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1

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

2

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 inf...

Cataldo, F.; Garcia-hernandez, D. A.; Manchado, A.; Iglesias-groth, S.

2013-01-01

3

Airborne hyperspectral imaging in the visible-to-mid wave infrared spectral range by fusing three spectral sensors  

Science.gov (United States)

Airborne hyperspectral imaging is widely used for remote sensing of environment. The choice of spectral region usually depends on the availability and cost of the sensor. Visible-to-near infrared (400-1100 nm) spectral range corresponds to spectral sensitivity of relatively cheap Si detectors therefore it is the most commonly used. The implementation of shortwave infrared (1100-3000 nm) requires more expensive solutions, but can provide valuable information about the composition of the substance. Mid wave infrared (3000-8000 nm) is rarely used for civilian applications, but it provides information on the thermal emission of materials. The fusion of different sensors allows spectral analysis of a wider spectral range combining and improving already existing algorithms for the analysis of chemical content and classification. Here we introduce our Airborne Surveillance and Environmental Monitoring System (ARSENAL) that was developed by fusing seven sensors. The first test results from the fusion of three hyperspectral imaging sensors in the visible-to-mid wave infrared (365-5000 nm) are demonstrated. Principal component analysis (PCA) is applied to test correlation between principal components (PCs) and common vegetation indices.

Jakovels, Dainis; Filipovs, Jevgenijs; Erinš, Gatis; Taskovs, Juris

2014-10-01

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.)

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

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 Lam...

Bo?ttger, U.; Preusker, R.

2006-01-01

8

A synchrotron-radiation-based variable angle ellipsometer for the visible to vacuum ultraviolet spectral range.  

Science.gov (United States)

A rotating analyzer spectroscopic polarimeter and ellipsometer with a wide-range ?-2? goniometer installed at the Insertion Device Beamline of the Metrology Light Source in Berlin is presented. With a combination of transmission- and reflection-based polarizing elements and the inherent degree of polarization of the undulator radiation, this ellipsometer is able to cover photon energies from about 2 eV up to 40 eV. Additionally, a new compensator design based on a CaF2 Fresnel rhomb is presented. This compensator allows ellipsometric measurements with circular polarization in the vacuum ultraviolet spectral range and thus, for example, the characterization of depolarizing samples. The new instrument was initially used for the characterization of the polarization of the beamline. The technical capabilities of the ellipsometer are demonstrated by a cohesive wide-range measurement of the dielectric function of epitaxially grown ZnO. PMID:24880425

Neumann, M D; Cobet, C; Kaser, H; Kolbe, M; Gottwald, A; Richter, M; Esser, N

2014-05-01

9

Optical constants of liquid UO2 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.)

10

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

CERN Document Server

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

11

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2012-01-01

12

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

13

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

14

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

15

Asymmetric one-dimensional photonic crystal for optical sensing in the visible spectral range  

Science.gov (United States)

A gas sensor based on an asymmetric one-dimensional (1D) photonic band gap structure with one defect layer was designed and fabricated through layer-by-layer deposition of spin-coated poly methyl methacrylate (PMMA) and vacuum-deposited As2S3. Initially, the thickness variations, ?d, were determined of the thin films resulting from the poly methyl methacrylate exposure to chloroform vapor in the concentration range 100 - 9000 ppm. It was found that the value of ?d depends on the gas concentration and the exposure time. A two-layer structure was prepared consisting of PMMA and vacuum-deposited As2S3. Further, the permeability of thin As2S3 films to chloroform vapors was investigated. The asymmetric photonic structure consisted of 11 alternating layers of As2S3 and PMMA. The defect PMMA layer was located before the last high-refractive-index film of chalcogenide glass. The thickness of the defect layer of PMMA was pre-calculated so that the pass band be centered at the wavelength of 550 nm. An offset was observed of the position of the pass band to the larger wavelengths after exposure to chloroform vapor. The multilayered structure proposed is promising for optical sensor applications.

Lalova, A.; Todorov, R.

2014-05-01

16

TiN/(Al,Sc)N metal/dielectric superlattices and multilayers as hyperbolic metamaterials in the visible spectral range  

Science.gov (United States)

Hyperbolic metamaterials (HMMs) based on metal/dielectric multilayers have garnered attention in recent years due to their extraordinary optical properties emanating from hyperbolic dispersion of isofrequency surfaces. We have developed a new class of epitaxial metal/dielectric superlattice HMMs based on transition-metal nitrides—titanium nitride (TiN) and aluminum scandium nitride (AlxSc1-xN)—that could potentially lead to better HMM performance without requiring any traditional plasmonic materials such as gold (Au) and silver (Ag). Our results suggest that the TiN/(Al,Sc)N superlattices grown on (001) MgO substrates are nominally monocrystalline and pseudomorphic, exhibiting sharp interfaces with interface roughnesses of about one to two atomic layers. HMMs deposited on (0001) sapphire substrates grow in 111 orientation with local epitaxy inherent to individual grains, while on (001) Si substrates, the HMMs are polycrystalline. The HMM properties extracted with effective medium theory along with nonlocal field corrections indicate that the TiN/(Al,Sc)N superlattices grown on MgO substrates have both transverse negative (type-I) and transverse positive (type-II) hyperbolic dispersion of the isofrequency surfaces in the visible to near-IR spectral regions. The carrier concentration of TiN layers was varied deliberately by tuning the deposition conditions, thereby shifting the spectral range of both type-I and type-II HMM dispersions. The epitaxial thin-film-based HMMs developed here mark the beginning of a new generation of optical metamaterials with enhanced electromagnetic properties.

Saha, Bivas; Naik, Gururaj V.; Saber, Sammy; Akatay, Cem; Stach, Eric A.; Shalaev, Vladimir M.; Boltasseva, Alexandra; Sands, Timothy D.

2014-09-01

17

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

International Nuclear Information System (INIS)

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)

18

Optical, spectral and phase-matching properties of BIBO, BBO and LBO crystals for optical parametric oscillation in the visible and near-infrared wavelength ranges  

International Nuclear Information System (INIS)

The phase-matching properties of BIBO, BBO and LBO crystals for optical parametric oscillators (OPO) with wavelength tuning in the visible and near infrared spectral ranges were numerically investigated. The phase-matching configurations with a pump wavelength of 520 nm that provide the largest effective nonlinearity in each crystal were considered and compared. In addition, dispersive characteristics, including the group velocity mismatch and group velocity dispersion, which are of significant importance in femtosecond OPOs, were calculated. Finally, the attainable gain bandwidths for each crystal were estimated. (paper)

19

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range  

Energy Technology Data Exchange (ETDEWEB)

Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time.

Laity, G.; Neuber, A.; Rogers, G.; Frank, K. [Department of Electrical and Computer Engineering and Department of Physics, Center for Pulsed Power and Power Electronics, Texas Tech University, Lubbock, Texas 79409 (United States)

2010-08-15

20

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range.  

Science.gov (United States)

Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time. PMID:20815599

Laity, G; Neuber, A; Rogers, G; Frank, K

2010-08-01

 
 
 
 
21

Role of Al coordination in barium phosphate glasses on the emission features of Ho3+ ion in the visible and IR spectral ranges  

International Nuclear Information System (INIS)

The glasses of the composition (39-x)BaO-xAl2O3-60P2O5:1.0Ho2O3 (in mol%) with x value ranging from 1.0 to 4.0 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al3+ ions from tetrahedral to octahedral with increase in the concentration of Al2O3 up to 3.0 mol%. Optical absorption and fluorescence spectra (in the visible and NIR regions) of these glasses have been recorded at room temperature. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of Ho3+ ions in these glasses. From the luminescence spectra, various radiative properties like transition probability A, branching ratio ?r, the radiative lifetime ?r and emission cross-section ?E for various emission levels of these glasses have been evaluated. The radiative lifetime of the 5S2?5I8 (green emission) transition has also been measured. The variations observed in these parameters have been discussed in the light of varying co-ordinations (tetrahedral and octahedral positions) of Al3+ ions in the glass network. The influence of hydroxyl groups on the luminescence efficiency of the transition 5S2?5I8 has also been discussed. Finally the optimum con discussed. Finally the optimum concentration of Al2O3 for getting maximum luminescence output has also been identified and reported.

22

An Impurity Emission Survey in the near UV and Visible Spectral Ranges of Electron Cyclotron Heated (ECH) Plasma in the TJ-II Stellarator  

International Nuclear Information System (INIS)

We report on a near-ultraviolet and visible spectroscopic survey (220-600 nm) of electron cyclotron resonance (ECR) heated plasmas created in the TJ-II stellarator, with central electron temperatures up to 2 keV and central electron densities up to 1.7 x 10 ''19 m''-3. Approximately 1200 lines from thirteen elements have been identified. The purpose of the work is to identify the principal impurities and spectral lines present in TJ-II plasmas, as well as their possible origin to search for transitions from highly ionised ions. This work will act as a base for identifying suitable transitions for following the evolution of impurities under different operating regimens and multiplet systems for line polarisation studies. It is intended to use the database creates as a spectral line reference for comparing spectra under different operating and plasma heating regimes. (Author)

23

Properties of InGaAlAs/AlGaAs quantum dots for single photon emission in the near infrared and visible spectral range  

Science.gov (United States)

We have carried out a detailed characterization of individual self-assembled InGaAlAs/AlGaAs quantum dots grown on GaAs substrate and emitting in the 680-780 nm spectral range. Exciton, biexciton and charged exciton emission lines originating from the same quantum dot have been identified, and the biexciton and charged exciton binding energies have been derived to be equal ˜ 5 and ˜ 9 meV, respectively. The second-order photon correlation experiments allowed us to show a clear antibunching for exciton emission with a value of g(2)(0) = 0.04±0.02, confirming distinctly that such GaAs-based quantum dots can be considered as single photon quantum emitters in the abovementioned wavelength range.

Dusanowski, ?.; Golnik, A.; Syperek, M.; Suffczy?ski, J.; Nawrocki, M.; Sek, G.; Misiewicz, J.; Schlereth, T. W.; Schneider, C.; Höfling, S.; Kamp, M.; Forchel, A.

2013-12-01

24

Night illumination in the visible, NIR, and SWIR spectral bands  

Science.gov (United States)

This paper describes a spectral night illumination model. The model provides spectral irradiance on a horizontal surface for wavelengths between 0.4 and 2.0 microns. These wavelengths encompass the visible, near infrared, and short wave infrared spectral bands. The primary significance of this model is that consistent estimates of spectral irradiance are now provided for the visible through SWIR spectral bands. The primary sources of night illumination are described. The paper also describes how the new model was derived from spectroscopic data gathered by astronomers. Model predictions are compared to standard references commonly used to predict night illuminations.

Vollmerhausen, Richard H.; Maurer, Tana

2003-08-01

25

Analysis of visible spectral lines in LHD helium discharge  

International Nuclear Information System (INIS)

In this study, visible spectral lines in LHD helium discharges are analyzed and it was found that they could be well fitted with gaussian profile. The results reveal a simple mechanism of helium atom recycling. Ion temperatures were also derived from the fitting. A typical value of the ion temperature obtained was about 6 eV. (author)

26

Hyper-spectral imager of the visible band for lunar observations  

Science.gov (United States)

A prototype hyper-spectral imager in the visible spectral band was developed for the planned Korean lunar missions in the 2020s. The instrument is based on simple refractive optics that adopted a linear variable filter and an interline charge-coupled device. This prototype imager is capable of mapping the lunar surface at wavelengths ranging from 450 to 900 nm with a spectral resolution of ˜8 nm and selectable channels ranging from 5 to 252. The anticipated spatial resolution is 17.2 m from an altitude of 100 km with a swath width of 21 km

Lim, Y.-M.; Choi, Y.-J.; Jo, Y.-S.; Lim, T.-H.; Ham, J.; Min, K. W.; Choi, Y.-W.

2013-06-01

27

Imaging systems for the delineation of spectral properties of geologic materials in the visible and near-infrared  

Science.gov (United States)

The current status of imaging systems for the identification of the spectral properties of geologic minerals in the visible and near infrared ranges is reviewed. The technical characteristics of the most important instruments are given, including the MSS and TM, the Airborne Imaging Spectrometer, (AIS) the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), and the Shuttle Imaging Spectrometer Experiment (SISEX). It is pointed out that none of the current systems have sufficient spectral resolution to identify mineralogy on the basis of absorption characteristics in the visible, near-infrared or shortwave-infrared bands. The development of new systems with higher spectral resolution is discussed.

Marsh, S. E.; Podwysocki, M. H.; Goetz, A. F. H.; Vane, G.; Slater, P. N.; Townsend, T. E.

1983-01-01

28

Globally integrated measurements of the Earth's visible spectral albedo  

CERN Document Server

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

29

Brightness Control in Dynamic Range Constrained Visible Light OFDM Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Visible light communication (VLC) systems can provide illumination and communication simultaneously via light emitting diodes (LEDs). Orthogonal frequency division multiplexing (OFDM) waveforms transmitted in a VLC system will have high peak-to-average power ratios (PAPRs). Since the transmitting LED is dynamic-range limited, OFDM signal has to be scaled and biased to avoid nonlinear distortion. Brightness control is an essential feature for the illumination function. In thi...

Yu, Z.; Baxley, R. J.; Zhou, G. T.

2013-01-01

30

A review of visible-range Fabry-Perot microspectrometers in silicon for the industry  

Science.gov (United States)

This review presents microspectrometers in silicon for the industry for measuring light in the visible range, using the Fabry-Perot interferometric technique. The microspectrometers are devices able to do the analysis of the individual spectral components in a given signal and are extensively used on spectroscopy. The analysis of the interaction between the matter and the radiated energy can found huge applications in the industrial sector. The microspectrometers can be divided on three types, determined by the dispersion element or the used approach and can be found microspectrometers based on prisms, gratings interferometers. Both types of microspectrometers can be used to analyze the spectral content ranging from the ultraviolet (UV, below 390 nm), passing into the visible region of the electromagnetic spectrum (VIS, 390-760 nm) up to the infrared (IR, above 760 nm). The microspectrometers in silicon are versatile microinstruments because silicon-compatible techniques can be used to assembly both the optical components with the readout and control electronics, thus resulting high-volume with high-reproducibility and low-cost batch fabrications. A compensation technique for minimizing the scattered light effects on interferometers was implemented and is also a contribution of this paper. Fabry-Perot microspectrometers for the visible range are discussed in depth for use in industrial applications.

Carmo, João Paulo; Rocha, Rui Pedro; Bartek, Marian; de Graaf, Ger; Wolffenbuttel, Reinoud F.; Correia, José Higino

2012-10-01

31

New fractal structures for frequencies close to the visible range  

DEFF Research Database (Denmark)

In this paper we present a new type of fractal resonator to be used in the red/NIR region of the spectra. The structure presents high-transmission band in 795-825nm range. The stop band is in the 683-731 nm range. Due to the huge difference in the spectra within such a short range, the structure can be used as an efficient sensor, both in transmission as well as in reflection. Thus, a variation of only 0.09 in the refraction index will for example change the structure’s behaviour from 90% reflection to 90% transmission. Such resonances lead to a sensitivity of 780 nm/RIU. Another advantage of this resonator is the independency of the incidence angle - in the spectral re-gion of interest; the incidence angle has very little influence over the response.

Malureanu, Radu; Sandru, A.

2011-01-01

32

Modified semi-empirical calculations of the Ga II Stark widths in the visible spectral region  

International Nuclear Information System (INIS)

Stark widths of the singly ionized gallium lines for several triplets and singlets in the visible spectral region are calculated using a modified semi-empirical method (MSEM). Results are given at electron density Ne=1017 cm-3 and at electron temperature ranging from 5000 to 40 000 K. The comparison of our MSEM calculated data with both experimental and semi-classical method (SCM) calculated data, available in the literature, shows good agreement for the triplet lines. But, for the singlet lines, there are no data for comparison

33

Passive signatures concealed objects recorded by multispectral and hyperspectral systems in visible, infrared and terahertz range  

Science.gov (United States)

Risks to the safety of public zones (generally available for people) are related mainly to the presence of hidden dangerous objects (such as knives, guns, bombs etc.) and their usage. Modern system for the monitoring of such zones attempt to detect dangerous tools using multispectral cameras working in different spectral ranges: the visible radiation, near, medium and long range infrared and recently also in terahertz range. In order to develop methods and algorithms to detect hidden objects it is necessary to determine the thermal signatures of such objects of interest. The laboratory measurements were conducted to determine the thermal signatures of dangerous tools hidden under various clothes in different ambient conditions. Cameras used for measurements were working in spectral range 0.6-12.5 µm. An infrared imaging Fourier transform spectroradiometer was also used, working in spectral range 7.7-11.7 µm. Analysis of registered thermograms and hyperspectral datacubes has yielded the thermal signatures for: two types of guns, two types of knives and home-made explosive bombs. The determined thermal signatures will be used in the development of method and algorithms of image analysis implemented in proposed monitoring systems.

Kastek, Mariusz; Kowalski, Marcin; Polakowski, Henryk; Lagueux, Philippe; Gagnon, Marc-André

2014-06-01

34

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

35

Spectral characteristics of epidermis in UV and visible ranges  

Science.gov (United States)

New technology for the definition of the skin epidermis optical parameters, which includes upper layers of epidermis stripping, diffuse reflection, transmission, and angular measurement of scattered light by stripping samples, calculations using 4-flux Kubelka-Munk approximation, have been obtained. This technology was successfully used for depth dependence monitoring of epidermis optical parameters, and for laser light dosimetry in percutaneous irradiation of blood and laser PUVA therapy.

Tuchin, Valery V.; Utz, Sergei R.; Yaroslavsky, Ilya V.; Yaroslavskaya, Anna N.; Kukavsky, Vladimir G.; Barabanov, Alexander Y.

1993-07-01

36

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

37

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

38

Potential material for narrow-band detectors in the visible range  

International Nuclear Information System (INIS)

The photoconductivity spectrum of the magnetic semiconductor Cd/sub 1-x/Mn/sub x/Te has been studied at 300 K for various compositions of Mn. It has been found that this system is photosensitive and shows a remarkably sharp peak in the photoresponse curve for each composition. The half-widths for some of them are as small as 100 A. Spectral position varies from 0.68 to 0.49 ? as X varies form 0.3 to 0.7. The sharp photoresponse suggests that Cd/sub 1-x/Mn/sub x/Te is a potential candidate as a narrow-band detector in the visible range

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

Ultraviolet and visible range plasmonics of a topological insulator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 mater...

Ou, Jun-yu; So, Jin-kyu; Adamo, Giorgio; Sulaev, Azat; Wang, Lan; Zheludev, Nikolay I.

2014-01-01

 
 
 
 
41

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

42

Stark broadening of visible Ar I spectral lines  

International Nuclear Information System (INIS)

Stark broadening parameters (width and shift) of six Ar I spectral lines: 522.1, 549.6, 518.6, 560.7, 603.2 and 696.5 nm, corresponding to the transitions 3p5nd ?3p5 4p for n=7-5 and 4p'?4s have been calculated on the basis of the impact theory within the semi-classical perturbation approach. The case of the quasistatic ions has also been examined. The conditions of use of the presented results have been discussed. The considered lines are in the optical part of the spectrum and are of interest for laboratory research, particularly surface wave sustained discharges, and astrophysical purposes. The obtained results are compared with published experimental results and values calculated by other authors. The influence of the used coupling (j{/text-}L or LS) and oscillator strengths (The Opacity Project (TOP) database or Coulomb approximation) has also been considered

43

Visible/Near-Infrared Spectral Properties of MUSES C Target Asteroid 25143 Itokawa  

Science.gov (United States)

The Japanese MUSES C mission launched the Hayabusa spacecraft last May 15, 2003, to encounter and study the near-Earth asteroid 25143 Itokawa. The spacecraft will obtain visible images through broadband filters similar to the ECAS filters, and near-infrared spectra from 0.85 - 2.1 microns. In preparation for this encounter, opportunities to study the asteroid with Earth-based telescopes have been fully leveraged. Visible and near-infrared spectral observations were made of asteroid 25143 Itokawa during several nights of March, 2001, around the last apparition. We report here on the results of extensive spectral observations made to address the questions of compositional variations across the surface of the asteroid (as determined by the rotational period and shape model); variations in phase angle (Sun-Itokawa-Earth angle) on spectral characteristics; and predictions of Itokawa observations by Hayabusa based on the spectral resolution and responsivity of the NIRS and AMICA instruments.

Jarvis, K. S.; Vilas, F.; Kelley, M. S.; Abell, P. A.

2004-01-01

44

Studying soil properties using visible and near infrared spectral analysis  

Science.gov (United States)

This research is carried out inside the DIGISOIL Project, whose purposes are the integration and improvement of in situ and proximal measurement technologies, for the assessment of soil properties and soil degradation indicators, going form the sensing technologies to their integration and their application in digital soil mapping. The study area is located in the Virginio river basin, about 30 km south of Firenze, in the Chianti area, where soils with agricultural suitability have a high economic value connected to the production of internationally famous wines and olive oils. The most common soil threats, such as erosion and landslide, may determine huge economic losses, which must be considered in farming management practices. This basin has a length of about 23 km for a basin area of around 60,3 Km2. Geological formations outcropping in the area are Pliocene to Pleistocene marine and lacustrine sediments in beds with almost horizontal bedding. Vineyards, olive groves and annual crops are the main types of land use. A typical Mediterranean climate prevails with a dry summer followed by intense and sometimes prolonged rainfall in autumn, decreasing in winter. In this study, three types of VNIR and SWIR techniques, operating at different scales and in different environments (laboratory spectroscopy, portable field spectroscopy) are integrated to rapidly quantify various soil characteristics, in order to acquire data for assessing the risk of occurrence for typically agricultural practice-related soil threats (swelling, compaction, erosion, landslides, organic matter decline, ect.) and to collect ground data in order to build up a spectral library to be used in image analysis from air-borne and satellite sensors. Difficulties encountered in imaging spectroscopy, such as influence of measurements conditions, atmospheric attenuation, scene dependency and sampling representation are investigated and mathematical pre-treatments, using proper algorithms, are applied and tested. Data on detection limits of ground-based, airborne and satellite sensors are also provided. The problem of the influence of soil moisture and soil roughness on reflectance is also examined. Spectral indexes, derived from absorption features, are related to laboratory results on clay minerals, carbonate and iron content, soil moisture and organic matter amount, in order to investigate the potential of hyperspectral sensors to estimate soil properties, using empirical prediction models.

Moretti, S.; Garfagnoli, F.; Innocenti, L.; Chiarantini, L.

2009-04-01

45

Stark broadening of visible Ar I spectral lines  

Energy Technology Data Exchange (ETDEWEB)

Stark broadening parameters (width and shift) of six Ar I spectral lines: 522.1, 549.6, 518.6, 560.7, 603.2 and 696.5 nm, corresponding to the transitions 3p{sup 5}nd {yields}3p{sup 5} 4p for n=7-5 and 4p'{yields}4s have been calculated on the basis of the impact theory within the semi-classical perturbation approach. The case of the quasistatic ions has also been examined. The conditions of use of the presented results have been discussed. The considered lines are in the optical part of the spectrum and are of interest for laboratory research, particularly surface wave sustained discharges, and astrophysical purposes. The obtained results are compared with published experimental results and values calculated by other authors. The influence of the used coupling (j{l_brace}/text-{r_brace}L or LS) and oscillator strengths (The Opacity Project (TOP) database or Coulomb approximation) has also been considered.

Dimitrijevic, M S [Astronomical Observatory, Volgina 7, 11160 Belgrade (Serbia); Christova, M [Department of Applied Physics, Technical University of Sofia, 1000 Sofia (Bulgaria); Sahal-Brechot, S [Observatoire de Paris, LERMA-Meudon, F-92195 Meudon Cedex (France)

2007-06-15

46

Studies of the ECR plasma in the visible light range  

International Nuclear Information System (INIS)

High resolution visible light (VL) plasma photographs were taken at the ATOMKI-ECRIS by an 8 mega-pixel digital camera. Plasmas were generated from gases of He, methane, N, O, Ne, Ar, Kr, Xe and from their mixtures. The analysis of the photo series gave many qualitative and numerous valuable physical information on the nature of ECR plasmas. VL photos convey information mainly on the cold electron component of the plasma. Cold electrons are confined in the central part of the plasma. It is a further challenging task to understand the colors of this special type of plasmas. The colors can be determined by the VL electron transitions of the plasma atoms and ions combined with the human eye sensitivity. There is a good visual agreement between the calculated normalized color and the real color of the plasmas. Through the examples of He and Xe we analyze the physical processes which affect the characteristic colors of these plasmas. The paper is followed by the slides of the presentation. (authors)

47

Mossbauer and spectral (visible and near-IR) data for Fe(3+)-substituted rutile  

Science.gov (United States)

Titanohematite and rutile containing some Fe(3+) are possible highly oxidized weathering products of ilmenite and titanomagnetities. We report here Moessbauer and reflectivity data (visible and near-IR) for Fe(3+)-substituted rutile as a part of our continuing studies of ferric-substituted minerals that might have bearing on the interpretation of Martian spectral data.

Lauer, H. V., Jr.; Morris, R. V.; Vempati, R. K.

1994-01-01

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.

