral Emissions Between Nova-UNICAMP and TCABR Tokamaks  

Science.gov (United States)

A comparison between the visible spectrum emissions observed on the Nova-UNICAMP and TCABR tokamak plasmas has been made in this work using a hand top HR4000 Ocean Optics spectrometer equipped with a CCD detector. A number of 58 emission lines, in which 22 are common to both machines, have been observed and identified. The differences in the observed spectrum can be explained by the difference in the time integration used in these measurements and by the materials compositions of the limiter and electrode in the TCABR tokamak. Nearby peak emissions have been separated using multi-peak Gaussian fit curves obtaining separation between peak centres with the same order of the spectrometer resolution. The HR4000 spectrometer can be routinely used to monitor the impurity species in the visible spectrum from the different tokamak windows.

do Nascimento, F.; Machida, M.; Ronchi, G.; Schmutzler, L. M. F.; Severo, J. H. F.; Nascimento, I. C.; Sanada, E. K.

2014-05-01

91

Time-resolved photoluminescence spectroscopy of semiconductors for optical applications beyond the visible spectral range  

Energy Technology Data Exchange (ETDEWEB)

The work discussed in this thesis is focused on the experimental studies regarding these three steps: (1) investigation of the fundamental effects, (2) characterization of new material systems, and (3) optimization of the semiconductor devices. In all three cases, the experimental technique of choice is photoluminescence (PL) spectroscopy. The thesis is organized as follows. Chapter 2 gives a summary of the PL properties of semiconductors relevant for this work. The first section deals with the intrinsic processes in an ideal direct band gap material, starting with a brief summary of the theoretical background followed by the overview of a typical PL scenario. In the second part of the chapter, the role of the lattice-vibrations, the internal electric fields as well as the influence of the band-structure and the dielectric environment are discussed. Finally, extrinsic PL properties are presented in the third section, focusing on defects and disorder in real materials. In chapter 3, the experimental realization of the spectroscopic studies is discussed. The time-resolved photoluminescence (TRPL) setup is presented, focusing on the applied excitation source, non-linear frequency mixing, and the operation of the streak camera used for the detection. In addition, linear spectroscopy setup for continous-wave (CW) PL and absorption measurements is illustrated. Chapter 4 aims at the study of the interactions between electrons and lattice-vibrations in semiconductor crystals relevant for the proper description of carrier dynamics as well as the heat-transfer processes. The presented discussion covers the experimental studies of many-body effects in phonon-assisted emission of semiconductors due to the carriercarrier Coulomb-interaction. The corresponding theoretical background is discussed in detail in chapter 2. The investigations are focused on the two main questions regarding electron-hole plasma contributions to the phonon-assisted light-matter interaction as well as the impact of Coulomb-correlations on the carrier-phonon scattering. The experiments presented in chapter 5 deal with the characterization of recently synthesizedmaterial systems: ZnO/(ZnMg)O heterostructures, GaN quantum wires (QWires), as well as (GaAs)Bi quantum wells (QWs). TRPL spectroscopy is applied to gain insight as well as a better understanding of the respective carrier relaxation and recombination processes crucial for the device operation. The aim of the studies is the systematic investigation of carrier dynamics influenced by disorder. The measurements are supported by kinetic Monte- Carlo simulations, providing a quantitative analysis of carrier localization effects. In chapter 6, optimization and characterization studies of semiconductor lasers, based on the well-studied (GaIn)As material system designed for NIR applications, are performed. The device under investigation is the so-called vertical-external-cavity surface emitting laser (VECSEL). The experiments focus on the study of the thermal properties of a high-power VECSEL. The distribution and removal of the excess heat as well as the optimization of the laser for increased performance are addressed applying different heat-spreading and heat-transfer approaches. Based on these investigations, the possibility for power-scaling is evaluated and the underlying restrictions are analyzed. The latter investigations are performed applying spatially-resolved PL spectroscopy. An experimental setup is designed for monitoring the spatial distribution of heat in the semiconductor structure during laser operation.

Chernikov, Alexey A.

2011-07-01

92

AlGaInP quantum dots for optoelectronic applications in the visible spectral range  

International Nuclear Information System (INIS)

The scope of this work is the fabrication and characterization of AlGaInP quantum dots on GaP an GaAs substrates. Based on such quantum dots, semiconductor lasers have been realized, emitting between 660 nm and 730 nm at room temperature. The examination of broad-area lasers processed on these structures suggests that active layers of larger quantum dots with higher aluminium contents lead to lasers with better performance at similar emission wavelength. Additionally, quantum dots grown on GaP substrates have been characterized, that were embedded in AlGaP barriers. Since these barriers exhibit an indirect bandgap, a non-trivial band alignment within these structures is expected. In this work, numerical 3D-simulations are employed to calculate the band alignment including strain and internal fields. Also, ground state wavefunctions of charge carriers have been determined. A thorough comparison between theory and experiment connects the measured emission wavelength and luminescence intensities with calculated transition energies and wavefunction overlaps.

2013-01-01

93

Continuous Spatial Tuning of Laser Emissions in a Full Visible Spectral Range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In order to achieve a continuous tuning of laser emission, the authors designed and fabricated three types of cholesteric liquid crystal cells with pitch gradient, a wedge cell with positive slope, a wedge cell with negative slope, and a parallel cell. The length of the cholesteric liquid crystal pitch could be elongated up to 10 nm, allowing the lasing behavior of continuous or discontinuous spatial tuning determined by the boundary conditions of the cholesteric liquid crystal cell. In the w...

Mi-Yun Jeong; Jeong Weon Wu

2011-01-01

94

MEMS-based Tunable Optical Filter Arrays for Nano-Spectrometer in the Visible Spectral Range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Optische Spektrometer sind bekannte Instrumente für viele Anwendungen in Life Sciences, Produktion und Technik aufgrund ihrer guten Selektivität und Sensitivität zusammen mit ihren berührungslosen Messverfahren.

Setyawati, Onny

2012-01-01

95

Determination of the in-flight spectral and radiometric characteristics of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)  

Science.gov (United States)

AVIRIS is a science research imaging spectrometer that measures radiance in 224 channels between 400 to 2450 nm in the electromagnetic spectrum. To determine the inflight spectral and radiometric characteristics of AVIRIS a validation and calibration experiment was performed. Five data sets were acquired over a calibration site on the homogeneous playa of Rogers Dry Lake, California, U.S. Surface reflectance, atmospheric optical depths, and atmospheric water vapor measurements were acquired concurrently with the overflights. These in situ measurements were used to constrain the LOWTRAN 7 radiative transfer code to predict the total spectral radiance incident at the AVIRIS aperture. These predicted radiances and the AVIRIS measured radiances were analyzed to validate the inflight characteristics. Inflight spectral channel positions and response functions over the AVIRIS spectral range were derived. Radiometric calibration coefficients were calculated for each channel as well as radiometric accuracy, intraflight stability, and noise equivalent delta radiance.

Green, Robert O.; Conel, James E.; Carrere, Veronique; Bruegge, Carol J.; Margolis, Jack S.; Rast, Michael; Hoover, Gordon

1991-01-01

96

A new list of thorium and argon spectral lines in the visible  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Aims. We present a new list of thorium and argon emission lines in the visible obtained by analyzing high-resolution (R=110,000) spectra of a ThAr hollow cathode lamp. The aim of this new line list is to allow significant improvements in the quality of wavelength calibration for medium- to high-resolution astronomical spectrographs. Methods. We use a series of ThAr lamp exposures obtained with the HARPS instrument (High Accuracy Radial-velocity Planet Searcher) to detect pre...

Lovis, C.; Pepe, F.

2007-01-01

97

Sb{sub 2}O{sub 3} nanobelt networks for excellent visible-light-range photodetectors  

Energy Technology Data Exchange (ETDEWEB)

Excellent photoconductive properties have been found in Sb{sub 2}O{sub 3} nanobelts synthesized by a surfactant-assisted solvothermal method. Visible-light photodetectors have been designed from Sb{sub 2}O{sub 3} nanobelt networks using micrometer-wide gold wires as masks. Photodetectors show high sensitivity to visible light, high stability, and reproducibility. Fast response and decay times (<0.3 s) are comparable or even better than these parameters in many other metal oxide nanoscale photodetectors. The dominant mechanism of excellent photoconductivity is attributed to the barrier height modulations in the nanobelt-to-nanobelt contact regions. These results demonstrate that Sb{sub 2}O{sub 3} nanobelt networks can indeed serve as high-performance photodetectors in the visible light range.

Li, L; Fang, X S; Zhai, T Y; Bando, Y; Golberg, D [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan); Zhang, Y X; Wang, H Q; Li, G H [Key Laboratory of Material Physics, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Liao, M Y; Koide, Y, E-mail: LI.Liang@nims.go.jp, E-mail: yxzhang@issp.ac.cn, E-mail: ghli@issp.ac.cn [Sensor Materials Center, NIMS, Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan)

2011-04-22

98

Free spectral range measurement of a fiberized Fabry-Perot etalon with sub-Hz accuracy.  

Science.gov (United States)

In this work a narrow linewidth (1 kHz) laser source is used to measure the free spectral range of a fiberized Fabry-Perot etalon with sub-Hz accuracy (10(-8)). A previously demonstrated technique based on the Pound-Drever-Hall error signal is improved in accuracy by the use of a narrow linewidth laser swept in frequency via an acousto-optic modulator, or single sideband generation. The sub-Hz (10(-8)) accuracy attained enables the characterization of both the long-term drift and the polarization dependence of the free spectral range of the fiberized etalon. PMID:20588986

Mandridis, Dimitrios; Ozdur, Ibrahim; Bagnell, Marcus; Delfyett, Peter J

2010-05-24

99

A 2-dimensional gradual period photonic heterostructure possessing omnidirectional band gap in visible range made by holography  

Science.gov (United States)

A 2-dimensional gradual period photonic heterostructure was made with holography by use of non-uniform swelling effect of dichromated gelatin during processing. In this structure, the symmetric point group of triangle lattice was debased to C2 V from C6 V. Theoretical analysis and experimental results show that omnidirectional band gap in visible range can be achieved with this kind of heterostructure made by low refractive index materials.

Zhou, Ying; Zhai, Tianrui; Dai, Rui; Wang, Zhaona; Liu, Dahe

2012-03-01

100

Wide spectral range measurement of modal birefringence in polarization-maintaining fibres  

International Nuclear Information System (INIS)

We report on a substantially improved white-light spectral interferometric technique for measurement of the group and phase modal birefringence in polarization-maintaining fibres (PMFs) over a wide wavelength range (e.g. 480–1600 nm). The technique utilizes a tandem configuration of a Michelson interferometer and a PMF placed between Glan–Taylor polarizer and analyzer. Spectral signals are recorded by VIS–NIR and NIR fibre-optic spectrometers to measure the equalization wavelength as a function of the path length difference adjusted in the interferometer, or equivalently, the wavelength dependence of the group modal birefringence in the PMF. Moreover, a new procedure is used to specify the sign of the group modal birefringence. A polynomial fit is applied to the measured data to determine also the wavelength dependence of the phase modal birefringence in the PMF over a wide spectral range

2009-02-01

 
 
 
 
101

Study on the Incidence of Opportunity Crime on Residential Streets Considering Traffic Volume and Visible Range  

Directory of Open Access Journals (Sweden)

Full Text Available As a basic step, in this study we propose a model to describe the snatchincident on residential streets. This model is based on one of themethodologies of social science and the Crime Prevention ThroughEnvironmental Design’s concept. The objective variable is the feasibility ofsnatch and explanatory variables are physical factors concerning roadnetwork design and traffic regulation, like traffic volume and visible rangeon streets.As the result of the application to actual situations, the model providedreasonable predictions for distribution of point of incidence in a streetsection. It is possible to examine the influence that road network design andtraffic regulation have on snatch by extending this model to road network.

Chiaki MATSUNAGA

2011-11-01

102

Spectral solar irradiance in the range 300-1100 nm measured at Valencia, Spain  

Energy Technology Data Exchange (ETDEWEB)

A programme of measurements aimed at originating a database of spectral solar irradiance which is representative of a wide range of optical masses and atmospheric conditions is described. A preliminary analysis of the measurements for clear-sky conditions is also presented. (Author)

Martinez-Lozano, J.A.; Utrillas, M.P.; Tena, F. [Valencia Univ. (Spain). Dept. de Termodinamica

1995-12-31

103

The PTB high-accuracy spectral responsivity scale in the VUV and x-ray range  

Science.gov (United States)

At the electron storage ring BESSY II, the Physikalisch-Technische Bundesanstalt operates ten experimental stations at six synchrotron radiation beamlines for photon metrology in the spectral range from ultraviolet radiation to x-rays. Five of these beamlines are used to realize and disseminate a scale of spectral responsivity for photodetectors. Detector calibration is based on the use of cryogenic radiometers as primary detector standards. The current status of instrumentation and measurement capabilities is described. Best measurement capabilities (k = 2) for the calibration of photodiodes vary between 0.4% and 2.3%.

Gottwald, A.; Kroth, U.; Krumrey, M.; Richter, M.; Scholze, F.; Ulm, G.

2006-04-01

104

Minor planet spectrometry. 4 Vesta: spectral range 0.48-0.55?m  

International Nuclear Information System (INIS)

Two absorption bands at 0.51 and 0.54 ?m are found in the spectrum of 4 Vesta, obtained with the 20.48 A spectral resolution. These bands are due to spin-forbidden transitions of the d-electrons in Fe"2"+ ions in pyroxene. Analogous bands are present only in the basaltic achondritic spectra. A conclusion is drawn that detailed spectrophotometry of the S-, R-, U-asteroids in the spectral range 0.48-0.6 ?m can give information on the presence of the differentiated matter of the certain kind on their surface

1986-01-01

105

ETA CARINAE ACROSS THE 2003.5 MINIMUM: ANALYSIS IN THE VISIBLE AND NEAR-INFRARED SPECTRAL REGION  

International Nuclear Information System (INIS)

We present an analysis of the visible through near-infrared spectrum of Eta Carinae (? Car) and its ejecta obtained during the '? Car Campaign with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT)'. This is a part of larger effort to present a complete ? Car spectrum, and extends the previously presented analyses with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) in the UV (1240-3159 A) to 10,430 A. The spectrum in the mid- and near-UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow-emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 A, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground-based seeing and contributions of nebular-scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments' apertures. This paper provides a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 A.

2009-04-01

106

Eta Carinae across the 2003.5 Minimum: Analysis in the Visible and Near Infrared Spectral Region  

Science.gov (United States)

We present an analysis of the visible through near infrared spectrum of Eta Car and its ejecta obtained during the "Eta Car Campaign with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT)". This is a part of the larger effort to present a complete Eta Car spectrum, and extends the previously presented analyses with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) in the UV (1240-3159 Angstrom) to 10,430 Angstrom. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 Angstroms, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground based seeing and contributions of nebular scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments' apertures. This paper provides a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 Angstroms.

Nielsen, K. E.; Kober, G. Vieira; Weis, K.; Gull, T. R.; Stahl, O.; Bomans, D. J.

2009-01-01

107

The influence of thermal treatment of the porous glass plates on the character of their scattering in visible spectral region  

Directory of Open Access Journals (Sweden)

Full Text Available The pore structure and light transmission of the high-silica porous glasses in visible spectral region are investigated depending on a temperature of their thermal treatment and composition of the initial two-phase alkali borosilicate glasses. The character of light transmission in porous glasses is analyzed considering the features of their pore space structure and processes occurring in porous glass upon heating. It is shown that with an increase in temperature of thermal treatment of the porous glasses of different composition the pore size increases, and their specific surface decreases (at practically constant common porosity, which is due to the processes of pore overcondensation, that occur owing to the regrouping and change of packing density of the secondary silica particles. It is shown that introducting phosphate and fluoride ions in the basic alkali borosilicate glass results in an increase in the light attenuation factors of the porous glasses owing to an increase in the sizes of liquation areas of heterogeneity in initial two-phase glasses, formation of larger pores and presence of the nanostructured microcrystalline phases in the porous glasses.

Tatyana V. Antropova

2010-01-01

108

Eta Carinae across the 2003.5 Minimum: Analysis in the visible and near infrared spectral region  

CERN Multimedia

We present an analysis of the visible through near infrared spectrum of Eta Carinae and its ejecta obtained during the "Eta Carinae Campaign with the UVES at the ESO VLT". This is a part of larger effort to present a complete Eta Carinae spectrum, and extends the previously presented analyses with the HST/STIS in the UV (1240-3159 A) to 10,430 A. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 A, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for element...

Nielsen, K E; Weis, K; Gull, T R; Stahl, O; Bomans, D J

2009-01-01

109

Negative refraction and sub-wavelength focusing in the visible range using transparent metallo-dielectric stacks.  

Science.gov (United States)

We numerically demonstrate negative refraction of the Poynting vector and sub-wavelength focusing in the visible part of the spectrum using a transparent multilayer, metallo-dielectric photonic band gap structure. Our results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects. These structures offer several advantages: tunability and high transmittance (50% or better) across the visible and near IR ranges; large object-image distances, with image planes located beyond the range where the evanescent waves have decayed. From a practical point of view, our findings point to a simpler way to fabricate a material that exhibits negative refraction and maintains high transparency across a broad wavelength range. Transparent metallo-dielectric stacks also provide an opportunity to expand the exploration of wave propagation phenomena in metals, both in the linear and nonlinear regimes. PMID:19532269

Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Bloemer, Mark J; de Ceglia, Domenico; Centini, Marco; Mandatori, Antonio; Sibilia, Concita; Akozbek, Neset; Cappeddu, Mirko G; Fowler, Mark; Haus, Joseph W

2007-01-22

110

Dispersion properties and low infrared optical losses in epitaxial AlN on sapphire substrate in the visible and infrared range  

Science.gov (United States)

Optical waveguiding properties of a thick wurtzite aluminum nitride highly [002]-textured hetero-epitaxial film on (001) basal plane of sapphire substrate are studied. The physical properties of the film are determined by X-ray diffraction, atomic force microscopy, microRaman, and photocurrent spectroscopy. The refractive index and the thermo-optic coefficients are determined by m-lines spectroscopy using the classical prism coupling technique. The optical losses of this planar waveguide are also measured in the spectral range of 450-1553 nm. The lower value of optical losses is equal to 0.7 dB/cm at 1553 nm. The optical losses due to the surface scattering are simulated showing that the contribution is the most significant at near infrared wavelength range, whereas the optical losses are due to volume scattering and material absorption in the visible range. The good physical properties and the low optical losses obtained from this planar waveguide are encouraging to achieve a wide bandgap optical guiding platform from these aluminum nitride thin films.

Soltani, A.; Stolz, A.; Charrier, J.; Mattalah, M.; Gerbedoen, J.-C.; Barkad, H. A.; Mortet, V.; Rousseau, M.; Bourzgui, N.; BenMoussa, A.; De Jaeger, J.-C.

2014-04-01

111

Spectral 6DOF registration of noisy 3D range data with partial overlap.  

Science.gov (United States)

We present Spectral Registration with Multilayer Resampling (SRMR) as a 6 Degrees Of Freedom (DOF) registration method for noisy 3D data with partial overlap. The algorithm is based on decoupling 3D rotation from 3D translation by a corresponding resampling process of the spectral magnitude of a 3D Fast Fourier Transform (FFT) calculation on discretized 3D range data. The registration of all 6DOF is then subsequently carried out with spectral registrations using Phase Only Matched Filtering (POMF). There are two main aspects for the fast and robust registration of Euler angles from spherical information in SRMR. First of all, there is the permanent use of phase matching. Second, based on the FFT on a discrete Cartesian grid, not only one spherical layer but also a complete stack of layers are processed in one step. Experiments are presented with challenging datasets with respect to interference and overlap. The results include the fast and robust registration of artificially transformed data for ground-truth comparison, scans from the Stanford Bunny dataset, high end 3D laser range finder (LRF) scans of a city center, and range data from a low-cost actuated LRF in a disaster response scenario. PMID:22868648

Bülow, Heiko; Birk, Andreas

2013-04-01

112

Broadband superresolving lens with high transparency for propagating and evanescent waves in the visible range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a theoretical analysis of a super-resolving lens based on 1-dimensional metallo-dielectric photonic crystals composed of Ag/GaP multilayers. The lens contains a total of 10 optical skin depths of Ag, yet maintains a normal incidence transmittance of ~50% for propagating waves over the super-resolving wavelength range of 500-650 nm. The individual Ag layers are 22 nm thick and can be readily fabricated in conventional deposition systems. The importance of anti-refl...

Bloemer, Mark J.; D Aguanno, Giuseppe; Mattiucci, Nadia; Scalora, Michael; Akozbek, Neset

2006-01-01

113

Broadband superresolving lens with high transparency for propagating and evanescent waves in the visible range  

CERN Multimedia

We present a theoretical analysis of a super-resolving lens based on 1-dimensional metallo-dielectric photonic crystals composed of Ag/GaP multilayers. The lens contains a total of 10 optical skin depths of Ag, yet maintains a normal incidence transmittance of ~50% for propagating waves over the super-resolving wavelength range of 500-650 nm. The individual Ag layers are 22 nm thick and can be readily fabricated in conventional deposition systems. The importance of anti-reflection coatings for the transmission of evanescent and propagating waves is illustrated by comparison to periodic and symmetric structures without the coatings. In addition, the reflection for propagating waves is reduced to ~5% across the super-resolving wavelength band diminishing the interference between the object and the lens.

Bloemer, M J; D'Aguanno, G; Mattiucci, N; Scalora, M; Aguanno, Giuseppe D'; Akozbek, Neset; Bloemer, Mark J.; Mattiucci, Nadia; Scalora, Michael

2006-01-01

114

Direct milling and casting of polymer-based optical waveguides for improved transparency in the visible range  

DEFF Research Database (Denmark)

Polymer waveguides fabricated from photoresist have an inherent high propagation loss in the short visible wavelength range caused by absorption due to the added photosensitizers. We have addressed this problem by development of two novel methods for the fabrication of microfluidic systems with integrated optical waveguides. Polymethylinethacrylate (PMMA) is dissolved in anisole and 'doped' with styrene-arcylonitrile copolymer to vary the refractive index. The doped PMMA with a higher refractive index is then spin coated onto a PMMA substrate with a lower refractive index to provide waveguide properties. Direct micromilling enabled us to fabricate 100 mu m wide optical waveguides. Propagation losses of less than 1 dB cm(-1) could be achieved throughout the entire visual range down to a wavelength of 400 nm. A casting process amenable to high number production of such devices was furthermore developed.

Snakenborg, Detlef; Perozziello, Gerardo

2006-01-01

115

Dose dependence of visible range diffuse reflectivity for Si{sup +} and C{sup +} ion implanted polymers  

Energy Technology Data Exchange (ETDEWEB)

Detailed insight into the near-surface area of the ion beam modified polymer is supplied by the measured diffuse reflectivity spectra. The near-surface layer (50 to 150 nm) of bulk polymer samples have been implanted with silicon (Si{sup +}) and carbon (C{sup +}) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 5.10{sup 12}-2.10{sup 17} cm{sup +2}). The polymer materials studied were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-propylene (PP), and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra R{sub d} = f({lambda}) of the implanted samples have been measured in the visible range ({lambda} = 400 to 830 nm). In this paper the dose dependences of the size and sign of the diffuse reflectivity changes {delta}R{sub d} = f(D) have been analyzed.

Balabanov, S; Tsvetkova, T [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Borisova, E; Avramov, L [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Bischoff, L [Forschungszentrum Rossendorf e.V., PO Box 510119, D-01314 Dresden (Germany)], E-mail: sbalab@issp.bas.bg

2008-05-01

116

Inertial-range structure of Gross-Pitaevskii turbulence within a spectral closure approximation  

Science.gov (United States)

The inertial-range structure of turbulence obeying the Gross-Pitaevskii equation, the equation of motion for quantum fluids, is analyzed by means of a spectral closure approximation. It is revealed that, for the energy-transfer range, the spectrum of the order parameter field ? obeys k-2 law for k ? k* and k-1 law for k ? k*, where k* is the wavenumber where the characteristic timescales associated with linear and nonlinear terms are of the same order. It is also shown that, for the particle-number-transfer range, the spectrum obeys k-1 law for k ? k*, n and k-1/3 law for k ? k*, n, where k*, n is the wavenumber corresponding to k* in the particle-number-transfer range.

Yoshida, Kyo; Arimitsu, Toshihico

2013-08-01

117

Influence of polymer packaging films on hyperspectral imaging data in the visible-near-infrared (450-950 nm) wavelength range.  

Science.gov (United States)

Hyperspectral imaging (HSI) has recently emerged as a useful tool for quality analysis of consumer goods (e.g., food and pharmaceutical products). These products are typically packaged in polymeric film prior to distribution; however, HSI experiments are typically carried out on such samples ex-packaging (either prior to or after removal from packaging). This research examines the effects of polymer packaging films (polyvinyl chloride (PVC) and polyethylene terephthalate (PET)) on spectral and spatial features of HSI data in order to investigate the potential of HSI for quality evaluation of packaged goods. The effects of packaging film were studied for hyperspectral images of samples obtained in the visible-near-infrared (Vis-NIR, i.e., 450-950 nm) wavelength range, which is relevant to many food, agricultural, and pharmaceutical products. The dominant influence of the films tested in this wavelength range could be attributed to light scattering. Relative position of the light source, film, and detector were shown to be highly influential on the scattering effects observed. Detection of features on samples imaged through film was shown to be possible after some data preprocessing. This suggests that quality analysis of products packaged in polymer film is feasible using HSI. These findings would be useful in the development of quality monitoring tools for consumer products post-packaging using HSI. PMID:20223066

Gowen, A A; O'Donnell, C P; Esquerre, C; Downey, G

2010-03-01

118

Fluorescent dye labeled DNA size standards for molecular mass detection in visible/infrared range  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Targeting Induced Local Lesions in Genomes (TILLING is a high throughput reverse genetics tool which detects mismatches (single point mutations or small indels in large number of individuals of mutagenized populations. Currently, TILLING is intensively used for genomics assisted molecular breeding of several crop plants for desired traits. Most commonly used platform for mutation detection is Li-COR DNA Analyzer, where PCR amplified products treated with single strand mismatch specific nuclease are resolved on denaturing gels. The molecular size of any cut product can be easily estimated by comparing with IR dye labeled markers of known sizes. Similar fluorescent dye labeled size markers are also used for several genotyping experiments. Currently, commercially available size standards are expensive and are restricted up to only 700 bp which renders estimation of products of sizes greater than 700 bases inaccurate. Findings A simple protocol was developed for labeling 5' end of multiple DNA size markers with fluorescent dyes. This method involves cloning a pool of different size markers of DNA in a plasmid vector. PCR amplification of plasmid using IR dye labeled universal primers generates 5' fluorescent labeled products of various sizes. The size of products constituting the ladder can be customized as per the need. The generated size markers can be used without any further purification and were found to be stable up to one year at -20°C. Conclusions A simple method was developed for generating fluorescent dye labeled size standards. This method can be customized to generate different size standards as per experimental needs. The protocol described can also be adapted for developing labeled size standards for detection on platforms other than Li-COR i.e. other than infra red range of the spectrum.

Sreelakshmi Yellamaraju

2011-01-01

119

Valentin A. Fabrikant: negative absorption, his 1951 patent application for amplification of electromagnetic radiation (ultraviolet, visible, infrared and radio spectral regions) and his experiments  

Science.gov (United States)

This paper is devoted to Moscow physicist Valentin A. Fabrikant who is known for his 1939 thesis with suggestion of experiments on light amplification directly proving the existence of negative absorption in gas discharge, his 1951 patent application (jointly with M.M. Vudynsky and F.A. Butaeva) for amplification of electromagnetic radiation (ultraviolet, visible, infrared and radio spectral regions), and his experimental attempts (jointly with F.A. Butaeva) to observe light amplification in gas discharge (paper submission of December 1957).

Lukishova, S. G.

2010-09-01

120

Spectral distribution of UV range diffuse reflectivity for Si+ ion implanted polymers  

Science.gov (United States)

The analysis of the UV range spectral characteristics can supply additional information on the formed sub-surface buried layer with implanted dopants. The near-surface layer (50÷150 nm) of bulk polymer samples have been implanted with silicon (Si+) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 1.1013 ÷ 1, 2.1017 cm-2). The studied polymer materials were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-methyl-metacrylate (PMMA) and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra Rd = f(?) of the ion implanted samples have been measured in the UV range (? = 220÷350 nm). In this paper the dose dependences of the size and sign of the diffuse optical reflectivity changes ?Rd = f(D) have been analysed.

Balabanov, S.; Tsvetkova, T.; Borisova, E.; Avramov, L.; Bischoff, L.

2008-05-01

 
 
 
 
121

Spectral distribution of UV range diffuse reflectivity for Si{sup +} ion implanted polymers  

Energy Technology Data Exchange (ETDEWEB)

The analysis of the UV range spectral characteristics can supply additional information on the formed sub-surface buried layer with implanted dopants. The near-surface layer (50 to 150 nm) of bulk polymer samples have been implanted with silicon (Si{sup +}) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 1.10{sup 13} to 1, 2.10{sup 17} cm{sup -2}). The studied polymer materials were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-methyl-metacrylate (PMMA) and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra R{sub d} = f({lambda}) of the ion implanted samples have been measured in the UV range ({lambda} = 220 to 350 nm). In this paper the dose dependences of the size and sign of the diffuse optical reflectivity changes {lambda}Rd = f(D) have been analysed.

Balabanov, S; Tsvetkova, T [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Borisova, E; Avramov, L [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Bischoff, L [Forschungszentrum Rossendorf e.V., PO Box 510119, D-01314 Dresden (Germany)], E-mail: sbalab@issp.bas.bg

2008-05-01

122

High-fidelity imaging : the computational models of the human visual system in high dynamic range video compression, visible difference prediction and image processing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As new displays and cameras offer enhanced color capabilities, there is a need to extend the precision of digital content. High Dynamic Range (HDR) imaging encodes images and video with higher than normal bit-depth precision, enabling representation of the complete color gamut and the full visible range of luminance. This thesis addresses three problems of HDR imaging: the measurement of visible distortions in HDR images, lossy compression for HDR video, and artifact-free image processing. To...

Mantiuk, Rafal

2006-01-01

123

Large area double p-i-n heterostructure for signal multiplexing and demultiplexing in the visible range  

International Nuclear Information System (INIS)

Results on the use of a double a-SiC:H p-i-n heterostructure for signal multiplexing and demultiplexing applications in the visible range, are presented. Modulated monochromatic beams together (multiplexing mode), or a single polychromatic beam (demultiplexing mode) impinge in the device and are absorbed, accordingly to their wavelength, giving rise to a time and wavelength dependent electrical field modulation. Red, green and blue pulsed input channels are transmitted together, each one with a specific transmission rate. The combined optical signal is analyzed by reading out, under different applied voltages, the generated photocurrent. Results show that in the multiplexing mode the output signal is balanced by the wavelength and transmission rate of each input channel, keeping the memory of the incoming optical carriers. In the demultiplexing mode the photocurrent is controlled by the applied voltage allowing regaining the transmitted information. An electrical model gives insight into the device operation.

2009-10-01

124

Infrared absolute intensities of ozone in the 10 and 5 ?m spectral range: New investigations  

International Nuclear Information System (INIS)

Infrared high resolution spectra of ozone 16O3 have been recorded in the 10 and 5 ?m spectral ranges in order to derive their absolute intensities with a best achievable accuracy. Spectra have been recorded with the home made stepping mode FTS of GSMA (Reims). In the two spectral regions, we use UV-IR crossed beam cell. The quantification of ozone is achieved using UV cross section at 253.65 nm. A check of this UV calibration is also performed using direct pressure measurements of quasi-pure samples of O3. The intensities are derived from infrared spectra using multifit procedure already tested. In the 10 ?m range, where 12 different spectra have been recorded, 65 well selected lines led to a good agreement (better than 0.3%) with the HITRAN 2008 (or 2004) values, confirming our previous work [De Backer-Barilly MR, Barbe A. Absolute intensities of the 10 ?m bands of 16O3. J Mol Spectrosc 305:2001;43-53]. In the 5 ?m range, where 18 transitions are selected, we also note a correct agreement with HITRAN 2008, despite a slightly larger averaged value between (1.9%) experimental and theoretical (HITRAN). As conclusion, authors suggest the use of current HITRAN 2008 data for atmospheric retrievals.

2010-06-01

125

Spectral density method in quantum nonextensive thermostatistics and magnetic systems with long-range interactions  

CERN Document Server

Motived by the necessity of explicit and reliable calculations, as a valid contribution to clarify the effectiveness and, possibly, the limits of the Tsallis thermostatistics, we formulate the Two-time Green Functions Method in nonextensive quantum statistical mechanics within the optimal Lagrange multiplier framework, focusing on the basic ingredients of the related Spectral Density Method. Besides, to show how the SDM works we have performed, to the lowest order of approximation, explicit calculations of the low-temperature properties for a quantum $d$-dimensional spin-$1/2$ Heisenberg ferromagnet with long-range interactions decaying as $1/r^{p}$ ($r$ is the distance between spins in the lattice)

Cavallo, A; De Cesare, L

2005-01-01

126

Scattering of an ultrashort electromagnetic radiation pulse by an atom in a broad spectral range  

Energy Technology Data Exchange (ETDEWEB)

The scattering of an ultrashort electromagnetic pulse by atomic particles is described using a consistent quantum-mechanical approach taking into account excitation of a target and nondipole electromagnetic interaction, which is valid in a broad spectral range. This approach is applied to the scattering of single- and few-cycle pulses by a multielectron atom and a hydrogen atom. Scattering spectra are obtained for ultrashort pulses of different durations. The relative contribution of 'elastic' scattering of a single-cycle pulse by a hydrogen atom is studied in the high-frequency limit as a function of the carrier frequency and scattering angle.

Astapenko, V. A., E-mail: astval@mail.ru [Moscow Institute of Physics and Technology (Russian Federation)

2011-02-15

127

Low threshold, room-temperature microdisk lasers in the blue spectral range  

CERN Document Server

InGaN-based active layers within microcavity resonators offer the potential of low threshold lasers in the blue spectral range. Here we demonstrate optically pumped, room temperature lasing in high quality factor GaN microdisk cavities containing InGaN quantum dots (QDs) with thresholds as low as 0.28 mJ/cm2. This work, the first demonstration of lasing action from GaN microdisk cavities with QDs in the active layer, provides a critical step for the nitrides in realizing low threshold photonic devices with efficient coupling between QDs and an optical cavity.

Aharonovich, Igor; Russell, Kasey J; Zhu, Tongtong; Kappers, Menno J; Oliver, Rachel A; Hu, Evelyn L

2012-01-01

128

Calibrating image plate sensitivity in the 700 to 5000 eV spectral energy range  

Science.gov (United States)

This paper describes a method to calibrate image plate sensitivity for use in the low energy spectral range. Image plates, also known as photostimulable luminescence (PSL) detectors, have often proved to be a valuable tool as a detector for plasma physics studies. Their advantages of large dynamic range, high stopping power, and resistance to neutron damage sometimes outweigh the problems of limited resolution and the remote processing required. The neutron damage resistance is required when the X-ray source is producing a high neutron flux. The Static X-ray Imager (SXI) is a key diagnostic on the National Ignition Facility (NIF) target chamber at LLNL for use in determining the symmetry of the laser beams. The SXI is essential to proper interpretation of the data from the Dante diagnostic to determine the X-ray radiation temperature. It is comprised of two diagnostics located at the top and the bottom of the target chamber. The usual detector is a large array CCD camera. For shots giving high yields of neutrons, the camera would not only be blinded by the neutrons, it would be damaged. To get around this problem, an image plate (IP) is used as the detector. The NIF application covers the energy range from 700 to 5000 eV. The type of image plates typically used for plasma physics are the Fuji BAS-MS, BAS-SR, and BAS-TR models. All models consist of an X-ray sensitive material made of BaF(Br,I):Eu2+ embedded in a plastic binder. X-rays incident on the phosphor ionize the Eu 2+ producing Eu3+ and free electrons that are trapped in lattice defects (F-centers) produced by the absence of halogen ions in the BaF2 crystal. An image plate readout scanner irradiates the IP with a red laser causing reduction of the Eu3+ and emission of a blue photon. The photon is collected using a photomultiplier and digitized to make an electronic image. Image plates are cleared of all F-centers by putting them under a bright light for about 10 minutes. They are then ready for producing a new X-ray image. The MS IP model has the higher sensitivity and the SR IP and TR IP models are designed for higher resolution. The MS and SR IPs have a thin Mylar coating that protects the sensitive layer. The TR model has no protective layer and is more sensitive at the lower X-ray energies but must be handled more carefully. The raw image data from the Fuji scanner can be converted to units of PSL that are proportional to the photon count. The equation relating PSL to the raw greyscale value is: PSL = (R/100)2(4000/S)exp10{L(G/(2B-1)-1/2)} where R is the resolution in ?m S is the sensitivity setting L is the latitude B is the dynamic range (8 or 16 bits) G is the raw image greyscale value. The IP photon sensitivity is defined as the PSL output per photon input and is a function of the photon energy. Meadowcroft et al in 2008 published the sensitivity for the three types of image plates in the spectral range from 1 to 100 keV. Maddox et al measured the sensitivity for type MS and SR image plates from 8 to 80 keV using the NSTec High Energy X-ray (HEX) source, a fluorescer type X-ray source. The Meadowcroft and Maddox measurements used similar X-ray sources for the higher spectral and the same type of IP scanner, the FLA 7000. There is reasonable agreement between the Maddox and Meadowcroft sensitivity measurements of MS and SR type IP for the at spectral energies above 20 keV, but the Maddox sensitivities are much lower than those of Meadowcroft in the energy range below 20 keV. Recently Bonnet et al published a model for the photon sensitivity based upon the amount of energy deposited and Monte Carlo calculations to incorporate the specifics of the X-ray absorption and the readout process. The model was calibrated for sensitivity using radioactive sources. The model was compared to the previous publications cited. The Bonnet model tends to agree with the Meadocroft measurements at the low spectral energies. The present paper describes the measurement of IP sensitivity in the spectral range from 700 to 8000 eV. The sensitivity in this spectral range had not p

Haugh, Michael J.; Lee, Joshua; Romano, Edward; Schneider, Marilyn

2013-09-01

129

Pulsed, all solid-state light source in the visible spectral region based on non-linear cavity dumping  

DEFF Research Database (Denmark)

We propose a novel generic approach for generation of pulsed light in the visible spectrum, based on SFG between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser.