49

Synchronous photoelectrical observations of flare stars in the visible and near infrared ranges  

International Nuclear Information System (INIS)

The results of synchronous photoelectrical observations of the AD Leo and EV Lac flare stars made in 1975 in the Crimea in B-filter and in the near infrared region (i-band, lambdasub(ef) approximately 0.85 ?m) and the observations of the UV Cet and EV Lac stars made in 1976 in the Astronomical Institute Uzbek SSR in three passbands: U, isub(TiO)(lambdasub(ef)=0.71 ?) and isub(C)(lambdasub(ef)=0.80?m) are given. Practically all strong flares in the visible spectral range were followed by the IR-flares. In about 70% of the cases the predicted infrared negative preflares were observed. The amplitudes (in erg/s) of the negative flares are comparable with the amplitude of the optical flares. The analysis of the observed data shows that: a) the amplitudes and the energies of the positive IR flares are in average the larger the stronger is the optical flare; b) the amplitudes of the negative IR preflares are on the contrary the smaller the stronger is the optical flare; c) there are infrared flares the main energy out of which takes place in the infrared range of wavelengths; d) The U-i color shows a positive correlation with the amplitude of the flare in U: the stronger is the flare the bluer is its radiation

50

Use of a high resolution overview spectrometer for the visible range in the TEXTOR boundary plasma  

International Nuclear Information System (INIS)

Passive spectroscopy is a standard diagnostic to observe the boundary layer of fusion plasmas. This visible spectroscopy is focused on the measurement of the deuterium recycling flux as well as on the monitoring of impurity fluxes like e.g. O, He... or W, C.... which result from erosion of plasma-facing components. Moreover, the ro-vibrational analysis of molecular transitions provide information about the molecular break-up in the plasma. Spectrometer for the plasma boundary have to fulfil high demands with respect to the spectral, spatial and time resolution, to the observable wavelength range, to the sensitivity and dynamic range of the detector to observe and analyse simultaneously the emission of atomic and molecular species present in the observed region. We present an overview spectrometer system which is able a) to measure at once strong atomic lines (e.g. D?) and weak molecular bands (e.g. C2 Swan-band), b) to resolve narrow molecular lines (e.g. D2 Fulcher-? band) and allow their ro-vibrational analysis, and c) to provide information about the spatial distribution in the plasma boundary. A full characterisation of the custom-made system in cross-dispersion arrangement with respect to resolving power, simultaneous wavelength coverage, sensitivity etc. is done. Spectra examples ('footprints') taken from an injection of C3H4 into TEXTOR are presented. (author)

51

Composition, Mineralogy, and Porosity of Multiple Asteroid Systems from Visible and Near-infrared Spectral Data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We provide a taxonomic and compositional characterization of Multiple Asteroid Systems (MASs) located in the main belt (MB) using visible and near-infrared (0.45-2.5 um) spectral data of 42 MB MASs. The mineralogical analysis is applied to determine meteorite analogs for the MASs, which, in turn, are applied to the MAS density measurements of Marchis et al. (2012) to estimate the system porosity. The macroporosities are used to evaluate the primary MAS formation hypotheses. ...

Lindsay, Sean S.; Marchis, Franck; Emery, Joshua P.; Enriquez, J. Emilio; Assafin, Marcelo

2014-01-01

52

Spectral gap for the zero range process with constant rate  

CERN Document Server

We solve an open problem concerning the relaxation time (inverse spectral gap) of the zero range process in $Z^d/LZ^d$ with constant rate, proving an upper bound of $O((\\rho + 1)^2 L^2)$, where $\\rho$ is the density of particles.

Morris, B

2004-01-01

53

Sb2O3 nanobelt networks for excellent visible-light-range photodetectors  

Science.gov (United States)

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 (height modulations in the nanobelt-to-nanobelt contact regions. These results demonstrate that Sb2O3 nanobelt networks can indeed serve as high-performance photodetectors in the visible light range.

Li, L.; Zhang, Y. X.; Fang, X. S.; Zhai, T. Y.; Liao, M. Y.; Wang, H. Q.; Li, G. H.; Koide, Y.; Bando, Y.; Golberg, D.

2011-04-01

54

Sb(2)O(3) nanobelt networks for excellent visible-light-range photodetectors.  

Science.gov (United States)

Excellent photoconductive properties have been found in Sb(2)O(3) nanobelts synthesized by a surfactant-assisted solvothermal method. Visible-light photodetectors have been designed from Sb(2)O(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 (height modulations in the nanobelt-to-nanobelt contact regions. These results demonstrate that Sb(2)O(3) nanobelt networks can indeed serve as high-performance photodetectors in the visible light range. PMID:21393818

Li, L; Zhang, Y X; Fang, X S; Zhai, T Y; Liao, M Y; Wang, H Q; Li, G H; Koide, Y; Bando, Y; Golberg, D

2011-04-22

55

Evaluating potential spectral impacts of various artificial lights on melatonin suppression, photosynthesis, and star visibility.  

Science.gov (United States)

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, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED) and LED 2700 K lamps filtered with the new Ledtech's Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies. PMID:23861808

Aubé, Martin; Roby, Johanne; Kocifaj, Miroslav

2013-01-01

56

Using SCIAMACHY to improve corrections for spectral band differences when transferring calibration between visible sensors  

Science.gov (United States)

The advent of well-calibrated and well-characterized visible sensors, such as the MODerate resolution Imaging Spectroradiometer (MODIS), has allowed the opportunity to cross-calibrate other contemporary, un-calibrated visible sensors. Most of the operational geostationary-Earth-orbit satellite (GEOsat) visible sensors do not have a direct means of on-orbit calibration, and the cross-calibration of MODIS with GEOsats is plagued by the differences in the sensor spectral response functions (SRFs). Spectral band adjustment factors (SBAFs) are needed to correct for the solar flux and inter-band gaseous absorption discrepancies that are caused by SRF differences, which are sometimes significant. In addressing this problem, this manuscript describes a spectral band correction technique that employs Envisat SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) hyper-spectral radiances to derive pseudo-radiance, or equivalent-radiance, values for the MODIS and GEOsat sensors over the calibration targets, which include a desert, deep convective clouds, and a MODIS-with-GEOsat ray-matching ocean domain. The regressions from these equivalent-radiance comparisons constitute the necessary adjustment factor. The regressions of MODIS and GEOsat pseudo-radiance values are well-behaved, with small standard error and offsets, for spectral bands that are similar. When comparing narrowband to broadband, however, the correction difference between deep convective and maritime stratus clouds can be as large as 6%. New scene-selection criteria are investigated to derive spectral band adjustment factors that are dependent on the calibration-target domains, which reduces this uncertainty. Application of these SBAFs, which are validated for accuracy using ray-matched SCIAMACHY and GEOstat radiances, is shown to bring independently derived absolute calibrations to within 1% agreement, or better, with one-another. These spectral band adjustment factors are critical for obtaining accurate and consistent absolute calibration among multiple independent and scene-dependent inter-calibration techniques given that the variation of the SBAFs as a function of scene type can be close to 8% for a narrowband-to-broadband correction.

Scarino, Benjamin; Doelling, David R.; Morstad, Daniel L.; Bhatt, Rajendra; Gopalan, Arun; Lukashin, Constantine; Minnis, Patrick

2012-09-01

57

Composition, mineralogy, and porosity of multiple asteroid systems from visible and near-infrared spectral data  

Science.gov (United States)

We aim to provide a taxonomic and compositional characterization of Multiple Asteroid Systems (MASs) located in the main belt (MB) using visible (0.45-0.85 ?m) and near-infrared (0.7-2.5 ?m) spectral data of 42 MB MASs. The compositional and mineralogical analysis is applied to determine meteorite analogs for the MASs, which, in turn, are applied to the MAS density measurements of Marchis et al. (Marchis et al. [2012]. Icarus 221, 1130-1161) to estimate the porosity of the systems. The macroporosities are used to evaluate the primary MAS formation hypotheses. Our spectral survey consists of visible and near-infrared spectral data. The visible observing campaign includes 25 MASs obtained using the Southern Astrophysical Research (SOAR) telescope with the Goodman High Throughput Spectrometer. The infrared observing campaign includes 34 MASs obtained using the NASA Infrared Telescope Facility (IRTF) with the SpeX spectragraph. For completeness, both visible and NIR data sets are supplemented with publicly available data, and the data sets are combined where possible. The MASs are classified using the Bus-DeMeo taxonomic system. In order to determine mineralogy and meteorite analog, we perform a NIR spectral band parameter analysis using a new analysis routine, the Spectral Analysis Routine for Asteroids (SARA). The SARA routine determines band centers, areas, and depths by utilizing the diagnostic absorption features near 1- and 2-?m due to Fe2+ crystal field transitions in olivine + pyroxene and pyroxene, respectively. The band parameter analysis provides the Gaffey subtype for the S-complex MASs; the relative abundance olivine-to-pyroxene ratio; and olivine and pyroxene modal abundances for S-complex and V-type MASs. This mineralogical information is then applied to determine meteorite analogs. Through applying calibration studies, we are able to determine the H, L, and LL meteorite analogs for 15 MASs with ordinary chondrite-like (OC) mineralogies. We observe an excess (10/15) of LL-like mineralogies. Of the ten MASs with LL-like mineralogies, seven are consistent with Flora family membership, supporting the hypothesis that the Flora family is a source of LL-like NEAs and LL chondrites on Earth. Our band parameter analysis is unable to clearly distinguish between the HED subgroups for the 6 V-type MASs. Using the measured densities of the meteorite analog and the MAS densities from Marchis et al. (Marchis et al. [2012]. Icarus 221, 1130-1161), we estimate the macroporosity for 13 MASs. We find that all of the MASs with estimated macroporosities are in agreement with formation hypotheses.

Lindsay, S. S.; Marchis, F.; Emery, J. P.; Enriquez, J. E.; Assafin, M.

2015-02-01

58

High speed full range complex spectral domain optical coherence tomography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a high speed full range spectral domain optical coherence tomography system. By inserting a phase modulator into the reference arm and recording of every other spectrum with a 90° phase shift (introduced by the phase modulator) we are able to distinguish between negative and positive optical path differences with respect to the reference mirror. A modified two-frame algorithm eliminates the problem of suppressing symmetric structure terms in the final image. To demonstrate the per...

Go?tzinger, Erich; Pircher, Michael; Leitgeb, Rainer A.; Hitzenberger, Christoph K.

2005-01-01

59

Spectrally-resolved measurements of aerosol extinction at ultraviolet and visible wavelengths  

Science.gov (United States)

Aerosols play an important role in the Earth's radiative budget. Aerosol extinction includes both the scattering and absorption of light, and these vary with wavelength, aerosol diameter, and aerosol composition. Historically, aerosol absorption has been measured using filter-based or extraction methods that are prone to artifacts. There have been few investigations of ambient aerosol optical properties at the blue end of the visible spectrum and into the ultraviolet. Brown carbon is particularly important in this spectral region, because it both absorbs and scatters light, and encompasses a large and variable group of organic compounds from biomass burning and secondary organic aerosol. We have developed a laboratory instrument that combines new, high-power LED light sources with high-finesse optical cavities to achieve sensitive measurements of aerosol optical extinction. This instrument contains two broadband channels, with spectral coverage from 360 - 390 nm and 385 - 420 nm. Using this instrument, we report aerosol extinction in the ultraviolet and near-visible spectral region as a function of chemical composition and structure. We have measured the extinction cross-sections between 360 - 420 nm with 0.5 nm resolution using different sizes and concentrations of polystyrene latex spheres, ammonium sulfate, and Suwannee River fulvic acid. Fitting the real and imaginary part of the refractive index allows the absorption and scattering to be determined.

Flores, M.; Washenfelder, R. A.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2012-12-01

60

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

 
 
 
 
61

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

CERN Document Server

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

62

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

63

Anomalous aggregation growth of palladium nanosphere with SPR band in visible range  

International Nuclear Information System (INIS)

The morphology and properties of nanostructures are significantly influenced by the chemical coordination during their growth procedure. Using small molecule N-vinyl pyrolidone as stabilizer, this paper introduces a new strategy for synthesis of palladium nanospheres, which has a novel surface plasmon resonance band in the visible range. An aggregation growth mode was observed in the growth process. More specifically, the growth rate increases with increasing concentration of stabilizer. The absorption in visible region suggests new optical applications for these Pd nanospheres, such as photocatalysis, photothermal heating and surface enhanced Raman scattering

64

Diamond photonic crystals for the IR spectral range.  

Science.gov (United States)

2D photonic crystals formed inside monocrystalline diamond to operate in the IR spectral range are reported. The photonic structures consisting of 150-?m-long graphitized wires arranged in a square matrix with a period of 4 ?m were produced by laser writing with ultrashort pulses. Transmittance spectra (?=1-14???m) measured for the structures with increasing thickness demonstrate the occurrence of few minima being different for TM and TE polarization modes. Complex refraction index of the laser-modified material was evaluated for the first time in order to be used in computer simulation of the structures. PMID:25503041

Kononenko, T V; Dyachenko, P N; Konov, V I

2014-12-15

65

UV-visible spectral study on the latent tracks of light ions in CR-39 plastics detector  

International Nuclear Information System (INIS)

In this work, UV-visible spectral studies have been performed on irradiated CR-39 plastics detector by gamma-ray and light ions of proton (3.4 MeV), helium ion (5.1 MeV) and carbon ion (8.5 MeV). Based on the developed simple model for track accumulation process, the latent track radius of these light ions were assessed to be; 0.7 nm for proton, 1.1 nm for helium ion and 2.2 nm for carbon ion. The dependence of the track radius in nm on stopping power was found to be expressed by a following equation: rt=0.157(dE/dx)0.38, where dE/dx is in keV/?m. The normalized optical density of latent tracks to their range was found to be proportional to the stopping power. (author)

66

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.  

Science.gov (United States)

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (?(1)=905 nm) and visible (?(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm. PMID:22695673

Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

2012-06-10

67

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

68

FISM 2.0: Improved Spectral Range, Resolution, and Accuracy  

Science.gov (United States)

The Flare Irradiance Spectral Model (FISM) was first released in 2005 to provide accurate estimates of the solar VUV (0.1-190 nm) irradiance to the Space Weather community. This model was based on TIMED SEE as well as UARS and SORCE SOLSTICE measurements, and was the first model to include a 60 second temporal variation to estimate the variations due to solar flares. Along with flares, FISM also estimates the tradition solar cycle and solar rotational variations over months and decades back to 1947. This model has been highly successful in providing driving inputs to study the affect of solar irradiance variations on the Earth's ionosphere and thermosphere, lunar dust charging, as well as the Martian ionosphere. The second version of FISM, FISM2, is currently being updated to be based on the more accurate SDO/EVE data, which will provide much more accurate estimations in the 0.1-105 nm range, as well as extending the 'daily' model variation up to 300 nm based on the SOLSTICE measurements. with the spectral resolution of SDO/EVE along with SOLSTICE and the TIMED and SORCE XPS 'model' products, the entire range from 0.1-300 nm will also be available at 0.1 nm, allowing FISM2 to be improved a similar 0.1nm spectral bins. FISM also will have a TSI component that will estimate the total radiated energy during flares based on the few TSI flares observed to date. Presented here will be initial results of the FISM2 modeling efforts, as well as some challenges that will need to be overcome in order for FISM2 to accurately model the solar variations on time scales of seconds to decades.

Chamberlin, Phillip C.

2012-01-01

69

Attosecond broadband multilayer mirrors for the water window spectral range  

Science.gov (United States)

Recent advances in the development of attosecond soft X-ray sources ranging into the `water window' spectral range, between the carbon 1s and oxygen 1s states (284 eV - 543 eV), are also driving the development of suited broadband multilayer optics for attosecond beam steering and dispersion management. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of atomically smooth interfaces in broadband CrSc multilayer mirrors by an optimized ion beam deposition and assisted interface polishing process.

Guggenmos, A.; Radünz, S.; Rauhut, R.; Hofstetter, M.; Venkatesan, S.; Wochnik, A.; Scheu, C.; Gullikson, E.; Fischer, S.; Nickel, B.; Kleineberg, U.

2014-09-01

70

Experimental Demonstration of Non-Resonant Hyperlens in the Visible Range  

CERN Document Server

A metamaterial hyperlens offers a unique solution to overcome the diffraction limit by transforming evanescent waves responsible for imaging subwavelength features of an object into propagating waves. However, the first realizations of optical hyperlenses were limited by a narrow working bandwidth and significant resonance-induced loss. Here, we report the first experimental demonstration of a non-resonant waveguide-coupled hyperlens operating in the visible wavelength range. A detailed investigation of various materials systems proves that a radial fan-shaped configuration is superior to the concentric layer-based configuration in that it relies on non-resonant negative dielectric response, and, as a result, enables broadband and low-loss performance in the visible range.

Sun, Jingbo; Litchinitser, Natalia M

2014-01-01

71

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

72

A visibility matching tone reproduction operator for high dynamic range scenes  

Energy Technology Data Exchange (ETDEWEB)

The authors present a tone reproduction operator that preserves visibility in high dynamic range scenes. The method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. They compare the results to previous work and present examples the techniques applied to lighting simulation and electronic photography.

Larson, G.W. [Lawrence Berkeley National Lab., CA (United States); Rushmeier, H. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center; Piatko, C. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1997-01-15

73

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)

74

Visible and near-infrared spectral signatures for adulteration assessment of extra virgin olive oil  

Science.gov (United States)

Because of its high price, the extra virgin olive oil is frequently target for adulteration with lower quality oils. This paper presents an innovative optical technique capable of quantifying the adulteration of extra virgin olive oil caused by lowergrade olive oils. It relies on spectral fingerprinting the test liquid by means of diffuse-light absorption spectroscopy carried out by optical fiber technology in the wide 400-1700 nm spectral range. Then, a smart multivariate processing of spectroscopic data is applied for immediate prediction of adulterant concentration.

Mignani, A. G.; Ciaccheri, L.; Ottevaere, H.; Thienpont, H.; Conte, L.; Marega, M.; Cichelli, A.; Attilio, C.; Cimato, A.

2010-04-01

75

Micro- and nanophotonic structures in the visible and near infrared spectral region for optical devices  

Science.gov (United States)

In this paper we present some research results on the micro and nano-photonic structures in the visible and near infrared spectral region for optical devices that have been done within the framework of Nanoscience and Nanotechnology Program of Institute of Materials Science. In the first part, we report the design and fabrication of 1D photonic structure based on porous silicon layers fabricated by electrochemical etching method and some of their potential applications such as optical filters, microcavity and optical sensors for distinguishing the content of bio-gasoline. In addition, we demonstrate some results on preparation of the 2D and 3D nanophotonic structures based on silica opal layers prepared by sol–gel and self-assembled methods. In the second part, we demonstrate the results of lasing emissions of erbium ions in the visible and near infrared zone from microcavity. The observation of emission of single-mode green light at the wavelength of 537 nm from erbium ions in the microcavity is interesting for the study of atom–photon interaction phenomenon. In the last part, we will show some new results of design and fabrication of nanocomposite based on nanoscale TiO2 and/or ZnO and nanoparticles of semiconductors and metals, which are oriented to the fabrication of energy conversion and photo-reactor devices. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2012, 30 October–2 November, 2012, Ha Long, Vietnam.

Pham, Van Hoi; Bui, Huy; Van Nguyen, Thuy; Nguyen, The Anh; Son Pham, Thanh; Cam Hoang, Thi Hong; Ngo, Quang Minh

2013-06-01

76

Separate photosensitizers mediate degradation of the 32-kDa photosystem II reaction center protein in the visible and UV spectral regions  

International Nuclear Information System (INIS)

A component of the photosystem II reaction center, the 32-kDa protein, is rapidly turned over in the light. The mechanism of its light-dependent metabolism is largely unknown. We quantified the rate of 32-kDa protein degradation over a broad spectral range (UV, visible, and far red). The quantum yield for degradation was highest in the UVB (280-320 nm) region. Spectral evidence demonstrates two distinctly different photosensitizers for 32-kDa protein degradation. The data implicate the bulk photosynthetic pigments (primarily chlorophyll) in the visible and far red regions, and plastoquinone (in one or more of its redox states) in the UV region. A significant portion of 32-kDa protein degradation in sunlight is attributed to UVB irradiance

77

Design and fabrication of active spectral filter with metal-insulator-metal structure for visible light communication  

Science.gov (United States)

Visible light communication with LED is an important ICT for the ubiquitous network society. However visible light communication has the speed limit in the conventional blinking LED method. Therefore an active spectral filter would be useful in order to input information signals onto the LED spectrum. Plasmonic spectral filter based on a metalinsulator- metal (MIM) structure is one of the candidates of such active filter. We will explain our progress of fabrication of the MIM structures with the vacuum deposition technique and compare their absorption properties with the theoretical prediction.

Murai, Kensuke; Oshikane, Yasushi; Higashi, Takaya; Yamamoto, Fumihiko; Nakano, Motohiro; Inoue, Haruyuki

2013-02-01

78

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

79

Gravity-induced absorption changes in Phycomyces blakesleeanus during parabolic flights: first spectral approach in the visible.  

Science.gov (United States)

Gravity-induced absorption changes as experienced during a series of parabolas on the Airbus 300 Zero-G have been measured previously pointwise on the basis of dual-wavelength spectroscopy. Only the two wavelengths of 460 and 665 nm as generated by light-emitting diodes have been utilised during our first two parabolic-flight campaigns. In order to gain complete spectral information throughout the wavelength range from 400 to 900 nm, a miniaturized rapid scan spectrophotometer was designed. The difference of spectra taken at 0 g and 1.8 g presents the first gravity-induced absorption change spectrum measured on wild-type Phycomyces blakesleeanus sporangiophores, exhibiting a broad positive hump in the visible range and negative values in the near infrared with an isosbestic point near 735 nm. The control experiment performed with the stiff mutant A909 of Phycomyces blakesleeanus does not show this structure. These results are in agreement with those obtained with an array spectrophotometer. In analogy to the more thoroughly understood so-called light-induced absorption changes, we assume that gravity-induced absorption changes reflect redox changes of electron transport components such as flavins and cytochromes localised within the plasma membrane. PMID:17180493

Schmidt, Werner

2006-12-01

80

Scientometric analyses of the international visibility of German psychology researchers and their range of specialization  

Directory of Open Access Journals (Sweden)

Full Text Available With reference to the role of networking, accelerated by current developments within large parts of the scientific community, the assumption is examined that the range of specialization of scientists in terms of membership in professional sections of scientific societies is related to the international impact of their publications. The sample consists of 2,788 German psychologists enrolled in the German Psychological Society (Deutsche Gesellschaft für Psychologie, DGPs. A log-linear model suggests that the citation pattern of DGPs members with no citations of their papers published in 2000 or 2005 respectively in the time intervals 2000-2004 or 2005-2009 generally differs from that of their colleagues across four ranges of specialization categories. Configural Frequency Analysis led to the identification of distinct subgroups of scientific specialization and international visibility, i.e., citations by others. Specifically, for those individuals who enjoy international visibility, one key to success seems to be multiple professional specializations with reference to different subdisciplines of psychology.

Clemens B. Fell

2012-06-01

 
 
 
 
81

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

Science.gov (United States)

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.

Zhu, Jiang-Feng; Xu, Liang; Lin, Qing-Feng; Zhong, Xin; Han, Hai-Nian; Wei, Zhi-Yi

2013-05-01

82

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

83

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

84

Unattended real-time re-establishment of visibility in high dynamic range video and stills  

Science.gov (United States)

We describe a portable unattended persistent surveillance system that corrects for harsh illumination conditions, where bright sun light creates mixed contrast effects, i.e., heavy shadows and washouts. These effects result in high dynamic range scenes, where illuminance can vary from few luxes to a 6 figure value. When using regular monitors and cameras, such wide span of illuminations can only be visualized if the actual range of values is compressed, leading to the creation of saturated and/or dark noisy areas and a loss of information in these areas. Images containing extreme mixed contrast cannot be fully enhanced from a single exposure, simply because all information is not present in the original data. The active intervention in the acquisition process is required. A software package, capable of integrating multiple types of COTS and custom cameras, ranging from Unmanned Aerial Systems (UAS) data links to digital single-lens reflex cameras (DSLR), is described. Hardware and software are integrated via a novel smart data acquisition algorithm, which communicates to the camera the parameters that would maximize information content in the final processed scene. A fusion mechanism is then applied to the smartly acquired data, resulting in an enhanced scene where information in both dark and bright areas is revealed. Multi-threading and parallel processing are exploited to produce automatic real time full motion corrected video. A novel enhancement algorithm was also devised to process data from legacy and non-controllable cameras. The software accepts and processes pre-recorded sequences and stills, enhances visible, night vision, and Infrared data, and successfully applies to night time and dark scenes. Various user options are available, integrating custom functionalities of the application into intuitive and easy to use graphical interfaces. The ensuing increase in visibility in surveillance video and intelligence imagery will expand the performance and timely decision making of the human analyst, as well as that of unmanned systems performing automatic data exploitation, such as target detection and identification.

Abidi, B.

2014-05-01

85

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

86

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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 respectively 99.89% for healthy, and 93.7% for infected.

Tsvetelina Draganova

2010-08-01

87

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

88

Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD  

Energy Technology Data Exchange (ETDEWEB)

Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO{sub 2} thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters.