Tidemand-Lichtenberg, Peter; Andersen, Martin

130

Spectral Decay Characteristics in High Frequency Range of Observed Records from Crustal Large Earthquakes (Part 2)  

Science.gov (United States)

Spectral decay characteristics in high frequency range of observed records from crustal large earthquakes occurred in Japan is examined. It is very important to make spectral decay characteristics clear in high frequency range for strong ground motion prediction in engineering purpose. The authors examined spectral decay characteristics in high frequency range of observed records among three events, the 2003 Miyagi-Ken Hokubu earthquake (Mw 6.1), the 2005 Fukuoka-Ken Seiho-oki earthquake (Mw 6.6), and the 2008 Iwate-Miyagi Nairiku earthquake (Mw 6.9) in previous study [Tsurugi et al.(2010)]. Target earthquakes in this study are two events shown below. *EQ No.1 Origin time: 2011/04/11 17:16, Location of hypocenter: East of Fukushima pref., Mj: 7.0, Mw: 6.6, Fault type: Normal fault *EQ No.2 Origin time: 2011/03/15 22:31, Location of hypocenter: East of Shizuoka pref., Mj: 6.4, Mw: 5.9, Fault type: Strike slip fault The borehole data of each event are used in the analysis. The Butterworth type high-cut filter with cut-off frequency, fmax and its power coefficient of high-frequency decay, s [Boore(1983)], are assumed to express the high-cut frequency characteristics of ground motions. The four parameters such as seismic moment, corner frequency, cut-off frequency and its power coefficient of high-frequency decay are estimated by comparing observed spectra at rock sites with theoretical spectra. The theoretical spectra are calculated based on the omega squared source characteristics convolved with propagation-path effects and high-cut filter shapes. In result, the fmax's of the records from the earthquakes are estimated 8.0Hz for EQ No.1 and 8.5Hz for EQ No.2. These values are almost same with those of other large crustal earthquakes occurred in Japan. The power coefficient, s, are estimated 0.78 for EQ No.1 and 1.65 for EQ No.2. The value for EQ No.2 is notably larger than those of other large crustal earthquakes. It is seems that the value of the power coefficient, s, became large under the effect of complex ground structure and volcanic front. The obtained results may contribute to strong ground motion prediction in high frequency range for crustal earthquakes. Acknowledgement: This study commissioned by Japan Nuclear Energy Safety Organization. We thank the National Research Institute for Earth Science Disaster Prevention to provide the strong-motion data. References: Hanks,T.C. : fmax, Bulletin of Seismological Society of America, 72, 1867-1879, 1982. Boore,D.M. : Stochastic simulation of high-frequency ground motion based on seismological models of the radiated spectra, Bulletin of Seismological Society of America, 73, 1865-1894, 1983. Tsurugi,M., Kagawa,T., and Irikura,K. : Spectral Decay Characteristics in High Frequency Range of Observed Records from Crustal Large Earthquakes, AGU Fall Meeting, 2010.

Tsurugi, M.; Kagawa, T.; Irikura, K.

2012-12-01

131

Two-photon absorption spectra of luminescent conducting polymers measured over wide spectral range  

Science.gov (United States)

We report the two-photon absorption (TPA) spectra of poly(2,5-dibutoxy-p-phenylene acetylene) (PPA-DBO), poly(2,5-dioctyloxy-p-phenylene vinylene) (PPV-DOO), and poly(3-hexylthiophene) in the spectral range extending from 576 nm to 846 nm. Using the Z-scan technique on the polymers in solution, we measured a strong two-photon allowed transition in all three materials which we attribute to the mAg essential state. In the case of PPA-DBO and PPV-DOO, TPA peaks were coincident with dispersion in the nonlinear refractive indices as detected by reduced aperture Z scan. In all three polymers this peak occurs at approximately 1.3 the bandgap energy. The excitonic nature of the excited electronic states in PPA-DBO is indicated by the lack of a TPA band at or near the 1Bu exciton position. Saturation was observed in the nonlinear index of refraction near spectral peaks, as well as an apparent reverse Kramers- Kronig effect.

Meyer, Ron K.; Liess, Martin; Benner, Robert E.; Gellermann, Werner; Vardeny, Z. Valy; Ozaki, Masanori; Yoshino, Katsumi; Ding, Yi W.; Barton, Thomas J.

1997-12-01

132

Bremsstrahlung of fast charged particles when scattering on clusters in wide spectral range  

International Nuclear Information System (INIS)

Within the framework of the first Born approximation and a simple model of the structural factor, the bremsstrahlung of fast charged particles on polyatomic clusters is calculated and analyzed with regard to the polarization mechanism in a wide spectral range including a domain of high frequencies. The role of cooperative phenomena in the static and polarization channels of bremsstrahlung is investigated. It is established that these phenomena, being negligible for static bremsstrahlung, substantially influence the polarization bremsstrahlung. It is shown that the constructive interference between the contributions of the atoms of a cluster to the polarization bremsstrahlung substantially increases its intensity and changes its dependence on the basic parameters of the problem compared with the case of bremsstrahlung on an isolated atom

2005-07-01

133

A full free spectral range tuning of p-i-n doped Gallium Nitride microdisk cavity  

CERN Document Server

Effective, permanent tuning of the whispering gallery modes (WGMs) of p-i-n doped GaN microdisk cavity with embedded InGaN quantum dots over one free spectral range is successfully demonstrated by irradiating the microdisks with a ultraviolet laser (380nm) in DI water. For incident laser powers between 150 and 960 nW, the tuning rate varies linearly. Etching of the top surface of the cavity is proposed as the driving force for the observed shift in WGMs, and is supported by experiments. The tuning for GaN/InGaN microdisk cavities is an important step for deterministically realizing novel nanophotonic devices for studying cavity quantum electrodynamics.

Niu, Nan; Aharonovich, Igor; Russell, Kasey J; Woolf, Alexander; Sadler, Thomas C; El-Ella, Haitham A R; Kappers, Menno J; Oliver, Rachel A; Hu, Evelyn L

2012-01-01

134

CO-ANALYSIS OF SOLAR MICROWAVE AND HARD X-RAY SPECTRAL EVOLUTIONS. I. IN TWO FREQUENCY OR ENERGY RANGES  

International Nuclear Information System (INIS)

Solar microwave and hard X-ray spectral evolutions are co-analyzed in the 2000 June 10 and 2002 April 10 flares, and are simultaneously observed by the Owens-Valley Solar Array in the microwave band and by Yohkoh/Hard X-ray Telescope or RHESSI in the hard X-ray band, with multiple subpeaks in their light curves. The microwave and hard X-ray spectra are fitted by a power law in two frequency ranges of the optical thin part and two photon energy ranges, respectively. Similar to an earlier event in Shao and Huang, the well-known soft-hard-soft pattern of the lower energy range changed to the hard-soft-hard (HSH) pattern of the higher energy range during the spectral evolution of each subpeak in both hard X-ray flares. This energy dependence is actually supported by a positive correlation between the overall light curves and spectral evolution in the lower energy range, while it becomes an anti-correlation in the higher energy range. Regarding microwave data, the HSH pattern appears in the spectral evolution of each subpeak in the lower frequency range, which is somewhat similar to Huang and Nakajima. However, it returns back to the well-known pattern of soft-hard-harder for the overall spectral evolution in the higher frequency range of both events. This frequency dependence is confirmed by an anti-correlation between the overall light curves and spectral evolution in the lower frequency range, but it becomes a positive correlation in the higher frequency range. The possible mechanisms are discussed, respectively, for reasons why hard X-ray and microwave spectral evolutions have different patterns in different energy and frequency intervals.

2011-06-20

135

Using Visible Spectral Information to Predict Long-Wave Infrared Spectral Emissivity: A Case Study over the Sokolov Area of the Czech Republic with an Airborne Hyperspectral Scanner Sensor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Remote-sensing platforms are often comprised of a cluster of different spectral range detectors or sensors to benefit from the spectral identification capabilities of each range. Missing data from these platforms, caused by problematic weather conditions, such as clouds, sensor failure, low temporal coverage or a narrow field of view (FOV), is one of the problems preventing proper monitoring of the Earth. One of the possible solutions is predicting a detector or sensor’s missing data using ...

Simon Adar; Yoel Shkolnisky; Gila Notesco; Eyal Ben-Dor

2013-01-01

136

In-flight validation and calibration of the spectral and radiometric characteristics of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)  

Science.gov (United States)

Through an in-flight calibration experiment at Rogers Dry Lake, California on September 20, 1989, the radiometric and spectral properties of AVIRIS were determined. In-flight spectral channel positions and the spectral response function in 10 regions of the AVIRIS spectral range, taking in all four spectrometers, are shown to agree closely with the corresponding parameters measured in the laboratory. The intraflight stability for the Rogers Dry Lake calibration site is better than 2 percent with the exception of the strong atmospheric water absorptions where the measured radiance is close to zero. This experiment has provided both direct generation of an in-flight spectral and radiometric calibration and validation of the laboratory calibration at the reported level accuracy.

Green, Robert O.; Conel, James E.; Margolis, Jack S.; Carrere, Veronique; Bruegge, Carol J.; Rast, Michael; Hoover, Gordon

1990-01-01

137

Retrieval interval mapping, a tool to optimize the spectral retrieval range in differential optical absorption spectroscopy  

Directory of Open Access Journals (Sweden)

Full Text Available Remote sensing via differential optical absorption spectroscopy (DOAS has become a standard technique to identify and quantify trace gases in the atmosphere. The technique is applied in a variety of configurations, commonly classified into active and passive instruments using artificial and natural light sources, respectively. Platforms range from ground based to satellite instruments and trace-gases are studied in all kinds of different environments. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the parameters for each specific case and particular trace gas of interest. This becomes especially important when measuring close to the detection limit.

A well chosen evaluation wavelength range is crucial to the DOAS technique. It should encompass strong absorption bands of the trace gas of interest in order to maximize the sensitivity of the retrieval, while at the same time minimizing absorption structures of other trace gases and thus potential interferences. Also, instrumental limitations and wavelength depending sources of errors (e.g. insufficient corrections for the Ring effect and cross correlations between trace gas cross sections need to be taken into account. Most often, not all of these requirements can be fulfilled simultaneously and a compromise needs to be found depending on the conditions at hand.

Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach to find the optimal retrieval wavelength range and qualitative assessment is missing. Here we present a novel tool to determine the optimal evaluation wavelength range. It is based on mapping retrieved values in the retrieval wavelength space and thus visualize the consequence of different choices of retrieval spectral ranges, e.g. caused by slightly erroneous absorption cross sections, cross correlations and instrumental features.

The technique is demonstrated using the examples of a theoretical study of BrO retrievals for stratospheric BrO measurements and for BrO measurements in volcanic plumes. However, due to the general nature of the tool, it is applicable to any type (active or passive of DOAS retrieval.

L. Vogel

2012-06-01

138

Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation dynamics and saturation behavior  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the results of pump-probe experiments on multilayer graphene samples performed in a wide spectral range, namely from the near infrared (photon energy 1.5 eV) to the terahertz (photon energy 8 meV) spectral range. In the near infrared, exciting carriers and probing at higher photon energies provides direct evidence for a hot carrier distribution. Furthermore, spectroscopic signatures of the highly doped graphene layers at the interface to SiC are observed in the near-infrared range....

Winnerl, S.; Goettfert, F.; Mittendorff, M.; Schneider, H.; Helm, M.; Winzer, T.; Malic, E.; Knorr, A.; Orlita, M.; Potemski, M.; Sprinkle, M.; Berger, C.; Heer, W. A.

2013-01-01

139

Characterization of spectral hole depth in Tm3+:YAG within the cryogenic temperature range  

International Nuclear Information System (INIS)

In this paper, spectral hole depth dependence on temperature below 10 K in Tm3+:YAG crystal is investigated in detail. A novel model is proposed to analyze the temperature dependence on the spectral hole. By using the proposed model, we theoretically deduce the temperature dependence of spectral hole depth. The results are compared with experimental results and they are in good agreement. According to the theoretic results, the optimum temperature in experiment can be found

2013-06-01

140

Optically visible post-AGB/RGB stars and young stellar objects in the Small Magellanic Cloud: candidate selection, spectral energy distributions and spectroscopic examination  

CERN Document Server

We have carried out a search for optically visible post-AGB candidates in the Small Magellanic Cloud (SMC). We used mid-IR observations from the Spitzer Space Telescope to select optically visible candidates with a mid-IR excess. We obtained low-resolution optical spectra for 801 candidates. After removing contaminants and poor quality spectra, the final sample comprised of 63 post-AGB/RGB candidates of A - F spectral type. Using the spectra, we estimated the stellar parameters: effective temperature, surface gravity and [Fe/H]. We also estimated the reddening and deduced the luminosity using the stellar parameters combined with photometry. Based on a luminosity criterion, 42 of these 63 sources were classified as post-RGB candidates and the remaining as post-AGB candidates. From the spectral energy distributions we found that 6 of the 63 post-AGB/RGB candidates have a circumstellar shell suggesting that they are single stars, while 27 of them have a surrounding disc, suggesting that they are binaries. For th...

Kamath, D; Van Winckel, H

2014-01-01

 
 
 
 
141

Spectral conditions for strong local nondeterminism and exact Hausdorff measure of ranges of Gaussian random fields  

CERN Document Server

Let $X= \\{X(t), t \\in \\R^N\\}$ be a Gaussian random field with values in $\\R^d$ defined by \\[ X(t) = \\big(X_1(t),..., X_d(t)\\big),\\qquad t \\in \\R^N, \\] where $X_1, ..., X_d$ are independent copies of a real-valued, centered, anisotropic Gaussian random field $X_0$ which has stationary increments and the property of strong local nondeterminism. In this paper we determine the exact Hausdorff measure function for the range $X([0, 1]^N)$. We also provide a sufficient condition for a Gaussian random field with stationary increments to be strongly locally nondeterministic. This condition is given in terms of the spectral measures of the Gaussian random fields which may contain either an absolutely continuous or discrete part. This result strengthens and extends significantly the related theorems of Berman (1973, 1988), Pitt (1978) and Xiao (2007, 2009), and will have wider applicability beyond the scope of the present paper.

Luan, Nana

2011-01-01

142

PHENIX: a pseudo-spectral model of long-range atmospheric transport  

Energy Technology Data Exchange (ETDEWEB)

A code is described which uses a pseudo-spectral approach in calculating long-range transport and diffusion of atmospheric material. The code has been designed to handle transport from a number of sources over distances of hundreds to thousands of kilometers. It consequently assumes uniform vertical mixing and is thus a two-dimensional code. The running time for the code is independent of the number of emitting sources. Grid resolution is the determining factor in the code's running time. The current version is designed to handle a horizontal grid of up to 16 x 16; however, it can be easily modified to handle a larger grid. Because it employs a mixed radix fast Fourier transform technique, the grid dimensions are not restricted to being powers of 2. A precursor and successor pollutant pair can be handled by the code which accounts for ground deposition rates of both species, decay rate of the first species and generation and decay rates of the second species. Readily available upper-air wind data are used to generate wind fields; however, the code is structured such that an alternate wind field generator may be employed easily. The code yields output in the form of average ground level concentrations of the precursor and the successor pollutants as well as the total ground deposition pattern for each pollutant.

Murphy, B.D.

1981-07-01

143

Measuring the Range of Visibility in Dark Diurnal Time by Backwards Diffusion (Izmerenie Dalnosti Vidimosti V Temnoe Vremya Sutok Po Rasseyaniyu Nazad).  

Science.gov (United States)

Field tests have now been made of the NUOR, a nephelometric apparatus based on the backscattering principle, for determining the visibility range at night by the recording of scattering at an angle close to 180 degrees. The theory of the apparatus has bee...

M. A. Golberg

1967-01-01

144

Assessing the chronology of bedrock landslides in the Oregon Coastal Range using visible near-infrared spectroscopy  

Science.gov (United States)

Obtaining accurate chronological data for landslides is critical to understanding their causes as well as their dynamics. The ability to easily and inexpensively date various parts of a landslide can provide insight not only into the 'When' of landslides but also on the 'How' and 'Why' as well. In this study, we apply visible near-infrared (VisNIR) spectroscopy as a means to date landslide soils in a setting with uniform climate and bedrock lithology. In our Oregon Coast Range site, as sandstone-derived soils weather over time, pedogenic hematite accumulates and alters the color of the soil at a quantifiable and discernable rate. This rate having already been established through a soil chronosequence study, we can use the redness of a soil as a proxy for soil age. This is a potentially economical dating method as it does not rely on expensive radioisotopes and requires only a small amount of sample to process. We collected 39 B-horizon soil samples from 7 different slides and used VisNIR spectroscopy to identify the soil residence time of the landslides. The majority of the samples possessed ages between 75,000 and 150,000 years of age, though several slides registered ages over 200,000 years. The average percent error associated with the landslide ages was ~30-35%, although this value was lower for younger slides (200,000 years). Younger slides were more homogenous in age while older slides exhibited more variability. Additionally, there was lower variability in auger-collected samples when compared to samples collected from road-cuts. Our results suggest that VisNIR spectroscopy may prove a more useful dating method on younger, less disturbed landslides but fail to truly capture the age of older, more complicated slides due to its reliance on a specific pedogentic model for hematite weathering as well as the increased risk for complex slide history. This method could be useful in a regional characterization of landslide chronology for similar biomes and provide scientists with a currently lacking catalogue of ancient landslide ages. Such a catalogue could provide significant insight into the mechanisms and potential triggers of bedrock landslides. Landslide ages and geospatial distribution of the four largest slides sampled in the course of this study. There was significant local variability in slide ages, especially in older, redder slides like Vaughn and Wolf Creek.

Mathabane, N.; Cerovski-Darriau, C.; Sweeney, K. E.; Roering, J. J.

2013-12-01

145

Design and development of an injection-molded demultiplexer for optical communication systems in the visible range.  

Science.gov (United States)

Optical simulation software based on the ray-tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. For short distance communications, polymer optical fibers (POFs) are gradually gaining importance. This kind of fiber offers a larger core diameter, e.g., the step index POF features a core diameter of 980 ?m. Consequently, POFs have a large number of modes (>3 million modes) in the visible range, and ray tracing could be used to simulate the propagation of light. This simulation method is applicable not only for the fiber itself but also for the key components of a complete POF network, e.g., couplers or other key elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimizing the insertion loss (IL). The basis of the presented key element is a WDM device using a Rowland spectrometer setup. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic setup to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. However, designing the elements with regard to injection molding leads to some inherent challenges. The microstructure of an optical grating and the thick-walled 3D molded parts both result in high demands on the injection molding process. This also requires complex machining of the molding tool. Therefore, different experiments are done to optimize the process parameter, find the best molding material, and find a suitable machining method for the molding tool. The paper will describe the development of the demultiplexer by means of ray-tracing simulations step by step. Also, the process steps and the realized solutions for the injection molding are described. PMID:23842150

Höll, S; Haupt, M; Fischer, U H P

2013-06-20

146

Directional visible light scattering by silicon nanoparticles  

CERN Document Server

Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique scattering properties arise due to simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Directivity of the far-field radiation pattern can be controlled by changing light wavelength and the nanoparticle size. Forward-to-backward scattering ratio above 6 can be experimentally obtained at visible wavelengths. These unique properties of silicon nanoparticles make them promising for design of novel low-loss visible- and telecom-range nanoantenna devices.

Fu, Yuan Hsing; Miroshnichenko, Andrey E; Yu, Ye Feng; Lukiyanchuk, Boris

2012-01-01

147

Photoinduced catalytic adsorption of model contaminants on Bi/Cu pillared montmorillonite in the visible light range  

Science.gov (United States)

Montmorillonite K10 clay was pillared with BiCl3 and Cu(NO3)2 to extend its applicability as catalytic adsorbent to degrade aqueous solution of anionic azo-dye Methyl Orange (MO) in the presence of visible light irradiation. The preparation of Bi/Cu-montmorillonite utilized benig...

148

Spectral parameters and visible fluorescence of Sm3+ in alkali-barium-bismuth-tellurite glass with high refractive index  

International Nuclear Information System (INIS)

Sm3+-doped alkali-barium-bismuth-tellurite (LKBBT) glass with high refractive index has been fabricated and characterized optically. The refractive index, density, optical absorption, IR transmittance, Judd-Ofelt parameters and spontaneous transition probabilities have been measured, calculated and analyzed. In the LKBBT glass, Sm3+ ions emit intense reddish-orange lights under the excitation of long-wave UV and blue lights. Absorption and excitation spectra indicate that commercial UV and blue laser diodes, blue and bluish-green LEDs and Ar+ optical laser are powerful excitation sources for Sm3+ visible fluorescence in the glass with high optical refractive index

1160-01-00

149

Tunable Photoluminescence of CdTe Nanocrystals over Wide Spectral Range via Microwave-assisted Surface Modification  

Science.gov (United States)

An easy and fast microwave-assisted method of tuning the photoluminescence properties of CdTe nanocrystals in aqueous phase is presented. The photoluminescence could be tuned covering almost the whole visual spectral range (537-680 nm), and even partially extending to the near-infrared spectral range. The effect is probably related to the formation of core/shell structure and complex nano-assemblies. These results provide a promising means of tuning the photoluminescence of CdTe nanocrystals, leading to potential applications in biomedical labeling, solar cells, lasers, and other fields.

Liu, Bin; Li, Jun; Li, Jing-hong

2007-08-01

150

Spectral synthesis provides 2-D videos on a 1-D screen with 360{\\deg}-visibility and mirror-immunity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spatial-light-modulator (SLM)-based tunable sources have complex setups. A simpler setup, comprising an SLM-projector and a dispersive element, synthesizes light as effectively, based on a Superposition of Newtonian Spectra (SNS). As a generalization of SNS, two-dimensional (2-D) grayscale videos are spectrally encoded on a one-dimensional (1-D), translucent screen, and viewed through another dispersive element. This Projected-Image Circumlineascopy (PICS) produces semitrans...

Grusche, Sascha

2014-01-01

151

Single-shot, high-dynamic-range measurement of sub-15 fs pulses by self-referenced spectral interferometry.  

Science.gov (United States)

We explore theoretically and numerically the temporal contrast limitation of a self-referenced spectral interferometry measurement. An experimental confirmation is given by characterization and fine compression of hollow-core fiber generated sub-15 fs pulses, yielding an accurately measured coherent contrast of 50 dB on a ±400 fs time range. PMID:21082020

Moulet, A; Grabielle, S; Cornaggia, C; Forget, N; Oksenhendler, T

2010-11-15

152

Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter.  

Science.gov (United States)

We present a full range handheld probe type spectral domain optical coherence tomography (SD-OCT) method. Here, the sample arm is composed of a tilted fiber-optic cantilever scanner; thus, the phase shift concurrently occurs while sample scanning. With the phase shift, we could achieve a full range complex-conjugate-free OCT image with no additional phase shifters in the reference arm. To realize this technique, a magnetically actuated probe was adopted. Full range SD-OCT images of a pearl, human fingernail, and human tooth were subsequently obtained using this suggested probe. The scanning range and acquisition speed were 3 mm and 20 frames/s, respectively. PMID:22859100

Min, Eun Jung; Shin, Jun Geun; Lee, Jae Hwi; Yasuno, Yoshiaki; Lee, Byeong Ha

2012-08-01

153

Effects of short-range order on the spectral density function for a one-dimensional amorphous solid  

International Nuclear Information System (INIS)

The spectral density A (Q, E) is calculated exactly for a one-dimensional model of an amorphous solid. The model contains an adjustable short-range order parameter ?, and A (Q, E) is calculated for serveral values of ?. The harmonic-oscillator Hamiltonian appropriate to lattice vibrations and a tight-binding Hamiltonian describing in a simplified way either electrons or spin waves are studied for nearest-neighbor interactions. The calculated spectral densities are compared with the recent neutron-scattering measurements of Mook, Wakabayashi, and Pan

1977-06-15

154

Spectral synthesis provides 2-D videos on a 1-D screen with 360{\\deg}-visibility and mirror-immunity  

CERN Multimedia

Spatial-light-modulator (SLM)-based tunable sources have complex setups. A simpler setup, comprising an SLM-projector and a dispersive element, synthesizes light as effectively, based on a Superposition of Newtonian Spectra (SNS). As a generalization of SNS, two-dimensional (2-D) grayscale videos are spectrally encoded on a one-dimensional (1-D), translucent screen, and viewed through another dispersive element. This Projected-Image Circumlineascopy (PICS) produces semitransparent, rainbow-coloured, virtual 2-D videos that face every viewer anywhere around the 1-D screen. They are invariant under reflection of the 1-D screen in mirrors parallel to it. SNS bandwidth and PICS image geometry are calculated using geometric optics and Dispersion Diagrams.

Grusche, Sascha

2014-01-01

155

Multiline possibility of Nd:YAlO3 laser in spectral range 1.3-1.5 µm  

Science.gov (United States)

The goal of our research was investigation of diode pumped Nd:YAlO3 (Nd:YAP) laser tuning possibility in spectral range of general interest 1.3 - 1.5 ?m. Laser radiation in this region is very required for many applications in medicine, atmospheric physics, and spectroscopy due to high absorption of this radiation in liquid water and water vapors. We use 1.0 at. % doped Nd:YAP active medium ?5 x 8 mm in dimensions. As a pumping source, a fibre-coupled 808 nm laserdiode was utilized. Two particular Nd:YAP laser resonators (one for 1.3 ?m spectral region and the second one for 1.4 ?m spectral range) consisted of a flat pump mirror and a curved output coupler were designed and constructed. The laser line selection was realized by a single 1.5 mm thick quartz plate placed at the Brewster angle between the output coupler and laser active medium. Six single emission lines were reached within the desired spectral range (1340 nm, 1341 nm, 1342 nm, 1403 nm, 1408 nm, 1433 nm). Moreover, it was possible to realize the laser system generating in dual frequency regime for some line combination. The respective output laser characteristics in terms of output power, beam spatial structure, and temporal profile were also recorded.

N?mec, Michal; Fibrich, Martin; Šulc, Jan; Hambálek, Tomá?; Jelínková, Helena

2014-02-01

156

Spatially resolved diffuse reflectance in the visible and near-infrared wavelength range for non-destructive quality assessment of 'Braeburn' apples  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spectroscopic measurements in the visible and near infrared wavelength range have achieved success in non-destructive assessment of apple quality attributes contributed by chemical components inside the fruit such as sweetness. Nevertheless, the evaluation of quality attributes related to texture of the fruit (e.g. firmness) still remains a challenge. One of the proposed solutions is to acquire and utilize separately scattering and absorption information from spectroscopic readings for qualit...

2014-01-01

157

High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory  

International Nuclear Information System (INIS)

State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few ?W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples

1998-05-01

158

High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory.  

Science.gov (United States)

State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few micro W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500 eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples. PMID:15263679

Scholze, F; Henneken, H; Kuschnerus, P; Rabus, H; Richter, M; Ulm, G

1998-05-01

159

High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory  

Energy Technology Data Exchange (ETDEWEB)

State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few {mu}W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples. 14 refs.

Scholze, F.; Henneken, H.; Kuschnerus, P.; Rabus, H.; Richter, M.; Ulm, G. [Physikalisch-Technische Bundesanstalt, Berlin (Germany)

1998-05-01

160

THE SECOND STAGE OF FERMI at ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE  

International Nuclear Information System (INIS)

The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.

2009-08-23

 
 
 
 
161

THE SECOND STAGE OF FERMI@ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE  

Energy Technology Data Exchange (ETDEWEB)

The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.

Allaria, E.; DeNinno, G.; Fawley, W. M.

2009-08-14

162

Cascaded Nondegenerate Four-Wave Mixing Technique for High-Power Single-Cycle Pulse Synthesis in the Visible and Ultraviolet Ranges  

CERN Document Server

We present a new technique to synthesize high-power single-cycle pulses in the visible and ultraviolet ranges by coherent superposition of a multiband octave-spanning spectrum obtained by highly-nondegenerate cascaded four-wave mixing of femtosecond pulses in bulk isotropic nonresonant media. The generation of coherent spectra spanning over two octaves in bandwidth is experimentally demonstrated using a thin fused silica slide. Full characterization of the intervening multicolored fields using frequency-resolved optical gating, where multiple cascaded orders have been measured simultaneously for the first time, supports the possibility of direct synthesis of near-single-cycle 2.2 fs visible-UV pulses without recurring to complex amplitude or phase control, which should enable many applications in science and technology.

Weigand, Rosa; Crespo, Helder M

2009-01-01

163

Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As a part of the IGAC (International Global Atmospheric Chemistry) Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E) in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC) ratio showed clear monthly...

Jung, J.; Kim, Y. J.; Lee, K. Y.; -cayetano, M. G.; Batmunkh, T.; -h Koo, J.; Kim, J.

2010-01-01

164

Infrared Spectroscopy of Gas-phase Polycyclic Aromatic Hydrocarbon Cations in the 10-50 ?m Spectral Range  

Science.gov (United States)

The gas-phase infrared spectra of four polycyclic aromatic hydrocarbon (PAH) cations have been recorded in the 10-50 ?m (or 1000-200 cm-1) spectral range via IR multiple photon dissociation (IRMPD) spectroscopy. Ionized PAHs are formed by UV laser ionization in an effusive beam and subsequently irradiated with a single pulse of narrowband tunable infrared light produced by the Free-Electron Laser for IntraCavity Experiments FELICE. The ion population is then analyzed in a time-of-flight mass spectrometer. Upon resonance, dissociation is induced so that IR spectra can be recorded by monitoring either the depleted parent ion intensity or the appearance of fragment ions as a function of the wavelength. The intracavity IR fluence enables the recording of IRMPD spectra of strongly bound PAH cations in the hitherto inaccessible far-IR spectral range. Experimental spectra are presented for the radical cations of anthracene, tetracene, pentacene, and coronene. Spectra calculated with density functional theory at the B3LYP/6-311g(2df,2pd) level reproduce IR frequencies reasonably accurately in this spectral range when a uniform scaling factor of 0.94 over the complete 10-50 ?m spectral range is employed. We show that even vibrational modes with a calculated IR intensity lower than 1 km mol-1 can be observed. For the catacondensed PAH cations we find CH out-of-plane bending vibrations involving four adjacent CH groups within a few wavenumbers of 733 cm-1, closely matching the 13.6 ?m UIR band. For the larger systems, pentacene and coronene, we observe a continuous structureless background absorption above 400 cm-1 which is attributed to the high density of IR dipole allowed combination modes for these systems.

Bakker, Joost M.; Redlich, Britta; van der Meer, Alexander F. G.; Oomens, Jos

2011-11-01

165

INFRARED SPECTROSCOPY OF GAS-PHASE POLYCYCLIC AROMATIC HYDROCARBON CATIONS IN THE 10–50 ?m SPECTRAL RANGE  

International Nuclear Information System (INIS)

The gas-phase infrared spectra of four polycyclic aromatic hydrocarbon (PAH) cations have been recorded in the 10-50 ?m (or 1000-200 cm–1) spectral range via IR multiple photon dissociation (IRMPD) spectroscopy. Ionized PAHs are formed by UV laser ionization in an effusive beam and subsequently irradiated with a single pulse of narrowband tunable infrared light produced by the Free-Electron Laser for IntraCavity Experiments FELICE. The ion population is then analyzed in a time-of-flight mass spectrometer. Upon resonance, dissociation is induced so that IR spectra can be recorded by monitoring either the depleted parent ion intensity or the appearance of fragment ions as a function of the wavelength. The intracavity IR fluence enables the recording of IRMPD spectra of strongly bound PAH cations in the hitherto inaccessible far-IR spectral range. Experimental spectra are presented for the radical cations of anthracene, tetracene, pentacene, and coronene. Spectra calculated with density functional theory at the B3LYP/6-311g(2df,2pd) level reproduce IR frequencies reasonably accurately in this spectral range when a uniform scaling factor of 0.94 over the complete 10-50 ?m spectral range is employed. We show that even vibrational modes with a calculated IR intensity lower than 1 km mol–1 can be observed. For the catacondensed PAH cations we find CH out-of-plane bending vibrations involving four adjacent CH groups within a few wavenumbers of 733 cm–1, closely matching the 13.6 ?m UIR band. For the larger systems, pentacene and coronene, we observe a continuous structureless background absorption above 400 cm–1 which is attributed to the high density of IR dipole allowed combination modes for these systems.

2011-11-10

166

Broadband superluminescent diodes and semiconductor optical amplifiers for the spectral range 750 - 800 nm  

International Nuclear Information System (INIS)

We have studied superluminescent diodes (SLDs) and semiconductor optical amplifiers (SOAs) based on an (AlxGa1-x)As/GaAs single quantum well structure with an Al content x ? 0.1 in a 10-nm-thick active layer. Depending on the length of the active channel, the single-mode fibre coupled cw output power of the SLDs is 1 to 30 mW at a spectral width of about 50 nm. The width of the optical gain band in the active channel exceeds 40 nm. Preliminary operating life tests have demonstrated that the devices are sufficiently reliable. (lasers)

2011-08-31

167

Nonlinear spectral imaging of biological tissues  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The work presented in this thesis demonstrates live high resolution 3D imaging of tissue in its native state and environment. The nonlinear interaction between focussed femtosecond light pulses and the biological tissue results in the emission of natural autofluorescence and second-harmonic signal. Because biological intrinsic emission is generally very weak and extends from the ultraviolet to the visible spectral range, a broad-spectral range and high sensitivity 3D spectral imaging system i...

Palero, J. A.

2007-01-01

168

A wide spectral range single-photon avalanche diode fabricated in an advanced 180 nm CMOS technology:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a single-photon avalanche diode (SPAD) with a wide spectral range fabricated in an advanced 180 nm CMOS process. The realized SPAD achieves 20 % photon detection probability (PDP) for wavelengths ranging from 440 nm to 820 nm at an excess bias of 4V, with 30 % PDP at wavelengths from 520 nm to 720 nm. Dark count rates (DCR) are at most 5 kHz, which is 30 Hz/?m2, at an excess bias of 4V when we measure 10 ?m diameter active area structure. Afterpulsing probability, timing jitter, ...

Mandai, S.; Fishburn, M. W.; Maruyama, Y.; Charbon, E.

2012-01-01

169

Velocity Dealiased Spectral Estimators of Range Migrating Targets using a Single Low-PRF Wideband Waveform  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Wideband radars are promising systems that may provide numerous advantages, like simultaneous detection of slow and fast moving targets, high range-velocity resolution classification, and electronic countermeasures. Unfortunately, classical processing algorithms are challenged by the range-migration phenomenon that occurs then for fast moving targets. We propose a new approach where the range migration is used rather as an asset to retrieve information about target velocitiesand, subsequently...

Deudon, Francois; Bidon, Ste?phanie; Besson, Olivier; Tourneret, Jean-yves

2013-01-01

170

Improving prediction selectivity for on-line near-infrared monitoring of components in etchant solution by spectral range optimization  

Energy Technology Data Exchange (ETDEWEB)

The components (H{sub 3}PO{sub 4}, HNO{sub 3}, CH{sub 3}COOH and water) in an etchant solution have been accurately measured in an on-line manner using near-infrared (NIR) spectroscopy by directly illuminating NIR radiation through a Teflon line. In particular, the spectral features according to the change of H{sub 3}PO{sub 4} or HNO{sub 3} concentrations were not mainly from NIR absorption themselves, but from the perturbation (or displacement) of water bands; therefore, the resulting spectral variations were quite similar to each other. Consequently partial least squares (PLS) prediction selectivity among the components should be the most critical issue for continuous on-line compositional monitoring by NIR spectroscopy. To improve selectivity of the calibration model, we have optimized the calibration models by finding selective spectral ranges with the use of moving window PLS. Using the optimized PLS models for each component, the resulting prediction accuracies were substantially improved. Furthermore, on-line prediction selectivity was evaluated by spiking individual pure components step by step and examining the resulting prediction trends. When optimized PLS models were used, each concentration was selectively and sensitively varied at each spike; meanwhile, when whole or non-optimized ranges were used for PLS, the prediction selectivity was greatly degraded. This study verifies that the selection of an optimal spectral range for PLS is the most important factor to make Teflon-based NIR measurements successful for on-line and real-time monitoring of etching solutions.