Justicia, I. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Garcia, G. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain)]. E-mail: gemma@icmab.es; Battiston, G.A. [ICIS/CNR, Corso Stati Uniti 4, 35127 Padova (Italy); Gerbasi, R. [ICIS/CNR, Corso Stati Uniti 4, 35127 Padova (Italy); Ager, F. [CNA/CSIC Parque Tecnologico Cartuja 93, Avda Thomas A, Edison, 41092 Sevilla (Spain); Guerra, M. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Caixach, J. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Pardo, J.A. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Rivera, J. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Figueras, A. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Instituto de Fisica, UNAM, Campus UNAM Juriquilla, 76230 Queretaro (Mexico)

2005-08-25

89

Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD  

International Nuclear Information System (INIS)

Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO2 thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters

90

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

91

Near-Infrared to Visible Spectral Lines of Cold H_3^+  

Science.gov (United States)

The triatomic hydrogen ion H_3^+ is the cornerstone of interstellar chemistry. It's properties and reactional behavior at cold temperatures can give important insight in amongst other isotopic fractionation and pathways to the production of larger molecules. As simplest polyatomic molecule, it is also a pivot theoretical benchmark molecule. Especially the highly excited region of H_3^+ is an important benchmark towards a treatment for strongly distorted molecular symmetries and non-adiabatic interactions. We have investigated the H_3^+ ion in a cryogenic 22-pole ion trap using chemical probing spectroscopy with argon. The H_3^+ ions are buffer-gas cooled by Helium to interstellar temperatures populating only the lowest three rotational levels {J,G}=(1,1) and (2,2) of para symmetry and (1,0) of ortho symmetry. The level populations may be changed by the set trap temperature or by manipulating the ortho-to-para ratio with the use of para-H_2 parent gas. As the reaction with argon is endothermic, only the laser excited H_3^+ will react and form ArH^+ which is used as highly sensitive spectroscopic signal. We have measured near-infrared to visible spectral lines of H_3^+ giving, as a first, transition frequencies and probabilities for transitions that are up to 10^6 times weaker than the fundamental transition. Energy levels up to 17000 cm-1 were determined, leading to a correction improving predictions to spectroscopic accuracy in this region. Moreover, our measurements agree well with the expected intensities of the bulk states. The strong intensities predicted for excitation to highly excited bending states, called Horseshoe states, however, are surprisingly not found. Further investigation, both in theory and in experiment, is required. Our spectroscopy technique has not yet reached its sensitivity limit, paving the way to the investigation of forbidden infrared lines and of excitation closer to and beyond the dissociation limit.

Petrignani, A.; Berg, M.; Bing, D.; Grussie, F.; Wolf, A.

2011-05-01

92

Ultra low-loss hypocycloid-core Kagome hollow-core photonic crystal fiber for green spectral-range applications.  

Science.gov (United States)

We report on the development of a hypocycloidal-core Kagome hollow-core photonic crystal fiber guiding, with low transmission loss in the 450-650 nm visible spectral range. Transmission loss records have been achieved with 70??dB/km at 600 nm, and 130??dB/km at 532 nm. As a demonstration of the fiber potential applications, we report on a compact 600 THz wide Raman comb generator, centered around 532 nm, and on a 10 W average power frequency-doubled Yb-fiber picosecond laser beam delivery, along with its use for organic material laser micro-processing. PMID:25361325

Debord, B; Alharbi, M; Benoît, A; Ghosh, D; Dontabactouny, M; Vincetti, L; Blondy, J-M; Gérôme, F; Benabid, F

2014-11-01

93

Extending the spectral range of CdSe/ZnSe quantum wells by strain engineering  

Science.gov (United States)

We demonstrate efficient room-temperature photoluminescence and spectral tuning of epitaxially grown ZnSe/CdSe quantum well structures almost over the whole visible spectrum (470-600 nm wavelength). The key element to achieve the observed high quantum efficiency and enormous tuning range was the implementation of a special strain engineering technique, which allows us to suppress substantial lattice relaxation of CdSe on ZnSe. Previous studies indicated that a CdSe coverage exceeding 3 ML on ZnSe results in the formation of extensive lattice defects and complete quenching of the photoluminescence at low and room temperature. In contrast, our approach of strain engineering enables the deposition of planar CdSe quantum wells with a thickness ranging from 1 to 6 ML with excellent optical properties. We attribute the observed experimental features to a controllable strain compensation effect that is present in an alternating system of tensile and compressively strained epitaxial layers and supported this model by calculations of the transition energies of the ZnSe/CdSe quantum wells.

Finke, A.; Ruth, M.; Scholz, S.; Ludwig, A.; Wieck, A. D.; Reuter, D.; Pawlis, A.

2015-01-01

94

Single-order operation of lamellar multilayer gratings in the soft x-ray spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We demonstrate single-order operation of Lamellar Multilayer Gratings in the soft x-ray spectral range. The spectral resolution was found to be 3.8 times higher than from an unpatterned multilayer mirror, while there were no significant spectral sideband structures adjacent to the main Bragg peak. The measured spectral bandwidths and peak reflectivities were in good agreement with our theoretical calculations.

Robert van der Meer; Igor Kozhevnikov; Balachander Krishnan; Jurriaan Huskens; Petra Hegeman; Christian Brons; Boris Vratzov; Bert Bastiaens; Klaus Boller; Fred Bijkerk

2013-01-01

95

Single-order operation of lamellar multilayer gratings in the soft x-ray spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available We demonstrate single-order operation of Lamellar Multilayer Gratings in the soft x-ray spectral range. The spectral resolution was found to be 3.8 times higher than from an unpatterned multilayer mirror, while there were no significant spectral sideband structures adjacent to the main Bragg peak. The measured spectral bandwidths and peak reflectivities were in good agreement with our theoretical calculations.

Robert van der Meer

2013-01-01

96

Measurements of ZEFF spatial profiles from bremsstrahlung emission in the visible and near infrared spectral region  

International Nuclear Information System (INIS)

Measurement of plasma radiation (i.e., breusstrahlung) in the infrared (IR) range (?=933, 978 nm), at six lines of sight from z=-20 cm to z=8 cm above the equatorial plane, using the detection system of the Frascati Tokamak Upgrade (FTU) Thomson scattering system (TSS) are reported. The agreement of IR with visible (?=540 nm) bremsstrahlung intensity S, [S=photons/(m2srnms)] measurements is within 20%endash 30% and depends upon the absolute calibration of both systems. The intensity is equal S(z)=left-angle ZeffGn2/Te1/2 right-angle, where left-angle · right-angle means average on a line of sight. For determining the Zeff the Gaunt factor(G) is needed, and analysis the Born endash Elwert formula is used. The Zeff spatial profiles (i.e., Zeff(r)), are determined using the plasma temperature (Te) and density (ne) measured by the TSS and the Abel inverted intensity profiles, determined using the plasma radiation S(z) measured from six horizontal chords. Zeff(r) behavior in a variety of FTU discharges is presented. copyright 1997 American Institute of Physics

97

Quantitative analysis of the UV-visible spectral profile of hemoglobin after exposure to microwave radiation  

International Nuclear Information System (INIS)

Adult male albino mice were exposed to 950 MHz continuous microwave field 2 h/ day, 3 days/week for total period of two weeks. The selected power density range was 0.25 mW/ cm2 equivalent to specific absorption rate (SAR) 0.1 W/ kg body wt. The effects of microwave radiation on the conformation of the hemoglobin were investigated through analysis of the UV-visible absorption spectrum. The following parameters were calculated: maximum and total molar absorption coefficient, total absorption cross-section, dipole strength, transition dipole moment, dipole length and oscillator strength. The recorded hemoglobin spectrum of the exposed group showed significant increase in the maximum and integrated absorption coefficient of all characteristic peaks compared to the control group. The Sort and Qo bands, exhibited significant increase in all calculated parameters. The obtained results showed that the exposure to microwave fields could affect the conformation of the hemoglobin molecule through re-orientation of the molecular dipole moments

98

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

99

Practical Atmospheric Correction Algorithms for a Multi-Spectral Sensor From the Visible Through the Thermal Spectral Regions  

Energy Technology Data Exchange (ETDEWEB)

Deriving information about the Earth's surface requires atmospheric corrections of the measured top-of-the-atmosphere radiances. One possible path is to use atmospheric radiative transfer codes to predict how the radiance leaving the ground is affected by the scattering and attenuation. In practice the atmosphere is usually not well known and thus it is necessary to use more practical methods. The authors will describe how to find dark surfaces, estimate the atmospheric optical depth, estimate path radiance and identify thick clouds using thresholds on reflectance and NDVI and columnar water vapor. The authors describe a simple method to correct a visible channel contaminated by a thin cirrus clouds.

Borel, C.C.; Villeneuve, P.V.; Clodium, W.B.; Szymenski, J.J.; Davis, A.B.

1999-04-04

100

On-line measurement of soil properties without direct spectral response in near infrared spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

So far, the majority of reports on on-line measurement considered soil properties with direct spectral responses in near infrared spectroscopy (NIRS). This work reports on the results of on-line measurement of soil properties with indirect spectral responses, e.g. pH, cation exchange capacity (CEC), exchangeable calcium (Ca-ex) and exchangeable magnesium (Mg-ex) in one field in Bedfordshire in the UK. The on-line sensor consisted of a subsoiler coupled with an AgroSpec mobile, fibre type, vis...

Mari?n Gonza?lez, Omar; Kuang, Boyan; Quraishi, Mohammed Z.; Mun?oz-garci?a, Miguel Angel; Mouazen, Abdul Mounem

2013-01-01

 
 
 
 
101

Effective medium model for the spectral properties of nanoporous gold in the visible  

Science.gov (United States)

The spectral properties of nanoporous gold are distinguished by two peaks in the transmission spectrum. Unlike earlier works, we do not attribute the peaks in the transmission to two separate localized plasmon resonances. Instead we show that the spectral shape can be understood as that of diluted gold with a spectrally narrow dip in transmission that arises from the averaged electric field approaching zero. Thus, the transmission characteristics are rather featured by a dip in one broad transmission curve than by two distinct peaks. Nanoporous gold is approximated by the effective medium model of a cubic grid of gold wires.

Jalas, D.; Canchi, R.; Petrov, A. Yu.; Lang, S.; Shao, L.; Weissmüller, J.; Eich, M.

2014-12-01

102

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

103

Rare earth ions doped chalco-halide glasses and glass ceramics for luminescence in the visible range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present work deals with the study of new chalco halide glass-ceramics doped with rare earth ions for visible luminescence. The effect of the addition of different alkali-halide into glasses belonging to the Ga2S3-GeS2 system has been studied with the aim to extend their transparency into the ultraviolet region. Glasses transparent over the visible range (400-750 nm) up to the mid infrared (11,5 ?m) have been obtained in the Ga2S3-GeS2-CsCl system. Transparent and homogeneous glass-cerami...

Ledemi, Yannick

2008-01-01

104

First Experiences Using Small Unmanned Aerial Vehicles for Volcano Observation in the Visible Range  

Science.gov (United States)

Many of the most active volcanoes in the world are located in Middle and South America. While permanently installed sensors for seismicity give reliable supervision of volcanic activities, they lack the possibility to determine occurrence and extent of surface activities. Both from the point of science and civil protection, visible documentation of activities is of great interest. While satellites and manned aircraft already offer many possibilities, they also have disadvantages like delayed or poor image data availability or high costs. The Institute of Aerospace Systems of the Technical University of Braunschweig, in collaboration with the spin-off company Mavionics, developed a family of extremely small and lightweight Unmanned Aerial Vehicles (UAV), with the smallest aircraft weighting only 550~g (19~ounces) at a wing span of 50 cm (20~inch). These aircraft are operating completely automatically, controlled by a highly miniaturized autopilot system. Flight mission is defined by a list of GPS waypoints using a conventional notebook. While in radio range, current position and status of the aircraft is displayed on the notebook and waypoints can easily be changed by the user. However, when radio connection is not available, the aircraft operates on its on, completing the flight mission automatically. This greatly increases the operating range of the system. Especially for the purpose of volcano observation in South America, the aircraft Carolo~P330 was developed, weighting 5~kg (11~pounds) at a wing span of 3.3~m ( 11~ft). The whole system can be easily carried by car and the electric propulsion system avoids handling of flammable liquids. The batteries can be recharged in the field. Carolo~P330 has an endurance of up to 90~minutes at a flight speed of 25~m/s, giving it a maximum range of 67 km (41~miles). It was especially designed to operate under harsh conditions. The payload is a digital still camera, which delivers aerial images with a resolution of up to 8~megapixel. On a field campaign in 2005, the performance of the system was evaluated at the two active Ecuadorian volcanoes Cotopaxi and El~Reventador. After hand-launch at Mt. Cotopaxi, the autopilot brought the aircraft up to 7,000~m above sea level (starting from a plateau on 4,500~m a.s.l.), with temperatures around the freezing point. At El~Reventador active lava flows were documented in the tropical montane rain forest. Since the position and attitude of the aircraft is recorded within the autopilot system, the single aerial images can be referenced automatically after the flight to form a mosaic of images. The whole processing chain from mission planning to image mosaic takes less than half a day. Besides the technical details of this cost-effective remote sensing system, the results of the measurement campaign in 2005 will be presented. An outlook will discuss the installation of other payload for thermal imaging or air sampling.

Buschmann, M.; Krüger, L.; Bange, J.

2007-05-01

105

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

106

The Relation Between the Spectral Synthesis of Galaxies in the Visible Region and Their UV Emission  

Science.gov (United States)

The STARLIGHT Project has analyzed almost a million spectra extracted from the Sloan Digital Sky Survey (SDSS) by using the empirical spectral synthesis approach described by Cid Fernandes et al.(2005). Spectral synthesis consists on the optical spectrum fitting by using simple stellar population libraries, such as Bruzual & Charlot (2003). It also considers the reddening caused by dust and the velocity dispersion due to the motion of the stars within the galaxy. Since the model that best fits the optical region can also be extended to the ultraviolet, we compare our predictions to the UV photometry of the same galaxies measured by the GALEX satellite, studying the systematics and nature of the differences. In this current presentation, we show the upcoming challenges in order to accomplish this investigation. The main motivation of this study is to obtain realistic spectral models from the UV to the optical regions for the study of high redshift galaxies.

Dantas, M. L.; Sodré, L., Jr.

2014-10-01

107

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.

108

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

109

Spectral and radiometric calibration of the Airborne Visible/Infrared Imaging Spectrometer  

International Nuclear Information System (INIS)

The laboratory spectral and radiometric calibration of the AVIRIS science data collected since 1987 is described. The instrumentation and procedures used in the calibration are discussed and the accuracy achieved in the laboratory as determined by measurement and calculation is compared with the requirements. Instrument performance factors affecting radiometry are described. The paper concludes with a discussion of future plans. 9 references

110

An improved digital global map of spectral parameters of Vesta from the Visible and Infrared mapping Spectrometer onboard Dawn  

Science.gov (United States)

The NASA/Dawn discovery mission has been designed to study in detail two of the largest proto-planets of the asteroid belt: Vesta and Ceres. From July 2011 to September 2012, Dawn has been orbiting around Vesta and the instruments have returned scientific data from three different orbital altitudes: the survey, the high altitude, and the low altitude mapping orbits. From these orbits, Dawn's Visible and Infrared mapping Spectrometer (VIR) acquired infrared and visible spectra from 0.2 to 5 microns, sampled in 864 channels with a spatial resolution reaching about 150 m/pixel. VIR spectra of Vesta have been analyzed to derive spectral parameters, which synthesize specific characteristics of the single spectra and are diagnostic of the mineralogical composition and the physical state of the portion of surface being observed. In particular, we focus on spectral parameters related to the 1.0- and 2.0-micron bands (band I and band II) typical of pyroxenes. In general, a shift in band center suggests a change in composition while the change in band depths are diagnostic of a change in the physical state of the material. Combined analysis of spectral parameters leads towards specific studies, as for example the detection of a specific mineral assemblage. Since the acquisition of first VIR data, we have worked in gathering into maps the spectral parameters extracted from every single spectrum, resulting in a global view of the mineralogical diversity of the surface of Vesta. The maps are being produced in the same projection as the camera mosaics, enabling to observe and analyze the spatial correlation between mineralogy and morphology. Here we present the global maps of spectral parameters of Vesta, improved from the previously presented ones. Filtering has been applied to input data, on the base of experience acquired during the mission. The resulting maps are more consistent, and the coverage has not been affected (practically) by the filtering process applied. The digital maps are being produced in several digital formats, allowing both the spectroscopists and non-spectroscopists to work on the same data using the software tools they are more familiar with. In particular, among other formats, the digital maps are produced in a Geographic Information System (GIS) -compatible digital format, so they can be used together with other digital maps as image mosaics, topography and geologic maps, introducing interesting perspectives for the scientific investigation of the proto-planet Vesta.

Frigeri, A.; De Sanctis, M.; Ammannito, E.; Tosi, F.; Capaccioni, F.; Capria, M.; Zambon, F.; Palomba, E.; Longobardo, A.; Fonte, S.; Giardino, M.; Magni, G.; Jaumann, R.; Raymond, C.; Russell, C.

2014-07-01

111

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

112

Spectral characteristics of autofluorescence and second harmonic generation from ex vivo human skin induced by femtosecond laser and visible lasers.  

Science.gov (United States)

The spectral properties of one-photon, two-photon excited autofluorescence and second harmonic generation (SHG) from ex vivo human skin induced by a femtosecond (fs) laser and three visible lasers in backscattering geometry are systematically investigated. Our experimental results indicate that peak position of autofluorescence spectra from the dermis and epidermis shift toward long wavelengths, and the fluorescent intensity decreases when the excitation wavelength increases due to an effect of the excitation wavelength on autofluorescence signals. However, the intensity of the SHG signal in collagen has the maximal value of 800 nm excitation wavelength. This may be the result that the energy of the SHG signal is in resonance with an electronic absorption band. The two-photon excited autofluorescence and SHG intensity all obey a quadratical dependence on the excitation power. Compared with the two-photon excited fluorescence and SHG, the one-photon excited fluorescence in the dermis and epidermis exhibits different spectral characteristics. The investigation of the spectral characteristics of autofluorescence and SHG from ex vivo human skin can provide new insights into morphologic structures and biochemical components of tissues, which are vital for improving the application of laser-induced autofluorescence and SHG spectroscopy technique for noninvasive in vivo tissue diagnostics. PMID:17181133

Chen, Jianxin; Zhuo, Shuangmu; Luo, Tianshu; Jiang, Xingshan; Zhao, Jingjun

2006-01-01

113

Multi range spectral feature fitting for hyperspectral imagery in extracting oilseed rape planting area  

Science.gov (United States)

Spectral feature fitting (SFF) is a commonly used strategy for hyperspectral imagery analysis to discriminate ground targets. Compared to other image analysis techniques, SFF does not secure higher accuracy in extracting image information in all circumstances. Multi range spectral feature fitting (MRSFF) from ENVI software allows user to focus on those interesting spectral features to yield better performance. Thus spectral wavelength ranges and their corresponding weights must be determined. The purpose of this article is to demonstrate the performance of MRSFF in oilseed rape planting area extraction. A practical method for defining the weighted values, the variance coefficient weight method, was proposed to set up criterion. Oilseed rape field canopy spectra from the whole growth stage were collected prior to investigating its phenological varieties; oilseed rape endmember spectra were extracted from the Hyperion image as identifying samples to be used in analyzing the oilseed rape field. Wavelength range divisions were determined by the difference between field-measured spectra and image spectra, and image spectral variance coefficient weights for each wavelength range were calculated corresponding to field-measured spectra from the closest date. By using MRSFF, wavelength ranges were classified to characterize the target's spectral features without compromising spectral profile's entirety. The analysis was substantially successful in extracting oilseed rape planting areas (RMSE ? 0.06), and the RMSE histogram indicated a superior result compared to a conventional SFF. Accuracy assessment was based on the mapping result compared with spectral angle mapping (SAM) and the normalized difference vegetation index (NDVI). The MRSFF yielded a robust, convincible result and, therefore, may further the use of hyperspectral imagery in precision agriculture.

Pan, Zhuokun; Huang, Jingfeng; Wang, Fumin

2013-12-01

114

Thin chalcogenide capillaries as efficient waveguides in the mid-IR - THz spectral range  

CERN Document Server

We present chalcogenide glass As2Se3 capillaries as efficient waveguides in the mid-IR and THz spectral ranges. The capillaries are fabricated using a double crucible glass drawing technique. The wall thickness of the glass capillary is properly designed and controlled during drawing, and we are able to produce capillaries with different wall thickness, starting from 12 \\mum and up to 130 \\mum. Such capillaries show low loss properties in the whole target wavelength region. In the mid-IR range guidance is governed by Fresnel reflection and antiguidance mechanisms (ARROWs), while in the THz spectral range thin walls capillaries guide via total internal reflection.

Mazhorova, Anna; Ung, Bora; Rozé, Mathieu; Gorgutsa, Stepan; Skorobogatiy, Maksim

2011-01-01

115

Optical properties of mucous membrane in the spectral range 350-2000 nm  

Science.gov (United States)

The optical characteristics of the mucous membrane from the human maxillary sinus are studied experimentally. The experiments were carried out in vitro in the spectral range 350-2000 nm. On the basis of the measured total transmittance and diffuse reflectance spectra, the absorption and transport scattering coefficients are calculated in the entire range in terms of the inverse adding-doubling method.

Bashkatov, A. N.; Genina, É. A.; Kochubey, V. I.; Tuchin, V. V.; Chikina, E. É.; Knyazev, A. B.; Mareev, O. V.

2004-12-01

116

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

117

Design of an artificial three-dimensional composite metamaterial with magnetic resonances in the visible range of the electromagnetic spectrum.  

Science.gov (United States)

We propose an artificial three-dimensional material that exhibits a strong resonance in the effective permeability in the visible spectral domain. This material may be implemented in a two-step procedure. First, a metamaterial made of densely packed metallic nanoparticles is fabricated that shows a Lorentz-type resonance in the permittivity at the collective plasmon frequency. Second, spheres are formed out of this material and arranged in a cubic lattice. This meta-metamaterial exhibits a strong resonance in the permeability which is caused by a Mie resonance associated with the magnetic mode of a single metamaterial sphere. Realization of this material based on self-organization in liquid crystals and the limitations of the approach are discussed. PMID:17678187

Rockstuhl, Carsten; Lederer, Falk; Etrich, Christoph; Pertsch, Thomas; Scharf, Toralf

2007-07-01

118

Measurement of transition probabilities in Kr II UV and visible spectral lines  

International Nuclear Information System (INIS)

This work reports an extensive collection of 120 atomic transition probabilities of Kr II lines in the spectral region 350-720 nm, all of them measured in an emission experiment. For many of them, these are the first data up to the authors' knowledge. Relative intensity measurements have been obtained on a pulsed discharge lamp and the absolute Aki-values have been calculated by considering the available data from the literature as reference for the plasma temperature diagnosis. Excitation temperature (14 000-28 000 K) has been determined by using the Boltzmann-plot method. The plasma electron density (0.2-0.8 x 1023 m-3) has been determined by two-wavelength interferometry. This work extends a previous one already published by our laboratory [1, 2]. Comparisons have also been made with previous literature values

119

Method And Apparatus For Examining A Tissue Using The Spectral Wing Emission Therefrom Induced By Visible To Infrared Photoexcitation.  

Science.gov (United States)

Method and an apparatus for examining a tissue using the spectral wing emission therefrom induced by visible to infrared photoexcitation. In one aspect, the method is used to characterize the condition of a tissue sample and comprises the steps of (a) photoexciting the tissue sample with substantially monochromatic light having a wavelength of at least 600 nm; and (b) using the resultant far red and near infrared spectral wing emission (SW) emitted from the tissue sample to characterize the condition of the tissue sample. In one embodiment, the substantially monochromatic photoexciting light is a continuous beam of light, and the resultant steady-state far red and near infrared SW emission from the tissue sample is used to characterize the condition of the tissue sample. In another embodiment, the substantially monochromatic photoexciting light is a light pulse, and the resultant time-resolved far red and near infrared SW emission emitted from the tissue sample is used to characterize the condition of the tissue sample. In still another embodiment, the substantially monochromatic photoexciting light is a polarized light pulse, and the parallel and perpendicular components of the resultant polarized time-resolved SW emission emitted from the tissue sample are used to characterize the condition of the tissue sample.

Alfano, Robert R. (3777 Independence Ave., Bronx, NY 10463); Demos, Stavros G. (3550 Pacific Ave., Apt. 304, Livermore, CA 94550); Zhang, Gang (3 Rieder Rd., Edison, NJ 08817)

2003-12-16

120

Light field camera as a Fourier transform spectrometer sensor: instrument characterization and passive spectral ranging.  

Science.gov (United States)

This paper presents a concept using field cameras in combination with Fourier transform spectrometers. The device can produce five-dimensional (position-angle-spectra) data cubes. This can lead to accurate measurements in both spectrum and distance and allows a thorough characterization of the interferometer, as well as adds passive ranging information to hyperspectral images. Shear and tilt fringes are simultaneously observed in a fixed optical path difference interferometer, and a passive spectral ranging demonstration is done in both absorption and emission for the 500-900 nm spectral bands. PMID:25089997

Côté, Alex; Levasseur, Simon; Boudreau, Sylvain; Genest, Jérôme

2014-07-01

 
 
 
 
121

Spectral Characteristics of Tropical Anvils Obtained by Combining TRMM Precipitation Radar with Visible and Infrared Scanner Data  

Science.gov (United States)

The spectral characteristics of anvils in tropical areas (25°S-25°N) have been investigated on the basis of data from the tropical rainfall measuring mission's (TRMM) precipitation radar (PR) and a visible and infrared scanner (VIRS), from 1998 to 2007. The anvils' vertical structures were captured by TRMM PR and categorized into two subtypes: ice anvils with an echo base of ?6 km and mixed anvils with an echo base between 3 and 6 km. Visible and infrared signals for the anvils, which are from reflectance at 0.63 and 1.6 ?m (hereafter referred to as RF1 and RF2, respectively) and the equivalent brightness temperatures of a black body at 3.7, 10.8, and 12.0 ?m (hereafter referred to as TB3, TB4, and TB5, respectively), were derived simultaneously by use of TRMM VIRS. The findings reveal that the normalized frequency distribution (i.e., probability density functions, PDF) of anvil tops and bases have a bimodal distribution whereas that of anvil thickness has a single-peak curve. For visible signals, the PDF distribution of RF1 (RF2) for anvils, mixed anvils, and ice anvils has an approximately symmetric distribution with a tropics-wide averages of 0.74, 072, and 0.80 (0.21, 0.21, and 0.20), respectively. It can be concluded that ice anvils are optically thicker and contain many more ice-cloud droplets at the cloud top than mixed anvils. RF1 of anvils is usually lower over land than over ocean, by ~0.1, whereas RF2 of anvils is usually higher over land than over ocean, by ~0.3. This implies that anvil clouds have thinner optical depth and their cloud tops consist of many more small ice droplets over land than over ocean. For infrared signals, TB4 is regarded as a representative channel. The PDF distribution of TB4 for anvils and mixed anvils is broad, with tropics-wide averages of 229.2 and 232 K, respectively. They contain two peaks and the secondary peak lies at a much lower value. For ice anvils, the PDF distribution of TB4 is a single-peak curve with a tropics-wide average of 219.5 K. Mean TB4 of anvils, mixed anvils, and ice anvils is usually lower over land than over ocean, by ~3.6 K, ~1.6 K, and 5 K, respectively. In addition, land-ocean differences between RF1-to-RF2 reflectance ratios are more obvious than those between TB4 and TB5 brightness temperatures. Furthermore, these spectral signals have been proved to be a potentially useful way of revealing the presence of anvils over land and ocean, and especially for separating anvils into the mixed and ice subtypes. Finally, long-term mean values reveal that the spectral signals of anvils and of stratiform and convective precipitating clouds are indeed different, and that the difference varies with different geographical location. In real time, however, uncertainty still exists when only spectral signals are used to discriminate anvils from stratiform and convective precipitating clouds, which means active satellite observations are indispensable.

Yang, Yuan-Jian; Lu, Da-Ren; Fu, Yun-Fei; Chen, Feng-Jiao; Wang, Yu

2014-12-01

122

Integration of visible-through microwave-range multispectral image data sets for geologic mapping  

Science.gov (United States)

Multispectral remote sensing data sets collected during the Geologic Remote Sensing Field Experiment (GRSFE) conducted during 1989 in the southwestern U.S. were used to produce thematic image maps showing details of the surface geology. LANDSAT TM (Thematic Mapper) images were used to map the distribution of clays, carbonates, and iron oxides. AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) data were used to identify and map calcite, dolomite, sericite, hematite, and geothite, including mixtures. TIMS (Thermal Infrared Multispectral Scanner) data were used to map the distribution of igneous rock phases and carbonates based on their silica contents. AIRSAR (Airborne Synthetic Aperture Radar) data were used to map surface textures related to the scale of surface roughness. The AIRSAR also allowed identification of previously unmapped fault segments and structural control of lithology and minerology. Because all of the above data sets were geographically referenced, combination of different data types and direct comparison of the results with conventional field and laboratory data sets allowed improved geologic mapping of the test site.

Kruse, Fred A.; Dietz, John B.

1991-01-01

123

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

124

Room temperature photoluminescence in the visible range from silicon nanowires grown by a solid-state reaction  

International Nuclear Information System (INIS)

The solid-liquid-solid method (also known as the solid-state method) is used to produce silicon nanowires at the core of silica nanowires with a support catalyst layer structure of nickel and titanium layers sputtered on oxide-coated silicon wafers. This silane-free process is low cost and large-area compatible. Using electron microscopy and Raman spectroscopy we deduce that the wires have crystalline silicon cores. The nanowires show photoluminescence in the visible range (orange), and we investigate the origin of this band. We further show that the nanowires form a random mesh that acts as an efficient optical trap, giving rise to an optically absorbing medium.

125

Multiterawatt femtosecond hybrid system based on a photodissociation XeF(C-A) amplifier in the visible range  

International Nuclear Information System (INIS)

This paper describes a multiterawatt hybrid laser system based on a Ti : sapphire front end and 25-cm-aperture photodissociation XeF(C - A) amplifier. The front end generates 50-fs pulses with second-harmonic (? = 475 nm) energies of up to 5 mJ. The gainmedium of the amplifier is produced in a XeF2 - N2 mixture by VUV radiation excited in xenon by a high-power electron beam. Through amplification of a negatively chirped 1-ps pulse, followed by pulse compression in bulk fused silica, a peak power of 14 TW, record-high for the visible range, has been achieved.

126

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

Energy Technology Data Exchange (ETDEWEB)

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., E-mail: ali.soltani@iemn.univ-lille1.fr; Stolz, A.; Gerbedoen, J.-C.; Rousseau, M.; Bourzgui, N.; De Jaeger, J.-C. [Institut d' Électronique, Microélectronique et Nanotechnologie, UMR-CNRS 8520, PRES Université Lille Nord de France, Cité Scientifique, Avenue Poincaré, CS 60069, 59652 Villeneuve d' Ascq Cedex (France); Charrier, J. [Fonctions Optiques pour les Technologies de l' informatiON, UMR-CNRS 6082, ENSSAT 6, rue de Kerampont, CS 80518, 22305 Lannion Cedex (France); Mattalah, M. [Laboratoire de Microélectronique, Université Djilali Liabes, 22000 Sidi Bel Abbes (Algeria); Barkad, H. A. [Institut Universitaire Technologique Industriel, Université de Djibouti, Avenue Georges Clémenceau, BP 1904 Djibouti (Djibouti); Mortet, V. [Institute of Physics of Academy of Sciences of Czech Republic, Fyzikální ústav AV CR, v.v.i., Na Slovance 1999/2 (Czech Republic); BenMoussa, A. [Solar Terrestrial Center of Excellence, Royal Observatory of Belgium, Circular 3, B-1180 Brussels (Belgium)

2014-04-28

127

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

128

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

International Nuclear Information System (INIS)

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

129

Optical properties of human colon tissues in the 350 – 2500 nm spectral range  

Science.gov (United States)

We present the optical characteristics of the mucosa and submucosa of human colon tissue. The experiments are performed in vitro using a LAMBDA 950 spectrophotometer in the 350 – 2500 nm spectral range. The absorption and scattering coefficients and the scattering anisotropy factor are calculated based on the measured diffuse reflectance and total and collimated transmittance spectra using the inverse Monte Carlo method.

Bashkatov, A. N.; Genina, E. A.; Kochubey, V. I.; Rubtsov, V. S.; Kolesnikova, E. A.; Tuchin, V. V.

2014-08-01

130

Modal spectral analysis of piping: Determination of the significant frequency range  

International Nuclear Information System (INIS)

This paper investigates the influence of the number of modes on the response of a piping system in a dynamic modal spectral analysis. It shows how the analysis can be limited to a specific frequency range of the pipe (independent of the frequency range of the response spectrum), allowing cost reduction without loss in accuracy. The 'missing mass' is taken into account through an original technique. (orig./HP)

131

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 average 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.

132

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

Science.gov (United States)

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. Polymethylmethacrylate (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 µm 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, D.; Perozziello, G.; Klank, H.; Geschke, O.; Kutter, J. P.

2006-02-01

133

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

134

Natural variability of bio-optical properties in Case 1 waters: attenuation and reflectance within the visible and near-UV spectral domains, as observed in South Pacific and Mediterranean waters  

Directory of Open Access Journals (Sweden)

Full Text Available The optical properties of Case 1 waters have been empirically related to the chlorophyll concentration, [Chl], historically used as an index of the trophic state and of the abundance of the biological materials. The well-known natural variability around the mean statistical relationships is here examined by comparing the apparent optical properties (spectral downward irradiance attenuation and reflectance as a function of [Chl] in two Case 1 environments, the Pacific and Mediterranean waters. These oceanic zones apparently represent two extremes of the possible bio-optical variability range around the mean. The systematic deviations, in both directions with respect to the average laws, mainly result from the differing contents in non-algal detrital materials and dissolved colored substance for a given [Chl] level. These contents are higher than the average in the Mediterranean Sea, and lower in the Pacific Ocean, respectively. These divergences between the two water bodies, detectable in the visible spectral domain, are considerably accentuated in the UV domain. The bio-optical properties in this spectral domain (310–400 nm are systematically explored. They are more varying for a given [Chl] than those in the visible domain. Their prediction based on the sole [Chl] index is thus problematic, although it is probably possible on a regional scale if reliable field data are available. It does not seem, however, that ubiquitous relationships exist for this spectral domain for all Case 1 waters at global scale.

A. Morel

2007-10-01

135

Spectral characteristics of precipitating electrons associated with visible aurora in the premidnight oval during periods of substorm activity  

International Nuclear Information System (INIS)

Three late evening passes of the DMSP/F2 satellite over the northern auroral zone have been studied using simultaneous visible emissions and measurements from a zenith-looking, 16-channel, electron spectrometer. All three orbits occurred during periods of substorm activity; the second and third passes were consecutive. The auroral oval is conveniently divided into three latitudinal segments: a most pole-ward bright arc: a region of structured inverted-V precipitation; and the diffuse auroral region. The most poleward bright arc is characterized by directional fluxes occasionally in excess of 1010 (cm2s sr)-1 carried by two populations with temperatures of approx.100 eV and approx.600 eV. These fluxes, which apparently continue well into substorm recovery, are not easily reconciled with a simple model for pressure balance in the magnetotail. Presumably they reflect not well understood dynamic processes in the distant magnetotail. In the second regions precipitating electrons had average energies in excess of 1 keV and had spectral shapes that were either quasi-thermal or monoenergetic peaks superimposed on a secondary-electron background. Beams of low-energy (10 (cm2 sr keV)-1 were found in all three cases. We interpret these electrons as part of an originally cold plasma that became detached from the plasmasphere due to time-varying convective electric fields. The electrons were subsequently heated by the Landau damping of electromagnetic ion-cyclotron waves

136

Visible to vacuum-UV range optical absorption of oxygen dangling bonds in amorphous SiO2  

International Nuclear Information System (INIS)

Synthetic silica glass with an optical absorption spectrum dominated by oxygen dangling bonds (nonbridging oxygen hole centers, or NBOHCs) and having negligible (2 laser (7.9 eV) at T = 80 K. This allowed us to obtain the up-to-now controversial optical absorption spectrum of NBOHC in the ultraviolet and vacuum-ultraviolet (UV-VUV) region of the spectrum and to show that it is semicontinuous from 4 to 7.8 eV and cannot be represented by a pair of distinct Gaussian bands. Since NBOHC is one of the main UV-VUV range optical absorbers in silica, its spectral shape provides a tool to disentangle contributions of different color centers to optical losses in this spectral region.

137

Collision-induced emission of singlet oxygen in the visible spectral region at temperatures of 90-315 K  

Science.gov (United States)

Collision-induced emission of singlet oxygen molecules is studied using spectrometers calibrated for absolute spectral sensitivity. The collision-induced emission-rate constants at wavelengths of 479, 514, 577, 634, and 703 nm are determined within the temperature range 90-315 K. It is found that the intensities of the emission bands increase with decreasing temperature below 100 K. The interrelation between the collision-induced emission-rate constants and the intensities of the collision-induced absorption bands is discussed. The Einstein coefficients for spontaneous emission of excited free O2: O2 complexes are estimated.

Zagidullin, M. V.; Svistun, M. I.; Khvatov, N. A.; Insapov, A. S.

2014-04-01

138

Wide spectral-range imaging spectroscopy of photonic crystal microbeads for multiplex biomolecular assay applications  

Science.gov (United States)

Suspension assay using optically color-encoded microbeads is a novel way to increase the reaction speed and multiplex of biomolecular detection and analysis. To boost the detection speed, a hyperspectral imaging (HSI) system is of great interest for quickly decoding the color codes of the microcarriers. Imaging Fourier transform spectrometer (IFTS) is a potential candidate for this task due to its advantages in HSI measurement. However, conventional IFTS is only popular in IR spectral bands because it is easier to track its scanning mirror position in longer wavelengths so that the fundamental Nyquist criterion can be satisfied when sampling the interferograms; the sampling mechanism for shorter wavelengths IFTS used to be very sophisticated, high-cost and bulky. In order to overcome this handicap and take better usage of its advantages for HSI applications, a new wide spectral range IFTS platform is proposed based on an optical beam-folding position-tracking technique. This simple technique has successfully extended the spectral range of an IFTS to cover 350-1000nm. Test results prove that the system has achieved good spectral and spatial resolving performances with instrumentation flexibilities. Accurate and fast measurement results on novel colloidal photonic crystal microbeads also demonstrate its practical potential for high-throughput and multiplex suspension molecular assays.

Li, Jianping

2014-05-01

139

Measurement of optical-transport coefficients of Intralipid in visible and NIR range  

Science.gov (United States)

This article presents a modified method of measuring the optical-transport-coefficients of intralipid: the diffuse reflectance of intralipid with added-ink Rdink is measured by using an integrating sphere to calculate the scattering coefficient (mu) 's, the effective attenuation coefficient (mu) eff is measured by scanning the surface of pure intralipid suspension with a cut-end, high NA fiber-optic tip ((phi) 600micrometers , NA equals 0.48) in order to directly derive the absorption (mu) a of pure intralipid. In the same way, their wavelength dependencies between 0.48 - 0.85 micrometers are measured by utilizing Ar+, dye and Ti:Sapphire lasers. Experiments show that (mu) s((lambda) ) varies with (lambda) according to the previously reported Mie theory, (mu) 's((lambda) ) decreases with (lambda) while Rdink((lambda) ) is nearly invariant within the wavelength range; the scattering anisotropy g((lambda) ) tends to decrease linearly with (lambda) from 0.91 to 0.78; (mu) a((lambda) ) first decreases with (lambda) till (lambda) approximately equals 0.61 micrometers and then gradually increases with (lambda) . In the Rdink experiments, it has been found that when the port of the integrating sphere is lifted above the liquid surface, the dependence of the measured intensity with the height H can be well-fitted into an exponential relation for H

Pan, Yingtian; Engelhardt, R.; Rosperich-Palm, Juergen; Huettmann, Gereon; Birngruber, Reginald

1994-08-01

140

Narrow Angle Wide Spectral Range Radiometer Design FEANICS/REEFS Radiometer Design Report  

Science.gov (United States)

A critical measurement for the Radiative Enhancement Effects on Flame Spread (REEFS) microgravity combustion experiment is the net radiative flux emitted from the gases and from the solid fuel bed. These quantities are measured using a set of narrow angle, wide spectral range radiometers. The radiometers are required to have an angular field of view of 1.2 degrees and measure over the spectral range of 0.6 to 30 microns, which presents a challenging design effort. This report details the design of this radiometer system including field of view, radiometer response, radiometric calculations, temperature effects, error sources, baffling and amplifiers. This report presents some radiometer specific data but does not present any REEFS experiment data.

Camperchioli, William

2005-01-01

 
 
 
 
141

One-dimensional Dirac operators with zero-range interactions: Spectral, scattering, and topological results  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The spectral and scattering theory for 1-dimensional Dirac operators with mass $m$ and with zero-range interactions are fully investigated. Explicit expressions for the wave operators and for the scattering operator are provided. These new formulae take place in a representation which links, in a suitable way, the energies $-\\infty$ and $+\\infty$, and which emphasizes the role of $\\pm m$. Finally, a topological version of Levinson's theorem is deduced, with the threshold eff...

Pankrashkin, Konstantin; Richard, Serge

2014-01-01

142

Micro-spectrometry in the visible range with full-field optical coherence tomography for single absorbing layers  

Science.gov (United States)

A time-domain full-field OCT adapted to the visible range and with an original configuration using an interferometric objective, that minimizes mechanical vibrations and some settings and that performs imaging without moving the sample, is presented. This setup achieves micrometer scale imaging, 1.5 ?m in the axial direction and 1.2 ?m in the lateral one. The principle of micro-spectrometry from OCT data by Fourier transform is described and the influence of some key data processing parameters is simulated and discussed. The experimental spectra reconstruction from tomographic data is validated by comparison with transmittance spectra. Imaging and spectra of dyes at a micrometer scale are obtained from the same data volume.

Latour, Gaël; Moreau, Julien; Elias, Mady; Frigerio, Jean-Marc

2010-12-01

143

Ultraviolet-visible spectral analysis for the reaction of hydrogen peroxide with a titanium(IV)-porphyrin reagent.  

Science.gov (United States)

A Ti-TPyP reagent, i.e., an acidic aqueous solution of oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) complex, TiO(tpyp), was developed as a highly sensitive and selective spectrophotometric reagent for the determination of traces of hydrogen peroxide. The reagent exhibited a single absorption peak at 432 nm, and the addition of hydrogen peroxide to the reagent gave rise to a new peak at 450 nm, with height being proportional to the added hydrogen peroxide concentration. Recently we succeeded in clarifying the reaction specificity of the TiO(tpyp) complex to hydrogen peroxide from the viewpoint of the reaction mechanisms and molecular orbitals based on ab initio calculations. In the present study, we performed ultraviolet-visible (UV-Vis) spectral simulations for individual species in the proposed reaction mechanisms based on the theoretical calculations carried out using the Zerner's intermediate neglect of differential overlap (ZINDO) method, since the assignment of the observed absorption peaks to the respective reaction species is important to confirm the reliability of the analysis of hydrogen peroxide using the Ti-TPyP reagent. The absorption peaks at 432 nm and 450 nm were assigned to a H(2)O-adduct structure of the protonated TiO(tpyp) complex and the important structure corresponding to the monoperoxo TiO(tpyp) complex, respectively, under acidic conditions. Particularly, it should be noted that the addition of water molecules to the protonated TiO(tpyp) complex affects the maximum absorption wavelength appreciably. Taking the addition of water molecules to the complex into consideration, the reaction mechanism proposed previously was revised in this study. The results should contribute to providing a new way to evaluate analytical reagents. PMID:19470217

Takamura, Kiyoko; Matsumoto, Takatoshi

2009-05-01

144

Spectral characteristics of precipitating clouds during the Meiyu over the Yangtze-Huaihe River Valley from merged TRMM precipitation radar and visible/infrared scanner data  

Science.gov (United States)

As the similar cross track scanning mode of the measurements of Tropical Rainfall Measuring Mission's (TRMM) Precipitation Radar (PR) and visible and infrared scanner (VIRS) results in near instantaneous synchronization in observing the same target, it is feasible to jointly use these two measurements to explore exactly the spectral characteristics of precipitating clouds (PCs). Meanwhile, it will effectively improve and extend the abilities to identify PCs using visible/infrared (VIR) measurements, because VIR sensors can be loaded aboard geostationary satellites with the opportunity of high sampling frequency. In this paper, PR and VIRS onboard TRMM are respectively used to capture PCs and identify their spectral signals during the Meiyu over the Yangtze-Huaihe River Valley from 1998 to 2007. Visible/infrared signals for PCs, which are the reflectance at 0.63?m and 1.6?m (referred to as RF1 and RF2, respectively), and the equivalent brightness temperature of a blackbody at 3.7?m, 10.8 ?m and 12.0?m (referred to as TB3, TB4 and TB5, respectively), were derived by TRMM VIRS. Firstly, characteristics of rain rate, rain top and vertical profiles for stratiform and convective precipitations are investigated during the Meiyu periods. Moreover, VIRS individual-channel signals, and multi-channel indices for PCs of the Meiyu are evaluated quantitatively. Finally, revealed by long-term mean values, the differences of spectral signals between stratiform and convective PCs and their relationships with surface rain rates are explored.

Yang, Yuan-Jian; Fu, Yun-Fei; Chen, Feng-Jiao; Zheng, Xiao-Yi; Chen, Yi-Lun

2014-11-01

145

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

146

Model-Independent Sum Rule Analysis Based on Limited-Range Spectral Data  

CERN Document Server

Partial sum rules are widely used in physics to separate low- and high-energy degrees of freedom of complex dynamical systems. Their application, though, is challenged in practice by the always finite spectrometer bandwidth and is often performed using risky model-dependent extrapolations. We show that, given spectra of the real and imaginary parts of any causal frequency-dependent response function (for example, optical conductivity, magnetic susceptibility, acoustical impedance etc.) in a limited range, the sum-rule integral from zero to a certain cutoff frequency inside this range can be safely derived using only the Kramers-Kronig dispersion relations without any extra model assumptions. This implies that experimental techniques providing both active and reactive response components independently, such as spectroscopic ellipsometry in optics, allow an extrapolation-independent determination of spectral weight 'hidden' below the lowest accessible frequency.

Kuzmenko, A B; Carbone, F; Marsiglio, F

2007-01-01

147

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

148

Unique Spectral Features Search In The 20 - 35 Micron Range of Mgs Tes Data  

Science.gov (United States)

TES is the Thermal Emission Spectrometer aboard the NASA mission Mars Global Surveyor (MGS) orbiting around Mars since September 1997. It is collecting 6 - 50 micron thermal emission spectra and one of its principal purposes is to determine and map the Mars surface composition. Spectral features directly ascribable to sur- face minerals have been identified in the 20 - 35 micron spectral range: deposits of crystalline gray hematite have been localized in three regions, Sinus Meridiani, Aram Chaos and Valles Marineris [1, 2], and outcrops of olivines have been individuated in Nili Fossae [3]. The crystalline gray hematite areas have been interpreted to be formed by aqueous mineralization, indicating that liquid water was stable near the Mars sur- face for a long period of time in some limited regions. On the other hand there is no evidence in TES data for large scale occurrences ( 50 micron) carbonates exposed at the surface at a detection limit of 10 % [2]. Mars thermal emission spectra show, in general, significant variance between 20 and 35 mi- cron. This variance is not directly attributable to surface mineralogical components for the difficulty of discriminating the contribute of atmospheric components: CO2 and water vapour gas, dust and water ice aerosols. Moreover, the dust layer deposited on the soil has a spectral masking effect, obscuring superficial signature related to smaller mineral deposit and making difficult their identification. In this study we report some examples of single TES spectra with typical hematite and olivine bands and spectra with other unique features in the 20 - 35 micron range likely related to superficial components. For some of them we have analysed how the spectral features change in two different Mars seasons. These single TES pixels could be best investigated by instruments with an higher spatial resolution, as THEMIS and OMEGA. References: [1] Christensen P. R., et al., JGR, 105, 9623-9642, 2000. [2] Christensen P. R., et al., JGR,106, 23823-23871, 2001. [3] Hoefen T. M. and Clark R. N., LPS XXXII, 2049, 2001.

Altieri, F.; Bellucci, G.

149

Marine biogeochemistry from space: recent developments in measuring the carbon cycle in the ocean using visible spectral reflectance  

Science.gov (United States)

Optical sensors on-board satellite have given over the last two decades another dimension to marine biology and ecosystem studies providing key information on the timing and spatial distribution of phytoplankton blooms and the magnitude of primary production The radiance backscattered from the upper layer of the ocean or the water leaving radiances at various spectral bands relates to the so-called ocean colour and varies with the concentration and composition of optically-active components OACs in suspension In reality these constituents cover a broad size range from water molecules to large zooplankton particles and include a large number of different organisms such as bacteria virus phytoplankton organic detritus minerals and more A quantitative description of the water-leaving radiances results theoretically from the additive contribution of all these constituents and their capacity to absorb and scatter the surrounding photons Remote observations of ocean colour from space represent therefore a major tool directly related to these biogeochemical distributions and associated processes and complement traditional ship measurements in the global assessment of the flux of material through the water column Present satellite instruments such SeaWiFS MODIS and MERIS are providing unprecedented and accurate views of the marine systems owing to some advanced characteristics of the sensors themselves but also to a substantial progress in the performance of bio-optical models to support the signal processing and the calibration of

Hoepffner, N.

150

Reflective and transmissive broadband coating polarizers in a spectral range centered at 121.6 nm  

Science.gov (United States)

Polarimetry is a powerful tool for the interpretation of the role of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. One of the key lines for observations is H I Lyman ? (121.6 nm) among few spectral lines in the far ultraviolet (FUV), and hence efficient linear polarizers at this line are demanded. New designs based on (Al/MgF2)n multilayer coatings have been developed to obtain the smallest possible reflectance in the parallel plane of polarization (Rpar) with a simultaneous high reflectance in the perpendicular plane of polarization (Rper). Samples stored in nitrogen for ?8–17 months resulted in efficient polarizers at 121.6 nm, with Rpar ? 0.01–0.017 and Rper ? 0.69–0.725. The designs with a number n = 3–4 bilayers of Al/MgF2 result in a wider spectral range of efficient linear polarizers, compared to what can be obtained with n = 2. Coatings following various designs with good polarizing performance in a 7–8 nm wide FUV range were prepared. For the first time, a transmissive coating polarizer has been developed for this range, which has the benefit that it involves no deviation of the beam; it is based on another design of (Al/MgF2)3 multilayer coating. The transmissive polarizer has a good transmittance ratio between the two polarization components and, even though its figure of merit is not as high as that of the reflective polarizers, it incorporates filtering properties to reject wavelengths both below and above 121.6 nm; this property might enable a polarimeter for solar physics with an improved global figure of merit if a filter to isolate the H I Lyman ? line could be avoided.