Namkung, Hankyu; Lee, Youngbok [Department of Chemistry, College of Natural Sciences, Hanyang University, Haengdang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of); Chung, Hoeil [Department of Chemistry, College of Natural Sciences, Hanyang University, Haengdang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of)], E-mail: hoeil@hanyang.ac.kr

2008-01-07

171

Full range complex spectral domain optical coherence tomography for volumetric imaging at 47?000 A-scans per second  

International Nuclear Information System (INIS)

In this paper we demonstrate a high speed spectral domain optical coherence tomography (SDOCT) system capable of achieving full range complex imaging at a line scan rate of 47 kHz. By applying a beam-offset method, a constant modulation frequency is introduced into each B-scan that enables reconstruction of the full range complex SDOCT images of in vivo tissue samples. To make use of the full capacity of the detection camera used in the system, system control software is developed that streams the raw spectral fringe data directly into the computer memory. In order to assess performance of the high speed full range SDOCT system for imaging biological specimen, we present results imaged from the cuticle of the fingernail of a human volunteer in vivo and from chick embryos ex vivo. We also show the high sensitivity advantages of full range complex imaging as compared to conventional SDOCT. To the best of our knowledge, an imaging rate of 47?000 A-scans per second is the highest imaging rate that has ever been reported for full range complex imaging. Notwithstanding, the method reported here has no limitations on the imaging speed and thus offers a useful tool to achieve volumetric imaging of living samples where the high sensitivity region around zero delay line in the system can be utilized for imaging

2010-08-01

172

High dynamic range measurement of spectral responsivity and linearity of a radiation thermometer using a super-continuum laser and LEDs  

Science.gov (United States)

To realize the temperature scale above the freezing point of silver according to the definition of ITS-90, the dynamic range of the spectral responsivity is one of the most important factors which limit its uncertainty. When the residual spectral response at both side bands of a spectral band is not negligible, a significant uncertainty can be caused by a low dynamic range of the spectral responsivity measurement. In general, incandescent lamps are used to measure the spectral responsivity and the linearity. The dynamic range of the spectral responsivity measurement is often limited by a trade-off with the desired spectral resolution, which is less than 6 decades. Nonlinearity is another limiting fact of uncertainties of the temperature scale. Tungsten lamps have disadvantage in the nonlinearity measurements in terms of adjustability of radiance level and spectral selectivity. We report spectral responsivity measurements of which the measurable dynamic range is enhanced 50 times after replacing a QTH lamp with a super continuum laser. We also present a spectrally selected linearity measurement over a wide dynamic range using high-brightness light emitting diode arrays to observe a slight saturation of linearity.

Yoo, Y. S.; Lee, D. H.; Park, C. W.; Park, S. N.

2013-09-01

173

High dynamic range measurement of spectral responsivity and linearity of a radiation thermometer using a super-continuum laser and LEDs  

International Nuclear Information System (INIS)

To realize the temperature scale above the freezing point of silver according to the definition of ITS-90, the dynamic range of the spectral responsivity is one of the most important factors which limit its uncertainty. When the residual spectral response at both side bands of a spectral band is not negligible, a significant uncertainty can be caused by a low dynamic range of the spectral responsivity measurement. In general, incandescent lamps are used to measure the spectral responsivity and the linearity. The dynamic range of the spectral responsivity measurement is often limited by a trade-off with the desired spectral resolution, which is less than 6 decades. Nonlinearity is another limiting fact of uncertainties of the temperature scale. Tungsten lamps have disadvantage in the nonlinearity measurements in terms of adjustability of radiance level and spectral selectivity. We report spectral responsivity measurements of which the measurable dynamic range is enhanced 50 times after replacing a QTH lamp with a super continuum laser. We also present a spectrally selected linearity measurement over a wide dynamic range using high-brightness light emitting diode arrays to observe a slight saturation of linearity

2013-09-11

174

Fourier transform measurements of H218O and HD18O in the spectral range 1000-2300 cm-1  

Science.gov (United States)

The spectra of water vapor enriched by 18O were recorded in the 1000-2300 cm-1 spectral range, which corresponds to the spectral region studied by IASI instrument (Infrared Atmospheric Sounding Spectrometer) instrument. The spectra were recorded by a step by step Fourier Transform Spectrometer (FTS) at room temperature with absorption path lengths up to 36 m. Positions, intensities and self broadening coefficients of about 1800 lines of H218O and 900 of HD18O were analyzed and all the transitions were assigned. This paper focuses on lines intensities and comparisons with data from literature are presented. An average difference of 10% with HITRAN2008 database H218O line intensities is found with a maximum discrepancy of about 25% for the ?1-?2 band.

Oudot, C.; Régalia, L.; Mikhailenko, S.; Thomas, X.; Von Der Heyden, P.; Décatoire, D.

2012-07-01

175

Calculation of spectral shifts in UV-visible region and photoresponsive behaviour of fluorinated liquid crystals: Effect of solvent and substituent  

Energy Technology Data Exchange (ETDEWEB)

The photoresponsive behaviour of fluorinated liquid crystals p-phenylene-4-methoxy benzoate-4-trifluoromethylbenzoate (FLUORO1), and 4-propyloxyphenyl-4-(4-trifluoromethylbenzoyloxy) benzoate (FLUORO2) has been systematically investigated using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate/analyze the spectral shifts, and absorbance measurements in UV-visible region of the systems. The electronic transitions, absorption wavelength, HOMO (highest occupied molecular orbital), and LUMO (lowest unoccupied molecular orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters have also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Highlights: Black-Right-Pointing-Pointer The strongest bands of FLUORO molecules can be assigned as {pi} {yields} {pi}{sup Asterisk-Operator} transitions. Black-Right-Pointing-Pointer A small red-shift indicates a weak exciton coupling of chromophores. Black-Right-Pointing-Pointer No n {yields} {pi}{sup Asterisk-Operator} transition occurs due to the rigidity of the ring system of the molecules. Black-Right-Pointing-Pointer The HOMO, LUMO, and E{sub g} values have been found to be independent of solvent effect.

Lakshmi Praveen, P. [Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada 520 008, A.P. (India); Ojha, Durga P., E-mail: durga_ojha@hotmail.com [Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada 520 008, A.P. (India)

2012-08-15

176

Photoionization and electron radical recombination dynamics in photoactive yellow protein investigated by ultrafast spectroscopy in the visible and near-infrared spectral region.  

Science.gov (United States)

Photoinduced ionization of the chromophore inside photoactive yellow protein (PYP) was investigated by ultrafast spectroscopy in the visible and near-infrared spectral regions. An absorption band that extended from around 550 to 850 nm was observed and ascribed to solvated electrons, ejected from the p-hydroxycinnamic acid anion chromophore upon the absorption of two 400 nm photons. Global kinetic analysis showed that the solvated electron absorption decayed in two stages: a shorter phase of around 10 ps and a longer phase of more than 3 ns. From a simulation based on a diffusion model we conclude that the diffusion rate of the electron is about 0.8 Å(2)/ps in wild type PYP, and that the electron is ejected to a short distance of only several angstroms away from the chromophore. The chromophore-protein pocket appears to provide a water-similar local environment for the electron. Because mutations at different places around the chromophore have different effect on the electron recombination dynamics, we suggest that solvated electrons could provide a new method to investigate the local dielectric environment inside PYP and thus help to understand the role of the protein in the photoisomerization process. PMID:23477674

Zhu, Jingyi; Paparelli, Laura; Hospes, Marijke; Arents, Jos; Kennis, John T M; van Stokkum, Ivo H M; Hellingwerf, Klaas J; Groot, Marie Louise

2013-09-26

177

Calculation of spectral shifts in UV–visible region and photoresponsive behaviour of fluorinated liquid crystals: Effect of solvent and substituent  

International Nuclear Information System (INIS)

The photoresponsive behaviour of fluorinated liquid crystals p-phenylene-4-methoxy benzoate-4-trifluoromethylbenzoate (FLUORO1), and 4-propyloxyphenyl-4-(4-trifluoromethylbenzoyloxy) benzoate (FLUORO2) has been systematically investigated using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate/analyze the spectral shifts, and absorbance measurements in UV–visible region of the systems. The electronic transitions, absorption wavelength, HOMO (highest occupied molecular orbital), and LUMO (lowest unoccupied molecular orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters have also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Highlights: ? The strongest bands of FLUORO molecules can be assigned as ? ? ?? transitions. ? A small red-shift indicates a weak exciton coupling of chromophores. ? No n ? ?? transition occurs due to the rigidity of the ring system of the molecules. ? The HOMO, LUMO, and Eg values have been found to be independent of solvent effect.

2012-08-15

178

Simultaneous resolution of spectral and temporal properties of UV and visible fluorescence using single-photon counting with a position-sensitive detector  

International Nuclear Information System (INIS)

A new fluorescence spectrometer has been assembled at the U9B beamline of the National Synchrotron Light Source to allow simultaneous multiwavelength and time-resolved fluorescence detection, as well as spatial imaging of the sample fluorescence. The spectrometer employs monochromatized, tunable UV and visible excitation light from a synchrotron bending magnet and an imaging spectrograph equipped with a single-photon sensitive emission detector. The detector is comprised of microchannel plates in series, with a resistive anode for encoding the position of the photon-derived current. The centroid position of the photon-induced electron cascade is derived in a position analyzer from the four signals measured at the corners of the resistive anode. Spectral information is obtained by dispersing the fluorescence spectrum across one dimension of the detector photocathode. Timing information is obtained by monitoring the voltage divider circuit at the last MCP detector. The signal from the MCP is used as a ''start'' signal to perform a time-correlated single photon counting experiment. The analog signal representing the position, and hence wavelength, is digitized concomitantly with the start/stop time difference and stored in the two-dimensional histogramming memory of a multiparameter analyzer

1995-02-01

179

Mapping wetland species and the impact of oil from the Deep Horizon using the Airborne/Visible Imaging Spectrometer and Multiple Endmember Spectral Mixture Analysis  

Science.gov (United States)

Between April 20, 2010 and July 15, 2010 an estimated 4.4 million barrels of oil leaked from the Maconda well, making the Deep Horizon oil spill the largest in US history. In response to a need to determine the distribution of wetland plant species and quantify their condition prior to, during and after oil reached the shore, the Airborne/Visible Infrared Imaging Spectrometer (AVIRIS) was deployed multiple times in the gulf on high altitude and low altitude airborne platforms. Significant research questions included 1) What is the distribution of key wetland species in the impacted area?; 2) which areas were impacted by oil, when and to what extent?; 3) how much oil must be present to be detected in various cover types? and 4) which wetland species are more sensitive to oil? In an effort to answer some of these questions, we applied Multiple Endmember Spectral Mixture Analysis (MESMA) to AVIRIS data acquired prior to significant impacts in May, 2010 and after oil had reached wetlands in late summer and fall, 2010. Reference polygons for species dominants were located on the images and used to build a spectral library for all dominant wetland species and surface types. This spectral library was augmented by field spectra, acquired using a contact probe for senesced plants materials and beach sands. Spectra of heavily oiled surfaces were identified using the Hydrocarbon Index to identify potential oil endmembers and the Cellulose Absorption Index to discriminate oil from Non-photosynthetic Vegetation (NPV). Wetland species and cover fractions for Green Vegetation (GV), NPV, soils/beaches, oil and water were mapped using MESMA applied to images acquired in the Birds Foot Delta, Chandeleur Islands and Barataria Bay. Species maps, showing dominant species such as Phragmites australis, Spartina alternifolia and S. patens proved to be accurate. OIl was mapped along coastal areas of Barataria Bay, expressed as high oil fractions. However, significant confusion was also observed between oiled vegetation and senesced vegetation, either resulting from oil-induced mortality or natural senescence.

Roberts, D. A.; Beland, M.; Kokaly, R. F.; Couvillion, B.; Ustin, S.; Peterson, S.

2011-12-01

180

Infrared normal spectral emissivity of Ti-6Al-4V alloy in the 500-1150 K temperature range  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer First heating cycle acts as a annealing, relieving the surface stresses. Black-Right-Pointing-Pointer Stress relieving occurs mainly above 900 K. Black-Right-Pointing-Pointer Emissivity decreases between 0.35 and 0.10 in the 2.5-22 {mu}m spectral range. Black-Right-Pointing-Pointer Emissivity increases linearly with temperature, with the same slope for {lambda} > 10 {mu}m. Black-Right-Pointing-Pointer Good agreement between resistivity and emissivity by means of Hagen-Rubens relation. - Abstract: Thermal radiative emissivity is related to the optical and electrical properties of materials, and it is a key parameter required in a large number of industrial applications. In the case of Ti-6Al-4V, spectral emissivity experimental data are not available for the range of temperatures between 400 and 1200 K, where almost all industrial applications take place. The experimental results in this paper show that the normal spectral emissivity decreases with wavelength from a value of about 0.35 at 2.5 {mu}m to about 0.10 at 22 {mu}m. At the same time, the spectral emissivity shows a slight linear increase with temperature between 500 and 1150 K, with approximately the same slope for all wavelengths. Additionally, the influence of the samples thermal history on the emissivity is studied. A strong decrease in the emissivity values appears due to the effect of surface stress relaxation processes. This means that the radiative properties of this alloy strongly depend on the surface stress state. A thermal treatment to relieve the surface stress should be carried out to achieve a steady state of the radiative properties. In addition, a good qualitative agreement is found between the temperature dependence of the electrical resistivity obtained using conventional measurements and the one obtained from the emissivity experimental results by using the Hagen-Rubens equation.

Gonzalez-Fernandez, L. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Industria de Turbo Propulsores, S.A., Planta de Zamudio, Edificio 300, 48170 Zamudio, Bizkaia (Spain); Risueno, E. [CIC Energigune, Parque Tecnologico, Albert Einstein 48, 01510 Minano, Alava, Spain. (Spain); Perez-Saez, R.B., E-mail: raul.perez@ehu.es [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Instituto de Sintesis y Estudio de Materiales, Universidad del Pais Vasco, Apdo. 644,48080 Bilbao, Spain. (Spain); Tello, M.J. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Instituto de Sintesis y Estudio de Materiales, Universidad del Pais Vasco, Apdo. 644,48080 Bilbao, Spain. (Spain)

2012-11-15

 
 
 
 
181

Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008  

Directory of Open Access Journals (Sweden)

Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, ?abs(=babs/EC at 550 nm at the measurement site was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g?1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g?1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP events. Satellite aerosol optical thickness (AOT and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

J. Jung

2010-02-01

182

Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008  

Directory of Open Access Journals (Sweden)

Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, ?abs (=babs/EC at 550 nm was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g?1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g?1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP events. Satellite aerosol optical thickness (AOT and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

J. Jung

2010-06-01

183

Infrared normal spectral emissivity of Ti–6Al–4V alloy in the 500–1150 K temperature range  

International Nuclear Information System (INIS)

Highlights: ? First heating cycle acts as a annealing, relieving the surface stresses. ? Stress relieving occurs mainly above 900 K. ? Emissivity decreases between 0.35 and 0.10 in the 2.5–22 ?m spectral range. ? Emissivity increases linearly with temperature, with the same slope for ? > 10 ?m. ? Good agreement between resistivity and emissivity by means of Hagen–Rubens relation. - Abstract: Thermal radiative emissivity is related to the optical and electrical properties of materials, and it is a key parameter required in a large number of industrial applications. In the case of Ti–6Al–4V, spectral emissivity experimental data are not available for the range of temperatures between 400 and 1200 K, where almost all industrial applications take place. The experimental results in this paper show that the normal spectral emissivity decreases with wavelength from a value of about 0.35 at 2.5 ?m to about 0.10 at 22 ?m. At the same time, the spectral emissivity shows a slight linear increase with temperature between 500 and 1150 K, with approximately the same slope for all wavelengths. Additionally, the influence of the samples thermal history on the emissivity is studied. A strong decrease in the emissivity values appears due to the effect of surface stress relaxation processes. This means that the radiative properties of this alloy strongly depend on the surface stress state. A thermal treatment to relieve the surface stress should be carried out to achieve a steady state of the radiative properties. In addition, a good qualitative agreement is found between the temperature dependence of the electrical resistivity obtained using conventional measurements and the one obtained from the emissivity experimental results by using the Hagen–Rubens equation.

2012-11-15

184

Diode laser spectroscopy in extended wavelength ranges  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Diode laser spectroscopy performed in the ultraviolet, visible and infrared spectral regions is presented. The accessible wavelength range for visible and near-infrared diode lasers is extended by the use of sum- and difference-frequency generation. Sum-frequency generation to the ultraviolet spectral region was employed using a blue and a red diode laser. Mercury spectroscopy was demonstrated with the generated ultraviolet beam. Difference-frequency generation with two near-in...

Gustafsson, Ulf

2000-01-01

185

Operation of linac based FELs in IR- and visible-range at the FELI (Free Electron Laser Research Institute, Inc.)  

International Nuclear Information System (INIS)

Two infrared free electron lasers (FELs) facilities covering the wavelength range of 1-20 ?m are opened for FEL users in this October. We are also challenging 0.3 ?m-FEL oscillations using a 2.68m undulator (?u=4cm) installed at the 160-MeV beam line of the FELI linac with a thermionic gun. A 0.52-?m spontaneous radiation of 0.1W has been observed using a 145-MeV electron beam and the undulator. (author)

1995-10-01

186

New generation of dyes in the 688-860-nm spectral range for laser excitation  

Energy Technology Data Exchange (ETDEWEB)

The generation characteristics of a new class of dyes under laser pumping were investigated. It is shown that these new dyes are more efficient than those used previously in the near-IR range both under ruby-laser (694-nm) pumping and N/sub 2/-laser (337-nm) pumping. The high photostability of these dyes is noted. 9 references.

Stepanov, B.I.; Bychkov, N.N.; Levshin, L.V.; Konstantinov, B.A.; Akimov, A.I.

1988-04-01

187

Flow-radiated noise. Study of the propagative spectral range of the wall pressure field  

Science.gov (United States)

The complete model of the wall pressure field developed here incorporates many experimentally observed and proven partial similarities, as well as hypotheses to offset experimental gaps in certain frequency ranges and wave numbers. Initial comparisons show good agreement with experimental results across a wide range of frequencies and wave numbers. The main advantages of the model are: non-dependent adjustment constants; the explicit dependence of local, boundary layer scales; the explicit formulation of physical scales that control the similarity of frequencies and levels; incorporation of the whole range of frequencies and wave numbers; complete determination of the spectrum and interspectrum; and calculation of the root mean square. The study's acoustical range model explains the asymptotic behavior of the low-frequency spectrum, by separating incompressible and acoustic factors. This can be used to calculate the share of wall pressure fluctuations migrating in the form of a sound wave, thus providing an essential element in the problem of antenna or SONAR dome set noise and radiated noise.

Benarrous, E.

188

Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind  

CERN Document Server

We measure the power and spectral index anisotropy of high speed solar wind turbulence from scales larger than the outer scale down to the ion gyroscale, thus covering the entire inertial range. We show that the power and spectral indices at the outer scale of turbulence are approximately isotropic. The turbulent cascade causes the power anisotropy at smaller scales manifested by anisotropic scalings of the spectrum: close to k^{-5/3} across and k^{-2} along the local magnetic field, consistent with a critically balanced Alfvenic turbulence. By using data at different radial distances from the Sun, we show that the width of the inertial range does not change with heliocentric distance and explain this by calculating the radial dependence of the ratio of the outer scale to the ion gyroscale. At the smallest scales of the inertial range, close to the ion gyroscale, we find an enhancement of power parallel to the magnetic field direction coincident with a decrease in the perpendicular power. This is most likely ...

Wicks, R T; Chen, C H K; Schekochihin, A A

2010-01-01

189

Light absorption in undoped congruent and magnesium-doped lithium niobate crystals in the visible wavelength range  

Science.gov (United States)

Light absorption measurements of nominally undoped congruent lithium niobate crystals (CLN) as well as 5 mol% magnesium-oxide-doped lithium niobate (MgO:LN) crystals were performed in the light wavelength range of 350 to 800 nm. Absorption spectra reveal that—besides iron (Fe) impurities—chromium (Cr) impurities of less than 0.5 wt. ppm concentration contribute significantly to the total optical absorption in the CLN crystals with a maximum of 0.035 cm-1 around 500 nm. The axial distribution of Cr within a CLN boule is examined, revealing that the bottom part of the boule contains less Cr and therefore light absorption is reduced as well. In the case of the MgO:LN crystals, Cr impurities also contribute significantly to the total optical absorption, which is on the order of 0.025 cm-1 for ordinarily polarized light and 0.015 cm-1 for extraordinarily polarized light around 500 nm.

Schwesyg, J. R.; Kajiyama, M. C. C.; Falk, M.; Jundt, D. H.; Buse, K.; Fejer, M. M.

2010-07-01

190

The explanation of the spectral relation of radio range and X-ray range by the effect of random magnetic fields.  

Science.gov (United States)

We calculate numerically the radiation spectrum from relativistic electrons moving in small-scale turbulent magnetic fields, in relevance to the collisionless shocks of high energy celestial objects. The radiation spectrum is characterized by the strength parameter a = ? e B/mc^2 (? is the length of the turbulent field), If a >> ?, synchrotron approximation is valid ( ? is the Lorentz factor of radiating electron). However, for a 1 we can no longer assume the straight electron orbit. For the most interesting case of 1 Lienard-Wiechert potential. We performed calculations for several values of a, with ? = 10, and we obtain various types of spectra ranging between jitter radiation and synchrotron radiation. For a = 7, the spectrum takes a novel shape which had not been noticed before. It is like a synchrotron spectrum in the middle energy region, but in the low energy region it is a broken power law and in the high frequency region an extra power-law component appears beyond the synchrotron cutoff. Therefore, if the spectral break is detected at the radio range and extra component is detected at the X-ray range when someone observe the synchrotron spectra of some high energy celstial object, the feature may be caused by random magnetic fields.

Teraki, Yuto; Takahara, Fumio

2012-07-01

191

Retrieval interval mapping: a tool to visualize the impact of the spectral retrieval range on differential optical absorption spectroscopy evaluations  

Directory of Open Access Journals (Sweden)

Full Text Available Remote sensing via differential optical absorption spectroscopy (DOAS has become a standard technique to identify and quantify trace gases in the atmosphere. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the retrieval parameters for each specific case and particular trace gas of interest. Of these parameters, the retrieval wavelength range is one of the most important ones. Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach for finding the optimal retrieval wavelength range and quantitative assessment is missing. Here we present a novel tool to visualize the effect of different evaluation wavelength ranges. It is based on mapping retrieved column densities in the retrieval wavelength space and thus visualizing the consequences of different choices of spectral retrieval ranges caused by slightly erroneous absorption cross sections, cross correlations and instrumental features. Based on the information gathered, an optimal retrieval wavelength range may be determined systematically.

The technique is demonstrated using examples of a theoretical study of BrO retrievals for stratospheric BrO and BrO measurements in volcanic plumes. However, due to the general nature of the tool, it is applicable to any type of DOAS retrieval (active or passive.

L. Vogel

2013-02-01

192

The relationship between professional operatic soprano voice and high range spectral energy  

Science.gov (United States)

Operatic sopranos need to be audible over an orchestra yet they are not considered to possess a singer's formant. As in other voice types, some singers are more successful than others at being heard and so this work investigated the frequency range of the singer's formant between 2000 and 4000 Hz to consider the question of extra energy in this range. Such energy would give an advantage over an orchestra, so the aims were to ascertain what levels of excess energy there might be and look at any relationship between extra energy levels and performance level. The voices of six operatic sopranos (national and international standard) were recorded performing vowel and song tasks and subsequently analyzed acoustically. Measures taken from vowel data were compared with song task data to assess the consistency of the approaches. Comparisons were also made with regard to two conditions of intended projection (maximal and comfortable), two song tasks (anthem and aria), two recording environments (studio and anechoic room), and between subjects. Ranking the singers from highest energy result to lowest showed the consistency of the results from both vowel and song methods and correlated reasonably well with the performance level of the subjects. The use of formant tuning is considered and examined.

Barnes, Jennifer J.; Davis, Pamela; Oates, Jennifer; Chapman, Janice

2004-07-01

193

Temperature-dependent dielectric function of germanium in the UV-vis spectral range: A first-principles study  

Science.gov (United States)

The study of temperature dependence of thermophysical parameter dielectric function is key to understanding thermal radiative transfer in high-temperature environments. Limited by self-radiation and thermal oxidation, however, it is difficult to directly measure the high-temperature dielectric function of solids with present experimental technologies. In this work, we implement two first-principles methods, the ab initio molecular dynamics (AIMD) and density functional perturbation theory (DFPT), to study the temperature dependence of dielectric function of germanium (Ge) in the UV-vis spectral range in order to provide data of high-temperature dielectric function for radiative transfer study in high-temperature environments. Both the two methods successfully predict the temperature dependence of dielectric function of Ge. Moreover, the good agreement between the calculated results of the AIMD approach and experimental data at 825 K enables us to predict the high-temperature dielectric function of Ge with the AIMD method in the UV-vis spectral range.

Yang, J. Y.; Liu, L. H.; Tan, J. Y.

2014-07-01

194

Visible-range hybrid femtosecond systems based on a XeF(C-A) amplifier: state of the art and prospects  

Energy Technology Data Exchange (ETDEWEB)

Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C-A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF{sub 2} - N{sub 2} subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C - A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C-A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 10{sup 8}. The measured power of an amplified spontaneous emission of the XeF(C-A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 10{sup 12} for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of selfcompression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C-A) amplifier. (extreme light fields and their applications)

Alekseev, S V; Aristov, A I; Grudtsyn, Ya V; Ivanov, N G; Koval' chuk, B M; Losev, B F; Mamaev, S B; Mesyats, Gennadii A; Mikheev, L D; Panchenko, Yu N; Polivin, A V; Stepanov, S G; Ratakhin, N A; Yalovoi, V I; Yastremskii, Arkadii G

2013-03-31

195

Extension of the spectral range of bacteriorhodopsin functional activity by energy transfer from quantum dots  

Science.gov (United States)

Monodispersed semiconductor nanocrystals or quantum dots (QDs) specifically immobilized on the surface of purple membranes (PMs) containing bacteriorhodopsin (bR) can harvest light in the UV to blue region, which cannot be absorbed efficiently by the PMs alone, and transfer the harvested energy to the retinal chromophores of bR via highly efficient Förster resonance energy transfer (FRET). CdTe or CdSe/ZnS QDs with a quantum yield as high as 70% have been used to estimate different parameters characterizing the improvement of the bR biological function caused by nanocrystals. AFM examination has shown that the most FRET-efficient QD-PM hybrid structures are characterized by the highest level of QD ordering; hence, AFM imaging of bR-PM hybrid materials provides the basis for optimization of the assembly design in order to engineer bio-hybrid structures with advanced optical and photovoltaic properties. Oriented bR-containing proteoliposomes tagged with QDs at a QD-to-bR molar ratio of up to 1:5 have been engineered and used to analyze the photoresponse, with the bR proton pumping considerably increased. Finally, the kinetics of the potential/current generation in films of oriented bR containing or not containing QDs have been analyzed. Incorporation of QDs resulted in an increase in the potential/current generation rate and in an almost fourfold increase in the rate of Mform formation. Thus, the improvement of the bR native function by QDs may be caused by two reasons: an extension of the range of utilized light and an increase in the rate of the bR photocycle.

Oleinikov, Vladimir; Bouchonville, Nicolas; Sukhanova, Alyona; Molinari, Michael; Sizova, Svetlana; Mochalov, Konstantin; Chistyakov, Anton; Lukashev, Evgeniy; Rakovich, Aliaksandra; Donegan, John F.; Nabiev, Igor

2012-10-01

196

RF magnetron sputtered (BiDy)3(FeGa)5O12:Bi2O3 composite garnet-oxide materials possessing record magneto-optic quality in the visible spectral region.  

Science.gov (United States)

Bismuth-substituted iron garnets are considered to be the most promising magneto-optical materials because of their excellent optical transparency and very high magneto-optical figures of merit in the near-infrared spectral region. However, the practical application of garnets in the visible and short-wavelength infrared parts of spectrum is currently limited, due to their very high optical absorption (especially in sputtered films) in these spectral regions. In this paper, we identify the likely source of excess absorption observed in sputtered garnet films in comparison with epitaxial layers and demonstrate (Bi,Dy)(3)(Fe,Ga)(5)O(12): Bi(2)O(3) composites possessing record MO quality in the visible region. PMID:19997172

Vasiliev, Mikhail; Alam, Mohammad Nur-E; Kotov, Viacheslav A; Alameh, Kamal; Belotelov, Vladimir I; Burkov, Vladimir I; Zvezdin, Anatoly K

2009-10-26

197

Full-range spectral domain optical coherence tomography using fiber-based sample scanner as self-phase shifter  

Science.gov (United States)

We propose full-range spectral domain optical coherence tomography equipped with a fiber-based sample scanner, which is used for sample scanning and phase shifting for full-range image at the same time. For a fiber-based sample scanner, since the fiber tip oscillates as a free standing cantilever in general, unintentional phase shift occurs inevitably. The unintentional phase shift was used for eliminating the bothersome complex conjugate ghost image of OCT. In addition, fiber was tilted a few degree to give proper phase shift. In this scheme, moreover, image can be obtained without any physical modification of the scanner. To realize this technique, we constructed the SD-OCT system and fabricated a magnetically actuated single-body lensed fiber scanner due to advantages of simple design, low operating voltage, cost-effectiveness and low insertion loss. The scanner was made of lensed fiber loaded with an iron-based bead and a solenoid which is placed perpendicular to the lensed fiber. When a sinusoidal current is applied into the solenoid, the lensed fiber oscillated due to magnetic force between the iron-based bead and the solenoid. With the suggested full range method, we obtained contrast enhanced full-range SD OCT images of pearl and tooth. This simple and effective method can be applied to any fiber-based scanner and it has great potential as a handheld probe/endoscopic probe in biomedical imaging field.

Min, Eun Jung; Shin, Jun Geun; Lee, Jae Hwi; Lee, Byeong Ha

2012-05-01

198

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization  

International Nuclear Information System (INIS)

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

2009-10-01

199

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization  

Energy Technology Data Exchange (ETDEWEB)

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

Thoen, D. J.; Bongers, W. A.; Westerhof, E.; Baar, M. R. de; Berg, M. A. van den; Beveren, V. van; Goede, A. P. H.; Graswinckel, M. F.; Schueller, F. C. [Association EURATOM-FOM, Trilateral Euregio Cluster, FOM-Institute for Plasma Physics Rijnhuizen, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Oosterbeek, J. W.; Buerger, A. [Association EURATOM-FZJ, Institut fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich GMBH, 52425 Juelich (Germany); Hennen, B. A. [Association EURATOM-FOM, Trilateral Euregio Cluster, FOM-Institute for Plasma Physics Rijnhuizen, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Control Systems Technology Group, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven (Netherlands)

2009-10-15

200

Acquisition and visualization techniques for narrow spectral color imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper introduces a new approach in narrow-band imaging (NBI). Existing NBI techniques generate images by selecting discrete bands over the full visible spectrum or an even wider spectral range. In contrast, here we perform the sampling with filters covering a tight spectral window. This image acquisition method, named narrow spectral imaging, can be particularly useful when optical information is only available within a narrow spectral window, such as in the case of deep-water transmitta...

Neumann, Laszlo; Garcia, Rafael; Basa, Janos; Hegedues, Ramon

2013-01-01

 
 
 
 
201

Direct measurement of the complex refractive index of thin foils in the XUV spectral range by point diffraction interferometry  

Science.gov (United States)

In this paper, we demonstrate the application of point diffraction interferometry to determine the complex refractive index of thin foils in the extreme ultraviolet spectral range. Results are cross-checked by an independent interferometric measurement of the refractive index and a direct transmission measurement of the foils. As the light source, we apply high-order harmonics of a titanium-sapphire laser generated in a gas jet. This interferometric method has the advantage to simultaneously and directly deliver the refractive and absorptive part of the refractive index without relying on the Kramers-Kronig relations or the Fresnel equations. We present results for a set of materials (aluminum, silicon, germanium, boron, and parylene), which are of interest for the design of bandpass filters or multilayer coatings.

Hemmers, D.; Benzid, M.; Pretzler, G.

2012-07-01

202

Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard  

CERN Document Server

Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

Rabus, H; Richter, M; Ulm, G; Friese, J; Gernhäuser, R; Kastenmüller, A; Maier-Komor, P; Zeitelhack, K

1999-01-01

203

Transmission imaging of sodium in the vacuum ultra-violet spectral range: new application for an intense VUV source  

Science.gov (United States)

Metallic sodium (Na) was proposed as a transparent material in the vacuum ultra-violet (VUV) spectral range in 1930s and in 1960s. However no clear transmission has ever been demonstrated. In this paper we describe firstly the direct measurement of actual transmittance of a sodium samples in a spectral range longer than 115 nm which corresponds to the shortest transmission wavelength of magnesium fluoride (MgF2) windows, resulting in several tens of % transmittance of a 3 mm-thick solid sodium sample including MgF2 windows at the wavelength of ~120 nm. We also find very weak temperature dependency of the transmittance up to 150 degrees centigrade where the solid sample is melted at 97 degrees. The measured transmittance pushes us to make a simple imaging experiment illuminated by the VUV light through a 2-mm thick sodium sample, resulting in obtaining a clear image composed of 100 ?m diameter tungsten mesh recorded on a two dimensional Charge Coupled Device detector. The result also opens a way to construct an optical imaging device for objects inside or through a solid or a liquid sodium medium. According to the present experiment, we can make a continuous real time transmission imaging for a liquid sodium sample if we use proper optical setup including an intense continuous VUV source or high repetition rated intense coherent source for holographic data acquisition. Such an experiment opens up a way to perform transmission imaging through or inside a sodium medium for characterization of hydrodynamic and material properties.

Daido, Hiroyuki; Suzuki, Yoji; Kawachi, Tetsuya; Fukuda, Takeshi; Nakagiri, Toshio; Kaku, Masanori; Kubodera, Shoichi; Pirozhkov, Alexander S.

2013-09-01

204

Spectral counting assessment of protein dynamic range in cerebrospinal fluid following depletion with plasma-designed immunoaffinity columns  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In cerebrospinal fluid (CSF, which is a rich source of biomarkers for neurological diseases, identification of biomarkers requires methods that allow reproducible detection of low abundance proteins. It is therefore crucial to decrease dynamic range and improve assessment of protein abundance. Results We applied LC-MS/MS to compare the performance of two CSF enrichment techniques that immunodeplete either albumin alone (IgYHSA or 14 high-abundance proteins (IgY14. In order to estimate dynamic range of proteins identified, we measured protein abundance with APEX spectral counting method. Both immunodepletion methods improved the number of low-abundance proteins detected (3-fold for IgYHSA, 4-fold for IgY14. The 10 most abundant proteins following immunodepletion accounted for 41% (IgY14 and 46% (IgYHSA of CSF protein content, whereas they accounted for 64% in non-depleted samples, thus demonstrating significant enrichment of low-abundance proteins. Defined proteomics experiment metrics showed overall good reproducibility of the two immunodepletion methods and MS analysis. Moreover, offline peptide fractionation in IgYHSA sample allowed a 4-fold increase of proteins identified (520 vs. 131 without fractionation, without hindering reproducibility. Conclusions The novelty of this study was to show the advantages and drawbacks of these methods side-to-side. Taking into account the improved detection and potential loss of non-target proteins following extensive immunodepletion, it is concluded that both depletion methods combined with spectral counting may be of interest before further fractionation, when searching for CSF biomarkers. According to the reliable identification and quantitation obtained with APEX algorithm, it may be considered as a cheap and quick alternative to study sample proteomic content.

Borg Jacques

2011-06-01

205

Evidence for Alteration in Chemical and Physical Properties of Water and Modulation of its Biological Functions by Sunlight Transmitted through Color Ranges of the Visible Spectrum-A Novel Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigated the changes in the properties of water when exposed to sunlight for 40 days. We hypothesize and prove that solar irradiation to water entraps electromagnetic radiation as potential energy, which becomes kinetic energy in various systems. It is postulated that photochemically-induced energy transfers, associated with individual spectral emission of visible spectrum of solar light, exert diverse influences on biological systems. Bottles of distilled water, individually wrapped i...

Cohly, Hari H. P.; Asit Panja; Reno, William L.; Don Obenhuber; Koelle, Margot S.; Das, Suman K.; Angel, Michael F.; Rajeswara Rao, M.

2005-01-01

206

Transmittance and optical constants of Sr films in the 6-1220 eV spectral range  

Science.gov (United States)

Strontium (Sr) is a material with low-absorption bands in the extreme ultraviolet (EUV), which makes it a potential candidate for band pass filters and multilayer coatings. Yet, a better knowledge of the optical properties of Sr is required for these developments. The optical constants n and k of Sr thin films have been obtained in the 6-1220 eV range from transmittance measurements performed at room temperature. These are the first experimental optical constant data of Sr in most of the range. Thin films of Sr with various thicknesses were deposited by evaporation in ultrahigh vacuum conditions, and their transmittance was measured in situ. Sr films were deposited onto grids coated with a thin C support film. Transmittance measurements were used to directly obtain the extinction coefficient k of Sr films. The refractive index n of Sr was calculated with Kramers-Krönig analysis. For this, k data were extrapolated both on the high- and on the low-energy sides by using experimental and calculated k data available in the literature. It was found that, similar to other alkaline-earth metals, Sr has a low absorption band in the EUV, which for Sr is below its N2,3 edge, with a minimum at ~18.5 eV, a range where most materials in nature have a large absorption. A second spectral range of interest for the low absorption of Sr is below its M4,5 edge at 132 eV. In spite of these remarkable properties, Sr is a very reactive material and the stability of coatings encompassing Sr may be an issue. Good consistency of the data resulted from the application of f and inertial sum rules.

Rodríguez-de Marcos, Luis; Larruquert, Juan I.; Aznárez, José A.; Vidal-Dasilva, Manuela; García-Cortés, Sergio; Méndez, José A.; Poletto, Luca; Frassetto, Fabio; Marco Malvezzi, A.; Bajoni, Daniele; Giglia, Angelo; Mahne, Nicola; Nannarone, Stefano

2012-06-01

207

Valid ranges for using the cross-power spectral density phase angle for moderator temperature coefficient sign determination  

International Nuclear Information System (INIS)

The value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. The absolute magnitude of the MTC is obtained from noise analysis by using the root-mean-square method and the frequency response function technique. Both approaches are used in conjunction with the phase angle method, which determines the MTC sign, to obtain complete information about the MTC. Analytical expressions that are derived show that a limitation exists on the range of MTC values for which the cross-power spectral density phase angle can be used to establish the MTC sign. This research shows that small positive values of the MTC (an unstable condition) can result in a -180-deg phase angle shift, contrary to earlier studies that indicated a stable reactor. The range of sign determinate MTC values is dependent on the driving noise source. Simulated noise data are generated for different MTC values and analyzed to verify the theoretical work. A comparison of the indeterminate regions to allowable MTC values for an operating pressurized water reactor is also presented

1995-03-01

208

Range-Gated LADAR Coherent Imaging Using Parametric Up-Conversion of IR and NIR Light for Imaging with a Visible-Range Fast-Shuttered Intensified Digital CCD Camera  

Energy Technology Data Exchange (ETDEWEB)

Research is presented on infrared (IR) and near infrared (NIR) sensitive sensor technologies for use in a high speed shuttered/intensified digital video camera system for range-gated imaging at ''eye-safe'' wavelengths in the region of 1.5 microns. The study is based upon nonlinear crystals used for second harmonic generation (SHG) in optical parametric oscillators (OPOS) for conversion of NIR and IR laser light to visible range light for detection with generic S-20 photocathodes. The intensifiers are ''stripline'' geometry 18-mm diameter microchannel plate intensifiers (MCPIIS), designed by Los Alamos National Laboratory and manufactured by Philips Photonics. The MCPIIS are designed for fast optical shattering with exposures in the 100-200 ps range, and are coupled to a fast readout CCD camera. Conversion efficiency and resolution for the wavelength conversion process are reported. Experimental set-ups for the wavelength shifting and the optical configurations for producing and transporting laser reflectance images are discussed.

YATES,GEORGE J.; MCDONALD,THOMAS E. JR.; BLISS,DAVID E.; CAMERON,STEWART M.; ZUTAVERN,FRED J.

2000-12-20

209

X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility  

Energy Technology Data Exchange (ETDEWEB)

An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution {approx} 50. It has been used at the LULI-2000 laser facility at Ecole Polytechnique (France) to measure the {Delta}n = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

Reverdin, Charles; Caillaud, T.; Gilleron, F.; Pain, J. C.; Silvert, V.; Soullie, G.; Villette, B. [CEA, DAM, DIF, 91297 Arpajon (France); Thais, Frederic; Loisel, Guillaume; Blenski, T.; Poirier, M. [CEA, DSM, IRAMIS, Service Photons, Atomes et Molecules, 91191 Gif-sur-Yvette (France); Busquet, M. [ARTEP Inc, Ellicott City, Maryland 21042 (United States); Bastiani-Ceccotti, S.; Serres, F. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau (France); Ducret, J. E. [CELIA, UMR5107, CEA, CNRS, Universite de Bordeaux, 33400 Talence (France); Foelsner, W. [Max Planck Instituet fuer Quantum Optik, 85748 Garching (Germany); Gilles, D.; Turck-Chieze, S. [CEA, DSM, IRFU, Service d' astrophysique, 91191 Gif-sur-Yvette (France)

2012-10-15

210

A high resolution, multi-epoch spectral atlas of peculiar stars including RAVE, GAIA and HERMES wavelength ranges  

CERN Multimedia

We present an Echelle+CCD, high S/N, high resolution (R = 20\\,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 Ang, and includes the RAVE, Gaia and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of observed stars. A total of 425 spectra of peculiar stars are presented, which have been collected during 56 observing nights between November 1998 and August 2002. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectro-photometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve the planning for and training...

Tomasella, L; Zwitter, T

2010-01-01

211

Highly sensitive dispersion spectroscopy by probing the free spectral range of an optical cavity using dual-frequency modulation  

Science.gov (United States)

Dual-frequency modulation (DFM) has been used to continuously track the frequency shifts of optical cavity modes in the vicinity of an optical transition of a gas inside the cavity for assessment of the gas concentration. A theoretical description of the size and lineshape of the DFM dispersion spectroscopy (DFM-DS) signal is given. Since the signal is measured in terms of a radio frequency the technique is insensitive to laser intensity fluctuations. The signal strength, which can accurately be obtained by curve fitting, only depends on fundamental parameters (including the line strength), thus enabling quantitative detection without calibration procedure. In a first demonstration, using a compact setup based on a narrowband fiber laser, the change in free spectral range around a value of 379.9 MHz due to an acetylene transition near 1531 nm was measured with a resolution of 6 Hz (i.e. with an accuracy of 1.5 parts in 108) in 12.5 s acquisition time, which corresponds to a minimum detectable integrated absorption (SNR=3) of 3×10-9 cm-1.

Schmidt, F. M.; Ma, W.; Foltynowicz, A.; Axner, O.

2010-11-01

212

Temperature dependent dielectric function in the near-infrared to vacuum-ultraviolet ultraviolet spectral range of alumina and yttria stabilized zirconia thin films  

Science.gov (United States)

The dielectric function of nano-/polycrystalline alumina and yttria stabilised zirconia thin films has been investigated in a wide spectral range from 1.0 eV to 7.5 eV and temperatures between 10 K and room temperature. In the near band-edge spectral range, we found a broad distribution of optical transitions within the band gap, the so-called Urbach absorption tail which is typical for amorphous or polycrystalline materials due to the lack of long range order in the crystal structure. The coupling properties of the electronic system to the optical phonon bath and thermal lattice vibrations strongly depend on the ratio of the spectral extent of these disorder states to the main phonon energy, which we correlate with the different crystalline structure of our samples. The films have been grown at room temperature and 650 °C by pulsed laser deposition.

Schmidt-Grund, R.; Lühmann, T.; Böntgen, T.; Franke, H.; Opper, D.; Lorenz, M.; Grundmann, M.

2013-12-01

213

Viewer Makes Radioactivity "Visible"  

Science.gov (United States)

Battery operated viewer demonstrates feasibility of generating threedimensional visible light simulations of objects that emit X-ray or gamma rays. Ray paths are traced for two pinhold positions to show location of reconstructed image. Images formed by pinholes are converted to intensified visible-light images. Applications range from radioactivity contamination surveys to monitoring radioisotope absorption in tumors.

Yin, L. I.

1983-01-01

214

Effect of particle size and spectral sub-range within the UV-VIS-NIR range using diffuse reflectance spectra on multivariate models in evaluating the severity of fusariosis in ground wheat.  

Science.gov (United States)

Control (crops grown in natural conditions) and Fusarium head blight (FHB) damaged (crops inoculated with Fusarium culmorum conidia) grain of four wheat cultivars was ground and sieved into three fractions of different particle size. A series of blended samples differing in content of damaged material were prepared within fractions and cultivars, and diffuse reflectance spectra recorded within the 200-2500 nm wavelength range. Partial least-squares (PLS) models for the percentage of damaged material in blended samples were built for each of twelve series within different spectral ranges, and the root-mean-squared error of cross-validation (RMSECV) was used for the assessment of model performance. Errors using the models were lowest for the finest fraction independent of spectral range; however, their values depended on the cultivar. RMSECV for the finest fraction averaged over cultivars ranged from a little below 3.0 (when the ultraviolet light sub-range was used or participated with another one) to 8.1% (when only the near infrared (NIR) sub-range was used). For the medium and coarse fractions, averaged errors showed the same tendency of dependence on the sub-range(s); however, with higher values that increased with an increase in particle size. In conclusion, within the different fractions of particle size and spectral ranges, the most sensitive to the presence of damaged material were models developed for the finest fraction and when the ultraviolet light sub-range was used in modelling. PMID:19680944

Balcerowska, G; Siuda, R; Skrzypczak, J; ?ukanowski, A; Sadowski, C

2009-05-01

215

Spectral Imaging by Upconversion  

DEFF Research Database (Denmark)

We present a method to obtain spectrally resolved images using upconversion. By this method an image is spectrally shifted from one spectral region to another wavelength. Since the process is spectrally sensitive it allows for a tailored spectral response. We believe this will allow standard silicon based cameras designed for visible/near infrared radiation to be used for spectral images in the mid infrared. This can lead to much lower costs for such imaging devices, and a better performance.

Dam, Jeppe Seidelin; Pedersen, Christian

2011-01-01

216

Wavelength dispersion measurement of electro-optic coefficients in the range of 520 to 930 nm in rubidium titanyl phosphate using spectral interferometry.  

Science.gov (United States)

Rubidium titanyl phosphate (RTP) is widely used for electro-optical applications at low switching voltages. RTP is nonhygroscopic and does not induce piezoelectric ringing up to the megahertz range. It has large electro-optic (EO) coefficients and a high damage threshold. We present here the EO coefficient wavelength dispersion measurements in the [550,950] nm spectral range using a method based on spectral interferometry. These data are necessary for, among other things, a quantitative modelization of an EO carrier-envelope phase shifter. PMID:22330291

Gobert, Olivier; Fedorov, Nikita; Mennerat, Gabriel; Lupinski, Dominique; Guillaumet, Delphine; Perdrix, Michel; Bourgeade, Antoine; Comte, Michel

2012-02-10

217

Radiometric measurements in the spectral range of far ultraviolet radiation for diagnostics of fusion and electron cyclotron resonance plasmas  

International Nuclear Information System (INIS)

The radiation losses from 18 prominent spectral lines of carbon and oxygen in the range of 150-1200 A emitted from the tokamak ASDEX have been measured absolutely using VUV-spectrometers calibrated with a radiometric standard based on electron impact induced line emission from gases. These lines represent a power loss PVUV=131.5 kW which has to be compared with the bolometrically determined radiation loss PRAD=150 kW and the total ohmic input power POH=440 kW. About one third of the radiation loss was found in the O VI2s2S-2p2P-doublet at 1032 A and 1037.6 A. Moreover the measurements enabled us to determine the density of Be-like C III and O V ions in the metastable triplet system relative to the ground state density. About one half of these Be-like ions was found in the metastable 2s2p3P state. In the plasma model used at ASDEX the density and temperature profiles were improved, especially the steep gradients at the plasma edge. The rate coefficients for electron impact ionisation and excitation were examined and with improved excitation rate coefficients the number of calculable line intensities was extended. A comparison of experimental line intensity ratios with model calculations was used as a test for the reliability of the plasma model in the important plasma edge region. Impurity concentrations and fluxes were determined. Finally we have investigated selected line intensity ratios emitted from an Electron Cyclotron Resonance Ion Source and made an attempt to determine the electron density as a function of the neutral gas pressure in the second stage of the ECR. (orig.)

1991-01-01

218

Composite films prepared by plasma ion-assisted deposition (IAD) for design and fabrication of antireflection coatings in visible and near-infrared spectral regions  

Science.gov (United States)

Ion-assisted deposition (IAD) processes configured with a well-controlled plasma source at the center base of a vacuum chamber, which accommodates two independent e-gun sources, is used to deposition TiO2MgF2 and TiO2-SiO2 composite films of selected component ratios. Films prepared by this technology are found durable, uniform, and nonabsorbing in visible and near-IR regions. Single- and multilayer antireflection coatings with refractive index from 1.38 to 2.36 at (lambda) equals 550 nm are presented. Methods of enhancement in optical performance of these coatings are studied. The advantages of AR coatings formed by TiO2-MgF2 composite films over those similar systems consisting of TiO2-SiO2 composite films in both visible and near-IR regions are also presented.

Tsai, Rung-Ywan; Ho, Fang C.

1994-11-01

219

High-spectral-resolution solar irradiance in the 184.5 to 232.5 nm range from the SOLSPEC and UVSP spectrometers  

Science.gov (United States)

The study of the minor constituents of the planetary atmospheres from the analysis of the scattered light properties requires the knowledge of the absolute incident solar irradiance at high resolution. The data were obtained from the UVSP experiment on board the Solar Maximum Mission satellite in the 184.5 232.5 nm spectral range. We have reconstituted the solar spectrum measured in three different regions of the solar disk with a spectral resolution of 0.01 nm and a spatial resolution of 3 arc sec. The wavelength scale was determined with a standard deviation of 0.0025 nm. The comparison of the relative intensities in three locations of the solar disk with those obtained by other authors allowed us to determine these positions accurately and to derive the integrated spectrum of the whole disk. Finally, the resulting spectrum has been expressed in absolute units using the spectral irradiance by the SOLSPEC and SUSIM spectrometers, respectively operated with the ATLAS 1 mission and from the Upper Atmosphere Research Satellite. We obtained the absolute solar irradiance with an accuracy of 10% in the 184.5 232.5 nm spectral range with a spectral resolution of 0.01 nm for the first time using data from space observations.

Tartag, A.; Bénilan, Y.; Samain, D.; Thuillier, G.; Bruston, P.

2001-07-01

220

VERUCLAY – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant  

Science.gov (United States)

Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

 
 
 
 
221

Spectroscopic and laser characteristics of new efficient luminophores for a wide spectral range based on complexes of dipyrrolylmethene derivatives with difluorine borate  

Science.gov (United States)

We have studied the spectral-luminescent, lasing, photochemical, and endurance characteristics of a series of new efficiently emitting difluorine borate complexes with dipyrrolylmethenes of different structures. Experimental data have been obtained in polar and nonpolar organic solvents and in solid polymer films involving the participation of silicate structures. We have discussed relations of the structure of investigated compounds and formed solvates with their optical characteristics, and have given guidelines on the use of particular compounds as active media of tunable lasers for determining spectral ranges.

Kuznetsova, R. T.; Aksenova, Yu. V.; Solodova, T. A.; Bashkirtsev, D. E.; Kopylova, T. N.; Tel'minov, E. N.; Mayer, G. V.; Berezin, M. B.; Semeikin, A. S.; Yutanova, S. L.; Antina, E. V.; Arabei, S. M.; Pavich, T. A.; Solovyov, K. N.

2013-11-01

222

Optical absorption behaviour of platinum core-silica shell nanoparticle layer and its influence on the reflection spectra of a multi-layer coating system in the visible spectrum range  

International Nuclear Information System (INIS)

Platinum core-silica shell nanoparticles (Pt-SiO2) have been applied to the outermost layer of a three-layer film structure to yield a Pt-SiO2/SiO2/ITO (indium tin oxide) coating on a glass substrate. Optical properties of the three-layer film have been investigated in the visible spectrum regime. The absorption of visible light by the Pt core-SiO2 shell layer was higher in low- and high-wavelength regimes while it was minimal at a mid-visible light range, about 550 nm. This characteristic absorption of the core-shell layer resulted in a broad-band anti-reflectance behaviour of the multi-layer coating system in the entire visible light regime. Transmittance of the three-layer coating-glass system was in the range between 80% and 85% and thus the application of the platinum core-silica shell nanoparticle layer with such absorption characteristics is shown to provide flexibility of ways to achieve a broad-band anti-reflectance and transmittance of a multi-layer coating system

2004-05-12

223

Spectrometry of minor planets. Spectral curve of the 3 Juno asteroid in the 0.44-0.56 ?m range  

International Nuclear Information System (INIS)

The absorption band near 0.5 ?m has been found in the 3 Juno spectrum obtained with ? 25 A resolution. This band is caused by d-electrons transitions of Fe"2"+ ion in pyroxene. Taking into account the location of the asteroid on the spectral parameters diagrams for light stony meteorites it is concluded that in the surface material of the 3 Juno olivine abundance is much less than pyroxene one and the metallic phase is probably present

1986-01-01

224

Spectral analysis of ICRF (Ion Cyclotron Range of Frequencies) wave field measurements in the Tara Central Cell  

Energy Technology Data Exchange (ETDEWEB)

A simple spectral analysis technique has been developed to analyse the digital signals from an array of magnetic probes for ICRF field measurements in the Tara Tandem Mirror central cell. The wave dispersion relations of both the applied ICRF and the Alfven Ion Cyclotron Instability have been studied and the waves have been identified as slow in cyclotron waves. The radial profiles of field amplitude and wave vectors were also generated. 9 refs., 10 figs.

Wang, L.; Golovato, S.N.; Horne, S.F.

1987-12-01

225

Spectral analysis of ICRF [Ion Cyclotron Range of Frequencies] wave field measurements in the Tara Central Cell  

International Nuclear Information System (INIS)

A simple spectral analysis technique has been developed to analyse the digital signals from an array of magnetic probes for ICRF field measurements in the Tara Tandem Mirror central cell. The wave dispersion relations of both the applied ICRF and the Alfven Ion Cyclotron Instability have been studied and the waves have been identified as slow in cyclotron waves. The radial profiles of field amplitude and wave vectors were also generated. 9 refs., 10 figs

1987-01-01

226

Experimental and theoretical investigation of silver-coated ZnO nanorod arrays as antennas for the visible and near-IR spectral range  

Science.gov (United States)

A new design of optical antennas consisting of zinc oxide (ZnO) nanorods covered by a thin metal film is proposed. Arrays of highly oriented ZnO nanorods perpendicular to a substrate and covered by a thin silver film have been obtained using methods of carbothermal synthesis and magnetron sputtering. The problems of electromagnetic wave diffraction on a single metal/dielectric nanovibrator (situated at the interface of dielectrics) and on a two-dimensional periodic array of these nanovibrators have been solved. The results of calculations of the electrodynamic characteristics of optical antennas with various lengths have been compared to experimental data.

Kaidashev, E. M.; Lyanguzov, N. V.; Lerer, A. M.; Raspopova, E. A.

2014-04-01

227

AlGaInP quantum dots for optoelectronic applications in the visible spectral range; AlGaInP-Quantenpunkte fuer optoelektronische Anwendungen im sichtbaren Spektralbereich  

Energy Technology Data Exchange (ETDEWEB)

The scope of this work is the fabrication and characterization of AlGaInP quantum dots on GaP an GaAs substrates. Based on such quantum dots, semiconductor lasers have been realized, emitting between 660 nm and 730 nm at room temperature. The examination of broad-area lasers processed on these structures suggests that active layers of larger quantum dots with higher aluminium contents lead to lasers with better performance at similar emission wavelength. Additionally, quantum dots grown on GaP substrates have been characterized, that were embedded in AlGaP barriers. Since these barriers exhibit an indirect bandgap, a non-trivial band alignment within these structures is expected. In this work, numerical 3D-simulations are employed to calculate the band alignment including strain and internal fields. Also, ground state wavefunctions of charge carriers have been determined. A thorough comparison between theory and experiment connects the measured emission wavelength and luminescence intensities with calculated transition energies and wavefunction overlaps.

Gerhard, Sven

2013-01-10

228

UV—visible spectral characterization and density functional theory simulation analysis on laser-induced crystallization of amorphous silicon thin films  

Science.gov (United States)

The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon (a-Si:H) thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled (? = 532 nm) Nd:YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical (TO) peak can produce higher stress. The highest crystalline fraction (84.5%) is obtained in the optimized laser energy density (1000 mJ/cm2) with a considerable stress release. The absorption edge energy measured by the UV-visible spectra is in fairly good agreement with the bandgap energy in the density functional theory (DFT) simulation.

Huang, Lu; Jin, Jing; Shi, Wei-Min; Yuan, Zhi-Jun; Yang, Wei-Guang; Cao, Ze-Chun; Wang, Lin-Jun; Zhou, Jun; Lou, Qi-Hong

2014-03-01

229

Visible to short-wave infrared spectra and spectral features of clay and carbonate samples. Kashi@tanhacho sekigaiiki ni okeru nendoter dot tansan prime engan no hansha spectra to sono tokucho  

Energy Technology Data Exchange (ETDEWEB)

This paper reports a result of reflectance spectral measurements on clay and carbonate samples in a visible to short wave infrared region. The samples consist mainly of those collected from various parts in Japan, including some from the U.S.A. and China. An IRIS spectroradiometer made by Geophysical Environmental Research, Inc. was used to measure reflectance spectra without processing the samples, and minerals were identified using either chemical analysis or X-ray diffraction. The paper presents results of measurements on montmorillonite, kaolinite, pyrophyllite, sericite, alunite, and calcite. Further, the paper indicates that positions of absorption bands for reflectance spectra using unprocessed samples agree with existing measurement data using powdered samples, and samples containing much water reduce reflectance coefficients as a whole and may conceal features of reflectance spectra natural to particular minerals. 7 refs., 10 figs., 4 tabs.

Urai, M.; Sato, I.; Ninomiya, Y.; Koda, R.; Miyazaki, Y.; Yamaguchi, Y. (Geological Survey of Japan, Tsukuba (Japan))

1992-03-31

230

Green Gap Spectral Range Light-Emitting Diodes with Self-Assembled InGaN Quantum Dots Formed by Enhanced Phase Separation  

Science.gov (United States)

Light-emitting diodes (LEDs) emitting in the green gap spectral range (540--610 nm) were demonstrated using self-assembled In-rich InGaN quantum dots (QDs) grown on n-GaN by metal-organic chemical-vapor deposition. The study of structural and optical properties showed that the formation of InGaN QDs with larger size and higher In composition is enhanced by phase separation in the InGaN layer with increasing surface roughness of the underlying n-GaN layer. The emission wavelength of the LED was redshifted from the green (540 nm) to red (610 nm) spectral range due to an increase in the depth of potential wells of the InGaN QDs with increasing surface roughness of the underlying n-GaN layer.

Park, Il-Kyu

2011-04-01

231

Broadband photon time-of-flight spectroscopy of pharmaceuticals and highly scattering plastics in the VIS and close NIR spectral ranges.  

Science.gov (United States)

We present extended spectroscopic analysis of pharmaceutical tablets in the close near infrared spectral range performed using broadband photon time-of-flight (PTOF) absorption and scattering spectra measurements. We show that the absorption spectra can be used to perform evaluation of the chemical composition of pharmaceutical tablets without need for chemo-metric calibration. The spectroscopic analysis was performed using an advanced PTOF spectrometer operating in the 650 to 1400 nm spectral range. By employing temporal stabilization of the system we achieve the high precision of 0.5% required to evaluate the concentration of tablet ingredients. In order to further illustrate the performance of the system, we present the first ever reported broadband evaluation of absorption and scattering spectra from pure and doped Spectralon®. PMID:24103967

Khoptyar, Dmitry; Subash, Arman Ahamed; Johansson, Sören; Saleem, Muhammad; Sparén, Anders; Johansson, Jonas; Andersson-Engels, Stefan

2013-09-01

232

Efficient ion blocking in gaseous detectors and its application to gas-avalanche photomultipliers sensitive in the visible-light range  

CERN Document Server

A novel concept for ion blocking in gas-avalanche detectors was developed, comprising cascaded micro-hole electron multipliers with patterned electrodes for ion defocusing. This leads to ion blocking at the 10^{-4} level, in DC mode, in operation conditions adequate for TPCs and for gaseous photomultipliers. The concept was validated in a cascaded visible-sensitive gas avalanche photomultiplier operating at atmospheric pressure of Ar/CH_{4} (95/5) with a bi-alkali photocathode. While in previous works high gain, in excess of 10^{5}, was reached only in a pulse-gated cascaded-GEM gaseous photomultiplier, the present device yielded, for the first time, similar gain in DC mode. We describe shortly the physical processes involved in the charge transport within gaseous photomultipliers and the ion blocking method. We present results of ion backflow fraction and of electron multiplication in cascaded patterned-electrode gaseous photomultiplier with K-Cs-Sb, Na-K-Sb and Cs-Sb visible-sensitive photocathodes, operate...

Lyashenko, A V; Chechik, R; Santos, J M F Dos; Amaro, F D; Veloso, J F C A

2008-01-01

233

Construction of TSL lector equipment with spectral resolution for the determination of thermally stimulated luminescence (TSL) properties of NaCl: Tl+ induced by UV-visible radiation  

International Nuclear Information System (INIS)

A revision of physical models of thermally stimulated luminescence (TSL) in crystals induced by both ionizing and non-ionizing radiation is presented. Particular emphasis is given to the connection of TSL with other thermally stimulated processes and physico-chemical phenomena because basic information on physical mechanics for TSL can be obtained through them. Glow curves of TSL induced by UV-visible radiation in NaCl: Tl+ were measured. Additionally, the following spectrums were obtained for the same samples: optical absorption, excitation, fluorescent emission, and TSL emission. An optical absorption peak was correlated with the Thallium ion concentration. With respect to the TSL emission spectrums, some peaks associated to Thallium dimmers were at 298 and at 480 nm; others which were attributed to NaCl intrinsic properties were at 365, 430, 450 and 525 nm. Also TSL glow curves were studied as a function of the Thallium ion concentration (0.8 ppm to 14.8 ppm). They were de convoluted so as to calculate the activation energy, the frequency factor and the kinetic order for each separate TSL peak. Anomalous values were observed for some frequency factors. A method and TSL lector equipment to obtain TSL emission spectra were developed. (Author)

1993-01-01

234

Super dual auroral radar network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere  

Energy Technology Data Exchange (ETDEWEB)

The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity. Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUTLASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments. (orig.)

Arnold, N.F.; Robinson, T.R.; Lester, M.; Byrne, P.B.; Chapman, P.J. [Dept. of Physics and Astronomy, Univ. of Leicester (United Kingdom)

2001-04-01

235

Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere  

Directory of Open Access Journals (Sweden)

Full Text Available The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity. Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUT-LASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments.

Key words. Meterology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; instruments and techniques

N. F. Arnold

236

Third-harmonic generation in silicon and photonic crystals of macroporous silicon in the spectral intermediate-IR range; Erzeugung der Dritten Harmonischen in Silizium und Photonischen Kristallen aus makroporoesem Silizium im spektralen mittleren IR-Bereich  

Energy Technology Data Exchange (ETDEWEB)

Nonlinear optical spectroscopy is a powerful method to study surface or bulk properties of condensed matter. In centrosymmetric materials like silicon even order nonlinear optical processes are forbidden. Besides self-focussing or self phase modulation third-harmonic-generation (THG) is the simplest process that can be studied. This work demonstrates that THG is a adapted non-contact and non-invasive optical method to get information about bulk structures of silicon and Photonic crystals (PC), consisting of silicon. Until now most studies are done in the visible spectral range being limited by the linear absorption losses. So the extension of THG to the IR spectral range is extremely useful. This will allow the investigation of Photonic Crystals, where frequencies near a photonic bandgap are of special interest. 2D- photonic structures under investigation were fabricated via photoelectrochemical etching of the Si (100) wafer (thickness 500 {mu}m) receiving square and hexagonal arranged pores. The typical periodicity of the structures used is 2 {mu}m and the length of the pores reached to 400 {mu}m. Because of stability the photonic structures were superimposed on silicon substrate. The experimental set-up used for the THG experiments generates tuneable picosecond IR pulses (tuning range 1500-4000 cm{sup -1}). The IR-pulse hit the sample either perpendicular to the sample surface or under an angle {theta}. The sample can be rotated (f) around the surface normal. The generated third harmonic is analysed by a polarizer, spectrally filtered by a polychromator and registered by a CCD camera. The setup can be used either in transmission or in reflection mode. Optical transmission and reflection spectra of the Si bulk correspond well with the theoretical description, a 4-fold and a 8-fold dependencies of the azimuth angle resulting in the structure of the x{sup (3)}-tensor of (100)-Si. The situation changes dramatically if the PC with hexagonal structure is investigated. In reflection mode a six fold symmetry is observed. This can only be explained by the symmetry of the Photonic Crystal. Changing the transmission mode the result depends on the mount of the PC - fundamental entering from the structure side or fundamental entering from the bulk side. Common to both results are there six maxima. To explain the difference between the transmission and reflection results one has to recognise, that the effective interaction length is limited: so in the reflection geometry of generated TH is from the structured region, whereas in the transmission cases a combination of the structure and the bulk has to be taken into account. This work gives a first theoretical description of this effects. (orig.)

Mitzschke, Kerstin

2007-11-01

237

Human Contrast Threshold and Astronomical Visibility  

CERN Multimedia

The standard visibility model in light pollution studies is the formula of Hecht (1947), as used e.g. by Schaefer (1990). However it is applicable only to point sources and is shown to be of limited accuracy. A new visibility model is presented for uniform achromatic targets of any size against background luminances ranging from zero to full daylight, produced by a systematic procedure applicable to any appropriate data set (e.g Blackwell (1946)), and based on a simple but previously unrecognized empirical relation between contrast threshold and adaptation luminance. The scotopic luminance correction for variable spectral radiance (colour index) is calculated. For point sources the model is more accurate than Hecht's formula and is verified using telescopic data collected at Mount Wilson by Bowen (1947), enabling the sky brightness at that time to be determined. The result is darker than the calculation by Garstang (2004), implying that light pollution grew more rapidly in subsequent decades than has been sup...

Crumey, Andrew

2014-01-01

238

Detector calibration at the radiometry laboratory of the Physikalisch-Technische Bundesanstalt in the VUV and soft x-ray spectral ranges using synchrotron radiation  

Science.gov (United States)

In the vacuum ultraviolet and soft x-ray spectral ranges the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the synchrotron radiation facility BESSY offers two different methods for the calibration of radiation detectors. The electron storage ring BESSY, in combination with suitable monochromators, reproducible produces monochromatic radiation of tunable photon energy, high spectral purity, and high radiant power which can be reduced by twelve orders of magnitude. With this source of monochromatic radiation a cryogenic electrical substitution radiometer (ESR) is operated as a primary detector standard in the photon energy range from 3 eV to 1500 eV. The ESR is optimized for synchrotron radiation, capable of measuring radiant power in the order of some (mu) W with an uncertainty below 0.2%. Radiation detectors can be calibrated against the ESR with uncertainties well below 1%. Recent progress in this field will be demonstrated for the calibration of photodiodes. The electron storage ring BESSY is also used as a primary source standard, in the photon energy range from the infrared to the soft x-ray range. The spectral and spatial distribution of the broadband radiation, emitted in the range from 1 eV to 15 keV, is calculable from the known storage ring parameters with uncertainties from 0.04% to 0.35%, respectively. This allows the detection efficiency of energy-dispersive detectors such as solid-state detectors, charge- coupled devices, and others to be determined, provided the detector response function to monochromatic radiation is measured as well.

Lederer, Thomas; Rabus, Hans; Scholze, Frank; Thornagel, R.; Ulm, Gerhard

1995-06-01

239

Visible spectroscopy on ASDEX  

International Nuclear Information System (INIS)

In this report visible spectroscopy and impurity investigations on ASDEX are reviewed and several sets of visible spectra are presented. As a basis for identification of metallic impurity lines during plasma discharges spectra from a stainless steel - Cu arc have been recorded. In a next step a spectrum overview of ASDEX discharges is shown which reveals the dominating role of lines from light impurities like carbon and oxygen throughout the UV and visible range (2000 A ? ? ? 8000 A). Metallic impurity lines of neutrals or single ionized atoms are observed near localized surfaces. The dramatic effect of impurity reduction by boronization of the vessel walls is demonstrated in a few examples. In extension to some ivesti-gations already published, further diagnostic applications of visible spectroscopy are presented. Finally, the hardware and software system used on ASDEX are described in detail. (orig.)

1991-01-01

240

Gas-phase absorption cross sections of 24 monocyclic aromatic hydrocarbons in the UV and IR spectral ranges  

Science.gov (United States)

Absorption cross sections of 24 volatile and non-volatile derivatives of benzene in the ultraviolet (UV) and the infrared (IR) regions of the electromagnetic spectrum have been determined using a 1080 l quartz cell. For the UV a 0.5 m Czerny-Turner spectrometer coupled with a photodiode array detector (spectral resolution 0.15 nm) was used. IR spectra were recorded with an FT-IR spectrometer (Bruker IFS-88, spectral resolution 1 cm -1). Absolute absorption cross sections and the instrument function are given for the UV, while for the IR, absorption cross sections and integrated band intensities are reported. The study focused primarily on the atmospherically relevant methylated benzenes (benzene, toluene, o-xylene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, styrene) and their ring retaining oxidation products (benzaldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde, phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4,6-trimethylphenol and ( E,Z)- and ( E,E)-2,4-hexadienedial). The UV absorption cross sections reported here can be used for the evaluation of DOAS spectra (Differential Optical Absorption Spectroscopy) for measurements of the above compounds in the atmosphere and in reaction chambers, while the IR absorption cross sections will primarily be useful in laboratory studies on atmospheric chemistry, where FT-IR spectrometry is an important tool.

Etzkorn, Thomas; Klotz, Björn; Sørensen, Søren; Patroescu, Iulia V.; Barnes, Ian; Becker, Karl H.; Platt, Ulrich

 
 
 
 
241

Experimental verification of n = 0 structures for visible light.  

Science.gov (United States)

We fabricate and characterize a metal-dielectric nanostructure with an effective refractive index n = 0 in the visible spectral range. Light is excited in the material at deep subwavelength resolution by a 30-keV electron beam. From the measured spatially and angle-resolved emission patterns, a vanishing phase advance, corresponding to an effective [Symbol: see text] = 0 and n = 0, is directly observed at the cutoff frequency. The wavelength at which this condition is observed can be tuned over the entire visible or near-infrared spectral range by varying the waveguide width. This n = 0 plasmonic nanostructure may serve as a new building block in nanoscale optical integrated circuits and to control spontaneous emission as experimentally demonstrated by the strongly enhanced radiative optical density of states over the entire n = 0 structure. PMID:23383791

Vesseur, Ernst Jan R; Coenen, Toon; Caglayan, Humeyra; Engheta, Nader; Polman, Albert

2013-01-01

242

Model calculations and measurements of the emission of a barium plasma in the spectral range of high-n Rydberg levels in a near Ni-like state  

International Nuclear Information System (INIS)

The Los Alamos suite of atomic codes is used to model several high-resolution spectral measurements from recent laser-produced plasma experiments involving barium fluoride targets. The spectral range of observation is from 7.8 to 9.5 A and the observed lines correspond to 3-5, 3-6, 3-7 and 3-8 transitions of principal quantum number, for Ga-like through Co-like barium ions. The observed spectra are complicated because of many overlapping lines from the various ion stages in a small wavelength region. A MUTA model that includes many configurations is compared to a detailed level-to-level collisional-radiative model that includes fewer configurations. Spectra are calculated to show the sensitivity to plasma temperature, density and size. The contributions to the spectra for the individual ion stages are also presented. The model calculations are in reasonable agreement with experiment.

2010-09-14

243

InAs/GaSb type-II superlattices for single- and dual-color focal plane arrays for the mid-infrared spectral range  

International Nuclear Information System (INIS)

Focal Plane Arrays for high-performance thermal imaging systems operating in the mid-infrared spectral range between 3-5 ?m have been realized by type-II InAs/GaSb short-period superlattices. A fully operational 256 x 256 camera system showing a noise equivalent temperature difference below 10 mK is presented. The suitability of InAs/GaSb type-II superlattices for next generation thermal imagers is demonstrated with the first 288 x 384 dual color demonstrator camera which features a simultaneous and spatially coincident acquisition of two separate spectral regimes in the mid-infrared. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

2006-03-01

244

Transmittance and optical constants of Lu films in the 3-1800 eV spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The optical constants n and k of lutetium (Lu) films were obtained in the 3-1800 eV range from transmittance measurements performed at room temperature. These are the first experimental optical constant data of Lu in the whole range. Thin films of Lu with various thicknesses were deposited by evaporation in ultrahigh vacuum conditions and their transmittance was measured in situ. Lu films were deposited onto grids coated with a thin, C support film. Transmittance measurements were used to obt...

Garci?a-corte?s, S.; Rodri?guez-de Marcos, L.; Larruquert, Juan Ignacio; Azna?rez, Jose? Antonio; Me?ndez, Jose? Antonio; Poletto, L.; Frassetto, F.; Malvezzi, A. M.; Giglia, A.; Mahne, N.; Nannarone, S.