Larruquert, Juan I.; Malvezzi, A. Marco; Giglia, Angelo; Aznárez, José A.; Rodríguez-de Marcos, Luis; Méndez, José A.; Miotti, Paolo; Frassetto, Fabio; Massone, Giuseppe; Nannarone, Stefano; Crescenzio, Giuseppe; Capobianco, Gerardo; Fineschi, Silvano

2014-12-01

151

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

152

Photon counting detector with picosecond timing resolution for X to visible range on the basis of GaP  

International Nuclear Information System (INIS)

Avalanche photodiodes specifically designed for single photon counting devices have been developed on the basis of various semiconductor materials: Si, Ge, GaP, GaAsP, and InGaAs at the Czech Technical University within the last 20 years. All the semiconductor detectors operate at a room temperature or at thermoelectrically achievable temperatures except of the germanium-based detector, which requires liquid nitrogen cooling. Electronic circuits for these detectors biasing, quenching and control have been developed and optimized for different applications. Timing resolution of solid-state photon counters as high as 50 ps full width at a half maximum has been achieved when detecting single photon signals. Circuits permitting operation of solid-state photon counters in both single and multiple photon signal regimes have been developed and applied. The compact and rugged design, radiation resistance, and low operating voltage are attractive features of solid state photon counters in various applications including the space projects. The sensitivity of solid-state photon counters spans from X-ray up to 1800 nm in the near infrared region. The avalanche structures based on the GaP material exhibit several special features for X-ray operation: the timing resolution as high 100 ps may be achieved when detecting individual quanta, the wavelength range spans from 0.1 nm up to visible light. The GaP exhibits from all the existing solid-state photon counters the highest detectiostate photon counters the highest detection efficiency in X-ray, it reaches 14% at 0.1 nm band

153

Complex Refractive Index of Ammonium Nitrate in the 2-20 micron Spectral Range  

Science.gov (United States)

Using high resolution Fourier Transform Infrared Spectroscopy (FTIR) absorbance/transmittance spectral data for ammonium sulfate (AMS), calcium carbonate (CAC) and ammonium nitrate (AMN), comparisons were made with previously published complex refractive indices data for AMS and CAC to infer experimental parameters to determine the imaginary refractive index for AMN in the infrared wavelength range from 2 to 20 microns. Kramers-Kronig mathematical relations were applied to calculate the real refractive index for the three compositions. Excellent agreement for AMS and CAC with the published values was found, validating the complex refractive indices obtained for AMN. Backscatter calculations using a lognormal size distribution for AMS, AMN, and CAC aerosols were performed to show differences in their backscattered spectra.

Jarzembski, Maurice A.; Norman, Mark L.; Fuller, Kirk A.; Srivastava, Vandana; Cutten, Dean R.

2002-01-01

154

Circuit model optimization of a nano split ring resonator dimer antenna operating in infrared spectral range  

Science.gov (United States)

Metamaterials are comprised of metallic structures with a strong response to incident electromagnetic radiation, like, for example, split ring resonators. The interaction of resonator ensembles with electromagnetic waves can be simulated with finite difference or finite elements algorithms, however, above a certain ensemble size simulations become inadmissibly time or memory consuming. Alternatively a circuit description of metamaterials, a well developed modelling tool at radio and microwave frequencies, allows to significantly increase the simulated ensemble size. This approach can be extended to the IR spectral range with an appropriate set of circuit element parameters accounting for physical effects such as electron inertia and finite conductivity. The model is verified by comparing the coupling coefficients with the ones obtained from the full wave numerical simulations, and used to optimize the nano-antenna design with improved radiation characteristics.

Gneiding, N.; Zhuromskyy, O.; Shamonina, E.; Peschel, U.

2014-10-01

155

Circuit model optimization of a nano split ring resonator dimer antenna operating in infrared spectral range  

International Nuclear Information System (INIS)

Metamaterials are comprised of metallic structures with a strong response to incident electromagnetic radiation, like, for example, split ring resonators. The interaction of resonator ensembles with electromagnetic waves can be simulated with finite difference or finite elements algorithms, however, above a certain ensemble size simulations become inadmissibly time or memory consuming. Alternatively a circuit description of metamaterials, a well developed modelling tool at radio and microwave frequencies, allows to significantly increase the simulated ensemble size. This approach can be extended to the IR spectral range with an appropriate set of circuit element parameters accounting for physical effects such as electron inertia and finite conductivity. The model is verified by comparing the coupling coefficients with the ones obtained from the full wave numerical simulations, and used to optimize the nano-antenna design with improved radiation characteristics.

156

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

157

Laser diode photoacoustic detection in the infrared and near infrared spectral ranges.  

Science.gov (United States)

A new technique for high resolution photoacoustic detection based on application of laser diodes has been developed. This method was tested and compared using identical photoacoustic instrumentation (cell and microphone) to study gas absorption in three different spectral regions, namely: the infrared range near 2100 cm(-1), CO and OCS fundamental band absorption; the ranges near 4200 and 4350 cm(-1), CH4, NH3 and N2O overtone and combination band absorption; the near infrared range near 6500 cm(-1), CO, CO2 and NH3 overtone absorption. Several types of diode laser operating at room temperature or at liquid nitrogen temperature were compared. The optimum gas pressures for the maximum sensitivity of the photoacoustic signals were found and the detection limits were estimated for all of the gases studied. The best sensitivity was achieved for NH3 at 100 ppbv. The sensitivity of the developed system was tested on detection of traces of NH3 and CO2 gases from car exhaust. PMID:16021213

Horká, V; Civis, S; Xu, Li-Hong; Lees, R M

2005-08-01

158

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...

159

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

160

GOES-R Advanced Baseline Imager: spectral response functions and radiometric biases with the NPP Visible Infrared Imaging Radiometer Suite evaluated for desert calibration sites.  

Science.gov (United States)

The Advanced Baseline Imager (ABI), which will be launched in late 2015 on the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite R-series satellite, will be evaluated in terms of its data quality postlaunch through comparisons with other satellite sensors such as the recently launched Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership satellite. The ABI has completed much of its prelaunch characterization and its developers have generated and released its channel spectral response functions (response versus wavelength). Using these responses and constraining a radiative transfer model with ground reflectance, aerosol, and water vapor measurements, we simulate observed top of atmosphere (TOA) reflectances for analogous visible and near infrared channels of the VIIRS and ABI sensors at the Sonoran Desert and White Sands National Monument sites and calculate the radiometric biases and their uncertainties. We also calculate sensor TOA reflectances using aircraft hyperspectral data from the Airborne Visible/Infrared Imaging Spectrometer to validate the uncertainties in several of the ABI and VIIRS channels and discuss the potential for validating the others. Once on-orbit, calibration scientists can use these biases to ensure ABI data quality and consistency to support the numerical weather prediction community and other data users. They can also use the results for ABI or VIIRS anomaly detection and resolution. PMID:24216671

Pearlman, Aaron; Pogorzala, David; Cao, Changyong

2013-11-01

 
 
 
 
161

Natural variability of bio-optical properties in Case 1 waters: attenuation and reflectance within the visible and near-UV spectral domains, as observed in South Pacific and Mediterranean waters  

Directory of Open Access Journals (Sweden)

Full Text Available The optical properties of Case 1 waters have been empirically related to the chlorophyll concentration, [Chl], historically used as an index of the trophic state and of the abundance of the biological materials. The natural variability around the mean statistical relationships is here examined by comparing the apparent optical properties (spectral downward irradiance attenuation and reflectance as a function of [Chl] which were determined in two environments, the Pacific and Mediterranean waters. These oceanic zones apparently form two extremes of the bio-optical variability range. The systematic deviations, in both directions with respect to the average laws, mainly result from the differing contents in non-algal detrital materials and dissolved colored substance for a given [Chl] level. These contents are higher and lower than the average, in the Mediterranean Sea and Pacific Ocean, respectively. The divergences between the two water bodies, detected in the visible spectral domain, are considerably accentuated in the UV domain. The bio-optical properties in this spectral domain (310–400 nm are systematically explored. Their prediction based on the sole [Chl] index is problematic; although it is probably possible on a regional scale, an ubiquitous relationship does not seem to exist for the global scale.

A. Morel

2007-07-01

162

Spectral and spatial characteristics of x-ray film detectors in the wavelength range 20--150 angstrom  

International Nuclear Information System (INIS)

Investigations of spectral sensitivity, contrast coefficient, and spatial resolution of widely used x-ray films have been undertaken at the P.N. Lebedev Institute. A description of experimental methodologies and results are presented. These studies were carried out using synchrotron radiation in the range of 20--150 angstrom. Spectral sensitivity and contrast coefficient dependencies on wavelength for Kodak 10106, DEF, RAR2490, and TPF films and spatial resolution for Kodak 10106 and RAR2490 films are presented and discussed

163

Spectral and spatial characteristics of x-ray film detectors in the wavelength range 20--150 {angstrom}  

Energy Technology Data Exchange (ETDEWEB)

Investigations of spectral sensitivity, contrast coefficient, and spatial resolution of widely used x-ray films have been undertaken at the P.N. Lebedev Institute. A description of experimental methodologies and results are presented. These studies were carried out using synchrotron radiation in the range of 20--150 {angstrom}. Spectral sensitivity and contrast coefficient dependencies on wavelength for Kodak 10106, DEF, RAR2490, and TPF films and spatial resolution for Kodak 10106 and RAR2490 films are presented and discussed.

Fedin, D.A.; Fedorchuk, R.V.; Koshevoi, M.O.; Lukjantsev, I.V.; Rupasov, A.A.; Shikanov, A.S. [Russian Academy of Sciences, Moscow (Russian Federation). P.N. Lebedev Physics Inst.; Gullikson, E. [Lawrence Berkeley Lab., CA (United States)

1995-12-31

164

Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the anal...

Wagner, T.; Beirle, S.; Deutschmann, T.; Grzegorski, M.; Platt, U.

2007-01-01

165

Metallic resonant nanostructures for visible range metamaterials : contribution from generalized ellipsometry to the comprehension of their optical properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work deals with the optical properties of two types of layered composite materials containing metallic nanostructures which present multipolar plasmon resonances. Two methods were used to study the optical properties in the near IR-visible spectrum: finite elements model calculation and generalized ellipsometry. The first type of material contained an array of gold U-shaped resonators realized by e-beam lithography. Mueller-matrix measurements by ellipsometry allowed evidencing two speci...

Guth, Nicolas

2012-01-01

166

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

For the first time in visible part of the $D_2$ emission spectrum the pseudo doublets representing partly resolved fine structure of rovibronic lines have been observed. They are characterized by splitting values about 0.2 cm$^{-1}$ and relative intensity of the doublet components close to 2.0. It is shown that they are determined by triplet splitting in lower rovibronic levels of various $^3\\Lambda_g^\\pm \\to c^3\\Pi_u^-$ electronic transitions. It is proposed to use an exist...

Lavrov, B. P.; Umrikhin, I. S.; Zhukov, A. S.

2011-01-01

167

Applying spectral mixture analysis (SMA) for soil information extraction on the airborne visible/infrared imaging spectrometer (AVIRIS) data  

Science.gov (United States)

The research objectives of this study were formulated to produce the soil spectral maps using spectral mixture analysis on the AVIRIS data of the Walnut Gulch Experimental Watershed, Tombstone, Arizona. To accomplish this objective the spectral characteristics of eight soils of this Watershed were determined considering the effect of the source of illumination/sensor viewing geometry, degree of wetness (dry vs wet), surface roughness, and the source of the spectra (field, sieved samples and lab) on the selection of image and reference endmembers. The scale effect of the source of spectra was also studied in connection with AVIRIS spectral response. The soils presented anisotropic behavior which varied inversely with the wavelength, and it was reduced under wet conditions. Loss of information occurred when moving from large scale data set (lab, sieved sample, and field spectra) to small scale data (AVIRIS). Cluster analysis and factor analysis were used to extract information about how soil reference endmembers are grouped in relation to viewing angles, degree of wetness and the source of the spectra. Factor analysis was applied to identify the key set of bands that carried most of the information. Soil spectral classes varied as a result of scale effects, soil conditions (wet or dry), and viewing angles. Factor analysis showed that with four unique bands (located at 0.410, 1.310, 0.650, and 2.400 mum) it was possible to reconstruct the four basic soil spectral curves (Epitaph, Graham, McAllister, and Baboquivari) from the lab data set. AVIRIS image was modeled using mixture analysis on the basis of image endmembers and reference endmembers. Based on the four dimensions of the AVIRIS data image endmembers were defined by three soil spectra (McAllister, Stronghold-3, and Graham) and by one spectra of green vegetation. The shade fractions were separated from dark soils (Graham and Epitaph) on the basis of the spatial context. The target test identified at least seven reference endmembers in the AVIRIS scene of the Watershed however; mixture analysis failed in obtaining fraction images from these reference endmembers. Mixture analysis was able to produce fraction images with a relatively high error for a small set (3) of reference endmembers (McAllister and Graham soils, and walnut leaf). However when applied to a subset of pixel extracted from the AVIRIS image mixture analysis identified the reference endmembers and quantified their proportions.

Accioly, Luciano Jose De Oliveira

1997-11-01

168

Estudio de la respuesta espectral en el visible de películas delgadas de ZnSe / Study of the Spectral Response in the Visible Spectral Region the ZnSe thin Films  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish En este trabajo es presentado el estudio de la fotoconductividad en películas delgadas de ZnSe depositadas sobre sustratos de vidrio a diferentes temperaturas, en condiciones de alto vacío usando la técnica de evaporación térmica. El efecto de la temperatura de sustrato sobre la fotoconductividad es [...] pectral y las propiedades morfológicas de las películas delgadas de ZnSe fueron estudiados. Para las medidas de fotoconductividad se depositaron contactos de cobre sobre las muestras. Se midieron las respuestas espectrales para las muestras para el rango comprendido entre 290 y 500 nm. En todas las muestras la señal presento dos contribuciones asociadas a las transiciones con valores promedio de energía de 3,35 y 2,80 eV, respectivamente. El tiempo de respuesta de las muestras está asociado a la morfología de la muestras. En las muestras preparadas a bajas temperaturas se obtuvieron tiempos de respuesta del orden de los segundos, mientras que, el tiempo disminuye en un orden de magnitud en las muestras preparadas a temperatura de sustrato de 250°C. Abstract in english In this work are presented results in the study of photoconductivity of ZnSe thin films deposited on glass substrate. The effect of substrate temperature on the spectral photoconductivity and morphological properties of ZnSe thin films were studied. The Spectral response appeared between 290 and 500 [...] nm. In the spectral responses were found two contributions associated with transitions labeled , with energy values of 3:35 and 2:80 eV, respectively. The response time of the sample is associated with the morphology of the samples. In the samples prepared at lower temperatures were obtained response times on the order of seconds, whereas the time decreases by one magnitude order in the samples prepared at the substrate temperature of 250°C.

A, Pardo; H.G, Castro-Lora; J, Torres; L.D, López-Carreño; H. M, Martínez; N. T, Ramírez.

2014-07-30

169

A comparison of LOWTRAN-7 corrected Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data with ground spectral measurements  

Science.gov (United States)

Atmospheric correction of imaging spectroscopy data is required for quantitative analysis. Different models were proposed for atmospheric correction of these data. LOWTRAN-7 is a low-resolution model and computer code for predicting atmospheric transmittance and background radiance from 0 to 50,00 cm(sup -1) which was developed by the Air Force Geophysics Laboratory. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data used are radiometrically calibrated and include the 28 Sep. 1989 Providence Fan flight line segment 07, California. It includes a dark gravel surface defined as a calibration site by the Geologic Remote Sensing Field Experiment (GRSFE). Several ground measurements of portable spectrometer DAEDALUS AA440 Spectrafax were taken during the GRSFE, July 1989 field campaign. Comparisons of the LOWTRAN-7 corrected AVIRIS data with the ground spectrometer measurement were made.

Xu, Peng-Yang; Greeley, Ronald

1992-01-01

170

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

171

A fast radiative transfer model for visible through shortwave infrared spectral reflectances in clear and cloudy atmospheres  

International Nuclear Information System (INIS)

A computationally efficient radiative transfer model (RTM) for calculating visible (VIS) through shortwave infrared (SWIR) reflectances is developed for use in satellite and airborne cloud property retrievals. The full radiative transfer equation (RTE) for combinations of cloud, aerosol, and molecular layers is solved approximately by using six independent RTEs that assume the plane-parallel approximation along with a single-scattering approximation for Rayleigh scattering. Each of the six RTEs can be solved analytically if the bidirectional reflectance/transmittance distribution functions (BRDF/BTDF) of the cloud/aerosol layers are known. The adding/doubling (AD) algorithm is employed to account for overlapped cloud/aerosol layers and non-Lambertian surfaces. Two approaches are used to mitigate the significant computational burden of the AD algorithm. First, the BRDF and BTDF of single cloud/aerosol layers are pre-computed using the discrete ordinates radiative transfer program (DISORT) implemented with 128 streams, and second, the required integral in the AD algorithm is numerically implemented on a twisted icosahedral mesh. A concise surface BRDF simulator associated with the MODIS land surface product (MCD43) is merged into a fast RTM to accurately account for non-isotropic surface reflectance. The resulting fast RTM is evaluated with respect to its computational accuracy and efficiency. The simulation bias between DISORT and the fast RTM is large (e.g., relative error >5%) only when both the solar zenith angle (SZA) and the viewing zenith angle (VZA) are large (i.e., SZA>45° and VZA>70°). For general situations, i.e., cloud/aerosol layers above a non-Lambertian surface, the fast RTM calculation rate is faster than that of the 128-stream DISORT by approximately two orders of magnitude. -- Highlights: ? An efficient radiative transfer model is developed for cloud remote sensing. ? Multi-layered clouds and a non-Lambertian surface can be fully considered. ? A twisted icosahedral mesh is employed to accelerate the calculation.

172

Extended in vivo anterior eye-segment imaging with full-range complex spectral domain optical coherence tomography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We demonstrate the capability of full-range complex (FRC) spectral domain optical coherence tomography (SD-OCT) to image the anterior eye segment from the cornea to the posterior surface of the lens. With an adapted spectrometer design, we developed a SD-OCT system with an extended normal (single half-space) depth range of 7mm (in air). This OCT-intrinsic depth range was doubled with a FRC technique. We demonstrate the performance of our OCT system by imaging the whole anterior segment of a h...

Jungwirth, Johannes; Baumann, Bernhard; Pircher, Michael; Go?tzinger, Erich; Hitzenberger, Christoph K.

2009-01-01

173

The spectral opacity of triatomic carbon measured in a graphite tube furnace over the 280 to 600 nm wavelength range  

Science.gov (United States)

The paper presents the measurements of linear triatomic carbon opacity (C3) made in a graphite tube furnace to extend the wavelength range of Brewer and Engelke (1962) to the 280-600 nm range. An electrooptical method was used to determine C3 absorption in argon at 2720 to 3060 K; a quartic polynomial regression expression was derived to provide a complete temperature profile from pyrometer measurements. The C3 spectra were plotted for several opacity levels. It was concluded that the extension of the spectral range to the near u.v. levels made it easier to identify C3 particles.

Snow, W. L.; Wells, W. L.

1980-01-01

174

Extended in vivo anterior eye-segment imaging with full-range complex spectral domain optical coherence tomography  

Science.gov (United States)

We demonstrate the capability of full-range complex (FRC) spectral domain optical coherence tomography (SD-OCT) to image the anterior eye segment from the cornea to the posterior surface of the lens. With an adapted spectrometer design, we developed a SD-OCT system with an extended normal (single half-space) depth range of 7 mm (in air). This OCT-intrinsic depth range was doubled with a FRC technique. We demonstrate the performance of our OCT system by imaging the whole anterior segment of a healthy human eye in vivo.

Jungwirth, Johannes; Baumann, Bernhard; Pircher, Michael; Götzinger, Erich; Hitzenberger, Christoph K.

2009-09-01

175

New detections of O III lines in the UV and visible ranges in the terrestrial upper atmosphere  

Science.gov (United States)

Doubly-charged ions are peculiar atmospheric species interesting to study due to their exotic or unexpected photo-chemistry and their high reactivity. We focus here on the O++ doubly-charged ion, which was detected in the terrestrial atmosphere in 1967 by mass spectrometry. Its photochemistry has been characterized in a number of studies. Excited state fluorescence of this ion is well known, since its doublet centered around 500 nm has been used as a tracer of electron densities and temperatures in gaseous nebulae since the 1940's. O III emissions have been observed in the terrestrial atmosphere in the extreme ultraviolet region. We report here the new and unambiguous detection of two emission lines of O III at 495.8911 and 500.6843 nm, with the Ultraviolet and Visible Echelle Spectrograph (UVES) mounted on UT2 of the Very Large Telescope (VLT) in Chile. The measurements were performed after sunset, October 30, 2003 during the so-called "Halloween" storm. The intensities of these emissions are ~70 mRayleigh, and ~260 mRayleigh, respectively. We discuss the possible methods of production of the ion. We also discuss the potential identification of O III emission near 166 nm in a spectrum acquired with the Hopkins Ultraviolet Telescope (HUT) telescope on the dayside, in December 1990. These emissions constitute a new diagnostic of the state of the ionosphere, with potentially interesting applications to Venus and Mars.

Witasse, O. G.; Slanger, T. G.; Thissen, R.

2011-12-01

176

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

177

Ultraviolet and visible range plasmonics in the topological insulator Bi1.5Sb0.5Te1.8Se1.2  

Science.gov (United States)

The development of metamaterials, data processing circuits and sensors for the visible and ultraviolet parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations. This has driven the intense search for plasmonic materials beyond noble metals. Here we show that the semiconductor Bi1.5Sb0.5Te1.8Se1.2, also known as a topological insulator, is also a good plasmonic material in the blue-ultraviolet range, in addition to the already-investigated terahertz frequency range. Metamaterials fabricated from Bi1.5Sb0.5Te1.8Se1.2 show plasmonic resonances from 350 to 550?nm, while surface gratings exhibit cathodoluminescent peaks from 230 to 1,050?nm. The observed plasmonic response is attributed to the combination of bulk charge carriers from interband transitions and surface charge carriers of the topological insulator. The importance of our result is in the identification of new mechanisms of negative permittivity in semiconductors where visible range plasmonics can be directly integrated with electronics.

Ou, Jun-Yu; So, Jin-Kyu; Adamo, Giorgio; Sulaev, Azat; Wang, Lan; Zheludev, Nikolay I.

2014-10-01

178

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

179

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 ups 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.

180

Broad spectral range measurements and modelling of birefringence dispersion in two-mode elliptical-core fibres  

International Nuclear Information System (INIS)

We present the results of measurement and modelling of the birefringence dispersion in elliptical-core fibres (ECFs). The measurement is performed over a broad wavelength range (e.g. 450–1450 nm) by two spectral interferometric techniques. First, a technique employing a tandem configuration of a Michelson interferometer and an ECF under test is used for a broad spectral range measurement of the group modal birefringence for two spatial modes supported by the fibre. Second, a method with a lateral point-like force acting on the fibre and based on spectral interferometry is used for measuring the phase modal birefringence at one wavelength for the fundamental mode only. The measured value is combined with the dispersion of the group modal birefringence to obtain the phase modal birefringence over a broad wavelength range. We also modelled the dispersion characteristics taking into account contributions of both the elliptical shape of the core and the residual thermal stress. The dispersion characteristics measured for the three ECFs show very good agreement with the results of numerical modelling

 
 
 
 
181

A correlated-k distribution scheme for overlapping gases suitable for retrieval of atmospheric constituents from moderate resolution radiance measurements in the visible/near-infrared spectral region  

Science.gov (United States)

An accurate and fast radiative transfer scheme for the simulation of the spectral radiance measurements of a new generation of multichannel moderate resolution satellite spectrometers, such as GOME/ERS-2 (240-790 nm) and SCIAMACHY/ENVISAT-1 (240-2385 nm), has been developed. Representative absorption cross sections of the individual molecular line-absorbers CH4, CO, CO2; H2O, N2O, and O2 for relatively narrow spectral intervals (?0.2 nm) have been determined using a combined correlated-k (c-k) distribution and exponential sum fitting of transmittances (ESFT) scheme. The speed of the c-k calculations mainly depends on the channel-dependent spectral resolution of the instruments. For the measurements to be made by SCIAMACHY, this may be up to 800 times faster than line-by-line calculations. The agreement between c- k radiances and line-by-line reference radiances is in the range 1-2%. The dominant error (˜1%) is attributed to the correlation assumption made when applying the k distribution method to inhomogeneous atmospheres. As the commonly used c-k methods for overlapping gases are shown to result in large radiance errors at SCIAMACHY spectral resolution or do not permit individual representative absorption cross sections to be defined for each absorber separately, a new and novel method for the accurate simulation of overlapping absorption has been developed, verified, and validated. This technique enables overlapping line absorption to be considered for arbitrary spectral correlation of the monochromatic absorption cross sections of the individual gases. The new c-k scheme is based on a linear mixing of two radiance terms determined assuming correlation and anticorrelation of the monochromatic absorption cross sections of the overlapping gases.

Buchwitz, Michael; Rozanov, Vladimir V.; Burrows, John P.

2000-06-01

182

Observations of short-range, high-LET recoil tracks in CR-39 plastic nuclear track detector by visible light microscopy  

International Nuclear Information System (INIS)

Using standard visible light microscopy, we are able to observe particle tracks produced by oC, 6.25 N NaOH) for 2-4 h (removed layer B = 0.5-1.0 ?m) yielded secondary track densities of 105-106 cm-2 observable under a standard optical microscope with 500x-800x magnification. Ordinarily such a short duration etch would not be expected to enlarge the tracks sufficiently for them to be resolved by visible light optics. However, due to the short-range of the particles, a longer chemical processing would have over-etched the tracks until they were no longer recognizable. The tracks we observe in CR-39 PNTD irradiated in these experiments are the result of residual heavy recoil fragments returning to equilibrium via evaporation processes following proton-induced knock out of light particles via preequilibrium processes. Because the heavy recoil particles are very near the end of their ranges (i.e. in the Bragg peak), their LET is extremely high and changes rapidly. Consequently, the tracks they produce in CRuently, the tracks they produce in CR-39 PNTD often take the form of long tubes rather than the conical etch pits produced by higher energy particles.