2010-01-01

245

Efficient hybrid white polymer light-emitting devices with electroluminescence covered the entire visible range and reduced efficiency roll-off  

Science.gov (United States)

We report efficient hybrid white polymer light emitting devices (WPLEDs) fabricated via simple solution-proceeded process from a newly synthesized wide band-gap fluorene-co-dibenzothiophene-S,S-dioxide copolymer, which dually function as fluorescent blue emitter and host material for electrophosphorescent sky-blue, yellow, and saturated-red dyes. The Commission Internationale d'Énclairage coordinates of the best devices are (0.356, 0.334), with electroluminescence covered the entire visible light spectrum from 400 to 780 nm, resulting in a high color rendering index of 90. Incorporation of a bilayer electrode consisting of water/alcohol-soluble conjugated polymer and Al as electron-injection cathode boosts an enhancement of 50% in device efficiency, leading to external quantum efficiency of 12.6%, and peak power efficiency of 21.4 l m W-1 as measured in an integrating sphere. Both the efficiency and the color quality of the obtained device are ranking among one of the highest values for WPLEDs reported to date. Furthermore, as compared with those all-phosphorescent WPLEDs, the hybrid WPLEDs studied here exhibit a significantly reduced efficiency roll-off due to the very low doping concentration.

Hu, Sujun; Zhu, Minrong; Zou, Qinghua; Wu, Hongbin; Yang, Chuluo; Wong, Wai-Yeung; Yang, Wei; Peng, Junbiao; Cao, Yong

2012-02-01

246

Parametric modeling of the dielectric function and identification of the critical point of a CdMgTe alloy in the vacuum ultraviolet spectral range  

International Nuclear Information System (INIS)

We report the parameters necessary to construct the dielectric functions of Cd1-xMgxTe ternary alloys at room temperature for arbitrary compositions from x = 0 to x = 0.5. The experimental spectra were measured by using vacuum ultraviolet spectroscopic ellipsometry in the spectral range from 0.7 to 9.0 eV. By performing a band structure calculation with the linear augmented Slatertype orbital method, we newly identify the four higher band gaps as E2 + ?2, E2(?), E2(?), and E'1 transitions.

2012-04-01

247

Parametric modeling of the dielectric function and identification of the critical point of a CdMgTe alloy in the vacuum ultraviolet spectral range  

Energy Technology Data Exchange (ETDEWEB)

We report the parameters necessary to construct the dielectric functions of Cd{sub 1-x}Mg{sub x}Te ternary alloys at room temperature for arbitrary compositions from x = 0 to x = 0.5. The experimental spectra were measured by using vacuum ultraviolet spectroscopic ellipsometry in the spectral range from 0.7 to 9.0 eV. By performing a band structure calculation with the linear augmented Slatertype orbital method, we newly identify the four higher band gaps as E{sub 2} + ?{sub 2}, E{sub 2}(?), E{sub 2}(?), and E'{sub 1} transitions.

Kim, Tae Jung; Ghong, Tae Ho; Yoon, Jae Jin; Hwang, Soon Yong; Barange, Nilesh; Kim, Young Dong [Kyung Hee University, Seoul (Korea, Republic of); Chang, Yia Chung [Research Center for Applied Sciences, Academia Sinica, Taipei (China)

2012-04-15

248

Parametric modeling of the dielectric function and identification of the critical point of a CdMgTe alloy in the vacuum ultraviolet spectral range  

Science.gov (United States)

We report the parameters necessary to construct the dielectric functions of Cd1- x Mg x Te ternary alloys at room temperature for arbitrary compositions from x = 0 to x = 0.5. The experimental spectra were measured by using vacuum ultraviolet spectroscopic ellipsometry in the spectral range from 0.7 to 9.0 eV. By performing a band structure calculation with the linear augmented Slater-type orbital method, we newly identify the four higher band gaps as E 2 + ?2, E 2(?), E 2(?), and E'1 transitions.

Kim, Tae Jung; Ghong, Tae Ho; Yoon, Jae Jin; Hwang, Soon Yong; Barange, Nilesh; Kim, Young Dong; Chang, Yia-Chung

2012-04-01

249

Adjustment of a goniometer for X-rays optics calibration in the spectral range 1.5-20 KeV  

International Nuclear Information System (INIS)

The aim of this memoir is the adjustment of a (?, 2?) goniometer coupled to X-rays source to calibrate mirrors (single layers like C, Ni, Au, etc... and multilayers like C/W, Si/W, etc...) in the spectral range 1.5 - 20 keV. For each kind of tested optics the adjustment of the goniometer include the procedure alignment of the different components (X-ray source, collimation slits, optics, detectors) and the first reflectivity measurements. Those measurements are compared those realized at LURE, using synchrotron radiation provided by SUPER ACO storage ring, and to a theoretical simulation

1992-01-01

250

Site-controlled InP/GaInP quantum dots emitting single photons in the red spectral range  

Science.gov (United States)

We report on site-controlled growth of InP/GaInP quantum dots (QDs) on GaAs substrates. The QD nucleation sites are defined by shallow nanoholes etched into a GaInP layer. Optimized growth conditions allow us to realize QD arrays with excellent long range ordering on nanohole periods as large as 1.25 µm. Single QD lines with an average linewidth of 553 µeV and best values below 200 µeV are observed. Photoluminescence spectroscopy reveals excitonic and biexcitonic emission in the wavelength range of about 670 nm (1.85 eV) with an exciton-biexciton splitting of 1.8 meV. Second-order photon-autocorrelation measurements show clear single photon emission with g(2)(0) = 0.13 +/- 0.01.

Baumann, Vasilij; Stumpf, Florian; Schneider, Christian; Kremling, Stefan; Worschech, Lukas; Forchel, Alfred; Höfling, Sven; Kamp, Martin

2012-02-01

251

High resolution, large spectral range, in variable-included-angle soft X-ray monochromators using a plane VLS grating  

International Nuclear Information System (INIS)

We give a unified discussion of two different approaches to the design of grazing incidence monochromators with a variable line spacing (VLS) grating for soft X-ray undulator sources. Neither one uses an entrance slit and both work with a fixed position exit slit. In one approach, being constructed at LNLS and designed for the energy range 100< E<1000eV, the choice of the VLS parameters allows for the operation at a variable c-value with a single plane grating and little sacrifice in the maximum resolving power. In this case source size limited resolving power of circa 40000 is expected at 100eV. In the second approach, for the storage ring in Wisconsin, two gratings covering the energy range 40< E<1500eV are used, one capable of delivering a resolving power larger than 20000 at 860eV and the other lower resolving power but much higher flux

2005-02-11

252

UVMag: Space UV and visible spectropolarimetry  

CERN Document Server

UVMag is a project of a space mission equipped with a high-resolution spectropolarimeter working in the UV and visible range. This M-size mission will be proposed to ESA at its M4 call. The main goal of UVMag is to measure the magnetic fields, winds and environment of all types of stars to reach a better understanding of stellar formation and evolution and of the impact of stellar environment on the surrounding planets. The groundbreaking combination of UV and visible spectropolarimetric observations will allow the scientists to study the stellar surface and its environment simultaneously. The instrumental challenge for this mission is to design a high-resolution space spectropolarimeter measuring the full-Stokes vector of the observed star in a huge spectral domain from 117 nm to 870 nm. This spectral range is the main difficulty because of the dispersion of the optical elements and of birefringence issues in the FUV. As the instrument will be launched into space, the polarimetric module has to be robust and...

Pertenais, Martin; Pares, Laurent; Petit, Pascal; Snik, Frans; van harten, Gerard

2014-01-01

253

The potential for extending the spectral range accessible to the European XFEL down to 0.05 nm  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Specifications of the European XFEL cover a range of wavelengths down to 0.1 nm. The baseline design of the European XFEL assumes standard (SASE) FEL mode for production of radiation i.e. only one photon beam at one fixed wavelength from each baseline undulator with tunable gap. Recent developments in the field of FEL physics and technology form a reliable basis for an extensions of the mode of operation of XFEL facilities. This paper explores how the wavelength of the outpu...

Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

2010-01-01

254

High-power high-brightness semiconductor tapered diode lasers for the red and near infrared spectral range  

Science.gov (United States)

The most promising concept to achieve high-output power together with a good beam quality is the tapered laser consisting of a straight ridge waveguide (RW) section and a tapered gain-region. The RW section should support only the fundamental guided mode and should suppress higher order modes. The taper angle has to be selected with respect to the lateral divergence of the beam propagating from the RW to the tapered section. High brightness tapered devices in the wavelength range between 635 nm and 1085 nm will be presented. For red emitting tapered lasers around 650 nm, the output power is limited to about 1 W due to the properties of the laser material. At this output power a beam propagation ratio M2 of 1.3 and a brightness of 100 MW•cm-2•sr-1 will be shown. Devices made from laser structures with low vertical divergence down to 25° (95% power included) without a significant deterioration of device parameters will be presented for the longer wavelength range near 1 ?m. For tapered lasers manufactured from these structures, nearly diffraction limited output powers larger than 10 W and a brightness of 1 GW•cm-2•sr-1 were measured.

Sumpf, B.; Wenzel, H.; Erbert, G.

2010-02-01

255

Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range.  

Science.gov (United States)

Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear (13)C-(13)C correlation spectra. We demonstrate on model compounds and on 1-73-(U-(13)C,(15)N)/74-108-(U-(15)N) E. coli thioredoxin reassembly, that with appropriately constructed 50% NUS schedules inherent sensitivity gains of 1.7-2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear (13)C-(13)C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

Suiter, Christopher L; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David; Hoch, Jeffrey C; Rovnyak, David; Polenova, Tatyana

2014-06-01

256

Change of the spectral sensitivity range of thin-film AlGaAs/GaAs -photoreceivers under influence of ultrasonic waves  

International Nuclear Information System (INIS)

Full text: The task of controlled variation of the physical properties of semiconductor materials under the action of external factors is an important problem in the physics of semiconductors. As is well known, one such factor is ultrasonic radiation: propagating in a semiconductor crystal, acoustic (ultrasonic) waves change its properties, in particular, the optical characteristics. In the context of solving the above task, it is expedient to continue investigations of the effect of ultrasonic waves on the characteristics of semiconductor devices. This report presents the results of experimental investigations of the influence of ultrasonic waves on the spectral characteristics of photoreceivers based on AlGaAs/GaAs- heterostructures. The study showed that an exposure to ultrasonic radiation leads to a change, depending on the ultrasonic treatment (UST) parameters, in the spectral characteristics of gallium arsenide crystals, the base materials of modern semiconductor photoelectronics. Some results showed evidence of the positive character of changes in the characteristics of A3B5-based photoreceivers under the action of ultrasonic waves. The effect of ultrasonic waves on the spectral sensitivity of photoreceivers based on AlGaAs/GaAs- heterostructures has been studied. Ultrasonic treatment of a zinc-doped graded-gap AlxGa1-x As- film leads to the formation of a surface layer sensitive to electromagnetic radiation in the wavelength range < 0,55m. It is established that this layer is formed as a result of the acoustostimulated inward diffusion of zinc from the surface to the bulk of the graded-gap layer. The observed expansion of the short-wavelength sensitivity range and an increase in the efficiency of nonequilibrium charge carrier collection in AlGaAs/GaAs- photoreceivers are due to improvement of the crystal defect structure and the dopant redistribution under the action of ultrasound. (authors)

2007-09-01

257

Method to analyze remotely sensed spectral data  

Energy Technology Data Exchange (ETDEWEB)

A fast and rigorous multivariate curve resolution (MCR) algorithm is applied to remotely sensed spectral data. The algorithm is applicable in the solar-reflective spectral region, comprising the visible to the shortwave infrared (ranging from approximately 0.4 to 2.5 .mu.m), midwave infrared, and thermal emission spectral region, comprising the thermal infrared (ranging from approximately 8 to 15 .mu.m). For example, employing minimal a priori knowledge, notably non-negativity constraints on the extracted endmember profiles and a constant abundance constraint for the atmospheric upwelling component, MCR can be used to successfully compensate thermal infrared hyperspectral images for atmospheric upwelling and, thereby, transmittance effects. Further, MCR can accurately estimate the relative spectral absorption coefficients and thermal contrast distribution of a gas plume component near the minimum detectable quantity.

Stork, Christopher L. (Albuquerque, NM); Van Benthem, Mark H. (Middletown, DE)

2009-02-17

258

Phase-matching properties of PPKTP, MgO:PPSLT and MgO:PPcLN for ultrafast optical parametric oscillation in the visible and near-infrared ranges with green pump  

Science.gov (United States)

Ultrashort pulses with wavelength tuning in the visible and near-infrared (VNIR) ranges (here approximately 680 to 2000 nm) have wide application in many biomedical devices especially in imaging and spectroscopy. The theoretical studies here consider the phase-matching conditions of three periodically poled crystals (PPKTP, MgO:PPcLN and MgO:PPSLT) to use for femtosecond optical parametric oscillators (OPO) to generate wavelength tunability in this range. The basic optical properties and the wavelength tuning ranges are calculated with respect to different grating periods and temperature variation. Dispersive properties of crystals relevant to the ultrafast operation regime are also discussed. The excitation wavelength used here for the analysis is 520 nm which is the second harmonic wavelength of Yb-doped ultrashort pulse solid state lasers. The concept of the tunable femtosecond OPOs with green excitation presented here can be a better alternative to the widely used expensive Ti:Sapphire lasers.

Manjooran, S.; Zhao, H.; Lima, I. T.; Major, A.

2012-08-01

259

High resolution spectral survey of symbiotic stars in the near-IR over the GAIA wavelength range  

CERN Multimedia

High resolution (R~20,000), high signal-to-noise (S/N~100) spectra were collected for ~40 symbiotic stars with the Asiago echelle spectrograph over the same 8480-8740 Ang wavelength range covered by the ESA Cornerstone mission GAIA, centered on the near-IR CaII triplet and the head of the Paschen series. A large number (~140) of cool MKK giant and supergiant templates were observed with the same instrumentation to serve as a reference and classification grid. The spectra offer bright prospects in classifying and addressing the nature of the cool component of symbiotic stars (deriving T(eff), log g, [Fe/H], [alpha/Fe], V(rot)sin i both via MDM-like methods and syntetic atmosphere modeling) and mapping the physical condition and kinematics of the gas regions responsible for the emission lines.

Marrese, P M; Munari, U; Marrese, Paola M.; Sordo, Rosanna; Munari, Ulisse

2002-01-01

260

Variation of spectral properties of dielectric ionic crystal in the terahertz range due to the polariton absorption.  

Science.gov (United States)

The dispersion equations for polariton waves in dielectric ionic crystal with the absorption are obtained. The self-consistent solutions of the system of Maxwell electromagnetic field equations and the equations of motion of ions have been used. The elastic and absorption properties of the crystal are taken into account in the ion equations of motion. It is shown that the separated equations of motion for positive and negative ions allow obtaining all branches of phonon and polariton spectrum by the example of the ionic crystal of cubic symmetry at the terahertz range. It has been shown that the variation of absorption in the crystal leads to changing of the character of spectrum branch and the polariton velocities. PMID:24922221

Dzedolik, Igor V; Pereskokov, Vladislav

2014-05-20

 
 
 
 
261

Towards a comprehensive eye model for zebrafish retinal imaging using full range spectral domain optical coherence tomography  

Science.gov (United States)

In regenerative medicine, the zebrafish is a prominent animal model for studying degeneration and regeneration processes, e.g. of photoreceptor cells in the retina. By means of optical coherence tomography (OCT), these studies can be conducted over weeks using the same individual and hence reducing the variability of the results. To allow an improvement of zebrafish retinal OCT imaging by suitable optics, we developed a zebrafish eye model using geometrical data obtained by in vivo dispersion encoded full range OCT as well as a dispersion comprising gradient index (GRIN) lens model based on refractive index data found in the literature. Using non-sequential ray tracing, the focal length of the spherical GRIN lens (diameter of 0.96 mm) was determined to be 1.22 mm at 800 nm wavelength giving a Matheissen's ratio (ratio of focal length to radius of the lens) of 2.54, which fits well into the range between 2.19 and 2.82, found for various fish lenses. Additionally, a mean refractive index of 1.64 at 800 nm could be retrieved for the lens to yield the same focal position as found for the GRIN condition. With the aid of the zebrafish eye model, the optics of the OCT scanner head were adjusted to provide high-resolution retinal images with a field of view of 30° x 30°. The introduced model therefore provides the basis for improved retinal imaging with OCT and can be further used to study the image formation within the zebrafish eye.

Gaertner, Maria; Weber, Anke; Cimalla, Peter; Köttig, Felix; Brand, Michael; Koch, Edmund

2014-03-01

262

The potential for extending the spectral range accessible to the European XFEL down to 0.05 nm  

International Nuclear Information System (INIS)

Specifications of the European XFEL cover a range of wavelengths down to 0.1 nm. The baseline design of the European XFEL assumes standard (SASE) FEL mode for production of radiation i.e. only one photon beam at one fixed wavelength from each baseline undulator with tunable gap. Recent developments in the field of FEL physics and technology form a reliable basis for an extensions of the mode of operation of XFEL facilities. This paper explores how the wavelength of the output radiation can be decreased well beyond the European XFEL design, down to 0.05 nm. In the proposed scheme, which is based on the use ''fresh bunch'' technique, simultaneous operation at two different wavelengths possible. It is shown that one can generate simultaneously, in the same baseline undulator with tunable gap, high intensity radiation at 0.05 nm at saturation, and high intensity radiation around 0.15 nm according to design specifications. We present a feasibility study and we make exemplifications with the parameters of SASE2 line of the European XFEL. (orig.)

2010-01-01

263

Laser processing of ceramics and metals by high-intensity picosecond and nanosecond laser pulses in UV, visible, and IR range of spectrum  

Science.gov (United States)

Experimental investigations of ablation processes of AlN, Si3N4(MgO), Si3N4(YAI) ceramics, steels and aluminum have been conducted using first, second and fourth harmonics of picosecond and nanosecond Nd:YAP laser (1078 nm basic wavelength). The measurements have been carried out in a wide range of incident power density values: 1010 - 1014 W/cm2. The passive-active mode-locked/Q-switched laser with a high quality spatial and temporal distribution of output radiation operated at repetition rates of 1 - 10 Hz was used. The ablation rate dependencies obtained for multipulse irradiation regimes are presented and analyzed. The physical mechanisms responsible for ablation processes in pico- and nanosecond range of laser pulse duration are discussed. Special attention is paid to the role of plasma formation and modification of chemical composition of ceramic surface layers during the laser-matter interaction process. The scanning electron microscope pictures of ablated holes and cuts produced at different irradiation conditions are demonstrated. It is shown that at the relevant irradiation conditions the high quality regular microstructures consisted of holes, cuts, etc., with a typical size varied from tens to several microns could be produced using high peak power ultra short laser pulses.

Garnov, Sergei V.; Klimentov, Sergei M.; Kononenko, T. V.; Konov, Vitaly I.; Lubnin, E. N.; Dausinger, Friedrich; Raiber, Armin

1996-04-01

264

Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440-6810 A in the gamma Vel cluster, and calibration of spectral indices  

CERN Multimedia

We study spectral diagnostics available from optical spectra with R=17000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the gamma Vel young cluster, in order to determine the fundamental parameters of these stars. We define a set of spectroscopic indices, sampling TiO bands, H-alpha core and wings, and many temperature- and gravity-sensitive lines. Combined indices tau (gamma) are also defined as Teff (log g) indicators over a wide spectral-type range. H-alpha emission-line indices are also chromospheric activity or accretion indicators. A metallicity-sensitive index is also defined. These indices enable us to find a clear difference between gravities of main-sequence and pre-main-sequence stars (as well as giant stars): the (gamma,tau) diagram is thus argued to be a promising distance-independent age measurement tool for young clusters. Our indices were quantitatively calibrated by means of photometry and literature reference spectra (from UVES-POP and ELODIE 3.1 ...

Damiani, F; Micela, G; Randich, S; Gilmore, G; Drew, J E; Jeffries, R D; Frémat, Y; Alfaro, E J; Bensby, T; Bragaglia, A; Flaccomio, E; Lanzafame, A C; Pancino, E; Recio-Blanco, A; Sacco, G G; Smiljanic, R; Jackson, R J; de Laverny, P; Morbidelli, L; Worley, C C; Hourihane, A; Costado, M T; Jofré, P; Lind, K; Maiorca, E

2014-01-01

265

The gas turbulence in planetary nebulae: quantification and multi-D maps from long-slit, wide-spectral range echellogram  

CERN Multimedia

This methodological paper is part of a short series dedicated to the long-standing astronomical problem of de-projecting the bi-dimensional, apparent morphology of a three-dimensional distribution of gas. We focus on the quantification and spatial recovery of turbulent motions in planetary nebulae (and other classes of expanding nebulae) by means of long-slit echellograms over a wide spectral range. We introduce some basic theoretical notions, discuss the observational methodology, and develop an accurate procedure disentangling all broadening components of the velocity profile in all spatial positions of each spectral image. This allows us to extract random, non-thermal motions at unprecedented accuracy, and to map them in 1-, 2- and 3-dimensions. We present the solution to practical problems in the multi-dimensional turbulence-analysis of a testing-planetary nebula (NGC 7009), using the three-step procedure (spatio-kinematics, tomography, and 3-D rendering) developed at the Astronomical Observatory of Padua...

Sabbadin, F; Benetti, S; Ragazzoni, R; Cappellaro, E

2008-01-01

266

Application of multilayer structures to the determination of optical constants in the x-ray, soft x-ray and extreme ultra violet spectral ranges  

International Nuclear Information System (INIS)

The dispersion of x-rays (XR), soft x-rays (SXR) and extreme ultra-violet (EUV) light by multilayer structures is dependent on the scattering and absorption cross-sections of the elements used to synthesize the multilayer. In this paper it is shown that this dependence provides a means for the accurate experimental determination of the optical constants of the multilayer constituents. Two specific approaches are presented and discussed. It is shown that detailed analysis of the energy dependence of the reflectivity of a simple depth periodic multilayer allows the unfolding of the optical constants. A new optic structure, the multilayer diffraction grating, is described and it is demonstrated that such combined microstructure optics allow the scattering cross-sections of the multilayer constituents to be accurately determined over broad spectral ranges

1988-11-28

267

The spectral characteristics of Gd sub 2 SiO sub 5 :Eu sup 3 sup + in VUV-UV range  

CERN Multimedia

Synchrotron radiation source was used to investigated the spectral characteristics of Gd sub 2 SiO sub 5 :Eu sup 3 sup + in VUV-UV range. The various energy transfers at room temperature and 10 K, including from host or Gd sup 3 sup + ions to Eu sup 3 sup + ions and transfer between Eu sup 3 sup + ions at two different lattice sites, were discussed. In addition the emission spectra under 186 nm and 276 nm excitation were compared from the view of quantum cutting. The results indicate that Gd sub 2 SiO sub 5 :Eu sup 3 sup + is a kind of material with potential high efficiency quantum cutting

Chen Yong; Wei Ya Guang; Tao Ye

2002-01-01

268

Using Spectral Edge To Measure Doppler Shift  

Science.gov (United States)

New pulsed-laser ranging systems implement spectral-edge technique making high-resolution measurements of Doppler frequency shift in signals backscattered from targets. Pulsed laser emits at ultraviolet, visible, or infrared wavelength suitable for generation of desired target. Optical filter ("edge" filter) has sharp spectral transmission function such that middle frequency of laser emission lies on steep portion of slope ("edge") on one side of peak. Frequency inferred from relative amplitudes of signal with and without filtering. Intended for use in measuring velocities of solid and diffuse moving targets like wind, clouds, aerosols, or rain. Applications include measurements of wind shear from airports and aircraft.

Korb, Lawrence

1992-01-01

269

Applications of Suits spectral model to wheat  

Science.gov (United States)

Canopy reflectance calculations for a spring type Mexican wheat, Penjamo, are compared with published data on Scout winter wheat. Good agreement exists between model calculations and experimental data in the spectral range, 500 nm to 750 nm, suggesting that the model parameters for wheat can be applied to different cultivars of wheat in the same growth stage. Wheat canopy reflectance is dependent upon surface soil type and this dependency is examined with the Suits' spectral model. In this particular growth stage wheat reflectance is shown to be nearly independent of soil reflectance in the visible wavelengths and progressively dependent at longer wavelengths in the infrared.

Chance, J. E.

1977-01-01

270

Spectral measurements of aerosol particle extinction in the 0.4-3.7 {mu}m wavelength range, performed at Sagres with the IR-RAD sun-radiometer[Special issue with manuscripts related to the second Aerosol Characterization Experiment (ACE-2), 16 June-25 July 1997  

Energy Technology Data Exchange (ETDEWEB)

During the CLEARCOLUMN campaign which took place at Sagres (Portugal) from 16 June to 25 July 1997, more than 2000 spectral measurements of direct solar irradiance were performed at thirteen window-wavelengths in the 0.4-3.7 {mu}m range, on 27 days. The measurements were performed using the IR-RAD sun-radiometer designed and manufactured at the Institute ISAO (FISBAT), Bologna (Italy), and carefully calibrated by applying the Langley plot method to the measurements performed on 24 October 1996, at the Schneefernerhaus Observatory on the Zugspitze (Germany). From these measurements, the values of the total atmospheric optical depth were obtained at the various wavelengths, from which the corresponding spectral values of aerosol optical depth were determined through accurate corrections for Rayleigh scattering and gaseous absorption. Such values were found to be mostly smaller than 0.1 during June and early July, presenting almost neutral spectral dependence characteristics, closely related to the prevailing oceanic origins of particulate matter. Higher values of aerosol optical thickness, mainly ranging between 0.1 and 0.5 at visible wavelengths and sharply decreasing with wavelength, were found during the rest of July in the presence of predominant contents of continental and anthropogenic aerosol particles arriving from polluted European regions. The King inversion method was applied to the spectral series of aerosol optical depth to determine the particle size-distribution curves in the 0.2-20 {mu}m diameter range. For 2 of these cases (one chosen for a low atmospheric loading of marine aerosols and the other for a mean content of continental/anthropogenic aerosols), the changes in the outgoing solar radiation flux produced by aerosol particles were calculated, considering different surface albedo conditions. The results obtained in the second case show that changes of opposite sign can be caused by the same atmospheric aerosol loading when passing from oceanic to continental areas.

Vitale, Vito; Tomasi, Claudio; Bonafe, Ubaldo; Marani, Stefano; Lupi, Angelo; Cacciari, Alessandra; Ruggeri, Pietro [Istituto ISAO (FISBAT)-CNR, Bologna (Italy); Hoyningen-Huene, W. von [Bremen Univ. (Germany). Inst. fuer Umweltphysik

2000-04-01

271

Comparison between visible and near-IR flame spectra from natural gas-fired furnace for blackbody temperature measurements  

Energy Technology Data Exchange (ETDEWEB)

This paper reports the results from investigating the feasibility of calculating flame temperature from a natural gas-fired furnace based on blackbody radiation in the visible spectral range. If successful, the visible spectral range would provide data for multi-task applications such as emission line analysis and temperature calculation simultaneously. A probe containing a lens connected to the fiber-optic cables is inserted into the furnace and pointed towards the flame. Spectral intensity data are fed back to a spectrometer and then to a monitoring computer. The approach is first applied to various furnace types using the visible range to establish a baseline for the technique. The results for temperature calculations in the visible range are then compared with those taken in the near-IR (NIR) range under the same conditions. This comparison indicates that temperatures calculated from visible region could be as accurate as the one obtained from NIR region. Challenges associated with this technique are also discussed. 17 refs., 5 figs., 1 tab.

Shahla Keyvan; Rodney Rossow; Carlos Romero; Xianchang Li [University of Missouri, Columbia, MO (United States). Department of Mechanical and Aerospace Engineering

2004-06-01

272

Visible Light Communication  

Directory of Open Access Journals (Sweden)

Full Text Available Visible light communication (VLC is becoming an alternative choice for next-generation wireless technology by offering low cost, unregulated bandwidth and ubiquitous infrastructures support. This technology is envisioned to be used in a wide range of applications both indoor as well as outdoor. Visible Light Communication (VLC uses light emitting diodes (LEDs, for the dual role of illumination and data transmission. With this leading edge technology, data including video and audio, internet traffic etc can be transmitted at high speeds using LED light. Using LEDs is helping to drive this technology in the form of Visible Light Communication (VLC. In this paper, a visible light communications system is proposed that employs wavelength division multiplexing, to transmit multiple data streams from different data sources simultaneously andtransmission of audio song and also an image was demonstrated by using LED light. Not limit to this, multiple source signals simultaneously in different frequency bands were transmitted through the LED circuitry, and the signals were recovered successfully. This demonstrates the feasibility studies of our design in signals broadcasting

Rajan Sagotra, Reena Aggarwal

2013-04-01

273

Wavelength-resolved optical extinction measurements of aerosols using broad-band cavity-enhanced absorption spectroscopy over the spectral range of 445-480 nm.  

Science.gov (United States)

Despite the significant progress in the measurements of aerosol extinction and absorption using spectroscopy approaches such as cavity ring-down spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), the widely used single-wavelength instruments may suffer from the interferences of gases absorption present in the real environment. A second instrument for simultaneous measurement of absorbing gases is required to characterize the effect of light extinction resulted from gases absorption. We present in this paper the development of a blue light-emitting diode (LED)-based incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach for broad-band measurements of wavelength-resolved aerosol extinction over the spectral range of 445-480 nm. This method also allows for simultaneous measurement of trace gases absorption present in the air sample using the same instrument. On the basis of the measured wavelength-dependent aerosol extinction cross section, the real part of the refractive index (RI) can be directly retrieved in a case where the RI does not vary strongly with the wavelength over the relevant spectral region. Laboratory-generated monodispersed aerosols, polystyrene latex spheres (PSL) and ammonium sulfate (AS), were employed for validation of the RI determination by IBBCEAS measurements. On the basis of a Mie scattering model, the real parts of the aerosol RI were retrieved from the measured wavelength-resolved extinction cross sections for both aerosol samples, which are in good agreement with the reported values. The developed IBBCEAS instrument was deployed for simultaneous measurements of aerosol extinction coefficient and NO(2) concentration in ambient air in a suburban site during two representative days. PMID:23320530

Zhao, Weixiong; Dong, Meili; Chen, Weidong; Gu, Xuejun; Hu, Changjin; Gao, Xiaoming; Huang, Wei; Zhang, Weijun

2013-02-19

274

Portable on-ground hard- and software system for obtaining and processing spectrally spreaded images in the ranges of 3-5 and 8-14 um  

Science.gov (United States)

The use of thermovision systems for the remote sensing of surface temperatures has been conventional for a long time. In recent years serious progress has been achieved in the reduction of instrumental errors of IR receivers and increase of quality of thermal images visualization and registration. The smaller progress is observed in questions of reduction of methodical measuring errors, in a sense of the determination by thermovision methods of the true (thermodynamic) temperature of a radiating surface, its factor of radiation, and the determination of a ratio of own and reflected radiation. It is expected that the essential progress can be achieved by creation of thermovision systems, carrying out registration of objects in several spectral subranges of ranges 3-5 or 8-14 micrometer. A similar result can be achieved by use of single-channel devices with a set of spectral filters. Such an approach provides, in essence, the registration of multispectral thermal images, further mathematical processing of which (or processing in a real time scale), permits us to make approaches to solving the above mentioned problems. Thus, the problem of determination of a spectrum of radiation for each point of the image on the basis of results of multispectral measurements becomes the central one. As a criterion the most optimum accuracy and complete time of measurement (for single-channel systems) or amount of channels (for multichannel systems) should be used. Naturally, the term 'accuracy' must be determined. The offered technique was being created during scientific cooperation between the Institute of Radio-electronics of the Russian Academy of Sciences (IRE RAN), producing thermovision systems, and the State Research Institute of Aviation Systems (GosNIIAS) which makes software for such devices and realizes the multispectral processing.

Medvedev, Evgeny M.; Falkov, Edward J.; Kartzev, Alexander V.; Scherbakov, Michael I.

1995-12-01

275

Primary Reaction Dynamics of Green Absorbing Proteorhodopsin WT and D97N Mutant Observed by fs Infrared and Visible Spectroscopy  

Science.gov (United States)

We study the D97N mutant of the light driven proton pump proteorhodopsin and compare the results to experiments on the wild type at two pH values. The application of transient absorption spectroscopy in the visible and infrared spectral range provides detailed information on the first steps in the photocycle.

Neumann, Karsten; Verhoefen, Mirka-Kristin; Weber, Ingrid; Glaubitz, Clemens; Wachtveitl, Josef

276

Growth and characterization of visible diode lasers  

International Nuclear Information System (INIS)

The (AlxGa1-x)yIn1-yrho material system, lattice matched to GaAs substrates, has received much attention for use in visible laser diodes emitting in the spectral region ?--650-680 nm. When lattice matched to GaAs (y=0.5), this alloy spans a direct band gap range from --1.85 eV (at x=0) to --2.3 eV (near the T-X crossover at chi--0.7) It was only recently that device quality epitaxial layers have been prepared in this material due to difficulties with liquid phase epitaxial (LPE) and halide vapor phase epitaxial growth.Only organometallic vapor phase epitaxy (OMVPE) and molecular beam epitaxy (MBE) growth techniques have successfully produced AlGainP laser material

1988-04-25

277

Dielectric Function of Undoped and Doped Poly[2-methoxy-5-(3?,7?-dimethyloctyloxy)-1,4-phenylene-vinylene] by Ellipsometry in a Wide Spectral Range  

Science.gov (United States)

Ellipsometric measurements in a wide spectral range (from 0.05 to 6.5 eV) have been carried out on the organic semiconducting polymer, poly[2-methoxy-5-(3?,7?-dimethyloctyloxy)-1,4-phenylene-vinylene] (MDMO-PPV), in both undoped and doped states. The real and imaginary parts of the dielectric function and the refractive index are determined accurately, provided that the layer thickness is measured independently. After doping, the optical properties show the presence of new peaks, which could be well-resolved by spectroscopic ellipsometry. Also for the doped material, the complex refractive index, with respect to the dielectric function, has been determined. The broadening of the optical transitions is due to the delocalization of polarons at higher doping level. The detailed information about the dielectric function as well as refractive index function obtained by spectroscopic ellipsometry allows not only qualitative but also quantitative description of the optical properties of the undoped/doped polymer. For the direct characterization of the optical properties of MDMO-PPV, ellipsometry turns out to be advantageous compared to conventional reflection and transmission measurements.

2013-01-01

278

InSb quantum dots for the mid-infrared spectral range grown on GaAs substrates using metamorphic InAs buffer layers  

Science.gov (United States)

Type II InSb/InAs quantum dots (QDs) were successfully grown on GaAs substrates using three different metamorphic buffer layer (MBL) designs. The structural properties of the resulting metamorphic InAs buffer layers were studied and compared using cross-sectional transmission electron microscopy and high resolution x-ray diffraction measurements. Photoluminescence (PL) originating from the InSb QDs was observed from each of the samples and was found to be comparable to the PL of InSb QDs grown onto homo-epitaxially deposited InAs. The 4 K PL intensity and linewidth of InSb QDs grown onto a 3 µm thick InAs buffer layer directly deposited onto GaAs proved to be superior to that from QDs grown onto an InAs MBL using either AlSb or GaSb interlayers. Light-emitting diode structures containing ten layers of InSb QD in the active region were subsequently fabricated and electroluminescence from the QDs was obtained in the mid-infrared spectral range up to 180 K. This is the first step towards obtaining mid-infrared InSb QD light sources on GaAs substrates.

Lu, Q.; Zhuang, Q.; Marshall, A.; Kesaria, M.; Beanland, R.; Krier, A.

2014-07-01

279

Annual Variation of Local Photon Emissions’ Spectral Power within the mHz Range Overlaps with Seismic-Atmospheric Acoustic Oscillations  

Directory of Open Access Journals (Sweden)

Full Text Available Spheroidal modes of seismic and acoustic oscillations in the atmosphere occur within the 2 to 7 mHz range with peak-to-peak variations in the order of 10–12 to 10–11 m·s–2. Previous research indicated the amplitudes for 230 s and 270 s periods peak during the summer months. In the present study the amplitudes of a reliably apparent 3 mHz increment from spectral analyses of minute-to-minute measurements of background photon emissions by a photomultiplier tube housed in a dark room were sampled for a one year period. The peak increase in the power of this increment was maximal during the summer months and overlapped conspicuously with the annual variation in fundamental spheroidal modes of seismic free oscillations. Quantitative estimates indicate that relative shifts in the order of 10–11 W/m2 for photon emissions may reflect the annual variation in coupled oscillations between the earth and atmosphere.

Michael A. Persinger

2012-02-01

280

Investigation of hydroxyl-mediated spectral interference from easily ionized elements in laser-enhanced ionization spectrometry in the 281-285 nm range  

Energy Technology Data Exchange (ETDEWEB)

The spectral background from 281 to 285 nm in the laser-enhanced ionization (LEI) spectrum of aqueous samples containing easily ionized elements (EIE) at concentrations similar to those found in blood was investigated. A complex, structured spectral background was observed, which appears in the presence of Na or K, but does not match the spectral signature of either element. The same behavior was also observed for Li. It was established that this background originates from an energy transfer between laser-excited hydroxyl (OH) molecules and ground-state EIEs. The intensity of this spectral feature was found to increase with EIE concentration and applied electrode voltage. This unexpected source of spectral interference may complicate the determination of trace metals by LEI in the presence of EIEs, since it can not be prevented by simply avoiding interference from atomic lines.