183

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

184

TESIS experiment on study of solar corona in EUV spectral range (CORONAS-PHOTON project)  

International Nuclear Information System (INIS)

A new orbital station, namely: the CORONAS-PHOTON one (to be launched in 2006) equipped with systems to explore Sun at the intensification period of the solar activity 24-th cycle and at its peak is being designed within the framework of the CORONAS National Sun Space Exploration Program. The station equipment consists of systems to observe Sun within the spectral soft X-ray and vacuum ultraviolet bands. Paper lists and describes the TESIS experiment tools designed for the CORONAS-PHOTON Project to ensure the Sun atmospheric research within short-wave band

185

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

186

Imaging of the whole anterior eye segment with full-range complex spectral domain optical coherence tomography  

Science.gov (United States)

We demonstrate the capability of spectral domain optical coherence tomography (SD-OCT) with a full range complex (FRC) technique to image the anterior eye segment from the cornea to the back surface of the lens. We improved the spectrometer resolution with an adapted spectrometer design to achieve a single depth range of 7 mm in air. This depth range was doubled to an imaging range of 14 mm with a FRC-technique based on phase modulation introduced by off pivot point illumination of the galvanometer scanner. The performance of our system is demonstrated by recorded 2D and 3D datasets of the whole anterior eye segment of healthy human eyes in vivo. The system is also applicable to demonstrate the changes of the anterior eye segment during the accommodation of the eye.

Jungwirth, Johannes; Baumann, Bernhard; Pircher, Michael; Götzinger, Erich; Hitzenberger, Christoph K.

2009-07-01

187

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.

188

Thiol-stabilized PbS quantum dots with stable luminescence in the infrared spectral range  

Science.gov (United States)

Using thiol-stabilizing aqueous solution method, we have synthesized PbS quantum dots (QDs) that emit stable and spectrally tunable photoluminescence in the optical telecommunication band at around 1300 nm. The emission wavelength of the QDs was varied from 1295 to 1330 nm by increasing the synthesis time or Pb2+/TGA molar ratio. PbS nanocrystals (NCs) were directly imaged using high-resolution transmission electron microscopy, which gave an evaluation of the averaged sizes and the symmetry indexes of NCs. The symmetry index of NCs synthesized for 96 h was improved to 0.92 from 0.85, compared with that synthesized for 24 h. It has been found that chemically synthesized water-soluble PbS QDs are a potential source of entangled photon pairs in the near future.

Nakashima, Seisuke; Hoshino, Ai; Cai, Junjiang; Mukai, Kohki

2013-09-01

189

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

190

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 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.

191

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

192

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

Science.gov (United States)

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 XeF2 - N2 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 108. 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 1012 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.

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.

2013-03-01

193

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

International Nuclear Information System (INIS)

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 XeF2 – N2 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 108. 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 1012 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 recompressio 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)

194

Aperiodic normal-incidence antimony-based multilayer mirrors in the 8 - 13-nm spectral range  

International Nuclear Information System (INIS)

The optical properties of several materials were analysed from the standpoint of fabrication of broadband normal-incidence multilayer mirrors possessing maximal uniform reflectivity in the 8-13-nm range. By solving the inverse problem of multilayer optics we show that aperiodic Sb/(B4C, Sc, Si) multilayer structures optimised for maximum uniform reflectivity in the 8-13-nm range are able to afford a normal-incidence reflectivity R?10 % throughout this range. The best results are exhibited by the pair Sb/B4C, for which the average reflection coefficient amounts to about 13%. The dependence of optimisation result on the programmable limitation on the minimal layer thickness in the multilayer structure was numerically investigated. An empirical rule was established whereby setting the lower bound for a layer thickness at a level ??min/4 (in this case, ?min = 8 nm) does not result in an appreciable lowering of attainable uniform reflectivity. (quantum electronic devices)

195

A new undulator for the extension of the spectral range of the CLIO FEL  

International Nuclear Information System (INIS)

We built a new undulator in order to extend the lasing range of the CLIO infrared FEL. Presently, CLIO operates in the wavelength range 2 - 17 ?m. Beyond 14 ?m, the power decreases rapidly, because of the diffraction losses of the vacuum chamber (7 mm height and 2 m long). Thus, lasing at higher wavelengths implies installing a chamber with a height approximately twice. Then the minimum gap is increased and the maximum deflection parameter, K, is reduced from 2 to 1 : the laser tunability is greatly reduced. This is why a new undulator has been built

196

Visible Body  

Science.gov (United States)

The human body is an intricate, and often mysterious, place. With today's technology, however, many websites and apps provide entry into this fascinating world. Visible Body is one of the more compelling avenues for exploration. While there are paid products on the site, some of the content is available at no charge. Visitors can look over the Human Anatomy Atlas, which contains a range of visualizations that allow users to explore body systems in exquisite detail. For a small fee, users may access the other specific areas of the site, which include Digestive Anatomy, Respiratory Anatomy, and Reproductive & Urinary Anatomy.

197

Fine-tuning of whispering gallery modes in on-chip silica microdisk resonators within a full spectral range  

Science.gov (United States)

We investigate an efficient method for fine-tuning whispering gallery mode resonances in disk-type silica microresonators to reach an arbitrary frequency within the free spectral range of the system. This method is based on a post-production hydrofluoric acid etching process to precisely resize the radius of such microresonators. We show the effectiveness of this approach by tuning their resonance frequency within 10 GHz of specific hydrogen cyanide reference lines (P16, P18). This technique allows for simple and exact matching of narrow-linewidth lasers or spectroscopic lines with the high-Q resonances of on-chip silica microresonators.

Henze, Rico; Pyrlik, Christoph; Thies, Andreas; Ward, Jonathan M.; Wicht, Andreas; Benson, Oliver

2013-01-01

198

The heterojunction ZnSe-(Zn 1- xCd xTe) 1- y(In 2Te 3) y having high sensitivity in the visible light range and its applications  

Science.gov (United States)

The effect of a ZnSe film on the heterostructural ZnSe-(Zn 1- xCd xTe) 1- y(In 2Te 3) y film was studied from the standpoint of crystal growth. It is made clear that the ZnSe film improves the crystallinity of the Zn 1- xCd xTe) 1- y(In 2Te 3) y film evaporated on the ZnSe film and improves the spectral sensitivity of the heterostructure in the visible to the near-infrared light range. This heterostructure which consists of many elements can be fabricated by simple evaporation and anneal methods. One of the applications of this heterostructure is the photoconductive target in a camera tube. A camera tube with such a heterostructure is called "Newvicon" and has excellent features such as high sensitivity, low dark current, no burn-in and small lag. This heterostructure can be also applied to illuminometers photometers and solid state imagers.

Fujiwara, Shinji; Chikamura, Takao; Fukai, Masakazu

1983-05-01

199

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

200

Water vapor retrieval from OMI visible spectra  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 Astrophysi...

Wang, H.; Liu, X.; Chance, K.; Gonza?lez Abad, G.; Chan Miller, C.

2014-01-01

 
 
 
 
201

Estimation of a radiative transfer model in the longwave spectral range: sensitivity study and application to real cases  

Science.gov (United States)

The aerosol radiative effect in the longwave spectral range is often neglected in atmospheric aerosol forcing studies, hence very few researches are conducted in this field at local scale, and even less at regional scale. However, strong absorbing aerosols, like mineral dust, can have a small, but non-negligible heating effect in the longwave spectral range which can slightly counteract the aerosol cooling effect in the shortwave. The objective of this research is to perform a sensitivity study of an aerosol radiative transfer model as a function of dust particle properties. GAME model1, which can compute vertically resolved shortwave and longwave values of aerosol radiative forcing, is used. Before developing the sensitivity analysis, the aerosol radiative transfer model is validated by comparing its outputs with results published previously. Radiative forcing simulations in the longwave have shown an important sensitivity to the following parameters: aerosol size and refractive index, aerosol vertical distribution, humidity, surface temperature and albedo. A couple of strong mineral dust intrusion observed by means of lidar and sun-photometer are also presented in terms of shortwave and longwave radiative forcing.

Sicard, Michaël.; Bertolín, Santi; Mallet, Marc; Dubuisson, Philippe; Comerón, Adolfo

2013-10-01

202

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

203

Full anterior segment biometry with extended imaging range spectral domain optical coherence tomography at 1340 nm.  

Science.gov (United States)

We demonstrate an extended-imaging-range anterior-segment optical coherence tomography (eAS-OCT) system for the biometric assessment of full AS in human eye. This newly developed eAS-OCT operating at 1340-nm wavelength band is simultaneously capable of an imaging speed of 120 kHz A-line scan rate, an axial resolution of 7.2 ?m, and an extended imaging range of up to 16 mm in air. Imaging results from three healthy subjects and one subject with a narrow-angle demonstrate the instrument's utility. With this system, it can provide anatomical dimensions of AS, including central corneal thickness, anterior chamber width, anterior chamber depth, crystalline lens vault, crystalline lens thickness, angle opening distance (AOD500/AOD750), and the area described by the trabecular-iris space (TISA500/TISA750) at 500/750???m. We also use eAS-OCT to image and quantify dynamic functional changes of the AS in response to a light stimulus that induces physiological pupillary changes as well as accommodative efforts that induce lens changes. The results show that the described eAS-OCT is able to provide full anatomical biometry for AS and is useful for the studies where the dynamic response of AS compartment to certain stimulus is required. PMID:24752381

Li, Peng; Johnstone, Murray; Wang, Ruikang K

2014-04-01

204

Atlas and wavenumber tables for visible part of the rovibronic multiline emission spectrum of the $D_2$ molecule. II. Wavenumber range $18161 \\div 14379$ cm$^{-1}$ measured with moderate resolution  

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The visible part ($\\approx 550 \\div 696$ nm) of the multiline electronic-vibro-rotational emission spectrum of the $D_2$ molecule was recorded with moderate resolution (line widths $\\approx 0.013$ nm). The resolution was limited by Doppler broadening of spectral lines. After numerical deconvolution of the recorded intensity distributions and proper calibration of the spectrometer the new set of wavenumber values was obtained. The results are reported in the form of an atlas ...

Lavrov, B. P.; Umrikhin, I. S.

2012-01-01

205

Atlas and wavenumber tables for visible part of the rovibronic multiline emission spectrum of the $D_2$ molecule. I. Wavenumber range $23894 \\div 18161$ cm$^{-1}$ measured with moderate resolution  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The visible part ($\\approx 419 \\div 550$ nm) of the multiline electronic-vibro-rotational emission spectrum of the $D_2$ molecule was recorded with moderate resolution (line widths $\\approx 0.013$ nm). The resolution was limited by Doppler broadening of spectral lines. After numerical deconvolution of the recorded intensity distributions and proper calibration of the spectrometer the new set of wavenumber values was obtained. The results are reported in the form of an atlas ...

Lavrov, B. P.; Umrikhin, I. S.

2012-01-01

206

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...

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

2005-01-01

207

Novel SO2 spectral evaluation scheme using the 360–390 nm wavelength range  

Directory of Open Access Journals (Sweden)

Full Text Available Differential Optical Absorption Spectroscopy (DOAS is a well established spectroscopic method to determine trace gases in the atmosphere. During the last decade, passive DOAS, which uses solar radiation scattered in the atmosphere as a light source, has become a standard tool to determine SO2 column densities and emission fluxes from volcanoes and other large sources by ground based as well as satellite measurements. For the determination of SO2 column densities, the structured absorption of the molecule in the 300–330 nm region (due to the A1B1?X1A1 transition is used. However, there are several problems limiting the accuracy of the technique in this particular application. Here we propose to use an alternative wavelength region (360–390 nm due to the spin-forbidden a3B2?X1A1 transition for the DOAS evaluation of SO2 in conditions where high SO2 column densities prevail. We show this range to have considerable advantages in such cases, in particular when the particle content of the plume is high and when measurements are performed at large distances from the area of interest.

T. Wagner

2010-03-01

208

Dielectric function in the NIR-VUV spectral range of (InxGa1-x)2O3 thin films  

Science.gov (United States)

We determined the dielectric function of the alloy system (InxGa1-x)2O3 by spectroscopic ellipsometry in the wide spectral range from 0.5 eV to 8.5 eV and for In contents ranging from x = 0.02 to x = 0.61. The predicted optical transitions for binary, monoclinic ?-Ga2O3, and cubic bcc-In2O3 are well reflected by the change of the dielectric functions' lineshape as a function of the In content. In an intermediate composition range with phase-separated material (x ? 0.3…0.4), the lineshape differs considerably, which we assign to the presence of the high-pressure rhombohedral InGaO3-II phase, which we also observe in Raman experiments in this range. By model analysis of the dielectric function, we derived spectra of the refractive index and the absorption coefficient and energy parameters of electronic band-band transitions. We discuss the sub-band gap absorption tail in relation to the influence of the In 4d orbitals on the valence bands. The data presented here provide a basis for a deeper understanding of the electronic properties of this technologically important material system and may be useful for device engineering.

Schmidt-Grund, R.; Kranert, C.; Böntgen, T.; von Wenckstern, H.; Krauß, H.; Grundmann, M.

2014-08-01

209

Spectral shift by half free-spectral-range for microring resonator employing the phase jump phenomenon in coupled-waveguide and application on all-microring wavelength interleaver.  

Science.gov (United States)

Using coupled-mode theory, we have shown that there is a pi phase jump between the input and the through/drop fields of a codirectional coupler when the gap width between the coupled-waveguides reaches certain values such that the length of the coupler equals to the odd integer (for through field) or even integer (for drop field) times of the Transfer Distance. We introduced an efficient numerical method based on combining the scattering matrix method and FDTD method for analyzing a microring that has material loss. By applying this method, we found that the phase jump phenomenon also occurs in a half-ring coupler when the gap width between the coupled half-ring waveguides reaches a critical value. We showed that, for a given operating bandwidth, it is important that the gap width between the rings has to be larger than a certain value in order to avoid the phase jump, or smaller in order to take advantage of the phase jump. Based on the phase jump phenomenon, we found that the through and the drop spectra of the single-arm and the double-arm microring can be manipulated to shift about one half free spectral range by selecting appropriate gap widths. A novel all-microring wavelength interleaver, based on the phase jump phenomenon, is proposed and numerically demonstrated. PMID:19434107

Shih, Chih T'sung; Chao, Shiuh

2009-05-11

210

Identification of coronal sources of the solar wind from solar images in the EUV spectral range  

Science.gov (United States)

Methods of localizing coronal sources of the solar wind (SW), such as coronal holes, quasi-stationary fluxes from active regions, and transient sources associated with small-scale active phenomena are considered based on vacuum-ultraviolet (EUV) images of the corona at low solar activity during the initial period of the 24th solar cycle (2010). It is shown that a SW velocity profile can be calculated from the relative areas of coronal holes (CH) at the central part of the disk based on the images in the ranges of 193 and 171 Å. The images in the 193 Å describe the geometry of large HCs that represent sources of fast SW well. The images in 171 Å are a better visualization of small CHs, based on which the profile of a slow SW component was calculated to a high accuracy (up to 65 km/s). According to Hinode/EIS data of October 15, 2010, using the Doppler spectroscopy method at the streamer base over the active region 11112, the source of the outgoing plasma flux with the mean velocity of 17 km/s was localized in the magnetic field region with an intensity of less than 200 Gauss. According to the estimate, the density of the plasma flux from this source is an order of magnitude greater than the value required for explaining the distinction between the calculated and measured profiles of a slow SW velocity. For finding the transient SW component based on small-scale flare activity, SW parameters were analyzed for the periods of flares accompanied by coronal mass ejections (CMEs), and for the periods without flares, according to the data obtained in 2010 from the ACE and GOES satellites and by coronagraphs on the STEREO-A and - B spacecraft. The ion ratios C+6/C+5 and O+7/O+6 and the mean charge of Fe ions for periods with flares were shown to be shifted toward large values, suggesting the presence of a hot SW component associated with flare activity. A noticeable correlation between the maximum charge of Fe ions and the peak power of a flare, previously observed for flares of a higher class, was confirmed. The mean value of the SW flux density during the periods of flares was 30% higher than that in the periods without flares, which is possibly associated also with the growth of fluxes from other sources with an increasing solar activity level. Based on the example of a series of flares of October 13-14, 2010, it was supposed that transient SW fluxes from the weak flares at low solar activity can manifest themselves in the form of interplanetary ICME-transients.

Slemzin, V. A.; Shugai, Yu. S.

2015-01-01

211

Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers.  

Science.gov (United States)

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm(-1) to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ~70 as. The anharmonicity of smaller than 10(-4) cm(-1) was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 ?rad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy. PMID:25173248

Leger, Joel D; Nyby, Clara M; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I; Yue, Yuankai; Kireev, Victor V; Burtsev, Viacheslav D; Qasim, Layla N; Rubtsov, Grigory I; Rubtsov, Igor V

2014-08-01

212

Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS in the red spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm reflectance structures (i.e. "fingerprint" structures of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS, which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms. The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

T. Wagner

2007-01-01

213

Effect of random surface inhomogeneities on spectral properties of dielectric-disk microresonators: Theory and modeling at millimeter wave range  

Science.gov (United States)

The influence of random axially homogeneous surface roughness on spectral properties of dielectric resonators of circular disk form is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields, the method of eigenmode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering that is highly responsible for nondissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object, we use a dielectric disk resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigenfrequencies and the Q factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data.

Ganapolskii, E. M.; Eremenko, Z. E.; Tarasov, Yu. V.

2009-04-01

214

New methods of highly efficient controlled generation of radiation by liquid crystal nanostructures in a wide spectral range  

International Nuclear Information System (INIS)

We report the recent results of research focused on a new kind of soft matter-the liquid-crystal nanocomposites with controllable mechanical and nonlinear optical properties. These are promising media for implementation of ultra-compact photonic devices and efficient sources of coherent radiation in a wide spectral range. We overview the technology of preparation of nematic-liquid-crystal media saturated with disclination defects. The defects were formed in different ways: by embedding nanoparticles and molecular objects, by exposure to alpha-particle flux. The defect locations were controlled by applying an electric field. We also present and discuss the recently discovered features of nematic-liquid-crystal media: a thermal orientation effect leading to the fifth-order optical nonlinearity, enormous second-order susceptibility revealed by measurements, and structural changes upon exposure to laser radiation. We report on efficient generation of harmonics, sum and difference optical frequencies in nematic-liquid-crystal media. In addition, transformation of laser radiation spectra to spectral supercontinua, and filamentation of laser beams were also observed in nematic-liquid-crystal media. We conclude that most nonlinear optical effects result from changes of the orientational order in the examined nematic liquid crystals. These changes lead to the symmetry breaking and disclination appearances.

215

A HIGH-RESOLUTION, MULTI-EPOCH SPECTRAL ATLAS OF PECULIAR STARS INCLUDING RAVE, GAIA , AND HERMES WAVELENGTH RANGES  

International Nuclear Information System (INIS)

We present an Echelle+CCD, high signal-to-noise ratio, 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 A and includes the RAVE, Gaia, and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of the observed stars. A total of 425 spectra of peculiar stars, which were collected during 56 observing nights between 1998 November and 2002 August, are presented. 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, spectrophotometric 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 in the planning and development of automated classification algorithms designed for RAVE, Gaia, HERMES, and other large-scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas.

216

Lasers And Avalanche Photodiodes For IR Fiber Optics In The 2-2,5 µm Spectral Range  

Science.gov (United States)

In present work we report about development of semiconductor lasers and high-speed photodiodes based on GaInSbAs/GaAlSbAs solid solutions for 2.0-2.5 ?m spectral range, which operate at the room temperature. Characteristics of.the lasers of several types are described. Among them there are pulsed lasers with output optical power reaching 1 W, cw lasers operating at room temperature at the wavelength of 2.0-2.2 ?m, and pulsed lasers for the wavelength up to 2.5 ?m. Properties of the developed photodetectors are also presented. There are described high-speed (?SAM APD), characterizing by multiplication factor of 20-30 at room temperature.

Baranov, Alexej N.; Imenkov, Albert N.; Mikhailova, Maya P.; Rogachev, A. A.; Yakovlev, Yurii P.

1989-06-01

217

Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range  

International Nuclear Information System (INIS)

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nmydrated cement using the UV line 134.72 nm.

218

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

219

Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8  

Directory of Open Access Journals (Sweden)

Full Text Available Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8, which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

S. A. Buehler

2012-02-01

220

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

International Nuclear Information System (INIS)

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 ? 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the ?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.

 
 
 
 
221

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

222

A new facility for the synchrotron radiation-based calibration of transfer radiation sources in the ultraviolet and vacuum ultraviolet spectral range.  

Science.gov (United States)

The Physikalisch-Technische Bundesanstalt (PTB) has a long tradition in the calibration of radiation sources in the ultraviolet and vacuum ultraviolet spectral range, with traceability to calculable synchrotron radiation. Within this context, new instrumentation in the PTB laboratory at the Metrology Light Source (MLS) has been put into operation that opens up extended and improved calibration possibilities. A new facility for radiation source calibrations has been set up in the spectral range from 7 nm to 400 nm based on a combined normal incidence-grazing incidence monochromator. The facility can be used for the calibration of transfer sources in terms of spectral radiant intensity or mean spectral radiance, with traceability to the MLS primary source standard. We describe the design and performance of the experimental station and give examples of some commissioning results. PMID:25638071

Thornagel, Reiner; Fliegauf, Rolf; Klein, Roman; Kroth, Simone; Paustian, Wolfgang; Richter, Mathias

2015-01-01

223

A new facility for the synchrotron radiation-based calibration of transfer radiation sources in the ultraviolet and vacuum ultraviolet spectral range  

Science.gov (United States)

The Physikalisch-Technische Bundesanstalt (PTB) has a long tradition in the calibration of radiation sources in the ultraviolet and vacuum ultraviolet spectral range, with traceability to calculable synchrotron radiation. Within this context, new instrumentation in the PTB laboratory at the Metrology Light Source (MLS) has been put into operation that opens up extended and improved calibration possibilities. A new facility for radiation source calibrations has been set up in the spectral range from 7 nm to 400 nm based on a combined normal incidence-grazing incidence monochromator. The facility can be used for the calibration of transfer sources in terms of spectral radiant intensity or mean spectral radiance, with traceability to the MLS primary source standard. We describe the design and performance of the experimental station and give examples of some commissioning results.

Thornagel, Reiner; Fliegauf, Rolf; Klein, Roman; Kroth, Simone; Paustian, Wolfgang; Richter, Mathias

2015-01-01

224

Study of wave chaos in a randomly-inhomogeneous oceanic acoustic waveguide: spectral analysis of the finite-range evolution operator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The proplem of sound propagation in an oceanic waveguide is considered. Scattering on random inhomogeneity of the waveguide leads to wave chaos. Chaos reveals itself in spectral properties of the finite-range evolution operator (FREO). FREO describes transformation of a wavefield in course of propagation along a finite segment of a waveguide. We study transition to chaos by tracking variations in spectral statistics with increasing length of the segment. Analysis of the FREO...

Makarov, D. V.; Kon Kov, L. E.; Uleysky, M. Yu; Petrov, P. S.

2012-01-01

225

Quantum key distribution using quantum dot single-photon emitting diodes in the red and near infrared spectral range  

International Nuclear Information System (INIS)

We report on in-lab free space quantum key distribution (QKD) experiments over 40 cm distance using highly efficient electrically driven quantum dot single-photon sources emitting in the red as well as near-infrared spectral range. In the case of infrared emitting devices, we achieve sifted key rates of 27.2 kbit s-1 (35.4 kbit s-1) at a quantum bit error rate (QBER) of 3.9% (3.8%) and a g(2)(0) value of 0.35 (0.49) at moderate (high) excitation. The red emitting diodes generate sifted keys at a rate of 95.0 kbit s-1 at a QBER of 4.1% and a g(2)(0) value of 0.49. This first successful proof of principle QKD experiment based on electrically operated semiconductor single-photon sources can be considered as a major step toward practical and efficient quantum cryptography scenarios. (paper)

226

Multiple fiber Bragg grating sensor network with a rapid response and wide spectral dynamic range using code division multiple access  

Science.gov (United States)

Fiber Bragg grating (FBG) sensor networks have been intensively researched in optical sensor area and it developed in wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies which was adopted for its interrogating many optical sensors. In particular, WDM technology can be easily employed to interrogate FBG sensor however, the number of FBG sensors is limited. On the other hand, the TDM technique can extremely expand the number of sensor because the FBG sensors have same center wavelength. However, it suffers from a reduced sensor output power due to low reflectivity of FBG sensor. In this paper, we proposed and demonstrated the FBG sensor network based on code division multiple access (CDMA) with a rapid response and wide spectral dynamic range. The reflected semiconductor optical amplifier (RSOA) as a light source was directly modulated by the generated pseudorandom binary sequence (PRBS) code and the modulated signal is amplified and goes through FBG sensors via circulator. When the modulated optical signal experienced FBG sensor array, the optical signal which was consistent with center wavelength of FBGs is reflected and added from each sensors. The added signal goes into dispersion compensating fiber (DCF) as a dispersion medium. After through the DCF, the optical signal is converted into electrical signal by using photodetector (PD). For separate individual reflected sensor signal, the sliding correlation method was used. The proposed method improves the code interference and it also has advantages such as a large number of sensors, continuously measuring individual sensors, and decreasing the complexity of the sensor network.