Herreyre, Karine [Department of Chemistry and Centre d' optique, photonique et laser (COPL), Laval University, Quebec City (Ciheam), G1K 7P4 (Canada); Boudreau, Denis [Department of Chemistry and Centre d' optique, photonique et laser (COPL), Laval University, Quebec City (Ciheam), G1K 7P4 (Canada)]. E-mail: denis.boudreau@chm.ulaval.ca

2004-12-01

 
 
 
 
281

Ultraviolet-visible-near infrared spectra of 50 samples  

Energy Technology Data Exchange (ETDEWEB)

Under the subject contract, Unidynamics/Phoenix recorded the ultraviolet-visible-near infrared spectra of 50 samples supplied by LANL. A Varian Cary 2300 series spectrophotometer produced the spectral data. The spectrophotometer was interfaced to a Varian D5-15 Data Station, and hard copies of data were made. Baseline corrections throughout the wavelength range were established using Halon as a reference material. Corrected measurements were automatically made by the system on every sample. Two types of sample holders were tried. Before collecting data on the LANL samples, identical samples of PETN were examined using both holders.

Taylor, B. [Crane Unidynamics Phoenix, AZ (United States)

1988-08-30

282

Gallium Phosphide as a material for visible and infrared optics  

Directory of Open Access Journals (Sweden)

Full Text Available Gallium phosphide is interesting material for optical system working in both visible and MWIR or LWIR spectral ranges. Number of a material available for these applications is limited. They are typically salts, fluorides or sulphides and usually exhibit unfavorable properties like brittleness; softness; solubility in water and small chemical resistance. Although GaP has do not offer best optical parameters excels over most other material in mechanical and chemical resistance. The article describes its most important characteristics and outlines some applications where GaP should prove useful.

Václavík J.

2013-05-01

283

Morphology of the spectral resonance structure of the electromagnetic background noise in the range of 0.1–4 Hz at L = 5.2  

Directory of Open Access Journals (Sweden)

Full Text Available Continuous observations of fluctuations of the geomagnetic field at Sodankylä Geophysical Observatory (L = 5.2 were used for a comprehensive morphological study of the spectral resonance structure (SRS seen in the background electromagnetic noise in the frequency range of 0.1–4.0 Hz. It is shown that the occurrence rate of SRS is higher in the nighttime than in the daytime. The occurrence rate is higher in winter than in summer. The SRS frequencies and the difference between neighbouring eigenfrequencies (the frequency scale increase towards nighttime and decrease towards daytime. Both frequency scale and occurrence rate exhibit a clear tendency to decrease from minimum to maximum of the solar activity cycle. It is found that the occurrence rate of SRS decreases when geomagnetic activity increases. The SRS is believed to be a consequence of a resonator for Alfvén waves, which is suggested to exist in the upper ionosphere. According to the theory of the ionospheric Alfvén resonator (IAR, characteristics of SRS crucially depend on electron density in the F-layer maximum, as well as on the altitudinal scale of the density decay above the maximum.We compared the SRS morphological properties with predictions of the IAR theory. The ionospheric parameters needed for calculation were obtained from the ionosphere model (IRI-95, as well as from measurements made with the ionosonde in Sodankylä. We conclude that, indeed, the main morphological properties of SRS are explained on the basis of the IAR theory. The measured parameters of SRS can be used for improving the ionospheric models.Key words. Ionosphere (auroral ionosphere; wave propagation – Radio Science (electromagnetic noise and interference

J. Manninen

284

Energy transfers and spectral eddy viscosity in large-eddy simulations of homogeneous isotropic turbulence: Comparison of dynamic Smagorinsky and multiscale models over a range of discretizations:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Energy transfers within large-eddy simulation (LES) and direct numerical simulation (DNS) grids are studied. The spectral eddy viscosity for conventional dynamic Smagorinsky and variational multiscale LES methods are compared with DNS results. Both models underestimate the DNS results for a very coarse LES, but the dynamic Smagorinsky model is significantly better. For moderately to well-refined LES, the dynamic Smagorinsky model overestimates the spectral eddy viscosity at low wave numbers. ...

Hughes, T. J. R.; Wells, G. N.; Wray, A. A.

2004-01-01

285

A Fourier transform Raman spectrometer with visible laser excitation  

CERN Document Server

We present the development and performance of a Fourier transformation (FT) based Raman spectrometer working with visible laser (532 nm) excitation. It is generally thought that FT-Raman spectrometers are not viable in the visible range where shot-noise limits the detector performance and therein they are outperformed by grating based, dispersive ones. We show that contrary to this common belief, the recent advances of high-performance interference filters makes the FT-Raman design a valid alternative to dispersive Raman spectrometers for samples which do not luminesce. We critically compare the performance of our spectrometer to two dispersive ones: a home-built single channel and a state-of-the-art CCD based instruments. We demonstrate a similar or even better sensitivity than the CCD based dispersive spectrometer particularly when the laser power density is considered. The instrument possesses all the known advantages of the FT principle of spectral accuracy, high throughput, and economic design. We also d...

Dzsaber, S; Bernáth, B; Gyüre, B; Fehér, T; Kramberger, C; Pichler, T; Simon, F

2014-01-01

286

Inactivation of viruses by coherent excitations with a low power visible femtosecond laser  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M1...

2007-01-01

287

Water vapor retrieval from OMI visible spectra  

Science.gov (United States)

There are distinct spectral features of water vapor in the wavelength range covered by the Ozone Monitoring Instrument (OMI) visible channel. Although these features are much weaker than those at longer wavelengths, they can be exploited to retrieve useful information about water vapor. They have an advantage in that their small optical depth leads to fairly simple interpretation as measurements of the total water vapor column density. We have used the Smithsonian Astrophysical Observatory (SAO)'s OMI operational retrieval algorithm to derive the Slant Column Density (SCD) of water vapor from OMI measurements using the 430-480 nm spectral region after extensive optimization of retrieval windows and parameters. The Air Mass Factor (AMF) is calculated using look-up tables of scattering weights and monthly mean water vapor profiles from the GEOS-5 assimilation products. We convert from SCD to Vertical Column Density (VCD) using the AMF and generate associated retrieval averaging kernels and shape factors. Our standard water vapor product has a median SCD of ~ 1.3 × 1023 molecule cm-2 and a median relative uncertainty of ~ 11% in the tropics, about a factor of 2 better than that from a similar OMI algorithm but using narrower retrieval window. The corresponding median VCD is ~ 1.2 × 1023 molecule cm-2. We have also explored the sensitivities to various parameters and compared our results with those from the Moderate-resolution Imaging Spectroradiometer (MODIS) and the Aerosol Robotic NETwork (AERONET).

Wang, H.; Liu, X.; Chance, K.; Gonzalez Abad, G.; Miller, C. Chan

2014-01-01

288

Feature point descriptors: infrared and visible spectra.  

Science.gov (United States)

This manuscript evaluates the behavior of classical feature point descriptors when they are used in images from long-wave infrared spectral band and compare them with the results obtained in the visible spectrum. Robustness to changes in rotation, scaling, blur, and additive noise are analyzed using a state of the art framework. Experimental results using a cross-spectral outdoor image data set are presented and conclusions from these experiments are given. PMID:24566634

Ricaurte, Pablo; Chilán, Carmen; Aguilera-Carrasco, Cristhian A; Vintimilla, Boris X; Sappa, Angel D

2014-01-01

289

Feature Point Descriptors: Infrared and Visible Spectra  

Science.gov (United States)

This manuscript evaluates the behavior of classical feature point descriptors when they are used in images from long-wave infrared spectral band and compare them with the results obtained in the visible spectrum. Robustness to changes in rotation, scaling, blur, and additive noise are analyzed using a state of the art framework. Experimental results using a cross-spectral outdoor image data set are presented and conclusions from these experiments are given.

Ricaurte, Pablo; Chilan, Carmen; Aguilera-Carrasco, Cristhian A.; Vintimilla, Boris X.; Sappa, Angel D.

2014-01-01

290

Abnormal glow discharge detection of visible radiation.  

Science.gov (United States)

Extension of abnormal glow discharge detection of electromagnetic radiation to visible wavelengths is observed with inexpensive commercial indicator lamps. The spectral response and mechanisms of detection are discussed and advantages over gas-filled photodiodes noted. Responses from different discharge regions are observed and their implications considered. PMID:20165225

Kopeika, N S; Rosenbaum, J; Kastner, R

1976-06-01

291

Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow a...

Arnold, N. F.; Robinson, T. R.; Lester, M.; Byrne, P. B.; Chapman, P. J.

2001-01-01

292

Automated multifunction apparatus for spectral and polarization measurements  

International Nuclear Information System (INIS)

An automated spectral apparatus is described that is based on an SDL-2 spectrometer for spectral and polarization measurements with small specimens (0.15 x 0.15 mm) by the Fourier-coefficient method in the visible and ultraviolet regions over a wide range of temperatures. The absorption, dichroism, birefringence, and polarization orientation of natural waves are determined simultaneously in a single measurement cycle. Polarization-luminescence spectra can also be recorded from one region of the specimen without its adjustment. 3 refs., 3 figs

1992-08-01

293

The Visible and Near Infrared module of EChO  

CERN Multimedia

The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude Mv= 9-12 and to see contrasts of the order of 10-4 - 10-5 necessary to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR is a spectrometer in a cross-dispersed configuration, covering the 0.4-2.5 micron spectral range with a resolving power of about 330 and a field of view of 2 arcsec. It is functionally split into two channels respectively working in the 0.4-1 and 1.0-2.5 micron spectral ranges. Such a solution is imposed by the fact the light at short wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The spectromete...

Adriani, A; Gambicorti, L; Focardi, M; Oliva, E; Farina, M; Di Giorgio, A M; Santoli, F; Pace, E; Piccioni, G; Filacchione, G; Pancrazzi, M; Tozzi, A; Micela, G

2014-01-01

294

Validation of line and continuum spectroscopic parameters with measurements of atmospheric emitted spectral radiance from far to mid infrared wave number range  

International Nuclear Information System (INIS)

The latest release of a high-resolution transmission molecular absorption database along with two improved models of water vapor continuum absorption are used to check their impact on the improvement of state-of-art radiative transfer. Radiative transfer performance has been assessed using high mountains atmospheric emitted spectral downwelling radiance observations in the 360-1200 cm-1 spectral regions. These high mountains observations are particularly suited to check the behavior and performance in the water vapor rotation band. In addition, they also have allowed us to gain insight into understanding the quality of recent new compilation of lines and related treatment for the ?2 CO2 band and the O3 band at 9.6?m. Comparisons are made between forward calculations of atmospheric transmission spectra and spectral radiances measured using two ground-based Fourier transform instruments. The results demonstrate that water vapor absorption largely benefits from the recent improvement in the related continuum (both self and foreign). In addition, ozone absorption is very accurately reproduced and, although to a less extent, this is also the case of CO2 absorption in the long wave ?2 band.

2012-07-01

295

The ultrafast nonlinear optical response and multi-photon absorption of a new metal complex in the near-infrared spectral range  

International Nuclear Information System (INIS)

A new coordination compound, chloro(1,10-phenanthroline-N, N')(triphenylphosphine)copper(I) dichloromethane, incorporated in poly(methyl methacrylate) exhibits superior nonlinear optical properties in the near-infrared spectral region. Its nonlinear response time and third-order nonlinear optical susceptibility at 800 nm are ? 90 fs and 1.8 × 10?10 esu, respectively. Considerable nonlinear absorption is observed with this sample, near 800 and 1250 nm. The contribution of the excited states to the total nonlinear absorption process is discussed. The results reveal the potential of this newly designed compound for multi-photon absorption-based photonic applications

2010-03-01

296

Spectral variability of the particulate backscattering ratio  

Science.gov (United States)

The spectral dependency of the particulate backscattering ratio is relevant in the fields of ocean color inversion, light field modeling, and inferring particle properties from optical measurements. Aside from theoretical predictions for spherical, homogeneous particles, we have very limited knowledge of the actual in situ spectral variability of the particulate backscattering ratio. This work presents results from five research cruises that were conducted over a three-year period. Water column profiles of physical and optical properties were conducted across diverse aquatic environments that offered a wide range of particle populations. The main objective of this research was to examine the behavior of the spectral particulate backscattering ratio in situ, both in terms of its absolute magnitude and its variability across visible wavelengths, using over nine thousand 1-meter binned data points for each of five wavelengths of the spectral particulate backscattering ratio. Our analysis reveals no spectral dependence of the particulate backscattering ratio within our measurement certainty, and a geometric mean value of 0.013 for this dataset. This is lower than the commonly used value of 0.0183 from Petzold’s integrated volume scattering data. Within the first optical depth of the water column, the mean particulate backscattering ratio was 0.010.

Whitmire, A. L.; Boss, E.; Cowles, T. J.; Pegau, W. S.

2007-05-01

297

A new connection space for low-dimensional spectral color management  

Science.gov (United States)

Multi- or hyper-spectral pixels are usually represented as vectors with high dimensionality. For many applications, not all of these dimensions are actually necessary, and a few values are enough to measure and/or process the pixel with a very good accuracy. In this work, we introduce a new strategy to reduce the dimensionality of spectral images ranging in the visible wavelengths, for purposes of color management. We define a new Interim Connection Space (ICS) that contains only five dimensions, and show that it has numerous advantages over state-of-the-art ICS such as LabPQR. In particular, it allows for a better spectral reconstruction accuracy.

Le Moan, Steven; Urban, Philipp

2014-02-01

298

The interest of simultaneous spectral and spatial high resolution spectroscopy in the infrared  

International Nuclear Information System (INIS)

In the past, small scale structures on the sun have mostly been studied through observations made in the visible and ultraviolet. After having recalled some of the main advantages of infrared observations, the authors give a few samples of high spectral resolution/low noise solar spectra now routinely obtained in this spectral range by using Fourier Transform spectrometers (FTS). They then show that such high spectral resolution spectra could be obtained in a short period of time and for small scale solar structures, using a LEST type collector. Post focus instrumentation for the LEST telescope should include a multiple detector Fourier transform spectrometer for infrared observations

1985-01-01

299

Nanometer Scale Spectral Imaging of Quantum Emitters in Nanowires and Its Correlation to Their Atomically Resolved Structure  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report the spectral imaging in the UV to visible range with nanometer scale resolution of closely packed GaN/AlN quantum disks in individual nanowires using an improved custom-made cathodoluminescence system. We demonstrate the possibility to measure full spectral features of individual quantum emitters as small as 1 nm and separated from each other by only a few nanometers and the ability to correlate their optical properties to their size, measured with atomic resolutio...

Zagonel, Luiz Fernando; Mazzucco, Stefano; Tence?, Marcel; March, Katia; Bernard, Romain; Laslier, Benoi?t; Jacopin, Gwe?nole?; Tchernycheva, Maria; Rigutti, Lorenzo; Julien, Francois H.; Songmuang, Rudeesun; Kociak, Mathieu

2012-01-01

300

Effective medium theories for composite optical materials in spectral ranges of weak absorption: the case of Nb2O5 SiO2 mixtures  

Science.gov (United States)

The validity of effective medium theories (EMTs) for mixtures of dielectric materials in weak absorption regions is studied. Based on the Bergman spectral representation, it is possible to show that for any EMT the absorption properties of a mixture consist basically of scaling of the absorption properties of the material with highest absorption. The real part of the dielectric function remains unaffected by the absorption properties. Thin films consisting of Nb2O5-SiO2 mixtures are characterized using optical measurements and the results are compared with the calculations of EMTs. The large discrepancies between the absorption properties observed experimentally and those calculated using EMTs are justified by the failure of these theories to predict a compositional dependence of relevant structural parameters, such as the band-gap energy or the width of localized states. This failure, however, affects the calculation of the refractive index in the weak absorption regions to a less significant degree.

Sancho-Parramon, J.; Janicki, V.

2008-11-01

 
 
 
 
301

Air fluorescence measurements in the spectral range 300-420 nm using a 28.5 GeV electron beam  

CERN Multimedia

Measurements are reported of the yield and spectrum of fluorescence, excited by a 28.5 GeV electron beam, in air at a range of pressures of interest to ultra-high energy cosmic ray detectors. The wavelength range was 300 - 420 nm. System calibration has been performed using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air at 304 K the yield is 20.8 +/- 1.6 photons per MeV.

Abbasi, R; Belov, K; Belz, J; Cao, Z; Dalton, M; Fedorova, Y; Huentemeyer, P; Jones, B F; Jui, C C H; Loh, E C; Manago, N; Martens, K; Matthews, J N; Maestas, M; Smith, J; Sokolsky, P; Springer, R W; Thomas, J; Thomas, S; Chen, P; Field, C; Hast, C; Iverson, R; Ng, J S T; Odian, A; Reil, K; Walz, D; Bergman, D R; Thomson, G; Zech, A; Chang, F-Y; Chen, C-C; Chen, C-W; Huang, M A; Hwang, W-Y P; Lin, G-L

2007-01-01

302

Application of Visible and Near Infrared Spectroscopy for Rapid Analysis of Chrysin and Galangin in Chinese Propolis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A novel method for the rapid determination of chrysin and galangin in Chinese propolis of poplar origin by means of visible and near infrared spectroscopy (Vis-NIR) was developed. Spectral data of 114 Chinese propolis samples were acquired in the 325 to 1,075 nm wavelength range using a Vis-NIR spectroradiometer. The reference values of chrysin and galangin of the samples were determined by high performance liquid chromatography (HPLC). Partial least squares (PLS) models were established usin...

Pengcheng Nie; Zhengyan Xia; Da-Wen Sun; Yong He

2013-01-01

303

UV-Visible Spectroscopy  

Science.gov (United States)

This webpage, part of a larger project "Understanding Chemistry", provides an introduction to UV-visible spectroscopy suitable for use in introductory chemistry and introductory analytical chemistry courses. The pages discuss UV-visible light, absorption, Beer's law, the double-beam spectrometer, and introduce some standard applications of UV-vis spectroscopy.

Clark, Jim

2012-09-20

304

KEY COMPARISON: Final report on the key comparison CCPR-K2.a-2003: Spectral responsivity in the range of 900 nm to 1600 nm  

Science.gov (United States)

An international comparison of spectral responsivity in the near infrared region, 900 nm to 1600 nm, designated CCPR-K2.a, has been conducted under the Consultative Committee for Photometry and Radiometry (CCPR) as one of the key comparisons to support the Mutual Recognition Arrangement (MRA). This comparison was participated in by 15 laboratories and was piloted by National Institute of Standards and Technology (NIST). The comparison was carried out through calibration of a group of transfer standard detectors, which were indium gallium arsenide (InGaAs) photodiodes with sapphire windows, mounted with a thermistor. The comparison was organized in a star pattern, and conducted in four groups of participants. The report describes in detail the measurements made at NIST and summarizes the reports submitted by the participants. Key comparison reference values and degrees of equivalence have been determined from the comparison results. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Brown, Steven W.; Larason, Thomas C.; Ohno, Yoshi

2010-01-01

305

The metal complexes of heterocyclic ?-diketones and their derivatives—IX. Lanthanon chelates of 3-methyl-1-phenyl-4-trifluoroacetylpyrazol-5-one (HPMTFP). 1H, 13C and 19F NMR, i.r. and u.v.-visible spectral studies  

Science.gov (United States)

Lanthanon chelates of 3-methyl-1-phenyl-4-trifluoroacetylpyrazol-5-one (HPMTFP) have been synthesized and investigated. Characterization was by elemental analysis, conductivity measurements, Karl Fischer titrations, i.r. and proton magnetic resonance spectra. The complexes are shown to be neutral chelates with the empirical formula Ln(PMTFP) 3 · xH 2O · yC 2H 5OH where for Ln = La, Nd, Eu, Dy, Er, Pr and Lu, x = 2 and y = 0 while for Ln = Y and Gd, x = 2 and y = 1/2. 1H, 13C and 19F NMR, i.r. and u.v.—visible spectral data together with assignments are presented. Sinha's parameters have been calculated and discussed for Nd and Er.

Okafor, Emmanuel Chukwuemeka

306

An automatic atmospheric correction algorithm for visible/NIR imagery  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The automatic correction of atmospheric effects currently requires visible to short-wave spectral bands (400–2500nm) to derive high accuracy surface reflectance data. Common techniques employ spectral correlations of dark targets in the short-wave infrared (SWIR, around 2.2 mm), blue (480 nm) and red (660 nm) regions to derive the aerosol optical depth. A large number of current Earth-observing satellite sensors have only three or four spectral channels in the visible and near-infrared (VNI...

Richter, R.; Schla?pfer, D.; Mu?ller, A.

2006-01-01

307

Komatiites as Mercury surface analogues: Spectral measurements at PEL  

Science.gov (United States)

The elemental composition of Mercury's surface, which has been recently measured by the NASA MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, suggests a mineralogy dominated by magnesium-rich orthopyroxene and feldspar. The most magnesium-rich and aluminium-poor regions of Mercury's surface (which are presumably orthopyroxene-rich) have compositions, and possibly mineralogies, analogous to terrestrial boninites and basaltic komatiites. Unfortunately, little is known about the spectral properties of komatiites, especially at the high surface temperatures of Mercury. We therefore have collected three terrestrial komatiites with different compositions plus a synthetic komatiitic sample, and measured their reflectances in the visible and thermal infrared spectral ranges. Samples divided into four grain size ranges (when enough material was available) were measured fresh and after thermal processing in vacuum (10 Pa) at 500 °C, comparable to Mercury peak surface temperatures. Our measurements show that spectral changes between fresh and thermally processed samples occur in both spectral channels, but are stronger in the visible range, with reddening affecting all the samples, while darkening is more selective. It is important to note that darkening and reddening after thermally processing the samples are independent of the komatiites ferrous iron content. In fact the synthetic sample which is nearly iron-free is most strongly affected. From our study it turns out that thermally processing the samples in vacuum at Mercury surface temperature produces the removal of samples' colour centres. The results of our study show also that the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument on MESSENGER orbiting Mercury currently cannot distinguish between different compositions of komatiites, while the future MErcury Radiometer and Thermal infrared Imaging Spectrometer (MERTIS) on the upcoming ESA BepiColombo mission will resolve their differences in the 7-14 ?m spectral range.

Maturilli, Alessandro; Helbert, Jörn; St. John, James M.; Head, James W.; Vaughan, William M.; D'Amore, Mario; Gottschalk, Matthias; Ferrari, Sabrina

2014-07-01

308

Characteristics of visible fluorescence from ionic liquids.  

Science.gov (United States)

The observation of fluorescence in the visible spectral range in imidazolium-based ionic liquids, in which the peak of the fluorescence spectrum shifts with the change in the excitation wavelength by over 200 nm, was reported by Samanta and co-workers (Paul et al. J. Phys. Chem. B 2005, 109, 9148; Chem. Phys. Lett. 2005, 402, 375), and the aggregate structure in the bulk ionic liquid was suggested to explain this unique phenomenon. In this work, by employing 2D-scan fluorescence spectroscopy, we identified the long- and short-wavelength fluorescence components of the fluorescence spectrum of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]), of which only the long-wavelength fluorescence component was found to be responsible for the reported fluorescence properties. The fluorescence intensity of the long-wavelength component decreased much faster upon dilution in aqueous mixtures than the short-wavelength component, supporting the conclusion that the long-wavelength fluorescence is from molecular aggregates in the bulk ionic liquid. Fluorescence correlation spectroscopy (FCS), which was used to accurately account for the number density of the long-wavelength fluorescent species in aqueous solutions of the ionic liquid, also suggested that the fluorescence came from aggregate structures of molecules in ionic liquids. PMID:23978063

Cha, Seoncheol; Shim, Taekyu; Ouchi, Yukio; Kim, Doseok

2013-09-19

309

Spectral domain optical coherence tomography of multi-MHz A-scan rates at 1310 nm range and real-time 4D-display up to 41 volumes/second  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An ultrafast frequency domain optical coherence tomography system was developed at A-scan rates between 2.5 and 10 MHz, a B-scan rate of 4 or 8 kHz, and volume-rates between 12 and 41 volumes/second. In the case of the worst duty ratio of 10%, the averaged A-scan rate was 1 MHz. Two optical demultiplexers at a center wavelength of 1310 nm were used for linear-k spectral dispersion and simultaneous differential signal detection at 320 wavelengths. The depth-range, sensitivity, s...

Choi, Dong-hak; Hiro-oka, Hideaki; Shimizu, Kimiya; Ohbayashi, Kohji

2012-01-01

310

Ground Vehicle Spectral and Polarization Imaging Sensor.  

Science.gov (United States)

This paper summarizes the design of an Imaging Spectropolarimeter that operates in the visible wavelength region. The sensor uses computed tomographic imaging techniques to instantaneously form an object cube (spectral and spatial image) during each frame...

C. Vandervlugt R. Karlsen R. Sampson

2007-01-01

311

Mechanism for radiative energy transfer and expansion of the spectral lasing range in a rhodamine 6G--oxazine 17 system  

Energy Technology Data Exchange (ETDEWEB)

The nature of radiative transfer of electronic excitation energy from rhodamine 6G to oxazine 17 is determined. As a result of laser excitation, lasing in the acceptor (oxazine 17) is achieved due to absorption of donor (rhodamine 6G) luminescence by its molecules. The continuous tuning range of single-component ethanol solutions of rhodamine 6G and oxazine 17, and of a binary rhodamine 6G--oxazine 17 system with energy transfer, is determined.

Reva, M.G.; Akimov, A.I.; Korol' kova, N.V.; Kurokhtin, N.V.; Uzhinov, B.M.

1985-12-01

312

CHARACTERIZATION OF SOIL HUMIC SUBSTANCES BY ULTRAVIOLET-VISIBLE AND SYNCHRONOUS FLUORESCENCE SPECTROSCOPY  

Directory of Open Access Journals (Sweden)

Full Text Available We focused our study on ultraviolet-visible and synchronous fluorescence spectra and indexes of humic subctances isolated from five Czech soil samples: Haplic Chernozem, Luvic Chernozem, Gleyic Luvisol, Haplic Cambisol and Leptic Cambisol. Results indicated the following HS quality: Haplic Chernozem > Luvic Chernozem > Gleyic Luvisol > Haplic Cambisol > Leptic Cambisol. Humic acids and fulvic acids ratios (HA/FA were increasing together with decreasing values of Q4/6 measured in visible spectral range. Highest absorbance in visible spectral range was detected in Haplic Chernozem and Luvic Chernozem. Maximum relative fluorescence was found in Haplic Chernozem. SFS spectra (in emission mode at ??=20 nm showed five main fluorophore peaks at: 360, 470, 488, 502 and 512 nm. Fluorescence behaviour of studied samples was compared with Elliot soil humic acid standard (IHSS. Correlation between fluorescence indexes (F and humification degree (HD R2= 0.88 and between calculated humification degree (HD* and humic acids content (HA sum R2=0.84 and between fluorescence indexes F and HA/FA ratios (R2=0.88 were found.

NAD?ŽDA FASUROVÁ

2011-01-01

313

Spectral properties of common intraocular lens (IOL) types  

Science.gov (United States)

Currently over 50 kinds of intraocular lenses (IOLs) are approved for patient use in the treatment of cataracts and ametropia. These lenses are manufactured from at least 2 kinds of silicones as well as several kinds of acrylic polymers including polyHEMA, Poly HOXEMA, a range of polymethacrylate and polyacrylate formulations. We sought to measure spectral transmission curves of a range of IOLS in the UV-visible and near IR spectral regions in order to better characterize their optical properties and to provide a baseline from which to assess their alteration following implantation over time. Consideration of how this may best be achieved are discussed. The variable ability of both explained IOLs and some samples from a range of manufacturers to block UV wavelengths is commented upon.

Milne, Peter J.; Chapon, Pascal F.; Hamaoui, Marie; Parel, Jean-Marie A.; Clayman, H.; Rol, Pascal O.

1999-06-01

314

Acousto-optic tunable filter for spectral imaging  

Science.gov (United States)

In this paper we present a noncollinear TeO2 Acousto-Optic Tunable Filter (AOTF) device for a hyperspectral remote sensing system with moderate spatial and spectral resolution. The single beam configuration of the device will make the imaging optics behind it very simple and thus will make the whole system more compact. The power compensated circuit design of the RF driver of the acousto-optic filter gives relatively high and consistent diffraction efficiency over the whole tuning range in visible. The device can provide about 4° viewfield angle and 5 mm active aperture. The preliminary results have illustrated the capability of the device to be used for spectral imaging. The operation principle of AOTF will be introduced and its optical properties will be analyzed in this paper. The configuration of the AOTF device we developed for spectral imaging will be described and the measured performance of the filter will be summarized.

Dong, Ying; You, Zheng; Gao, Peng

2002-09-01

315

Thermal coagulation-induced changes of the optical properties of normal and adenomatous human colon tissues in vitro in the spectral range 400-1100 nm  

Energy Technology Data Exchange (ETDEWEB)

The absorption coefficients, the reduced scattering coefficients and the optical penetration depths for native and coagulated human normal and adenomatous colon tissues in vitro were determined over the range of 400-1100 nm using a spectrophotometer with an internal integrating sphere system, and the inverse adding-doubling method was applied to calculate the tissue optical properties from diffuse reflectance and total transmittance measurements. The experimental results showed that in the range of 400-1100 nm there were larger absorption coefficients (P < 0.01) and smaller reduced scattering coefficients (P < 0.01) for adenomatous colon tissues than for normal colon tissues, and there were smaller optical penetration depths for adenomatous colon tissues than for normal colon tissues, especially in the near-infrared wavelength. Thermal coagulation induced significant increase of the absorption coefficients and reduced scattering coefficients for the normal and adenomatous colon tissues, and significantly reduced decrease of the optical penetration depths for the normal and adenomatous colon tissues. The smaller optical penetration depth for coagulated adenomatous colon tissues is a disadvantage for laser-induced thermotherapy (LITT) and photodynamic therapy (PDT). It is necessary to adjust the application parameters of lasers to achieve optimal therapy.

Ao Huilan; Xing Da; Wei Huajiang; Gu Huaimin [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, ina Normal University, Guangzhou 510631 (China); Wu Guoyong; Lu Jianjun [Department of Surgery, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou 510080 (China)], E-mail: xingda@scnu.edu.cn

2008-04-21

316

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... this an exciting and educational program, highlighting the evolution to the no visible scar colectomy, and we’ ... was the process of what you call the evolution? Really, the evolution has taken place over the ...

317

Unit Rectangle Visibility Graphs  

CERN Multimedia

Over the past twenty years, rectangle visibility graphs have generated considerable interest, in part due to their applicability to VLSI chip design. Here we study unit rectangle visibility graphs, with fixed dimension restrictions more closely modeling the constrained dimensions of gates and other circuit components in computer chip applications. A graph $G$ is a unit rectangle visibility graph (URVG) if its vertices can be represented by closed unit squares in the plane with sides parallel to the axes and pairwise disjoint interiors, in such a way that two vertices are adjacent if and only if there is a non-degenerate horizontal or vertical band of visibility joining the two rectangles. Our results include necessary and sufficient conditions for $K_n$, $K_{m,n}$, and trees to be URVGs, as well as a number of general edge bounds.

Dean, Alice; Hamilton, Sarah; Pangborn, Greta

2007-01-01

318

[Study on the arc spectral information for welding quality diagnosis].  

Science.gov (United States)

Through collecting the spectral signals of TIG and MIG welding arc with spectrometer, the arc light radiations were analyzed based on the basic theory of plasma physics. The radiation of welding arc distributes over a broad range of frequency, from infrared to ultraviolet. The arc spectrum is composed of line spectra and continuous spectra. Due to the variation of metal density in the welding arc, there is great difference between the welding arc spectra of TIG and MIG in both their intensity and distribution. The MIG welding arc provides more line spectra of metal and the intensity of radiation is greater than TIG. The arc spectrum of TIG welding is stable during the welding process, disturbance factors that cause the spectral variations can be reflected by the spectral line related to the corresponding element entering the welding arc. The arc spectrum of MIG welding will fluctuate severely due to droplet transfer, which produces "noise" in the line spectrum aggregation zone. So for MIG welding, the spectral zone lacking spectral line is suitable for welding quality diagnosis. According to the characteristic of TIG and MIG, special spectral zones were selected for welding quality diagnosis. For TIG welding, the selected zone is in ultraviolet zone (230-300 nm). For MIG welding, the selected zone is in visible zone (570-590 nm). With the basic theory provided for welding quality diagnosis, the integral intensity of spectral signal in the selected zone of welding process with disturbing factor was studied to prove the theory. The results show that the welding quality and disturbance factors can be diagnosed with good signal to noise ratio in the selected spectral zone compared with signal in other spectral zone. The spectral signal can be used for real-time diagnosis of the welding quality. PMID:19455806

Li, Zhi-Yong; Gu, Xiao-Yan; Li, Huan; Yang, Li-Jun

2009-03-01

319

Switching of the photonic band gap in three-dimensional film photonic crystals based on opal-VO2 composites in the 1.3-1.6 ?m spectral range  

International Nuclear Information System (INIS)

The parameters of three-dimensional photonic crystals based on opal-VO2 composite films in the 1.3-1.6 ?m spectral range important for practical applications (Telecom standard) are numerically calculated. For opal pores, the range of filling factors is established (0.25-0.6) wherein the composite exhibits the properties of a three-dimensional insulator photonic crystal. On the basis of the opal-VO2 composites, three-dimensional photonic film crystals are synthesized with specified parameters that provide a maximum shift of the photonic band gap in the vicinity of the wavelength ?1.5 ?m (?170 meV) at the semiconductor-metal transition in VO2.

2010-12-01

320

On the spectral domain approach to long-range propagation of high-frequency waves along a strip conductor above a PEC surface  

CERN Document Server

A generic problem of high frequency wave propagation along a metallic strip in parallel above a PEC ground plane is considered. The wave is excited by an elemental electric dipole at an arbitrary location above the PEC plane. The full wave problem, for arbitrary widths of the strip, is solved by means of a mode matching approach and expansion of the strip surface current into Chebyshev polynomials. For narrow strips, an approximate method using only longitudinal currents is derived, and compared numerically with the full wave method. Utilizing the concept of equivalent radius, the approximate method for narrow strips is evaluated numerically against results for thin circular wires. It is concluded that the approximate method is suitable for handling multiple wires in layered structures, wherefore the method has potential usefulness for estimating long range propagation of high frequency waves in wire structures like power lines and railway feeding systems, containing over-head wires and wires submerged into g...

Norgren, Martin

2012-01-01

 
 
 
 
321

Method for the calibration of the spectral irradiance of tungsten filament transfer standard sources traceable to synchrotron radiation.  

Science.gov (United States)

The spectral irradiance calibration of tungsten strip and spiral filament lamps applying synchrotron radiation revealed that the spectral irradiance in the wavelength range from 280 to 400 nm can be well approximated by blackbody radiation according to Planck's law. Consequently, the spectral irradiance of the filament lamp can then be described by an effective irradiance temperature, which would be beneficial for practical measurements. Including the emissivity of tungsten into the approximation, the model can be expanded to visible and near-infrared wavelength regions. The effective irradiance temperature dependence of the lamp current was investigated and appeared to be close to linear. PMID:23872760

Anevsky, Sergey; Krutikov, Vladimir; Minaeva, Olga; Minaev, Roman; Senin, Dmitriy; Hollandt, Jörg; Taubert, Dieter R

2013-07-20

322

A technique of measuring spectral characteristics of detector arrays in amateur and professional photocameras and their application for problems of digital holography  

Science.gov (United States)

The possibility of using commercial digital cameras that support image saving in the RAW format in scientific applications for measuring spatial intensity distributions in different ranges of the visible spectrum is considered. Spectral characteristics of photo sensors were measured for three digital cameras: Canon EOS 1000D, Nikon D50, and Nikon D90. Ways of applying spectral characteristics in problems of improving the quality of multicolor digital holograms are considered.

Lesnichii, V. V.; Petrov, N. V.; Cheremkhin, P. A.

2013-10-01

323

Spectroscopy of 14NH3 and 15NH3 in the 2.3 ?m spectral range with a new VECSEL laser source  

Science.gov (United States)

A spectroscopic study of ammonia molecule in the 2.3 ?m water atmospheric window is presented. Compared to previous experimental works a narrow, broadly tunable, continuous laser source was applied in order to obtain high resolution spectra in this range. It was the first application of the newly developed Vertical External Cavity Surface Emitting Laser (VECSEL). The analysis of the absorption spectra of two different isotopologue admixtures allowed to identify 336 14NH3 and 244 15NH3 lines in the studied region from 4275 to 4340 cm-1. These data were compared to previous line list based on experimental data - the HITRAN database and the work of Urban et al., as well as to the theoretical predictions by Yurchenko et al. and Huang et al. Together for 235 14NH3 and 183 15NH3 lines a complete assignment was proposed. From those 63 14NH3 and 114 15NH3 transitions were newly assigned. The complete peaklist of transitions containing ro-vibrational state identifications is presented in Supplementary materials.

?ermák, P.; Hovorka, J.; Veis, P.; Cacciani, P.; Cosléou, J.; El Romh, J.; Khelkhal, M.