Kim, Youngbok; Jeon, Sie-Wook; Park, Chang-Soo

2011-05-01

227

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

CERN Document Server

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

228

GaInN/GaN quantum well laser structures emitting in the blue-green spectral range  

International Nuclear Information System (INIS)

Presently, GaN-based laser diodes are limited to the violet-blue region of the spectrum. Our aim is to obtain laser emission in the blue-green spectral range. In order to study GaInN-based laser structures, low pressure MOVPE was used to grow such structures on a variety of substrates (freestanding GaN, GaN templates, and SiC). This allows investigations of the influence of the substrate related dislocation densities on gain, losses and carrier recombination. Our samples were investigated by optical gain spectroscopy using the variable stripe length method. In order to reach wavelengths longer than 450 nm an increase of the indium concentration to more than 25 % is needed. Such high In content requires careful optimization of the growth conditions in order to avoid damaging of the quantum wells by thermal stress. Combining the results of the gain measurement with a theoretical calculation of the gain spectra we determine the threshold power, carrier density and the carrier recombination times of the sample. On bulk GaN substrates we find threshold power levels as low as 20 kW/cm2. Up to now we obtain optical gain up to a peak wavelength of 465 nm with losses of about 30 cm-1. Our next targets are a wavelength of 480 nm as well as a further reduction of the threshold power

229

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

Energy Technology Data Exchange (ETDEWEB)

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., E-mail: Schmidt-Grund@physik.uni-leipzig.de; Lühmann, T.; Böntgen, T.; Franke, H.; Lorenz, M.; Grundmann, M. [Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Universität Leipzig, Linnéstr. 5, D-04103 Leipzig (Germany); Opper, D. [PANalytical GmbH, Nürnberger Straße 113, D-34123 Kassel (Germany)

2013-12-14

230

Spectral emissivity modeling of steel 201 during the growth of oxidation film over the temperature range from 800 to 1100 K in air  

Science.gov (United States)

This study explores the spectral emissivity modeling of steel 201 during the growth of oxidation film over the temperature range from 800 to 1100 K at 1.5 ?m. The radiance coming from the specimen is received by an InGaAs photodiode detector. The specimen temperature is obtained by averaging the two platinum-rhodium thermocouples, which are tightly welded in the front surface of specimen near the measuring area viewed by the detector. The variation of spectral emissivity with the temperature is studied at a given heating time. The variation of spectral emissivity with the heating time is evaluated at a definite temperature. The strong oscillations of spectral emissivity are observed and discussed in detail, which originate from the interference effect between the radiation stemming from the oxidization film on the specimen surface and the radiation coming from the specimen surface. The measurement uncertainties of spectral emissivity contributed only by the surface oxidization are about 3.2-14.1%. At a given heating time, the variation of spectral emissivity with the temperature abides well by a simple analytic functional form. And at a definite temperature, the variation of spectral emissivity with the heating time can also be well reproduced by fitting except for the periodical oscillations.

Shi, Deheng; Zou, Fenghui; Wang, Shuai; Zhu, Zunlue; Sun, Jinfeng; Wang, Baokui

2014-11-01

231

Atlas and wavenumber tables for visible part of the rovibronic multiline emission spectrum of the $D_2$ molecule. I. Wavenumber range $23894 \\div 18161$ cm$^{-1}$ measured with moderate resolution  

CERN Document Server

The visible part ($\\approx 419 \\div 550$ nm) of the multiline electronic-vibro-rotational emission spectrum of the $D_2$ molecule was recorded with moderate resolution (line widths $\\approx 0.013$ nm). The resolution was limited by Doppler broadening of spectral lines. After numerical deconvolution of the recorded intensity distributions and proper calibration of the spectrometer the new set of wavenumber values was obtained. The results are reported in the form of an atlas divided into 36 sections covering about 1.5 nm, containing pictures of images in the focal plane of the spectrometer, intensity distributions in linear and logarithmic scales and the table containing wavenumber and relative intensity values for 6545 spectral lines together with existing line assignments.

Lavrov, B P

2012-01-01

232

Atlas and wavenumber tables for visible part of the rovibronic multiline emission spectrum of the $D_2$ molecule. II. Wavenumber range $18161 \\div 14379$ cm$^{-1}$ measured with moderate resolution  

CERN Document Server

The visible part ($\\approx 550 \\div 696$ nm) of the multiline electronic-vibro-rotational emission spectrum of the $D_2$ molecule was recorded with moderate resolution (line widths $\\approx 0.013$ nm). The resolution was limited by Doppler broadening of spectral lines. After numerical deconvolution of the recorded intensity distributions and proper calibration of the spectrometer the new set of wavenumber values was obtained. The results are reported in the form of an atlas divided into 43 sections covering about 1.5 nm, containing pictures of images in the focal plane of the spectrometer, intensity distributions in linear and logarithmic scales and the table containing wavenumber and relative intensity values for 5445 spectral lines together with existing line assignments.

Lavrov, B P

2012-01-01

233

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...

234

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

235

The Swift-UVOT ultraviolet and visible grism calibration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the calibration of the Swift UVOT grisms, of which there are two, providing low-resolution field spectroscopy in the ultraviolet and optical bands respectively. The UV grism covers the range 1700-5000 Angstrom with a spectral resolution of 75 at 2600 Angstrom for source magnitudes of u=10-16 mag, while the visible grism covers the range 2850-6600 Angstrom with a spectral resolution of 100 at 4000 Angstrom for source magnitudes of b=12-17 mag. This calibration exte...

Kuin, N. P. M.; Landsman, W.; Breeveld, A. A.; Page, M. J.; James, C.; Lamoureux, H.; Mehdipour, M.; Still, M.; Yershov, V.; Brown, P. J.; Carter, M.; Mason, K. O.; Kennedy, T.; Marshall, F.; Roming, P. W. A.

2015-01-01

236

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

237

Thermodynamic properties of a classical d-dimensional spin-S Heisenberg ferromagnet with long-range interactions via the spectral density method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The thermodynamic properties of a classical d-dimensional spin-S Heisenberg ferromagnet, with long-range interactions decaying as $r^{-p}$ and in the presence of an external magnetic field, is investigated by means of the spectral density method in the framework of classical statistical mechanics. We find that long-range order exists at finite temperature for $dd$ with $d>2$, consistently with known theorems. Besides, the related critical tem...

Cavallo, A.; Cosenza, F.; Cesare, L.

2003-01-01

238

Visible Embryo  

Science.gov (United States)

a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-01-30

239

Nonlinear-laser effects in NH4H2PO4 (ADP) and ND4D2PO4 (DADP) single crystals: almost two-octave multi-wavelength Stokes and anti-Stokes combs, cascaded lasing in UV and visible ranges with the involving of the second and third harmonic generation  

International Nuclear Information System (INIS)

We report the experimental investigation of nonlinear cascaded lasing ?(3) ? ?(2) effects in UV and visible ranges and high-order Stokes and anti-Stokes generation covering spectral space of about 18000 cm-1 by stimulated Raman scattering and multi-wave mixing processes under one-micron picosecond pumping in the paraelectric state of NH4H2PO4 and ND4D2PO4 single crystals. All recorded Raman induced laser wavelengths are identified and attributed to their SRS-promoting vibration modes. Brief review of nonlinear-laser processes in non-centrosymmetric phosphates of KH2PO4-family and some physical properties of NH4H2PO4 and ND4D2PO4 are given as well

240

Design of a sun tracker for the automatic measurement of spectral irradiance and construction of an irradiance database in the 330-1100 nm range  

Energy Technology Data Exchange (ETDEWEB)

An automatic global and direct solar spectral irradiance system has been designed based on two LICOR spectro radiometers equipped with fibre optics and remote cosine sensors. To measure direct irradiance a sun tracker based on step motors has been developed. The whole system is autonomous and works continuously. From the measurements provided by this system a spectral irradiance database in the 330-1100 nm range has been created. This database contains normal direct and global horizontal irradiances as well as diffuse irradiance on a horizontal plane, together with total atmospheric optical thickness and aerosol optical depth. (author)

Canada, J.; Maj, A. [Departamento de Termodinamica Aplicada, Universidad Politecnica de Valencia, Camino de Vera, s/n. 46022 Valencia (Spain); Utrillas, M.P.; Martinez-Lozano, J.A.; Pedros, R.; Gomez-Amo, J.L. [Departamento de Fisica de la Tierra y Termodinamica, Facultat de Fisica, Universitat de Valencia, 46100 Burjassot (Valencia) (Spain)

2007-10-15

 
 
 
 
241

Spectral redistribution of energy and the origin of inverse cascade for gyrokinetics in the sub-Larmor range  

CERN Document Server

It is known that an inverse cascade of energy occurs in two-dimensional neutral fluid turbulence and also, under certain conditions, in magnetized plasma turbulence. The reason for this phenomenon in both cases is due to the existence of two quadratic invariants. The crucial feature of these invariants is that they are {\\em mutually-constraining} in the sense that the spectral redistribution of one is constrained by the other. The gyrokinetic equation, a kinetic equation for magnetized plasma dynamics, has two collisionless quadratic invariants when restricted to two dimensions (in position-space). In this paper, we consider the consequences of this fact for scales smaller than the thermal Larmor radius, where turbulent fluctuations exist, with equal importance, in the position and velocity space dependence of the kinetic distribution function. Using a spectral formalism for position and velocity space, we find that the gyrokinetic invariants are mutually constraining with respect to spectral redistribution o...

Plunk, G G

2010-01-01

242

Dispersive parameters for complex refractive index of p- and n-type silicon from spectrophotometric measurements in spectral range 200-2500 nm  

Science.gov (United States)

The spectral reflectance R(?) and spectral transmittance T(?) of p- and n-type silicon samples, having plane-parallel faces, are measured with a UV-vis-NIR spectrophotometer at room temperature. Measured data are introduced into analytical expressions to retrieve the complex refractive indices of silicon slabs across 200-2500 nm spectral range. The Wemple-DiDomenico dispersion model for real refractive index in the transparent region is used. Correlation between two atomic parameters and the dispersion constants of this dispersion model is established. Effects of doping on dispersion parameters, atomic parameters, the density of valence electrons, nv, coordination number, Nc, and the energy gap, Eg, are investigated. A dispersion model for the imaginary refractive index in the absorption region is investigated.

El-Zaiat, El-Sayed Y.; Youssef, Gamal M.

2015-01-01

243

Human Contrast Threshold and Astronomical Visibility  

CERN Document Server

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

244

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.)

245

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

246

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.  

Science.gov (United States)

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 in spectral-colored cellophane were exposed to sunlight and compared to an unwrapped bottle to determine chemical and physical changes as well as modifications of biological properties. Each bottle of water was named according to the color of cellophane paper with letter E (stands for exposed) as a prefix with (E-violet, E-indigo, E-blue, E-green, E-yellow, E-orange, and E-red). E-control (without wrap) was exposed to polychromatic sunlight. This study addresses two main issues viz., the chemical and physical changes in E-water and its effect on biological activities. Chemical and physical composition analysis using inductively coupled plasma atomic emission spectrometry; physical conductance by a Wheatstone Bridge type conductivity meter; osmolarity by a vapor pressure osmometer; and, salt solubility profile of 10% sodium bicarbonate were determined. Furthermore, testing the effect of E-waters on human lymphocyte proliferation, mosquito larvae hatching and seed germination determined the functional role of solar radiation through specific spectrum/s of visible light on various biological processes. We found that water exposed to visible spectral emissions of sunlight had an altered elemental composition, electrical conductance, osmolarity and salt-solubility, as well as differences in bio-modulatory effects. A gradual increase in leaching of Boron from E-violet to E-red was noted. E-indigo showed maximal increase in electrical conductance and maximal salt solubility of sodium bicarbonate. E-blue inhibited phyto-hemagglutinin-induced immune cell proliferation and mosquito larvae hatching. E-orange stimulated root elongation in seed germination. We conclude that 40-day exposure of water to specific solar spectrum changes chemical and physical properties and influences on biological activity. PMID:16705821

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

2005-08-01

247

Spectral reflectance of carbonate minerals and rocks in the visible and near infrared (0.35 - 2.55 microns) and its applications in carbonate petrology  

Science.gov (United States)

Reflection spectroscopy in the visible and near infrared (0.35 to 2.55 micron) offers a rapid, inexpensive, nondestructive tool for determining the mineralogy and investigating the minor element chemistry of the hard-to-discriminate carbonate minerals, and can, in one step, provide information previously obtainable only by the combined application of two or more analytical techniques. When light interacts with a mineral certain wavelengths are preferentially absorbed. The number, positions, widths and relative intensities of these absorptions are diagnostic of the mineralogy and chemical composition of the sample. At least seven bands due to vibrations of the carbonate radical occur between 1.60 and 2.55 micron. Positions of these bands vary from one carbonae mineral to another and can be used for mineral identification. Cation mass is the primary factor controlling band position; cation radius plays a secondary role.

Gaffey, S. J.

1984-01-01

248

(Oxy)nitrides with d0-electronic configuration as photocatalysts and photoanodes that operate under a wide range of visible light for overall water splitting.  

Science.gov (United States)

Water splitting to form H2 and O2 using semiconductor photocatalysts under sunlight is a possible means of clean energy production from renewable resources. (Oxy)nitrides are regarded as suitable candidates for the application, because of their suitable band edge positions, small band gaps (oxidizing water in the presence of suitable electron donors and acceptors, respectively, under visible light (? > 400 nm). Some have achieved direct water splitting into H2 and O2 with good reproducibility. (Oxy)nitrides are also attractive as water-splitting photoelectrodes, and highly efficient photoelectrochemical water splitting has been accomplished using tantalum-based (oxy)nitrides under visible light with good stability. However, there still remain a lot of challenges that have to be addressed in this research field. This perspective highlights recent progress in the development of (oxy)nitride materials for application in photocatalytic and photoelectrochemical water splitting made by the author and his colleagues, especially in the last 5 years. PMID:23337977

Maeda, Kazuhiko

2013-07-14

249

Theoretical modeling of an U-shaped SPR fiber sensor in 1550-nm spectral range for sensing applications  

Science.gov (United States)

Currently, the surface plasmon resonance (SPR) based sensors are mainly focused in visible frequencies, being a barrier for a better integration with the typical fiber optical communication transmission bands. Here, it is presented a theoretical analysis of a SPR based fiber optic sensor with a uniform gold coating on a U-shaped probe. The sensor does not require any fiber etching treatment which eases and improves the control of the overall process. The response of the device to refractive index variations was investigated and a resolution of 10-8 is foreseen for refractive indices around 1.413, becoming the proposed sensor a useful tool for biological and chemical applications.

Duarte, Daniel P.; Alberto, Nélia J.; Bilro, Lúcia; Nogueira, Rogério N.

2014-08-01

250

Investigations of the March 2006 African dust storm using ground-based column-integrated high spectral resolution infrared (8-13 ?m) and visible aerosol optical thickness measurements: 1. Measurement procedures and results  

Science.gov (United States)

The infrared (IR) aerosol optical thickness (AOT) spectra of Saharan dust measured during the Portable Infrared Aerosol Transmission Experiment (PIRATE) are reported. Saharan dust optical thickness (extinction) spectra from 8 to 13 ?m were obtained using column-integrated solar transmission measurements in Puerto Rico in July 2005 and Senegal in January and March 2006 (during a dust plume) using a Fourier transform infrared (FTIR) spectrometer. The FTIR measured the solar spectral irradiance in the IR in the presence of Saharan dust, and the AOT was determined by comparing the measured spectra to modeled downwelling spectra without dust for the same atmospheric temperature profile, solar zenith angle, water vapor, and ozone concentrations. The modeled dust-free spectra are generated using the Santa Barbara Disort Atmospheric Radiative Transfer (SBDART) program. The measured dust AOT is compared with modeled AOT spectra obtained using Mie theory with dust indices of refraction from Volz and Fouquart with assumed lognormal size distributions. When the visible AOT values from nearby Aerosol Robotic Network (AERONET) sensors are compared to the IR AOT values, results from various dust loadings show that the IR dust AOT at 9.5 ?m is typically only one third that of the visible (670 nm) dust AOT, but there is some evidence that this ratio could increase for larger dust size distributions. The surface IR dust forcing is determined to be about -0.4 W/m2 by summing the dusty and clear irradiance differences.

Thomas, M.; Gautier, C.; Ricchiazzi, P.

2009-06-01

251

First spectral emissivity study of a solar selective coating in the 150-600°C temperature range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A complete experimental study of temperature dependence of the total spectral emissivity has been performed, for the first time, for absorber-reflector selective coatings used in concentrated solar power (CSP) systems for energy harvesting. The coating consist of double cermet layers of silicon oxide with different amounts of molybdenum over a silver infrared mirror layer. The experimental measurements were carried out by a high accurate radiometer (HAIRL) with controlled atmosphere in the mi...

Pe?rez-sa?ez, R. B.; Ce?spedes, E.; Sa?nchez-garci?a, J. A.; A?lvarez-fraga, L.; Escobar Galindo, R.; Albella, J. M.; Prieto, C.

2013-01-01

252

Simulation of a surface plasmon resonance-based fiber-optic sensor for gas sensing in visible range using films of nanocomposites  

International Nuclear Information System (INIS)

A surface plasmon resonance-based fiber-optic sensor coated with nanocomposite film for sensing small concentrations of gases in the visible region of the electromagnetic spectrum has been analyzed. The nanocomposites considered are nanoparticles of Ag, Au and indium tin oxide (ITO) with their varying fraction dispersed in the host dielectric matrix of WO3, SnO2 and TiO2. For analysis, the effective indices of nanocomposites are calculated by adopting the Maxwell–Garnett model for nanoparticles of dimensions much smaller than the wavelength of radiation used for investigation. The effects of the volume fraction of nanoparticles in different nanocomposites and the thickness of the nanocomposite layer on the sensitivity of the sensor have been studied. It has been found that the sensor with the ITO–TiO2 coated nanocomposite with a small volume fraction and optimized film thickness possesses higher sensitivity

253

Temperature dependence of the dielectric function in the spectral range (0.5–8.5) eV of an In2O3 thin film  

International Nuclear Information System (INIS)

We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from near-infrared to vacuum-ultraviolet and for temperatures 10?K–300?K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.

254

Temperature dependence of the dielectric function in the spectral range (0.5-8.5) eV of an In2O3 thin film  

Science.gov (United States)

We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from near-infrared to vacuum-ultraviolet and for temperatures 10 K-300 K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.

Schmidt-Grund, R.; Krauß, H.; Kranert, C.; Bonholzer, M.; Grundmann, M.

2014-09-01

255

The Swift-UVOT ultraviolet and visible grism calibration  

CERN Document Server

We present the calibration of the Swift UVOT grisms, of which there are two, providing low-resolution field spectroscopy in the ultraviolet and optical bands respectively. The UV grism covers the range 1700-5000 Angstrom with a spectral resolution of 75 at 2600 Angstrom for source magnitudes of u=10-16 mag, while the visible grism covers the range 2850-6600 Angstrom with a spectral resolution of 100 at 4000 Angstrom for source magnitudes of b=12-17 mag. This calibration extends over all detector positions, for all modes used during operations. The wavelength accuracy (1-sigma) is 9 Angstrom in the UV grism clocked mode, 17 Angstrom in the UV grism nominal mode and 22 Angstrom in the visible grism. The range below 2740 Angstrom in the UV grism and 5200 Angstrom in the visible grism never suffers from overlapping by higher spectral orders. The flux calibration of the grisms includes a correction we developed for coincidence loss in the detector. The error in the coincidence loss correction is less than 20%. The...

Kuin, N P M; Breeveld, A A; Page, M J; James, C; Lamoureux, H; Mehdipour, M; Still, M; Yershov, V; Brown, P J; Carter, M; Mason, K O; Kennedy, T; Marshall, F; Roming, P W A; Siegel, M; Oates, S; Smith, P J; De Pasquale, M

2015-01-01

256

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)

257

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

258

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

259

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.

260

Modifying ultrafast optical response of sputtered VOX nanostructures in a broad spectral range by altering post annealing atmosphere  

Science.gov (United States)

Nanostructured VOX thin films were grown in a dc magnetron sputter system under two different Ar:O2 gas flow ratios. The films were annealed under vacuum and various ratios of O2/N2 atmospheres. The insulator-to-metal transition properties of the thin films were investigated by temperature dependent resistance measurement. Photo induced insulator-to-metal transition properties were investigated by Z-scan and ultrafast white light continuum pump probe spectroscopy measurements. Experiments showed that not only insulator-to-metal transition, but also wavelength dependence (from NIR to VIS) and time scale (from ns to ultrafast) of nonlinear optical response of the VOX thin films could be fine tuned by carefully adjusting post annealing atmosphere despite different initial oxygen content in the production. Fabricated VO2 thin films showed reflection change in the visible region due to photo induced phase transition. The results have general implications for easy and more effective fabrication of the nanostructured oxide systems with controllable electrical, optical, and ultrafast optical responses.

Kürüm, U.; Yaglioglu, H. G.; Küçüköz, B.; Oksuzoglu, R. M.; Y?ld?r?m, M.; Ya?c?, A. M.; Yavru, C.; Özgün, S.; T?ra?, T.; Elmali, A.

2015-01-01

 
 
 
 
261

Nanohole-based SPR Instruments with Improved Spectral Resolution Quantify a Broad Range of Antibody-Ligand Binding Kinetics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We demonstrate an affordable low-noise SPR instrument based on extraordinary optical transmission (EOT) in metallic nanohole arrays and quantify a broad range of antibody-ligand binding kinetics with equilibrium dissociation constants ranging from 200 pM to 40 nM. This nanohole-based SPR instrument is straightforward to construct, align, and operate, since it is built around a standard microscope and a portable fiber-optic spectrometer. The measured refractive index resolution of this platfor...

Im, Hyungsoon; Sutherland, Jamie N.; Maynard, Jennifer A.; Oh, Sang-hyun

2012-01-01

262

Tailoring the shape of GaN/AlxGa1-xN nanostructures to extend their luminescence in the visible range  

International Nuclear Information System (INIS)

We show that the shape of GaN nanostructures grown by molecular beam epitaxy on AlxGa1-xN (0001) surfaces, for x?0.4, can be controlled via the ammonia pressure. The nanostructures are obtained from a two dimensional to three dimensional transition of a GaN layer occurring upon a growth interruption. Atomic force microscopy measurements show that depending on the ammonia pressure during the growth interruption, dot or dash-shaped nanostructures can be obtained. Low temperature photoluminescence measurements reveal a large redshift in the emission energy of the quantum dashes, as compared to the quantum dots. By simply adjusting the GaN deposited thickness, it is shown that quantum dashes enable to strongly extend the emission range of GaN/Al0.5Ga0.5N nanostructures from the violet-blue (?400-470 nm) to the green-orange range (?500-600 nm)

263

Monolithic integration of InGaN segments emitting in the blue, green, and red spectral range in single ordered nanocolumns  

Energy Technology Data Exchange (ETDEWEB)

This work reports on the selective area growth by plasma-assisted molecular beam epitaxy and characterization of InGaN/GaN nanocolumnar heterostructures. The optimization of the In/Ga and total III/V ratios, as well as the growth temperature, provides control on the emission wavelength, either in the blue, green, or red spectral range. An adequate structure tailoring and monolithic integration in a single nanocolumnar heterostructure of three InGaN portions emitting in the red-green-blue colors lead to white light emission.

Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.; Calleja, E. [ISOM and Dept. Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Kong, X.; Trampert, A. [Paul-Drude-Institut fuer Festkoeperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2013-05-06

264

Dielectric Function of Undoped and Doped Poly2-methoxy-5-(3 `,7 `-dimethyloctyloxy)-1,4-phenylene-vinylene] by Ellipsometry in a Wide Spectral Range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ellipsometric measurements in a wide spectral range (from 0.05 to 6.5 eV) have been carried out on the organic semiconducting polymer, poly2-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 b...

Gasiorowski, Jacek; Hingerl, Kurt; Menon, Reghu; Plach, Thomas; Neugebauer, Helmut; Wiesauer, Karin; Yumusak, Cigdem; Sariciftci, Niyazi S.

2013-01-01

265

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.

266

Diode-pumped rare-earth doped solid-state lasers emitting in the infrared spectral range 1 um and 1.5 um  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work is devoted to the study of diode-pumped rare-earth doped solid-state lasers emitting in the infrared spectral range: at 1 ?m for high-power laser and ultra-short pulses and at 1,5 ?m in the eye-safe domain. The first part of this work describes the study of two kinds of defects occurring in Yb:CALGO crystals: diffusing centres and colour centres. The non-stoechiometric compositions and the growth parameters we investigated do not eliminate the diffusing centers, whereas a solid so...

Jaffres, Anael

2013-01-01

267

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

268

Bessy SX/700: A monochromator system covering the spectral range 3 eV? h???700 eV  

Science.gov (United States)

A concept of a highly flexible synchrotron-radiation monochromator-system combining plane grating and Wadsworth optics is described. It is designed to cover the energy range 3 eV$?h?? 7?00 eV with fixed exit beam and excellent supression of higher orders.

Petersen, H.; Baumgärtel, H.