2014-04-01

324

Ultraviolet and visible imaging and spectrographic imaging (UVISI) experiment  

International Nuclear Information System (INIS)

The Ultraviolet and Visible Imaging and Spectrographic Imaging (UVISI) experiment consists of five spectrographic imagers and four imagers. These nine sensors provide spectrographic and imaging capabilities from ?110 nm to ?900 nm. The spectrographic imagers (SPIMs) share an off-axis parabolic design in which selectable slits (1.00 degree x0.10 degree or 1.00 degree x0.05 degree) provide spectral resolutions between ?0.5 nm and ?4.0 nm. SPIM image planes have programmable spectral dimensions with 68, 136 or 272 pixels and programmable spatial dimensions with 5, 10, 20, or 40 pixels. A scan mirror sweeps the slit through a second spatial dimension and generates a spectrographic image once every 5, 10, or 20 seconds. The four imagers provide narrow-field (1.3 degree x1.6 degree) and wide-field (13.1 degree x10.5 degree) viewing. Each imager has a six-position filter wheel that selects various spectral regimes and neutral densities. Each of the nine sensors use intensified CCD detectors that have an intrascene dynamic range of ?103 and an interscene dynamic range of ?105; neutral density filters provide and additional dynamic range of ?102-3. An automatic gain control adjusts the intensifiers to scenes of varying intensity. UVISI also includes an image processing system that uses the raw data from any single imager to acquire and track targets of various sizes, shapes, and brightnesses. The image processor relays its results to a master tracking system that uses the UVISI data (as well as other data) to point the satellite in real-time. UVISI will be launched on the MSX satellite in late 1994 and will investigate a multitude of celestial, atmospheric, and point sources during its planned five-year lifetime

1994-04-04

325

Quantifying solar spectral irradiance in aquatic habitats for the assessment of photoenhanced toxicity  

Energy Technology Data Exchange (ETDEWEB)

The spectra and intensity of solar radiation (solar spectral irradiance [SSI]) was quantified in selected aquatic habitats in the vicinity of an oil field on the California coast. Solar spectral irradiance measurements consisted of spectral scans and radiometric measurements of ultraviolet (UV): UVB and UVA. Solar spectral irradiance measurements were taken at the surface and at various depths in two marsh ponds, a shallow wetland, an estuary lagoon, and the intertidal area of a high-energy sandy beach. Daily fluctuation in SSI showed a general parabolic relationship with time; maximum structure-activity relationship (SAR) was observed at approximate solar noon. Solar spectral irradiance measurements taken at 10-cm depth at approximate solar noon in multiple aquatic habitats exhibited only a twofold variation in visible light and UVA and a 4.5-fold variation in UVB. Visible light ranged from 11,000 to 19,000 {micro}W/cm{sup 2}, UVA ranged from 460 to 1,100 {micro}W/cm{sup 2}, and UVB ranged from 8.4 to 38 {micro}W/cm{sup 2}. In each habitat, the attenuation of light intensity with increasing water depth was differentially affected over specific wavelengths of SSI. The study results allowed the development of environmentally realistic light regimes necessary for photoenhanced toxicity studies.

Barron, M.G.; Little, E.E.; Calfee, R.; Diamond, S.

2000-04-01

326

Towards 3D Electromagnetic Metamaterials in the THz Range  

Science.gov (United States)

SSLS has been using its lithography-based micro/nanofabrication facility LiMiNT (Lithography for Micro and Nanotechnology) and its infrared spectro/microscopy facility ISMI to develop and characterize the first electromagnetic metamaterials having their spectral response in the THz range. Derived from Pendry's nested-split-ring resonator design, these structures require micro/nanofabrication in order to have resonances in the THz range. They exhibit a negative refractive index and hold promise of sub-diffraction limit imaging. Besides the reduction of the size of the resonating structures to extend the spectral range towards the visible, outstanding issues include the production of high-aspect-ratio resonators that are sensitive for the magnetic field in any direction (3D sensitivity) and the capability to produce copious amounts of the electromagnetic metamaterials with a good yield. In this paper, we shall report on first results of 3D EM3 structures made by inclined exposures.

Casse, B. D. F.; Moser, H. O.; Bahou, M.; Gu, P. D.; Jian, L. K.; Kong, J. R.; Mahmood, S. B.; Wen, Li

2007-01-01

327

Effects of visible light on the skin.  

Science.gov (United States)

Electromagnetic radiation has vast and diverse effects on human skin. Although photobiologic studies of sunlight date back to Sir Isaac Newton in 1671, most available studies focus on the UV radiation part of the spectrum. The effects of visible light and infrared radiation have not been, until recently, clearly elucidated. The goal of this review is to highlight the effects of visible light on the skin. As a result of advances in the understanding of skin optics, and comprehensive studies regarding the absorption spectrum of endogenous and exogenous skin chromophores, various biologic effects have been shown to be exerted by visible light radiation including erythema, pigmentation, thermal damage and free radical production. It has also been shown that visible light can induce indirect DNA damage through the generation of reactive oxygen species. Furthermore, a number of photodermatoses have an action spectrum in the visible light range, even though most of the currently available sunscreens offer, if any, weak protection against visible light. Conversely, because of its cutaneous biologic effects, visible light is used for the treatment of a variety of skin diseases and esthetic conditions in the form of lasers, intense pulsed light and photodynamic therapy. PMID:18248499

Mahmoud, Bassel H; Hexsel, Camile L; Hamzavi, Iltefat H; Lim, Henry W

2008-01-01

328

Element-specific probing of ultrafast spin dynamics in multisublattice magnets with visible light.  

Science.gov (United States)

We demonstrate the feasibility of element-specific probing of ultrafast spin dynamics in the multisublattice magnet TbFe in the visible spectral range. In particular, we show that one can selectively study the dynamics of Tb and Fe sublattices choosing the wavelength of light below and above 610 nm, respectively. We observe that, despite their antiferromagnetic coupling in the ground state, the Tb and Fe spins temporarily align ferromagnetically after excitation with an intense 55-fs laser pulse, after which they relax to their initial states due to the strong anisotropy in Tb. PMID:23521292

Khorsand, A R; Savoini, M; Kirilyuk, A; Kimel, A V; Tsukamoto, A; Itoh, A; Rasing, Th

2013-03-01

329

Infrared to visible up?conversion using GaP light?emitting diodes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Electroluminescence excited by infrared radiation has been observed in GaP light?emitting diodes (LED’s) at low temperatures providing a new efficient method to convert infrared radiation within a broad spectral range into visible light. Using 10.6??m radiation of a CO2 laser an up?conversion quantum efficiency of 3.4×10?6 was found. If a low dark current photomultiplier is employed to detect the LED emission the dominant noise source is due to conversion of thermal background rad...

Eisfeld, W.; Werling, U.; Prettl, Wilhelm

1983-01-01

330

Visible photoluminescence of nanopowder of silicon, produced by silicon evaporation by powerful electron beam  

International Nuclear Information System (INIS)

The silicon nanopowders, formed by the silicon massive sample evaporation by the electron beam in the argon atmosphere, are studied through the methods of the photoluminescence (PL) and combination light scattering (CS). The PL peak is identified at the room temperature in the visible spectral range of the powders, consisting of the silicon nanocrystals. The PL peak strong short-wave shift may be explained as the effect of the electrons and holes dimensional quantization in the silicon small-size (about 2 nm) nanocrystals. The silicon nanocrystals dimensions are determined through the analytical data on the CS photoluminescence and they coincided with the evaluations based on the photoluminescence data

2004-10-01

331

UVISS preliminary visibility analysis  

DEFF Research Database (Denmark)

The goal of this work is to obtain a preliminary assessment of the sky visibility for anastronomical telescope located on the express pallet of the International SpaceStation (ISS)} taking into account the major constraints imposed on the instrument by the ISSattitude and structure. Part of the work is also to setup the kernel of a software tool for the visibility analysis thatshould be easily expandable to consider more complex strucures for future activities.This analysis is part of the UVISS assessment study and it is meant to provide elementsfor the definition and the selection of the instrument.The work done and the obtained results are drawn in this paper.

Betto, Maurizio

1998-01-01

332

ZnO nanowire based visible-transparent ultraviolet detectors on polymer substrates  

Science.gov (United States)

The fabrication and characterization of fully visible-transparent and flexible ultraviolet (UV) detectors, on polyethylene 2,6-naphthalate (PEN) with active channels of zinc oxide nanowires and ohmic indium tin oxide contacts, are reported and discussed. The fabricated detector has an average transmittance of 80% in the visible spectral range and is most responsive at or below 370 nm, the onset of UV light, with a UV/vis rejection ratio of 1.42 × 103. A five orders of magnitude difference in the photocurrent, between UV illumination and dark conditions, are also observed. The single-sided UV response further shows that the PEN substrate performs well as a UV reflector. The noise analysis on the nanowire UV detector indicates a noise equivalent power and detectivity (D*) of 5.88 × 10-13 WHz-0.5 and 2.13 × 109 cm Hz0.5 W-1, respectively.

Yu, Hongbin; Ali Azhar, Ebraheem; Belagodu, Tej; Lim, Swee; Dey, Sandwip

2012-05-01

333

Visible/infrared radiometric calibration station  

Energy Technology Data Exchange (ETDEWEB)

We have begun construction of a visible/infrared radiometric calibration station that will allow for absolute calibration of optical and IR remote sensing instruments with clear apertures less than 16 inches in diameter in a vacuum environment. The calibration station broadband sources will be calibrated at the National Institute of Standards and Technology (NIST) and allow for traceable absolute radiometric calibration to within {plus_minus}3% in the visible and near IR (0.4--2.5 {mu}m), and less than {plus_minus}1% in the infrared, up to 12 {mu}m. Capabilities for placing diffraction limited images or for sensor full-field flooding will exist. The facility will also include the calibration of polarization and spectral effects, spatial resolution, field of view performance, and wavefront characterization. The configuration of the vacuum calibration station consists of an off-axis 21 inch, f/3.2, parabolic collimator with a scanning fold flat in collimated space. The sources are placed, via mechanisms to be described, at the focal plane of the off-axis parabola. Vacuum system pressure will be in the 10{sup {minus}6} Torr range. The broadband white-light source is a custom design by LANL with guidance from Labsphere Inc. The continuous operating radiance of the integrating sphere will be from 0.0--0.006 W/cm{sup 2}/Sr/{mu}m (upper level quoted for {approximately}500 nm wavelength). The blackbody source is also custom designed at LANL with guidance from NIST. The blackbody temperature will be controllable between 250--350{degrees}K. Both of the above sources have 4.1 inch apertures with estimated radiometric instability at less than 1%. The designs of each of these units will be described. The monochromator and interferometer light sources are outside the vacuum, but all optical relay and beam shaping optics are enclosed within the vacuum calibration station. These sources are described, as well as the methodology for alignment and characterization.

Byrd, D.A.; Maier, W.B. II; Bender, S.C.; Holland, R.F.; Michaud, F.D.; Luettgen, A.L.; Christensen, R.W. [Los Alamos National Lab., NM (United States); O`Brian, T.R. [National Inst. of Standards and Technology (NML), Gaithersburg, MD (United States). Radiometric Physics Div.

1994-07-01

334

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... we’ve tried to make it a very standard approach, very similar to our standard laparoscopic colectomy. It’s app licable to right and left sigmoid colons. The only difference between standard laparoscopic colectomy and LESS colectomy or No Visible ...

335

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440-6810 Å in the ? Velorum cluster, and calibration of spectral indices  

Science.gov (United States)

We present a study of spectral diagnostics available from optical spectra with R = 17 000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the ? Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the H? line core and wings, and temperature- and gravity-sensitive sets of lines, each useful as a Teff or log g indicator over a limited range of stellar spectral types. H? line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global Teff- and log g-sensitive indices ? and ?, valid for the entire range of types in the observed sample. We find a clear difference between gravity indices of main-sequence and pre-main-sequence stars, as well as a much larger difference between these and giant stars. The potentially great usefulness of the (?,?) diagram as a distance-independent age measurement tool for young clusters is discussed. We discuss the effect on the defined indices of classical T Tauri star veiling, which is however detected in only a few stars in the present sample. Then, we present tests and calibrations of these indices, on the basis of both photometry and literature reference spectra, from the UVES Paranal Observatory Projectand the ELODIE 3.1 Library. The known properties of these stars, spanning a wide range of stellar parameters, enable us to obtain a good understanding of the performances of our new spectral indices. For non-peculiar stars with known temperature, gravity, and metallicity, we are able to calibrate quantitatively our indices, and derive stellar parameters for a wide range of stellar types. To this aim, a new composite index is defined, providing a good metallicity indicator. The ability of our indices to select peculiar, or otherwise rare classes of stars is also established. For pre-main-sequence stars outside the parameter range of the ELODIE dataset, index calibration relies on model isochrones. We check our calibrations against current Gaia-ESO UVES results, plus a number of Survey benchmark stars, and also against Gaia-ESO observations of young clusters, which contribute to establishing the good performance of our method across a wide range of stellar parameters. Our gravity determination for late-type PMS stars is found to be accurate enough to let us obtain gravity-based age estimates for PMS clusters. Finally, our gravity determinations support the existence of an older pre-main-sequence population in the ? Vel sky region, in agreement with evidence obtained from the lithium depletion pattern of the same stars. Based on observations collected with the FLAMES spectrograph at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia-ESO Large Public Survey (program 188.B-3002).Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/A50

Damiani, F.; Prisinzano, L.; Micela, G.; Randich, S.; Gilmore, G.; Drew, J. E.; Jeffries, R. D.; Frémat, Y.; Alfaro, E. J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A. C.; Pancino, E.; Recio-Blanco, A.; Sacco, G. G.; Smiljanic, R.; Jackson, R. J.; de Laverny, P.; Morbidelli, L.; Worley, C. C.; Hourihane, A.; Costado, M. T.; Jofré, P.; Lind, K.; Maiorca, E.

2014-06-01

336

Visible-light photon migration through myocardium in vivo.  

Science.gov (United States)

Empirical data between 510 and 590 nm of diffuse reflected light from the pig heart in vivo have shown that myoglobin and cytochrome c absorption peaks with little apparent contribution of red blood cell (RBC) Hb. Monte Carlo simulations of photon migration in tissue were performed to compare the effects of myoglobin and cytochromes with those of blood Hb on photon pathlengths and diffuse reflectance of visible wavelengths (450-600 nm) from the pig heart in vivo. Wavelength dependence of the input parameters, including the transport-corrected scattering coefficients (1.1-1.2 mm(-1)) and the absorption coefficients of blood-free solubilized heart tissue (0.43-1.47 mm(-1)), as well as the absorption coefficients of Hb, were determined by an integrating sphere method and standard spectrophotometry, respectively. The Monte Carlo simulations indicate that in the 510- to 590-nm range the mean path length within the myocardium for diffusely reflected light varies from 1.4 to 1.2 mm, whereas their mean penetration depth within the epicardium is only 330-400 micrometer for blood-free heart tissue. Analysis shows that the blood Hb absorption extrema are only observable between 510 and 590 nm when RBC concentration in tissue is >0.5%. Blood within vessels much larger than capillaries does not contribute significantly to the spectral features, because virtually all light in this spectral range is absorbed during transit through large vessels (>100 micrometer). This analysis suggests that diffuse reflected light in the 510- to 590-nm region will show spectral features uniquely associated with myoglobin and cytochrome c oxygenation states within 400 micrometer of the surface of the heart in situ as long as the capillary RBC concentration remains <0.5%. PMID:10444496

Gandjbakhche, A H; Bonner, R F; Arai, A E; Balaban, R S

1999-08-01

337

Simultaneous Spectral Temporal Adaptive Raman Spectrometer - SSTARS  

Science.gov (United States)

Raman spectroscopy is a prime candidate for the next generation of planetary instruments, as it addresses the primary goal of mineralogical analysis, which is structure and composition. However, large fluorescence return from many mineral samples under visible light excitation can render Raman spectra unattainable. Using the described approach, Raman and fluorescence, which occur on different time scales, can be simultaneously obtained from mineral samples using a compact instrument in a planetary environment. This new approach is taken based on the use of time-resolved spectroscopy for removing the fluorescence background from Raman spectra in the laboratory. In the SSTARS instrument, a visible excitation source (a green, pulsed laser) is used to generate Raman and fluorescence signals in a mineral sample. A spectral notch filter eliminates the directly reflected beam. A grating then disperses the signal spectrally, and a streak camera provides temporal resolution. The output of the streak camera is imaged on the CCD (charge-coupled device), and the data are read out electronically. By adjusting the sweep speed of the streak camera, anywhere from picoseconds to milliseconds, it is possible to resolve Raman spectra from numerous fluorescence spectra in the same sample. The key features of SSTARS include a compact streak tube capable of picosecond time resolution for collection of simultaneous spectral and temporal information, adaptive streak tube electronics that can rapidly change from one sweep rate to another over ranges of picoseconds to milliseconds, enabling collection of both Raman and fluorescence signatures versus time and wavelength, and Synchroscan integration that allows for a compact, low-power laser without compromising ultimate sensitivity.

Blacksberg, Jordana

2010-01-01

338

Spectral Methods  

CERN Document Server

Along with finite differences and finite elements, spectral methods are one of the three main methodologies for solving partial differential equations on computers. This book provides a detailed presentation of basic spectral algorithms, as well as a systematical presentation of basic convergence theory and error analysis for spectral methods. Readers of this book will be exposed to a unified framework for designing and analyzing spectral algorithms for a variety of problems, including in particular high-order differential equations and problems in unbounded domains. The book contains a large

Shen, Jie; Wang, Li-Lian

2011-01-01

339

[Study on the detection and pattern classification of pesticide residual on vegetable surface by using visible/near-infrared spectroscopy].  

Science.gov (United States)

A nondestructive testing based on visible/near-infrared reflectance spectroscopy was put forward for the common high pesticide residues of green plants in the wavelength range from 600 to 1100 nm. Firstly, spectral features were extracted by wavelet transform from original spectral data. Secondly, the principal component analysis (PCA) was done in the further analysis of spectral characteristics. Thirdly, the two PCs were applied as inputs of artificial neural network, and a multi-neuron perceptron neural network was established. Finally, It was proved that the type of pesticide residues was effectively identified and showed by classification results. In short, the study provides a new approach to the detection of pesticide residues in vegetables and fruits. PMID:22827060

Chen, Rui; Zhang, Jun; Li, Xiao-long

2012-05-01

340

Infrared and visible cooperative vehicle identification markings  

Science.gov (United States)

Airborne surveillance helicopters and aeroplanes used by security and defence forces around the world increasingly rely on their visible band and thermal infrared cameras to prosecute operations such as the co-ordination of police vehicles during the apprehension of a stolen car, or direction of all emergency services at a serious rail crash. To perform their function effectively, it is necessary for the airborne officers to unambiguously identify police and the other emergency service vehicles. In the visible band, identification is achieved by placing high contrast symbols and characters on the vehicle roof. However, at the wavelengths at which thermal imagers operate, the dark and light coloured materials have similar low reflectivity and the visible markings cannot be discerned. Hence there is a requirement for a method of passively and unobtrusively marking vehicles concurrently in the visible and thermal infrared, over a large range of viewing angles. In this paper we discuss the design, detailed angle-dependent spectroscopic characterisation and operation of novel visible and infrared vehicle marking materials, and present airborne IR and visible imagery of materials in use.

O'Keefe, Eoin S.; Raven, Peter N.

2006-06-01

 
 
 
 
341

Visibility Driven Hierarchical Radiosity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hierarchical radiosity (HR) simulations rapidly compute light exchanges in a given scene by subdividing the original objects to create an adaptive mesh representing light variations and shadows. Previous mesh subdivision strategies still suffer however from the limitations of regular (quadtree) subdivision. Discontinuity meshing solutions are usually limited to primary illumination and become intractable for more than two or three light sources. Visibility calculation is still done largely by...

Durand, Fre?do; Drettakis, George; Puech, Claude

1998-01-01

342

Variability in spectral absorbance metrics across boreal lake waters.  

Science.gov (United States)

Ultraviolet/visible (UV/Vis) absorbance spectroscopy is a commonly used technique for characterizing dissolved organic matter (DOM). We present an analysis of UV/Vis absorbance spectra from 983 lakes throughout Sweden, sampled during autumn 2009. Metrics included both specific absorbances (i.e. absorbance per mass unit of organic carbon), and descriptions of spectral shape. Overall, we found three factors to which all spectral metrics were similarly related: acidity, retention-time, and latitude. In general, alkaline lakes with a long retention time in northern Sweden have lower specific absorbance and steeper spectral slope than acidic lakes with a short retention time in southern Sweden. Relative to the specific absorbance measured at 254 nm (SUVA), commonly used as a measure of DOM aromaticity, the specific absorbance at longer wavelengths and metrics of spectral shape were more sensitive to acidity and less sensitive to latitude. Although different spectral metrics are hypothesized to reflect different properties of DOM, UV/Vis absorbance spectroscopy may not be useful for more refined characterization of organic matter because of the strong inter-correlation between metrics. Nevertheless, it remains useful as a quick, cheap and reliable method of estimating DOM quantity and describing quality. We suggest that the most informative range to measure absorbance is between approximately 250 and 360 nm, where the between-lake variability is largest and absorbance can, in general, be precisely measured. PMID:22885538

Erlandsson, Martin; Futter, Martyn N; Kothawala, Dolly N; Köhler, Stephan J

2012-10-26

343

Globally integrated measurements of the Earth's visible spectral albedo  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report spectroscopic observations of the earthshine reflected from the Moon. By applying our photometry methodology to spectroscopy, we were able to precisely determine the Earth's reflectance, and its variation as a function of wavelength through a single night as the Earth rotates. These data imply that planned regular monitoring of earthshine spectra will yield valuable, new inputs for climate models, which would be complementary to those from the more standard broadba...

Montanes-rodriguez, P.; Palle, E.; Goode, P. R.; Hickey, J.; Koonin, S. E.

2005-01-01

344

Design and fabrication of multiple airgap-based visible filters  

Science.gov (United States)

The efficiency of a Bragg reflector design for implementation in optical resonators is highly dependent on the ratio between the high-index material and the low-index material used for the quarter-wavelength (QWOT) layers. A higher contrast implies that fewer layers are required to achieve a specified spectral selectivity over a wider spectral band. In turn, the reduced total thickness of the filter stack reduces the effect of optical absorption in the layers. The research presented here focuses on implementation of filters on top of silicon detectors that are already fabricated in a CMOS process. This implies that the constraints of process compatibility, such as the materials to be used, process temperature and cleanroom reentrance related to contamination, need to be considered. Silicon-dioxide is often used in CMOS-compatible designs, which has an index of refraction n~1.5, thus limiting nHi/nLo to about 2. This value can be improved by 50% when using air-films as the low-n material. Surface micromachining is used for the fabrication of such mirrors. Multiple layers of Si and SiO2 were alternatingly deposited, and subsequently the Si layers are selectively removed in a sacrificial etch. The width of the ?/4 air-gaps is about 100 nm, which is narrower as compared to the typical layer thickness that is used in surface micromachining for conventional MEMS applications. Moreover, a demanding optical design requires more layers than typically used in a conventional MEMS device. Since the number of stacked layers is significantly higher as compared to the conventional MEMS, fabricating such filters is a challenge. However, unlike a conventional MEMS, electrical contacting to the structural layers is not required in optical filter application, which, eases the fabrication of such filters. This paper presents the design of several 4-layer structures for use in the visible spectral range, along with the fabrication sequence and preliminary measurement results.

Ghaderi, M.; Wolffenbuttel, R. F.

2014-05-01

345

Visible Hyperspectral Imaging for Standoff Detection of Explosives on Surfaces  

Energy Technology Data Exchange (ETDEWEB)

There is an ever-increasing need to be able to detect the presence of explosives, preferably from standoff distances. This paper presents an application of visible hyperspectral imaging using anomaly, polarization and spectral identification approaches for the standoff detection (13 meters) of nitroaromatic explosives on realistic painted surfaces based upon the colorimetric differences between tetryl and TNT which are enhanced by solar irradiation.

Bernacki, Bruce E.; Blake, Thomas A.; Mendoza, Albert; Johnson, Timothy J.

2010-11-01

346

Spectral-kinetic properties of heterostructures with GaAsSb/InGaAs/GaAs-based quantum wells emitting in the range of 1.0-1.2 {mu}m  

Energy Technology Data Exchange (ETDEWEB)

The spectral-kinetic properties of heterostructures with GaAs/GaAsSb-based and GaAsSb/InGaAs/GaAs-based quantum wells, emitting in the range of 1.0-1.2 {mu}m are studied with picosecond and nanosecond temporal resolution. Intense photoluminescence in the GaAsSb/InGaAs/GaAs structure, as well as an increase in the photoluminescence wavelength by a factor of 2.5 and a shift of the location of the maximum of the peak ({approx}100 meV) to the longer-wavelength region were observed up to room temperature. It is established that as the molar fraction of Sb and the thickness of the InGaAs layer increase, the energy of the fundamental transition decreases by a factor of 140 meV compared with the GaAsSb/InGaAs/GaAs structure with a lower Sb content and a smaller thickness of the InGaAs layer. At 300 K, the emission wavelength of such a structure was 1.18 {mu}m. In addition, an increase in the thickness of the InGaAs layer led to an increase in the room-temperature photoluminescence intensity by a factor of 60, which is associated with a decrease in the energy of the fundamental state for electrons in the InGaAs layer and, consequently, to larger electron localization and smaller temperature quenching of photoluminescence.

Morozov, S. V., E-mail: more@ipm.sci.-nnov.ru; Kryzhkov, D. I.; Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Zvonkov, B. N.; Vikhrova, O. I. [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)

2013-11-15

347

Spectral-kinetic properties of heterostructures with GaAsSb/InGaAs/GaAs-based quantum wells emitting in the range of 1.0–1.2 ?m  

International Nuclear Information System (INIS)

The spectral-kinetic properties of heterostructures with GaAs/GaAsSb-based and GaAsSb/InGaAs/GaAs-based quantum wells, emitting in the range of 1.0–1.2 ?m are studied with picosecond and nanosecond temporal resolution. Intense photoluminescence in the GaAsSb/InGaAs/GaAs structure, as well as an increase in the photoluminescence wavelength by a factor of 2.5 and a shift of the location of the maximum of the peak (?100 meV) to the longer-wavelength region were observed up to room temperature. It is established that as the molar fraction of Sb and the thickness of the InGaAs layer increase, the energy of the fundamental transition decreases by a factor of 140 meV compared with the GaAsSb/InGaAs/GaAs structure with a lower Sb content and a smaller thickness of the InGaAs layer. At 300 K, the emission wavelength of such a structure was 1.18 ?m. In addition, an increase in the thickness of the InGaAs layer led to an increase in the room-temperature photoluminescence intensity by a factor of 60, which is associated with a decrease in the energy of the fundamental state for electrons in the InGaAs layer and, consequently, to larger electron localization and smaller temperature quenching of photoluminescence

2013-11-01

348

Measurement of the refractive index dispersion of As2Se3 bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range  

International Nuclear Information System (INIS)

The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 ?m range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

2011-05-01

349

Cytochrome c oxidase acts as a primary photoacceptor in cell cultures subjected to visible and near IR laser irradiation  

International Nuclear Information System (INIS)

Low-power laser radiation of visible and near IR spectral ranges is widely used in clinical practice to treat wounds and ulcers of various etiologies. However, there are only a few works devoted to photobiological studies of the effect of light of these spectral ranges on the metabolism of nonphotosynthesizing cells. Our results suggested that the light absorbance by certain chromophores of cytochrome c oxidase alters the extent of oxidation of these chromophores, i.e., affects the rate (and, probably, the mechanism) of electron transfer within the molecule. Based on previous results and the data obtained, we suggest that these reactions are related to the molecular mechanism of the low-power laser therapy at the level of a single cell. 15 refs., 1 fig

1995-01-01

350

Photon path depth in tissue phantoms: a comparison of visible and near-infrared (NIR) wavelengths  

Science.gov (United States)

Optical spectroscopy is being used increasingly in medical applications to noninvasively investigate tissues below the skin. In order to assure adequate sampling of tissues underlying the skin, photon penetration depth must be known. Photon penetration in tissues has been studied with near-infrared (NIR) light, but experimental study of visible light propagation in tissue has been limited. In this study, a micro-motion system coupled with a reflectance spectroscopy system was used to determine the penetration depth of visible-range and NIR photons (535-800 nm) in phantoms composed of Intralipid and hemoglobin. An absorbing target was placed at intervals of 0.1mm along a 15mm line perpendicular to and bisecting the line between the ends of the source and detector optical fiber bundles. Comparisons between detected light intensities at different target positions were used to determine the most probable photon path depths at 576 nm and at 760 nm. Scattering coefficients, hemoglobin concentrations, and source-detector separations were varied to evaluate their effects on the penetration depth of photons. Results from phantoms containing Intralipid only showed that the most-probable penetration depth at 576 nm was comparable to that at 760 nm. Larger sourcedetector separations resulted in deeper photon penetration depths for both spectral regions. Changes in scattering over a 4-fold range did not affect the photon path depth appreciably. In the presence of hemoglobin with a source-detector separation of 13 mm, the most probable depth of photon penetration in the visible range was greater than 2.5 mm, and was within 1 mm of the most probable depth of photon penetration in the NIR. This study demonstrates the feasibility of using the visible and NIR regions in transcutaneous reflectance spectroscopy.

Asplund, Karin M.; Schenkman, Kenneth A.; Ciesielski, Wayne A.; Arakaki, Lorilee S. L.

2014-03-01

351

Some new possibilities in direct visible and x ray measurements  

International Nuclear Information System (INIS)

Subnanosecond photodetection measurements in visible and X ray range with vacuum cell and very thin microchannel plate phototube (coupled with a fast scintillator or not) in conjunction with fast oscilloscope (5 GHz) are presented. They are compared to those given by a visible or a gold photocathode X-ray streak camera (temporal resolution better than 20 ps). (author)

1978-08-25

352

Optical Conductivity of Graphene in the THz Frequency Range  

International Nuclear Information System (INIS)

Full text: Since its discovery in 2004, graphene - planar, hexagonal arrangements of carbon atoms - attracted much attention in different scientific fields. This is not only due to the fact, that truly two-dimensional crystalline systems like graphene were supposed not to exist, but mainly due to the unique electronic properties of this material. The crystal structure of graphene consists of two equivalent sublattices. Quantum mechanical hopping of electrons between these sublattices leads to the formation of two energy bands that intersect at the points K and K'. Around these crossing points, the electron dispersion relation is linear and gapless in contrast to conventional metals and semiconductors. This fact is expected to result in strong interaction between graphene and terahertz radiation under certain conditions, and thus makes graphene a very interesting material for the terahertz spectral range. In this context, the optical conductivity is a key property of graphene. While the optical conductivity of graphene is constant for the visible spectral region, it is expected to show strong deviation from this behaviour in the THz frequency region. This is due to the fact that interband transitions dominate in the visible range whereas, below the mid-infrared range, intraband transitions are dominant. We present an experimental approach to measure the optical conductivity of a graphene monolayer by means of THz time-domain-spectroscopy involving an on-chip coplanar waveguide structure for generation and detection of THz pulses. (author)

2010-09-06

353

Block Numerical Ranges  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The block numerical range (BNR) of a block operator matrix is a generalization of the numerical range of an operator acting on a Hilbert space. Main topics of this thesis are block diagonalizability of a block operator matrix if its BNR consists of the maximal number of connected components and spectral properties of corners of BNRs of block operator matrices and block operator functions.

Wagenhofer, Markus

2007-01-01

354

On spectropolarimetric measurements with visible lines  

CERN Multimedia

The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (e.g. Ruiz Cobo & Del Toro Iniesta, 1994). Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The response functions are used as well for estimating the uncertainties in the physical quantities due to noise in the observations. A usef...

Iniesta, J C del Toro; Rubio, L R Bellot

2010-01-01

355

Integrally and spectrally direct normal incidence radiation measurements and their bearing on atmospheric transmission on Baghdad  

Energy Technology Data Exchange (ETDEWEB)

The loss in the received amounts of normal incidence solar radiation at the ground level at noon time reaches 47% of that incident outside the earth's atmosphere. The corresponding depletion figures in the amount of direct radiation received in the studied spectral band were 33% in the band less than 530 {mu}m, 50% in the visible range (530 < {lambda} < 695 {mu}m) and 46% in the infrared range ({lambda} > 695 {mu}m) of the solar spectrum. The fractions of the spectral bands to the normal incidence solar radiation at the ground level are in the yearly average 30%, 20% and 49% for the above mentioned spectral bands, respectively. The extinction coefficient for normal incidence solar radiation range was 0.36-0.60 with a mean value of 0.50. Approximately, a similar trend occurs for the energy in the visible and in the infrared ranges of the solar spectrum. Extinction below 530 {mu}m was found to vary over 0.23-0.41 with smaller values occurring during the warmer months. (author)

Al-Riahi, M.; Ali, K. [Solar Energy Research Centre, Baghdad (Iraq); Al-Jumaily, K.J. [Al-Mustansiriyah University, Baghdad (Iraq). Dept. of Meteorology

2001-05-01

356

Huanglongbing (Citrus Greening) Detection Using Visible, Near Infrared and Thermal Imaging Techniques  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440–900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the average reflectance values of the healthy trees in the visible region were lower than those in the near infrared region, while the opposite was the case for HLB-infected...

Sindhuja Sankaran; Joe Mari Maja; Sherrie Buchanon; Reza Ehsani

2013-01-01

357

Visible Knowledge Project  

Science.gov (United States)

Located at Georgetown University, the Visible Knowledge Project (VKP) "aims to improve the quality of college and university teaching by focusing on both student learning and faculty developments in technology-enhanced environments." By drawing on the strengths of their 12 partner schools (which include large research universities and community colleges), the various faculty from each institution involved with VKP document the impact of their various pedagogical and technological innovations on student learning and present them in a variety of formats. Many of these engaging projects and tools are available on the website, and may be searched by institution or discipline title. Quite a few will be of interest to instructors, as they feature such topics as Dante and the Journey to Freedom and Multiple Media for Cultural Analysis. Along with these helpful resources, visitors can learn more about the project, read the quarterly newsletter, and learn about individual participants who have taken these ideas to heart throughout the duration of the VKP.

358

Spectral branes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the objects (called spectral branes or S-branes) which are obtained by imposing non-local spectral boundary conditions at the boundary of the world sheet of the bosonic string. They possess many nice properties which make them an ideal test ground for the string theory methods. Depending on a particular choice of the boundary operator S-branes may be commutative or non-commutative. We demonstrate that projection of the B-field on the brane directions (i.e. on the co...

Vassilevich, D. V.

2001-01-01

359

Spectral Ranking  

CERN Document Server

This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than fifty years ago, almost exactly in the same terms, and has been studied in psychology and social sciences. I will try to describe it in precise and modern mathematical terms, highlighting along the way the contributions given by previous scholars.

Vigna, Sebastiano

2009-01-01

360

UVMag: stellar formation, evolution, structure and environment with space UV and visible spectropolarimetry  

CERN Document Server

Important insights into the formation, structure, evolution and environment of all types of stars can be obtained through the measurement of their winds and possible magnetospheres. However, this has hardly been done up to now mainly because of the lack of UV instrumentation available for long periods of time. To reach this aim, we have designed UVMag, an M-size space mission equipped with a high-resolution spectropolarimeter working in the UV and visible spectral range. The UV domain is crucial in stellar physics as it is very rich in atomic and molecular lines and contains most of the flux of hot stars. Moreover, covering the UV and visible spectral domains at the same time will allow us to study the star and its environment simultaneously. Adding polarimetric power to the spectrograph will multiply tenfold the capabilities of extracting information on stellar magnetospheres, winds, disks, and magnetic fields. Examples of science objectives that can be reached with UVMag are presented for pre-main sequence,...

Neiner, C; Fullerton, A; Gry, C; Hussain, G; Lebre, A; Morin, J; Petit, P; Sundqvist, J O; ud-Doula, A; Vidotto, A A; Wade, G A

2014-01-01

 
 
 
 
361

ON SPECTROPOLARIMETRIC MEASUREMENTS WITH VISIBLE LINES  

International Nuclear Information System (INIS)

The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (RFs), for e.g., by Ruiz Cobo and Del Toro Iniesta. Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The RFs are also used for estimating the uncertainties in the physical quantities due to noise in observations. A useful formula has been derived that takes into account the measurement technique (number of polarization measurements, polarimetric efficiencies, and number of wavelength samples), the model assumptions (number of free parameters and the filling factor), and the radiative transfer (RFs). We conclude that a scenario with a weak magnetic field can reasonably be distinguished with visible lines from another with a strong field but a similar Stokes V amplitude, provided that the Milne-Eddington approximation is good enough to describe the solar atmosphere and the polarization signal is at least 3 or 4 times larger than the typical rms noise of 10-3 Ic reached in the observations.

2010-03-01

362

Hard X-ray Imaging of Solar Flares Using Interpolated Visibilities  

Science.gov (United States)

RHESSI produces solar flare images with the finest angular and spectral resolutions ever achieved at hard X-ray energies. Because this instrument uses indirect, collimator-based imaging techniques, the "native" output of which is in the form of "visibilities" (two-dimensional spatial Fourier components of the image), the development and application of robust, accurate, visibility-based image reconstruction techniques is required. Recognizing that the density of spatial-frequency (u, v) coverage by RHESSI is much sparser than that normally encountered in radio astronomy, we therefore introduce a method for image reconstruction from a relatively sparse distribution of sampled visibilities. The method involves spline interpolation at spatial frequencies less than the largest sampled frequency and the imposition of a positivity constraint on the image to reduce the ringing effects resulting from an unconstrained Fourier transform inversion procedure. Using simulated images consisting both of assumed mathematical forms and of the type of structure typically associated with solar flares, we validate the fidelity, accuracy, and robustness with which the new procedure recovers input images. The method faithfully recovers both single and multiple sources, both compact and extended, over a dynamic range of ~10:1. The performance of the method, which we term as uv_smooth, is compared with other RHESSI image reconstruction algorithms currently in use and its advantages summarized. We also illustrate the application of the method using RHESSI observations of four solar flares.

Massone, Anna Maria; Emslie, A. Gordon; Hurford, G. J.; Prato, Marco; Kontar, Eduard P.; Piana, Michele

2009-10-01

363

Visibilities and bolometric corrections for stellar oscillation modes observed by Kepler  

CERN Document Server

Kepler produces a large amount of data used for asteroseismological analyses, particularly of solar-like stars and red giants. The mode amplitudes observed in the Kepler spectral band have to be converted into bolometric amplitudes to be compared to models. We give a simple bolometric correction for the amplitudes of radial modes observed with Kepler, as well as the relative visibilities of non-radial modes. We numerically compute, for different effective temperatures Teff within the range 4000-7500 K, the bolometric correction c_{K-bol} and mode visibilities, using a similar approach to Michel et al (2009, A&A 495, 979). We derive a law for the correction to bolometric values: c_{K-bol} = 1 + a_1 (Teff-To) + a_2 (Teff-To)^2, with To = 5934 K, a_1 = 1.349e-4 K^{-1}, and a_2 = -3.120e-9 K^{-2} or, alternatively, as the power law c_{K-bol} = (Teff/To)^alpha with alpha = 0.80. We give tabulated values for the mode visibilities, based on limb-darkening (LD) computed from ATLAS9 model atmospheres for Teff in [...

Ballot, J; Veer-Menneret, C van 't

2011-01-01

364

Chromatic confocal spectral interferometry  

International Nuclear Information System (INIS)

Chromatic confocal spectral interferomertry (CCSI) is a novel scheme for topography measurements that combines the techniques of spectral interferometry and chromatic confocal microscopy. This hybrid method allows for white-light interferometric detection with a high NA in a single-shot manner. To the best of our knowledge, CCSI is the first interferometric method that utilizes a confocally filtered and chromatically dispersed focus for detection and simultaneously allows for retrieval of the depth position of reflecting or scattering objects utilizing the phase (modulation frequency) of the interferometric signals acquired. With the chromatically dispersed focus, the depth range of the sensor is decoupled from the NA of the microscope objective

2006-11-10

365

Chromatic confocal spectral interferometry.  

Science.gov (United States)

Chromatic confocal spectral interferometry (CCSI) is a novel scheme for topography measurements that combines the techniques of spectral interferometry and chromatic confocal microscopy. This hybrid method allows for white-light interferometric detection with a high NA in a single-shot manner. To the best of our knowledge, CCSI is the first interferometric method that utilizes a confocally filtered and chromatically dispersed focus for detection and simultaneously allows for retrieval of the depth position of reflecting or scattering objects utilizing the phase (modulation frequency) of the interferometric signals acquired. With the chromatically dispersed focus, the depth range of the sensor is decoupled from the NA of the microscope objective. PMID:17068567

Papastathopoulos, Evangelos; Körner, Klaus; Osten, Wolfgang

2006-11-10

366

An experimental system for spectral line ratio measurements in the TJ-II stellarator  

International Nuclear Information System (INIS)

The chord-integrated emissions of spectral lines have been monitored in the TJ-II stellarator by using a spectral system with time and space scanning capabilities and relative calibration over the entire UV-visible spectral range. This system has been used to study the line ratio of lines of different ionization stages of carbon (C5+ 5290 A and C4+ 2271 A) for plasma diagnostic purposes. The local emissivity of these ions has been reconstructed, for quasistationary profiles, by means of the inversion Fisher method described previously. The experimental line ratio is being empirically studied and in parallel a simple spectroscopic model has been developed to account for that ratio. We are investigating whether the role played by charge exchange processes with neutrals and the existence of non-Maxwellian electrons, intrinsic to Electron Cyclotron Resonance Heating (ECRH) heating, leave any distinguishable mark on this diagnostic method.

2008-10-01

367

An experimental system for spectral line ratio measurements in the TJ-II stellarator.  

Science.gov (United States)

The chord-integrated emissions of spectral lines have been monitored in the TJ-II stellarator by using a spectral system with time and space scanning capabilities and relative calibration over the entire UV-visible spectral range. This system has been used to study the line ratio of lines of different ionization stages of carbon (C(5+) 5290 A and C(4+) 2271 A) for plasma diagnostic purposes. The local emissivity of these ions has been reconstructed, for quasistationary profiles, by means of the inversion Fisher method described previously. The experimental line ratio is being empirically studied and in parallel a simple spectroscopic model has been developed to account for that ratio. We are investigating whether the role played by charge exchange processes with neutrals and the existence of non-Maxwellian electrons, intrinsic to Electron Cyclotron Resonance Heating (ECRH) heating, leave any distinguishable mark on this diagnostic method. PMID:19044682

Zurro, B; Baciero, A; Fontdecaba, J M; Peláez, R; Jiménez-Rey, D

2008-10-01

368

Visible and near-infrared multispectral analysis of geochemically measured rock fragments at the Opportunity landing site in Meridiani Planum  

Science.gov (United States)

We have used visible and near-infrared Panoramic Camera (Pancam) spectral data acquired by the Opportunity rover to analyze 15 rock fragments at the Meridiani Planum landing site. These spectral results were then compared to geochemistry measurements made by the in situ instruments Mössbauer (MB) and Alpha Particle X-ray Spectrometer (APXS) to determine the feasibility of mineralogic characterization from Pancam data. Our results suggest that dust and alteration rinds coat many rock fragments, which limits our ability to adequately measure the mineralogy of some rocks from Pancam spectra relative to the different field of view and penetration depths of MB and APXS. Viewing and lighting geometry, along with sampling size, also complicate the spectral characterization of the rocks. Rock fragments with the same geochemistry of sulfate-rich outcrops have similar spectra, although the sulfate-rich composition cannot be ascertained based upon Pancam spectra alone. FeNi meteorites have spectral characteristics, particularly ferric oxide coatings, that generally differentiate them from other rocks at the landing site. Stony meteorites and impact fragments with unknown compositions have a diverse range of spectral properties and are not well constrained nor diagnostic in Pancam data. Bounce Rock, with its unique basalt composition, is easily differentiated in the Pancam data from all other rock types at Meridiani Planum. Our Pancam analyses of small pebbles adjacent to these 15 rock fragments suggests that other rock types may exist at the landing site but have not yet been geochemically measured.

Weitz, Catherine M.; Farrand, William H.; Johnson, Jeffrey R.; Fleischer, Iris; Schröder, Christian; Yingst, Aileen; Jolliff, Brad; Gellert, Ralf; Bell, Jim; Herkenhoff, Kenneth E.; Klingelhöfer, Göstar; Cohen, Barbara; Calvin, Wendy; Rutherford, Malcolm; Ashley, James

2010-11-01

369

Visibility trends in Tehran during 1958-2008  

Science.gov (United States)

Visibility, in the absence of certain weather conditions (e.g., fog and rain), is an excellent indicator of air quality because its impairment results from light scattering and absorption by atmospheric particles and gases. In this study, the historical airport visibility database is explored during the last five decades for the city of Tehran, Iran. Seasonal and long-term variations of the visibility are investigated using cumulative percentiles. The correlation of the long-term visibility trend with precipitation, fog and high relative humidity are also examined.The trends of visual range of the best, median, and worst visibilities at 10th, 50th and 90th percentiles of daily visibility data indicate an overall downward trend for all the percentiles. Results show a larger decrease in visibility for the Tehran metropolitan area than the sparsely populated and less polluted parts of the city. The largest trend in decreasing visibility is observed during winter time followed by spring, fall and summer. Decreasing trends in visibility occur for all stations and do not significantly depend on the special weather events.

Sabetghadam, Samaneh; Ahmadi-Givi, Farhang; Golestani, Yahya

2012-12-01

370

Mechanism of yeast cell photoinactivation by visible light  

International Nuclear Information System (INIS)

The nature of inactivation of visible light without sensitizers added to the cells has been investigated. In particular, the problem on the nature of intracellular sensitizers has been studied. Visible light is shown to inactivate the cells only in the presence of oxygen, that gives evidence that the process of photoinactivation is carried out according a photodynamic mechanism with participation of the endogenic sensitizer. The pigment - sensitizer is identified as the protoporphyrin on the basis of comparison of data obtained for the absorption spectrum structure and pigment fluorescence with the literature data on the spectral properties of porphyrin compounds

1986-01-01

371

Nanoantennas for visible and infrared radiation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nanoantennas for visible and infrared radiation can strongly enhance the interaction of light with nanoscale matter by their ability to efficiently link propagating and spatially localized optical fields. This ability unlocks an enormous potential for applications ranging from nanoscale optical microscopy and spectroscopy over solar energy conversion, integrated optical nanocircuitry, opto-electronics and density-ofstates engineering to ultra-sensing as well as enhancement o...

Biagioni, Paolo; Huang, Jer-shing; Hecht, Bert

2011-01-01

372

Spectral Signatures of Leaf Fall Diseases in Hevea Brasiliensis Using a Handheld Spectroradiometer  

Directory of Open Access Journals (Sweden)

Full Text Available Subtle sensitive changes in leaf canopy reflectance of a disease infected trees can be detected by a spectroradiometer. A typical method of detecting tree stress caused by diseases or pest infestations includes the analysis of spectroradiometry. Early detection of forest tree stress would be useful to minimize tree losses especially in a forest plantation area.  The main purpose of this study is to develop the spectral library of individual rubber trees being attacked by diseases using a ground-based handheld field spectroradiometer. The specific objective is to identify the spectral signature characteristics of healthy (control and “unhealthy” or stressed rubber trees due to leaf diseases as causal factors. The spectral reflectance of each infected rubber tree was separated according to the different wavelength and percent reflectance. The spectral signatures of rubber trees being attacked by diseases were characterized by a low reflectance probably due to the low chlorophyll content in the leaves leading to the tree under stress, thus easily separated from the healthy rubber. Results indicated that three groups of infected trees were well separated at the 530 - 650 nm (visible wavelength averaging from 0 – 30 percent reflectance. The spectral reflectances of rubber trees with leaf disease in visible (VIS wavelength were not consistently separable. However, the spectral reflectance of leaf diseases can be well separated at the near infrared range region covering from 700 - 850 nm wavelength with a 30 – 80 percent reflectance for leaf diseases, respectively. The study implies that leaf diseases for rubber trees can only be identified successfully at the NIR range of wavelength from 700 – 850 nm with a 20-80 percent reflectance. The development of such signature library profile of disease affecting rubber trees will certainly assists in the development of an early disease warning system using an airborne hyperspectral imaging system technology being currently developed in UPM’s Forest Geospatial Information & Survey Laboratory, at Lebuh Silikon, Universiti Putra Malaysia, Serdang.

Hj.Kamaruzaman Jusoff

2010-01-01

373

Auroral spectral estimation with wide-band color mosaic CCDs  

Science.gov (United States)

Optical aurora can be structured over a wide range of spatial and temporal scales with spectral features that depend on the energy of precipitating particles. Scientific studies typically combine data from multiple instruments that are individually optimized for spatial, spectral, or temporal resolution. One recent addition combines all-sky optics with color mosaic CCD (charge-coupled device) detectors that use a matrix of different wide-band micro-filters to produce an image with several (often three) color channels. These devices provide sequences of two dimensional multispectral luminosity with simultaneous exposure of all color channels allowing interchannel comparison even during periods with rapidly varying aurora. At present color auroral image data are primarily used for qualitative analysis. In this study a quantitative approach based on Backus-Gilbert linear inversion was used to better understand the effective spectral resolution of existing and proposed instruments. Two spectrally calibrated commercial detectors (Sony ICX285AQ and ICX429AKL) with very different color mosaics (RGB (red, green, blue) vs. CYGM (cyan, yellow, green, magenta)) were found to have very similar spectral resolution: three channels with FWHM (full-width half-maximum) ?100 nm; a NIR (near infrared) blocking filter is important for stabilizing inversion of both three-channel configurations. Operating the ICX429AKL in a noninterlaced mode would improve spectral resolution and provide an additional near infrared channel. Transformations from arbitrary device channels to RGB are easily obtained through inversion. Simultaneous imaging of multiple auroral emissions may be achieved using a single-color camera with a triple-pass filter. Combinations of multiple cameras with simple filters should provide ~50 nm resolution across most of the visible spectrum. Performance of other instrument designs could be explored and compared using the same quantitative framework.

Jackel, B. J.; Unick, C.; Syrjäsuo, M. T.; Partamies, N.; Wild, J. A.; Woodfield, E. E.; McWhirter, I.; Kendall, E.; Spanswick, E.

2014-06-01

374

Spectral Predictors  

Energy Technology Data Exchange (ETDEWEB)

Many scientific, imaging, and geospatial applications produce large high-precision scalar fields sampled on a regular grid. Lossless compression of such data is commonly done using predictive coding, in which weighted combinations of previously coded samples known to both encoder and decoder are used to predict subsequent nearby samples. In hierarchical, incremental, or selective transmission, the spatial pattern of the known neighbors is often irregular and varies from one sample to the next, which precludes prediction based on a single stencil and fixed set of weights. To handle such situations and make the best use of available neighboring samples, we propose a local spectral predictor that offers optimal prediction by tailoring the weights to each configuration of known nearby samples. These weights may be precomputed and stored in a small lookup table. We show that predictive coding using our spectral predictor improves compression for various sources of high-precision data.

Ibarria, L; Lindstrom, P; Rossignac, J

2006-11-17

375

Studying the spectral characteristics of 121 impact craters on Mercury  

Science.gov (United States)

We have characterized the spectral reflectance of 121 complex impact craters on Mercury. To do so, we have combined Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Visible and Infrared Spectrograph (VIRS) data with Mercury Dual Imaging System (MDIS) images, both acquired from orbit by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. The MASCS spectra were taken from the DLR database, which currently contains several million MASCS VIRS spectra normalized at 700 nm wavelength to provide a first-order correction for variations in observing conditions. The craters for this study were selected on the basis of geological and physical criteria from the MDIS global dataset. For each impact crater, we mapped as independent geological units the central peak, floor deposits, wall deposits, and external ejecta from 1 to 10 crater radii outward of the crater rim (at a sampling step of 1 radius). From the DLR database, we retrieved MASCS VIRS observations for each geological unit of the 121 impact craters. We explored two different classification schemes. In the first scheme we included all reflectance observations, even those shared between units for different craters. In the second scheme, we excluded spectra that are shared by multiple areas. Under the first scheme, therefore, the same spectral unit can be assigned to two or more craters, whereas under the second scheme spectral units are uniquely linked to a single crater. Preliminary results of our study show a range of distinctive spectra for the crater central peaks. Spectral variations are also seen among crater floor deposits. The goal of the study is to complete a global spectral map as a basis for improving our understanding of crustal stratigraphy on Mercury using impact craters as stratigraphic markers.

D'Incecco, Piero; Helbert, Jörn; D'Amore, Mario; Maturilli, Alessandro; Ferrari, Sabrina; Head, James W.; Klima, Rachel L.; Izenberg, Noam R.; McClintock, William E.; Solomon, Sean C.

2014-05-01

376

Ultrahigh Resolution Spectroscopy Across the Visible to Infrared Spectrum Using Multi-Mode Interference in a Compact Tapered Fiber  

CERN Document Server

Optical spectroscopy is a fundamental tool in numerous areas of science and technology. Much effort has focused on miniaturizing spectrometers, but thus far at the cost of high spectral resolution and broad operating range. Here, we describe a compact spectrometer without this trade-off. The device relies on imaging multi-mode interference from leaky modes along a highly multimode tapered optical fiber, resulting in spectrally distinguishable images that form a basis for reconstructing an incident light spectrum. This tapered fiber multimode interference spectrometer enables the acquisition of broadband spectra in a single camera exposure with a measured resolution of 40 pm in the visible spectrum and 10 pm in the infrared spectrum, which are comparable to the performance of grating spectrometers. Spectroscopy from 500 nm to 1600 nm is demonstrated, though operation across the entire transparency window of silica fibers is possible. Multimode interference spectroscopy of leaky modes is suitable in a variety o...

Wan, Noel H; Shiue, Ren-Jye; Chen, Edward H; Schröder, Tim; Englund, Dirk

2014-01-01

377

Visible solar-pumped lasers  

Science.gov (United States)

We report on two visible solar pumped lasers; a red alexandrite laser with a potential tunability range between 700 and 818 nm, and a frequency doubled Nd:YAG laser operating at 532 nm. Highly concentrated solar energy was obtained by a 3-stage concentrator. An output power of up to 12 W was obtained from the alexandrite laser. The Q-switched Nd:YAG laser employed a type II KTP crystal for intracavity frequency doubling. Q-switching was obtained either passively or actively. In the passive Q-switching version, a water cooled Cr +4:YAG crystal was introduced into the laser cavity acting as both saturable absorber and laser rear mirror, and enforcing high repetition rate operation between 10 and 50 kHz. The average output power at 532 nm was 4.1 W. With an active acousto-optic modulator introduced between the laser rod and the high reflection rear mirror, the average output power at 532 nm and 7.3 kHz repetition rate was 8.7 W.

Lando, Mordechai; Shimony, Yehoshua; Benmair, Roth M. J.; Abramovich, Dov; Krupkin, Vladimir; Yogev, Amnon

1999-10-01

378

Visible spatial frequency domain imaging with a digital light microprojector.  

Science.gov (United States)

There is a need for cost effective, quantitative tissue spectroscopy and imaging systems in clinical diagnostics and pre-clinical biomedical research. A platform that utilizes a commercially available light-emitting diode (LED) based projector, cameras, and scaled Monte Carlo model for calculating tissue optical properties is presented. These components are put together to perform spatial frequency domain imaging (SFDI), a model-based reflectance technique that measures and maps absorption coefficients (?a) and reduced scattering coefficients (?s') in thick tissue such as skin or brain. We validate the performance of the flexible LED and modulation element (FLaME) system at 460, 530, and 632 nm across a range of physiologically relevant ?a values (0.07 to 1.5??mm-1) in tissue-simulating intralipid phantoms, showing an overall accuracy within 11% of spectrophotometer values for ?a and 3% for ?s'. Comparison of oxy- and total hemoglobin fits between the FLaME system and a spectrophotometer (450 to 1000 nm) is differed by 3%. Finally, we acquire optical property maps of a mouse brain in vivo with and without an overlying saline well. These results demonstrate the potential of FLaME to perform tissue optical property mapping in visible spectral regions and highlight how the optical clearing effect of saline is correlated to a decrease in ?s' of the skull. PMID:24005154

Lin, Alexander J; Ponticorvo, Adrien; Konecky, Soren D; Cui, Haotian; Rice, Tyler B; Choi, Bernard; Durkin, Anthony J; Tromberg, Bruce J

2013-09-01

379

Perceptually driven visibility optimization for categorical data visualization.  

Science.gov (United States)

Visualization techniques often use color to present categorical differences to a user. When selecting a color palette, the perceptual qualities of color need careful consideration. Large coherent groups visually suppress smaller groups and are often visually dominant in images. This paper introduces the concept of class visibility used to quantitatively measure the utility of a color palette to present coherent categorical structure to the user. We present a color optimization algorithm based on our class visibility metric to make categorical differences clearly visible to the user. We performed two user experiments on user preference and visual search to validate our visibility measure over a range of color palettes. The results indicate that visibility is a robust measure, and our color optimization can increase the effectiveness of categorical data visualizations. PMID:23929852

Lee, Sungkil; Sips, Mike; Seidel, Hans-Peter

2013-10-01

380

Visible charge exchange recombination spectroscopy on TFTR  

International Nuclear Information System (INIS)

Visible charge exchange recombination spectroscopy is routinely used to measure the time evolution of the ion temperature (T_i) and toroidal rotation velocity (v_?) profiles on TFTR. These measurements are made with the CHERS diagnostic, a fiber-optically coupled spectrometer equipped with a two-dimensional photodiode array detector which provides both spectral and spatial resolution. The instrumentation, data analysis techniques, and examples of T_i and v_? measurements are described. Recently, CHERS has been used to perform impurity transport experiments: radial profiles of diffusivities and convective velocities for helium and iron have been deduced from measurements of the time evolutions of He"2"+ and Fe"2"4"+ profiles following impurity injection. Examples of these measurements are given. 12 refs., 8 figs

1990-11-19

 
 
 
 
381

Visibility of dichalcogenide nanolayers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dichalcogenides with the common formula MX2 are layered materials with electrical properties that range from semiconducting to superconducting. Here, we describe optimal imaging conditions for the optical detection of ultrathin, two-dimensional dichalcogenide nanocrystals containing single, double and triple layers of MoS2, WSe2 and NbSe2. A simple optical model is used to calculate the contrast for nanolayers deposited on wafers with varying thicknesses of SiO2. The model is extended for ima...

2011-01-01

382

Study of the nature of Cu(II) complexes in aqueous ammonium oxalate solutions by ultraviolet-visible spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

Experimental results of an investigation of aqueous ammonium oxalate solutions containing Cu(II) impurity by ultraviolet-visible spectroscopy are described and discussed from the standpoint of speciation of complexes. The results show that absorption of light by aqueous ammonium oxalate solutions containing Cu(II) impurity in the range -5 < ln(c{sub i}/c) < 2.5 of the ratio of concentrations ci and c of impurity and solute, respectively, leads to decrease or increase in the intensity of bands of the ultraviolet-visible spectral regions, and these changes may be expressed by full width at half maximum, molar extinction coefficient, peak wavelength and oscillator strength. The changes are caused by the coordination of C{sub 2}O{sub 4}{sup 2-} ligand with Cu(H{sub 2}O){sub 6}{sup 2+} aquocomplex, and are related with the impurity-solute concentration ratio c{sub i}/c. The coordination of C{sub 2}O{sub 4}{sup 2-} ligand with Cu(H{sub 2}O){sub 6}{sup 2+} aquocomplex in the range 0 < ln(c{sub i}/c) < 2.5 leads to the formation of Cu(C{sub 2}O{sub 4}) complex, but the coordination of the C{sub 2}O{sub 4}{sup 2-} ligand with Cu(C{sub 2}O{sub 4}) complex in the concentration ratio range -5 < ln(c{sub i}/c) < 0 results in the formation of predominantly Cu(C{sub 2}O{sub 4}){sub 2}{sup 2-} complex. The effect of successive coordination of the C{sub 2}O{sub 4}{sup 2-} ligand is well-defined in the ultraviolet spectral region but poor in the visible region.

Mielniczek-Brzoska, E [Institute of Chemistry and Environment Protection, Jan Dlugosz University of Czestochowa, ul. Armii Krajowej 13/15, 42-200 Czestochowa (Poland); Sangwal, K, E-mail: e.mielniczek@ajd.czest.pl [Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin (Poland)

2011-04-01

383

Visible and UV coherent Raman spectroscopy of dipicolinic acid  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use time-resolved coherent Raman spectroscopy to obtain molecule-specific signals from dipicolinic acid (DPA), which is a marker molecule for bacterial spores. We use femtosecond laser pulses in both visible and UV spectral regions and compare experimental results with theoretical predictions. By exciting vibrational coherence on more than one mode simultaneously, we observe a quantum beat signal that can be used to extract the parameters of molecular motion in DPA. The signal is enhanced ...

Pestov, Dmitry; Zhi, Miaochan; Sariyanni, Zoe-elizabeth; Kalugin, Nikolai G.; Kolomenskii, Alexandre A.; Murawski, Robert; Paulus, Gerhard G.; Sautenkov, Vladimir A.; Schuessler, Hans; Sokolov, Alexei V.; Welch, George R.; Rostovtsev, Yuri V.; Siebert, Torsten; Akimov, Denis A.; Graefe, Stefanie

2005-01-01

384

Visible Imaging Fourier Transform Spectrometer: Design and Calibration  

International Nuclear Information System (INIS)

We present details of the design, operation and calibration of an astronomical visible-band imaging Fourier transform spectrometer (IFTS). This type of instrument produces a spectrum for every pixel in the field of view where the spectral resolution is flexible. The instrument is a dual-input/dual-output Michelson interferometer coupled to the 3.5 meter telescope at the Apache Point Observatory. Imaging performance and interferograms and spectra from calibration sources and standard stars are discussed

2002-08-22

385

Development of visible spectroscopic techniques for applications in plasma diagnostics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this thesis visible spectroscopy is developed and used for two applications. Studies of motional Stark effect spectra for diagnosing the current distribution in the fusion plasmas with two different spectroscopic diagnostic systems: ratiometry and interferometry. Both systems provide non-invasive method for diagnosis of the internal plasma properties, e.g. magnetic field. Pitch angle of magnetic field lines are obtained from polarisation of Stark split H? spectral lines emitted by energet...

Jakubowska, Katarzyna

2006-01-01

386

Spectral dependence of aerosol light absorption over the Amazon Basin  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia and at a primary forest site (Cuieiras Reserve, Amazonas, from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30 that covers the visible (VIS to near-infrared (NIR spectral range, and a 2-wavelength Aethalometer (AE20 that measures absorption in the UV and in the NIR. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the absorption Ångström exponent, defined as the negative slope of absorption versus wavelength in a log-log plot. At the pasture site, about 70 % of the absorption Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest absorption Ångström exponents (90 % of data below 1.5 were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with low Ångström exponents. This finding suggests that biogenic aerosols from Amazonia have a weaker spectral dependence for absorption than biomass burning aerosols, contradicting our expectations of biogenic particles behaving as brown carbon. In a first order assessment, results indicate a small (<1 % effect of variations in absorption Ångström exponents on 24-h aerosol forcings, at least in the spectral range of 450–880 nm. Further studies should be taken to assess the corresponding impact in the UV spectral range. The assumption that soot spectral properties represent all ambient light absorbing particles may cause a misjudgment of absorption towards the UV, especially in remote areas. Therefore, it is recommended to measure aerosol absorption at several wavelengths to accurately assess the impact of non-soot aerosols on climate and on photochemical atmospheric processes.

L. V. Rizzo

2011-09-01

387

Spectral dependence of aerosol light absorption over the Amazon Basin  

Science.gov (United States)

In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia) and at a primary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30) that covers the visible (VIS) to near-infrared (NIR) spectral range, and a 2-wavelength Aethalometer (AE20) that measures absorption in the UV and in the NIR. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the absorption Ångström exponent, defined as the negative slope of absorption versus wavelength in a log-log plot. At the pasture site, about 70 % of the absorption Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest absorption Ångström exponents (90 % of data below 1.5) were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with low Ångström exponents. This finding suggests that biogenic aerosols from Amazonia have a weaker spectral dependence for absorption than biomass burning aerosols, contradicting our expectations of biogenic particles behaving as brown carbon. In a first order assessment, results indicate a small (<1 %) effect of variations in absorption Ångström exponents on 24-h aerosol forcings, at least in the spectral range of 450-880 nm. Further studies should be taken to assess the corresponding impact in the UV spectral range. The assumption that soot spectral properties represent all ambient light absorbing particles may cause a misjudgment of absorption towards the UV, especially in remote areas. Therefore, it is recommended to measure aerosol absorption at several wavelengths to accurately assess the impact of non-soot aerosols on climate and on photochemical atmospheric processes.

Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.

2011-09-01

388

Spectral dependence of aerosol light absorption over the Amazon Basin  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia and at a primary forest site (Cuieiras Reserve, Amazonas, from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30 that covers the visible (VIS to near-infrared (NIR spectral range, and a 2-wavelength Aethalometer (AE20 that measures absorption in the UV and in the visible. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the Ångström exponent for absorption, defined as the negative slope of absorption vs. wavelength in a log-log plot. At the pasture site, about 70% of the Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest Ångström exponents (90% of data below 1.5 were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with Ångström exponents below 1.0. This finding suggests that biogenic aerosols from Amazonia may have a weak spectral dependence for absorption, contradicting our expectations of biogenic particles behaving as brown carbon. Nevertheless, additional measurements should be taken in the future, to provide a complete picture of biogenic aerosol absorption spectral characteristics from different seasons and geographic locations. The assumption that soot spectral properties represent all ambient light absorbing particles may cause a misjudgment of absorption towards the UV, especially in remote areas. Therefore, it is recommended to measure aerosol absorption at several wavelengths from UV to near IR to accurately assess the impact of non-soot aerosols on climate and on photochemical atmospheric processes.

L. V. Rizzo

2011-04-01

389

Skyglow effects in UV and visible spectra: radiative fluxes.  

Science.gov (United States)

Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment. PMID:23792881

Kocifaj, Miroslav; Solano Lamphar, H A

2013-09-30

390

No-visible-scar cholecystectomy  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: Single incision laparoscopic surgery (SILS is a laparoscopic method providing a good cosmetic effect,but requiring the application of special ports and instruments enabling the surgeon to perform the procedure.We report three-ports cholecystectomy through umbilical and suprapubic incisions performed with typical laparos -copic instruments which calls no-visible-scar cholecystectomy (NVSC.Material and methods: Twenty patients with symptomatic cholelithiasis were qualified for NVSC. Typical CO2 pneumoperitoneumwas done after umbilical skin incision. Two ports of 5 mm were inserted in the maximum externaledges of this incision. After cystic duct and cystic artery dissection the right one was exchanged for a port of 11 mm.The second incision for the 11-mm trocar for the laparoscope was done in the suprapubic median line within the hairarea.Results: Cholecystectomies were performed without any conversion to classical laparoscopic cholecystectomy (LCHor open surgery. They were not technically identical due to the gradual improvement in the access and manipulationof instruments. The time of the intervention ranged from 2 hours during the introduction of the new method to 50 minfor the last procedures. No postoperative complications were observed and all patients were discharged not later thanafter conventional LCH.Conclusions: NVSC is a three-port laparoscopic intervention performed with typical laparoscopic instruments. It ismore convenient for the surgeon than single incision LCH, because the placement of the optic in the suprapubic regiongives more space for the instruments. It also provides a very good cosmetic effect of the intervention. The describedprocedure is easy to learn and in case of technical problems additional ports can be applied (as in typical LCH.

Tadeusz M. Wróblewski

2010-12-01

391

Visible light communication for advanced driver assistant systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

VIsible light communication for advanced Driver Assistant Systems (VIDAS) is an outdoor application using the visible spectrum of light emitting diodes (LED). A simple traffic light set up based on LED traffic lights for traffic information transmission has been analyzed in this paper. Various important design parameters have been optimized through intensive investigation based on gain variation over 100 m of transmission range. This process is expected to simplify the front-end receiver desi...

Kumar, Navin; Nero, Luis Alves; Aguiar, Rui L.

2009-01-01

392

Search for Olivine Spectral Signatures on the Surface of Vesta  

Science.gov (United States)

The occurrence of olivines on Vesta were first postulated from traditional petrogenetic models which suggest the formation of olivine as lower crustal cumulates. An indirect confirmation is given by their presence as a minor component in some samples of diogenite meteorites, the harzburgitic diogenites and the dunitic diogenites, and as olivine mineral clasts in howardites. Another indication for this mineral was given by interpretations of groundbased and Hubble Space Telescope observations that suggested the presence of local olivine-bearing units on the surface of Vesta. The VIR instrument onboard the DAWN mission has been mapping Vesta since July 2011. VIR acquired hyperspectral images of Vesta s surface in the wavelength range from 0.25 to 5.1 m during Approach, Survey and High Altitude Mapping (HAMO) orbits that allowed a 2/3 of the entire asteroid surface to be mapped. The VIR operative spectral interval, resolution and coverage is suitable for the detection and mapping of any olivine rich regions that may occur on the Vesta surface. The abundance of olivine in diogenites is typically lower than 10% but some samples richer in olivine are known. However, we do not expect to have extensive exposures of olivine-rich material on Vesta. Moreover, the partial overlap of olivine and pyroxene spectral signatures will make olivine difficult to detect. Different spectral parameters have been used to map olivine on extraterrestrial bodies, and here we discuss the different approaches used, and develop new ones specifically for Vesta. Our new methods are based on combinations of the spectral parameters relative to the 1 and 2 micron bands (the most prominent spectral features of Vesta surface in the visible and the infrared), such as band center locations, band depths, band areas, band area ratios. Before the direct application to the VIR data, the efficiency of each approach is evaluated by means of analysis of laboratory spectra of HED meteorites, pyroxenes, olivines and their mixtures.

Palomba, E.; De Sanctis, M. C.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Longobardo, A.; Tosi, F.; Zambon, F.; McSween, H. Y.; Mittlefehldt, D. W.; Russell, C. T.; Raymond, C. A.; Sunshine, J.; McCord, T. B.

2012-01-01

393

Surface units on Mercury defined by unsupervised classification analysis of MESSENGER spectral reflectance data from the first year in orbit  

Science.gov (United States)

The Mercury Atmospheric and Surface and Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has mapped the entire surface of Mercury in the wavelength range from 400 to 1145 nm during the one-year primary orbital mission. Under the hypothesis that surface compositional information can be effectively derived from spectral reflectance measurements with the use of statistical techniques, we employ unsupervised hierarchical clustering analyses to identify and characterize spectral units (Visible and Infrared Spectrograph clustering units, or VCUs) from all observations made with MASCS during the primary mission. At the largest spatial scales, the results indicate a dichotomy in spectral reflectance: one VCU is seen predominantly at the two polar regions, whereas a spectrally distinct VCU is found at lower latitudes. The spatial extent of the polar VCU in the northern hemisphere includes all of the northern volcanic plains. This northern unit also corresponds spatially with regions of highest potassium abundance as mapped by the MESSENGER's Gamma-Ray Spectrometer. We further observe that 98% of all documented locations of hollows are seen in the equatorial spectral unit. On the other hand, the distributions of the two large-scale VCUs show no clear correlation with the locations of Mercury's hot and cold poles or areas likely to be subject to enhanced interaction with the solar wind. This body of evidence leads us to believe that the two major spectral units identified with this hierarchical clustering approach represent compositionally distinct units on the surface of Mercury.

Helbert, J.; D'Amore, M.; Izenberg, N. R.; Domingue, D. L.; Head, J. W.; D'Incecco, P.; Maturilli, A.; Holsclaw, G. M.; McClintock, W. E.; Solomon, S. C.

2012-12-01

394

Spectral CT of carotid atherosclerotic plaque: comparison with histology  

International Nuclear Information System (INIS)

To distinguish components of vulnerable atherosclerotic plaque by imaging their energy response using spectral CT and comparing images with histology. After spectroscopic calibration using phantoms of plaque surrogates, excised human carotid atherosclerotic plaques were imaged using MARS CT using a photon-processing detector with a silicon sensor layer and microfocus X-ray tube (50 kVp, 0.5 mA) at 38-?m voxel size. The plaques were imaged, sectioned and re-imaged using four threshold energies: 10, 16, 22 and 28 keV; then sequentially stained with modified Von Kossa, Perl's Prussian blue and Oil-Red O, and photographed. Relative Hounsfield units across the energies were entered into a linear algebraic material decomposition model to identify the unknown plaque components. Lipid, calcium, iron and water-like components of plaque have distinguishable energy responses to X-ray, visible on spectral CT images. CT images of the plaque surface correlated very well with histological photographs. Calcium deposits (>1,000 ?m) in plaque are larger than iron deposits (<100 ?m), but could not be distinguished from each other within the same voxel using the energy range available. Spectral CT displays energy information in image form at high spatial resolution, enhancing the intrinsic contrast of lipid, calcium and iron within atheroma. (orig.)

2012-12-01

395

Visible spectroscopy of the new ESO Large Program on trans-Neptunian objects and Centaurs: final results  

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A second large programme (LP) for the physical studies of TNOs and Centaurs, started at ESO Cerro Paranal on October 2006 to obtain high-quality data, has recently been concluded. In this paper we present the spectra of these pristine bodies obtained in the visible range during the last two semesters of the LP. We investigate the spectral behaviour of the TNOs and Centaurs observed, and we analyse the spectral slopes distribution of the full data set coming from this LP and from the literature. We computed the spectral slope for each observed object, and searched for possible weak absorption features. A statistical analysis was performed on a total sample of 73 TNOs and Centaurs to look for possible correlations between dynamical classes, orbital parameters, and spectral gradient. We obtained new spectra for 28 bodies, 15 of which were observed for the first time. All the new presented spectra are featureless, including 2003 AZ84, for which a faint and broad absorption band possibly attributed to hydrated sil...

Fornasier, S; de Bergh, C; Alvarez-Candal, A; DeMeo, F; Merlin, F; Perna, D; Guilbert, A; Delsanti, A; Dotto, E; Doressoundiram, A

2009-01-01