1980-05-01

269

Study of wave chaos in a randomly-inhomogeneous oceanic acoustic waveguide: spectral analysis of the finite-range evolution operator  

CERN Document Server

The proplem of sound propagation in an oceanic waveguide is considered. Scattering on random inhomogeneity of the waveguide leads to wave chaos. Chaos reveals itself in spectral properties of the finite-range evolution operator (FREO). FREO describes transformation of a wavefield in course of propagation along a finite segment of a waveguide. We study transition to chaos by tracking variations in spectral statistics with increasing length of the segment. Analysis of the FREO is accompanied with ray calculations using the one-step Poincar\\'e map which is the classical counterpart of the FREO. Underwater sound channel in the Sea of Japan is taken for an example. Several methods of spectral analysis are utilized. In particular, we approximate level spacing statistics by means of the Berry-Robnik and Brody distributions, explore the spectrum using the procedure elaborated by A. Relano with coworkers (Relano et al, Phys. Rev. Lett., 2002; Relano, Phys. Rev. Lett., 2008), and analyze modal expansions of the eigenfu...

Makarov, D V; Uleysky, M Yu; Petrov, P S

2012-01-01

270

A new method to extract gas concentrations in the ultraviolet and visible wavelength ranges, based on differential optical absorption technique and Fourier transform  

International Nuclear Information System (INIS)

By combining differential optical absorption technique with Fourier transformation we obtain a measuring method exhibiting high sensitivity, good accuracy and good robustness against wavelength displacements in the spectrum obtained. The method also separates different gases in the absorption spectrum from each other in an effective way. The above mentioned features make this method attractive. The ability to separate gases is especially rewarding; it means that we need not know which gases are present when we start to measure. The only prerequisite is that the gases involved absorb in the wavelength range that is to be measured. The method appears to be well suited for the detection of atmospheric pollutions

271

Regularities of color and brightness variations of R Coronae Borealis-type variable stars during the active state according to observational data in the visible range  

International Nuclear Information System (INIS)

Color and brightness variations of RCrB star during three brightness minima with different depth, that is: 1982, 1983-1984 and 1985 - are considered. Variations of color indices are shown to depend on minimum depth: color indices decreases in minimal brightness phase during deep minimum, while in 1982 minimum they increase as compared to brightness maximum of variable. Occurrence of additional radiation during brightness decrease the intensity of which is maximal one in shortwave range represents common feature for three minima of RCrB star. It is stressed, that high amplitude brightness pulsations at reduced brightness of these stars may be considered as brightness secondary minima. On the basis of photoelectric observations it is assumed, that distortions of brightness monotonous variation for RCrB type stars in weakened state (flanges, abrupt variations of brightness reduction velocity) results from overlap of brightness secondary weakenings on brightness curves during minima

272

Simulation of laser propagation through a three-layer human skin model in the spectral range from 1000 to 1900 nm.  

Science.gov (United States)

For understanding the mechanisms of low-level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. We present a three-dimensional, multilayer reduced-variance Monte Carlo simulation tool for studying light penetration and absorption in human skin. Local profiles of light penetration and volumetric absorption were calculated for uniform as well as Gaussian profile beams with different spreads over the spectral range from 1000 to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as achieve large penetration depths for treating deep tissues, without causing skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could increase as much as three times for otherwise similar lasers. We expect that this tool along with the results presented will aid researchers in selecting wavelength and laser power in LLLT. PMID:25003752

Nasouri, Babak; Murphy, Thomas E; Berberoglu, Halil

2014-07-01

273

A simple analysis method for measuring in real-time power spectral densities and coherence functions in a large frequency range  

International Nuclear Information System (INIS)

This paper describes a real-time method which allows the measurement of auto and cross power spectral densities in a large frequency range with almost constant relative frequency resolution. Based on a normal digital frequency analysis the resolution at low frequencies can be increased to any extend without additional electronic equipment. The long time signals needed for the low frequencies are won from the high frequency data by a digital low pass filter. Due to this decimation of the time series only moderate storage region is needed allowing the use of a small digital computer for on-line application. The method is suitable to monitor the spectra in a wide frequency range without time delay. (orig.)

274

Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range  

Science.gov (United States)

A method is proposed for the optimization of structural parameters of GaN/AlGaN quantum wells and Bragg-confined structures, with respect to peak intersubband absorption from the ground to the first excited electronic state in the mid and near infrared spectral range. It is based on the application of the Genetic Algorithm and delivers globally optimal structures with a preset number of embedded layers. Simple rectangular quantum well profile is investigated for the maximal Stark effect and applications to tunable mid-infrared photodetectors. In case of Bragg-confined structures, an above the barrier bound state is used to extend the range of transition energies above the values available in conventional quantum wells. The effects of band nonparabolicity are taken into account.

Radosavljevi?, Ana; Radovanovi?, Jelena; Milanovi?, Vitomir

2014-03-01

275

Modification of modulated plasma plumes for the quasi-phase-matching of high-order harmonics in different spectral ranges  

Science.gov (United States)

We demonstrate the technique allowing the fine tuning of the distance between the laser-produced plasma plumes on the surfaces of different materials, as well as the variation of the sizes of these plumes. The modification of plasma formations is based on the tilting of the multi-slit mask placed between the heating laser beam and target surface, as well as the positioning of this mask in the telescope placed on the path of heating radiation. The modulated plasma plumes with the sizes of single plume ranging between 0.1 and 1 mm were produced on the manganese and silver targets. Modification of the geometrical parameters of plasma plumes proved to be useful for the fine tuning of the quasi-phase-matched high-order harmonics generated in such structures during propagation of the ultrashort laser pulses. We show the enhancement of some groups of harmonics along the plateau range and the tuning of maximally enhanced harmonic by variable modulation of the plasma.

Ganeev, R. A.; Boltaev, G. S.; Sobirov, B.; Reyimbaev, S.; Sherniyozov, H.; Usmanov, T.; Suzuki, M.; Yoneya, S.; Kuroda, H.

2015-01-01

276

Polylogarithmic representation of radiative and thermodynamic properties of thermal radiation in a given spectral range: I. Blackbody radiation  

CERN Document Server

Using polylogarithm functions the exact analytical expressions for the radiative and thermodynamic properties of blackbody radiation, such as the Wien displacement law, Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, and pressure in the finite range of frequencies are constructed. The obtained expressions allow us to tabulate these functions in various finite frequency bands at different temperatures for practical applications. As an example, the radiative and thermodynamic functions using experimental data for the monopole spectrum of the Cosmic Microwave Background (CMB) radiation measured by the COBE FIRAS instrument in the 60 - 600 GHz frequency interval at the temperature T = 2.725 K are calculated. The expressions obtained for the radiative and thermodynamic functions can be easily presented in wavelength and wavenumber domains.

Fisenko, Anatoliy I

2014-01-01

277

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

278

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

279

Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light  

International Nuclear Information System (INIS)

The specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral dependence of the effective optical density of skin in the wavelength range from 650 to 700nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470nm, which correspond to the spectral ranges of maximum and minimum water absorption. (optical technologies in biophysics and medicine)

280

Radiation damage resistance of AlGaN detectors for applications in the extreme-ultraviolet spectral range  

International Nuclear Information System (INIS)

We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky-photodiode-based detectors. AlGaN layers were grown using metal-organic chemical vapor deposition (MOCVD) on Si(111) wafers. The diodes were characterized at a wavelength of 13.5 nm using a table-top extreme-ultraviolet (EUV) radiation source, consisting of a laser-produced xenon plasma and a Schwarzschild objective. The responsivity of the diodes was tested between EUV energies ranging from 320 nJ down to several picojoules. For low fluences, a linear responsivity of 7.14 mAs/J could be determined. Saturation starts at approximately 1 nJ, merging into a linear response of 0.113 mAs/J, which could be attributed to the photoeffect on the Au electrodes on top of the diode. Furthermore, degradation tests were performed up to an absolute dose of 3.3x1019 photons/cm2. AlGaN photodiodes were compared to commercially available silicon-based photodetectors. For AlGaN diodes, responsivity does not change even for the highest EUV dose, whereas the response of the Si diode decreases linearly to ?93% after 2x1019 photons/cm2.

 
 
 
 
281

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.)

282

Low temperature spectral studies of Mn3+-bearing andalusite and epidote type minerals in the range 30000 5000 cm-1  

Science.gov (United States)

Polarized absorption spectra of natural piemontite (Ca1.802Mn{0.178/2+}Mg0.025) (Mn{0.829/3+}Fe{0.346/3+}Al1.825) [(Si2.992Al0.008) O12OH], viridine (Al1.945Mn{0.033/3+}Fe{0.063/3+}Mg0.003) [O|Si0.970 O4], and kanonaite (Al1.291Mn{0.682/3+}Fe{0.019/3+}) [O|Si1.006 O4] were measured at 295 and ca. 100 K. For piemontite, lowering the temperature resulted in a sharpening of broad bands in the 10 000 25 000 cm-1 region supporting their assignment to single ion Mn3+ in M3 non-centrosymmetric sites. Alternatively, in kanonaite, temperature behaviour pointed to a slightly stronger influence of vibronic coupling on strong bands near 16 000 and 22 000 cm-1, which supported an interpretation of Mn3+ in nearly centrosymmetric M1 sites. Measurements at ca. 100 K show pronounced fine structure in the viridine spectra which is attributed to Fe3+. The ? values for Mn3+ spin-allowed bands in the three minerals lie in the range 18 to 227 [1·g-atom-1·cm-1]. For the same band and polarisation, ? values in Mn3+-bearing andalusite-type minerals viridine and kanonaite are the same, which indicates an absence of strong magnetic coupling effects between Mn3+ ions in the andalusite type structure down to ca. 100 K. In silicates, the high ? values for Mn3+ spin-allowed bands, in comparison to those obtained for Fe2+ spin-allowed bands from sites of “similar distortion”, is attributed to a higher degree of covalency in the Mn3+-O bonds compared to the Fe2+-O bonds, as a result of the higher valence state of manganese.

Smith, G.; Hålenius, U.; Langer, K.

1982-07-01

283

The Dallas winter visibility study  

Energy Technology Data Exchange (ETDEWEB)

For some years, a highly visible cloud of polluted air could be seen over the city during winter season stagnation conditions. A historical study of visual range data collected from local airports conducted by the Texas Air Control Board showed a decreasing trend in the number of good visibility days per year over the past 35 years and, that the average visibility has decreased by 50 percent since 1940. Specific data describing the haze composition or source contributions to the winter pollution haze were limited. The purpose of this study, was to determine the composition of the visible haze, and from that information, determine the relative contribution of the various air pollution sources in the Dallas area to winter visibility impairment. Two existing air quality monitoring stations were augmented with additional instrumentation for this study. 18 figs., 18 tabs.

Einfeld, W.; Dattner, S.; Zimmermann, K.

1988-09-01

284

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 Document Server

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

285

The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS): An overview of the 480 to 1902 GHz range  

CERN Document Server

Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program. This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. We obtained a spectrum of OMC-2 FIR 4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, line identification, and a broad analysis of the line profile components, excitation, and cooling. We detect 719 spectral lines from 40 species and isotopologs. The line flux is dominated by CO, H2O, and CH3OH. The line profiles ar...

Kama, M; Dominik, C; Ceccarelli, C; Fuente, A; Caux, E; Higgins, R; Tielens, A G G M; Alonso-Albi, T

2013-01-01

286

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

CERN Document Server

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

287

Influence of different spectral ranges of light and Ca2+ -channel blockers on Ca2+ and K+ levels in Phaseolus coccineus L. pulvini  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of different spectral ranges of light on the modification of transport processes in isolated parts of Phaseolus coccineus pulvini was analysed in a bath medium by determining the Ca2+ and K+ contents. After 1 h incubation of separated fragments of the extensor and flexor in solutions containing deionized water, medium, or medium with verapamil or nifedipine, the investigated material was irradiated with monochromatic light of different wavelengths. The concentration of Ca2+, K+ and the pH value were determined in the medium. The obtained results suggest the occurrence of a specific coupling between the concentration of Ca2+ and K+ dependend on the wavelength of the applied light and part of the pulvinus. Certain spectral ranges of light brought about opposite effects on ion transport in opposite parts of the pulvinus. Changes in the pH of mediums containing isolated parts of the pulvini part to different effects of blue, red, and far-red light on the activity of H+-pumps located in the motor cells. The use of verapamil and nifedipine, specific Ca2+-channel blockers, made it possible to demonstrate the significant effect of Ca2+ on the activity and functioning of K+ -channels. The two types of inhibitors decreased the influx of Ca2+ and K+ to motor cells of the pulvini, however they did not limit the efflux of ions to the medium. The obtained results suggest that Ca2+ ions take part in transduction of the light signal. It seems probable that the action of blue light is also mediated by part of the Ca2+ ions.

Jan Bia?czyk

1992-06-01

288

The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS). An overview of the 480 to 1902 GHz range  

Science.gov (United States)

Context. Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. Aims: A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program. This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. Methods: We obtained a spectrum of OMC-2 FIR 4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, line identification, and a broad analysis of the line profile components, excitation, and cooling. Results: We detect 719 spectral lines from 40 species and isotopologs. The line flux is dominated by CO, H2O, and CH3OH. The line profiles are complex and vary with species and upper level energy, but clearly contain signatures from quiescent gas, a broad component likely due to an outflow, and a foreground cloud. Conclusions: We find abundant evidence for warm, dense gas, as well as for an outflow in the field of view. Line flux represents 2% of the 7 L? luminosity detected with HIFI in the 480 to 1250 GHz range. Of the total line flux, 60% is from CO, 13% from H2O and 9% from CH3OH. A comparison with similar HIFI spectra of other sources is set to provide much new insight into star formation regions, a case in point being a difference of two orders of magnitude in the relative contribution of sulphur oxides to the line cooling of Orion KL and OMC-2 FIR 4. Appendix A is available in electronic form at http://www.aanda.org

Kama, M.; López-Sepulcre, A.; Dominik, C.; Ceccarelli, C.; Fuente, A.; Caux, E.; Higgins, R.; Tielens, A. G. G. M.; Alonso-Albi, T.

2013-08-01

289

Magnifying superlens in the visible frequency range.  

Science.gov (United States)

We demonstrate a magnifying superlens that can be integrated into a conventional far-field optical microscope. Our design is based on a multilayer photonic metamaterial consisting of alternating layers of positive and negative refractive index, as originally proposed by Narimanov and Engheta. We achieved a resolution on the order of 70 nanometers. The use of such a magnifying superlens should find numerous applications in imaging. PMID:17379804

Smolyaninov, Igor I; Hung, Yu-Ju; Davis, Christopher C

2007-03-23

290

Electromagnetic cloaking in the visible frequency range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 cl...

Smolyaninov, I. I.; Hung, Y. J.; Davis, C. C.

2007-01-01

291

Visible Human Project  

Science.gov (United States)

... Tools Media Productions Related Projects The Visible Human Project ® Overview The Visible Human Project ® is an outgrowth of the NLM's 1986 Long- ... The long-term goal of the Visible Human Project ® is to produce a system of knowledge structures ...

292

Nonlinear spectral imaging of biological tissues  

Science.gov (United States)

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 is developed. Imaging the spectral characteristics of the biological intrinsic emission reveals the structure and biochemistry of the cells and extra-cellular components. By using different methods in visualizing the spectral images, discrimination between different tissue structures is achieved without the use of any stain or fluorescent label. For instance, RGB real color spectral images of the intrinsic emission of mouse skin tissues show blue cells, green hair follicles, and purple collagen fibers. The color signature of each tissue component is directly related to its characteristic emission spectrum. The results of this study show that skin tissue nonlinear intrinsic emission is mainly due to the autofluorescence of reduced nicotinamide adenine dinucleotide (phosphate), flavins, keratin, melanin, phospholipids, elastin and collagen and nonlinear Raman scattering and second-harmonic generation in Type I collagen. In vivo time-lapse spectral imaging is implemented to study metabolic changes in epidermal cells in tissues. Optical scattering in tissues, a key factor in determining the maximum achievable imaging depth, is also investigated in this work.

Palero, J. A.

2007-07-01

293

The visible tunable filtergraph for the ATST  

Science.gov (United States)

The Kiepenheuer-Institut will develop for the Advanced Technology Solar Telescope (ATST) a narrowband tunable filter system (Visible Tunable Filter, VTF) for imaging spectroscopy and spectropolarimetry based on large-format Fabry Perot interferometers. A major challenge for the realization of this instrument is the development of large-format Fabry-Perots with a free aperture of about 250 mm. The instrument will operate in the spectral range between 500 and 900 nm with access to a host of magnetically sensitive lines. The instrument is designed to match the diffraction limit of the 4m-aperture ATST and will be able to observe processes on the sun at spatial scales of 35 km. Its multi-line capability, together with a field of view of one arc minute, and the ability to measure polarization states of the incoming light allow to probe different layers of the solar atmosphere within a couple of seconds. The instrument is capable to vary the spectral sampling, the integration time, and the temporal cadence over a wide range without changing or compromising the opto-mechanical setup. This versatility gives unique possibilities to apply different measurement schemes to a variety of science questions. The ATST is a fully funded US project, with the VTF as the only non-US contribution, and is ready to start construction at the Haleakala summit. The VTF is foreseen as one of the ATST's firstlight instruments and should become operational in 2018.

Kentischer, T. J.; Schmidt, W.; von der Lühe, O.; Sigwarth, M.; Bell, A.; Halbgewachs, C.; Fischer, A.

2012-09-01

294

Spectral emissivities at wavelengths in the range 500--653 nm, enthalpies, and heat capacities of the liquid phases of cobalt, titanium, and zirconium  

International Nuclear Information System (INIS)

A review is given of the literature data for spectral emissivities at wavelengths (?) in the range 500--653 nm, the enthalpies, and heat capacities of the liquid phases of cobalt, titanium, and zirconium. Emissivity measurements were carried out by means of electromagnetic levitation at the solid-to-liquid transition with a partial-radiation pyrometer operating at ? = 547 and 650 nm. Considering the sensitivity of the optical properties to surface impurities, investigations on the surfaces of several titanium and zirconium samples by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were performed that confirmed a nitrogen- and oxygen-free process atmosphere during the measurements. Liquid phase normal emissivities obtained were var-epsilon n,547 = 0.365 and var-epsilon n,650 = 0.331 for cobalt, var-epsilon n,547 = 0.409 and var-epsilon n,650 = 0.393 for titanium, and var-epsilon n,547 = 0.365 and var-epsilon n,650 = 0.355 for zirconium. Enthalpy measurements on the liquid metals were carried out by means of levitation-drop calorimetry in the range 1591--2159 K for cobalt, 1847--2430 K for titanium, and 2025--2897 K for zirconium. The resulting heat capacities (values in J·mol-1·K-1) obtained were 42.78 for cobalt, 43.79 for titanium, and 39.81 for zirconium

295

The benefits of visibility  

International Nuclear Information System (INIS)

The benefits of visibility improvement (or the damages with additional degradation) refer to increases (or decreases) in utility obtained in three different dimensions. The first of these is associated with the nature of the visibility change. Visual range may be improved so that features of an area become more distinct or the sky becomes clearer. Alternatively, normal features of an area may be marred, say by the site of a power plant or its plume (called plume blight). The second dimension is the location of the change: in an urban area, in a rural setting, or in a recreational area or area of particular beauty, such as the Grand Canyon. The third dimension is the type of value: use or non-use. Thus, a person who visits the Grand Canyon (or may visit it in the future) may hold use values for improving his view of the Canyon or its surroundings and may also old non-use values for improved visibility (whether for altruistic or other reasons) irrespective of present or planned visits. In all, therefore, there are 12 possible combinations of the elements in these three dimension, each of which is logically distinct from the others and which demands attention in the literature to derive willingness to pay (WTP)

296

Spectral Tagging  

International Nuclear Information System (INIS)

This research examines the feasibility of spectral tagging, which involves modifying the spectral signature of a target, e.g. by mixing an additive with the target's paint. The target is unchanged to the human eye, but the tag is revealed when viewed with a spectrometer. This project investigates a layer of security that is not obvious, and therefore easy to conceal. The result is a tagging mechanism that is difficult to counterfeit. Uniquely tagging an item is an area of need in safeguards and security and non-proliferation. The powdered forms of the minerals lapis lazuli and olivine were selected as the initial test tags due to their availability and uniqueness in the visible to near-infrared spectral region. They were mixed with paints and applied to steel. In order to verify the presence of the tags quantitatively, the data from the spectrometer was input into unmixing models and signal detection algorithms. The mixture with the best results was blue paint mixed with lapis lazuli and olivine. The tag had a 0% probability of false alarm and a 100% probability of detection. The research proved that spectral tagging is feasible, although certain tag/paint mixtures are more detectable than others

297

All-fiber frequency-doubled visible laser.  

Science.gov (United States)

All-fiber ns-pulsed visible laser at ?=521??nm is realized by frequency doubling an Yb-doped fiber laser with a periodically poled silica fiber. A 50-mW second-harmonic (SH) output power is produced that is over 6-orders of magnitude greater than previous results obtained with poled fibers in the visible spectral range. The normalized conversion efficiency of 0.3%/W is to date the largest demonstrated with poled fiber technology. Furthermore, 21% conversion efficiency is achieved for the doubling of 8-ps pulses from a neodymium-doped yttrium vanadate solid-state laser. The advances are made possible by the precision and flexibility offered by using the continuous periodic UV erasure, as opposite to photolithographic methods, for the fabrication of over 20-cm-long ?(2)-gratings for quasi-phase matched SH generation. PMID:25490505

Corbari, Costantino; Gladyshev, Alexey V; Lago, Laure; Ibsen, Morten; Hernandez, Yves; Kazansky, Peter G

2014-11-15

298

Human contrast threshold and astronomical visibility  

Science.gov (United States)

The standard visibility model in light-pollution studies is the formula of Hecht, as used e.g. by Schaefer. 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's), 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 in 1947, enabling the sky brightness at that time to be determined. The result is darker than the calculation by Garstang, implying that light pollution grew more rapidly in subsequent decades than has been supposed. The model is applied to the nebular observations of William Herschel, enabling his visual performance to be quantified. Proposals are made regarding sky quality indicators for public use.

Crumey, Andrew

2014-08-01

299

Fabrication of Multiple Heterojunctions with Tunable Visible-Light-Active Photocatalytic Reactivity in BiOBr-BiOI Full-Range Composites Based on Microstructure Modulation and Band Structures.  

Science.gov (United States)

The fabrication of multiple heterojunctions with tunable photocatalytic reactivity in full-range BiOBr-BiOI composites based on microstructure modulation and band structures is demonstrated. The multiple heterojunctions are constructed by precipitation at room temperature and characterized systematically. Photocatalytic experiments indicate that there are two types of heterostructures with distinct photocatalytic mechanisms, both of which can greatly enhance the visible-light photocatalytic performance for the decomposition of organic pollutants and generation of photocurrent. The large separation and inhibited recombination of electron-hole pairs rendered by the heterostructures are confirmed by electrochemical impedance spectra (EIS) and photoluminescence (PL). Reactive species trapping, nitroblue tetrazolium (NBT, detection agent of (•)O2(-)) transformation, and terephthalic acid photoluminescence (TA-PL) experiments verify the charge-transfer mechanism derived from the two types of heterostructures, as well as different enhancements of the photocatalytic activity. This article provides insights into heterostructure photocatalysis and describes a novel way to design and fabricate high-performance semiconductor composites. PMID:25525911

Huang, Hongwei; Han, Xu; Li, Xiaowei; Wang, Shichao; Chu, Paul K; Zhang, Yihe

2015-01-14

300

An ultra-high-vacuum double crystal monochromator Beam Line for studies in the spectral range 500-4000 eV  

International Nuclear Information System (INIS)

The design of an ultra-vacuum (UHV) compatible constant deviation double crystal monochromator installed on Beam Line III at SSRL is described. The overall concept of the beam line consists of a double-focusing toroidal X-ray mirror, the monochromator with a post-monochromator beam diagnostic station, and a PDP-11/34 computer for control and data acquisition. The X-ray mirror provides a 1:1 focus of the source onto the sample and intercepts up to 10 mrad of the horizontal X-ray beam divergence. The 10 angle of incidence eliminates radiation above approx. 4.3 keV. The UHV (1010 torr) compatible monochromator is designed to provide a spacially fixed exit beam and covers the 500-4000 eV spectral range with four in situ interchangeable pairs of crystals. The beam intensity emerging from the monochromtor is continuously monitored by measuring the total electron yield from a high transmission metal grid. The rotation and translation of the crystals is accomplished with computer controlled steppting motors. The control software allows the monochromator to be scanned as a function of energy either directly based on the equations of motions or adaptively based on a learned optimization table. (orig.)

 
 
 
 
301

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

302

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. PMID:24175008

Gasiorowski, Jacek; Hingerl, Kurt; Menon, Reghu; Plach, Thomas; Neugebauer, Helmut; Wiesauer, Karin; Yumusak, Cigdem; Sariciftci, Niyazi S

2013-10-24

303

Measurement of a free spectral range of a Fabry–Perot cavity using frequency modulation and null method under off-resonance conditions  

International Nuclear Information System (INIS)

In this paper, we discuss a method to measure the free spectral range (FSR) of a Fabry–Perot cavity (FP-cavity) using frequency modulation with one electric optical modulator (EOM) and the null method. A laser beam modulated by the EOM, to which a sine wave signal is supplied from a radio frequency (RF) oscillator, is incident on the FP-cavity. The transmitted or reflected light from the FP-cavity is observed and converted to an RF signal by a high-speed photodetector, and the RF signal is synchronously demodulated with a lock-in amplifier by referring to a cosine wave signal from the oscillator. We theoretically and experimentally demonstrate that the lock-in amplifier signal for the transmitted or reflected light becomes null with a steep slope when the modulation frequency is equal to the FSR under the condition that the carrier frequency of the laser is slightly detuned from the resonance of the FP-cavity. To reduce the measurement uncertainty for the FSR, we also discuss a selection method for laser power, a modulation index and the detuning shift of the carrier frequency, respectively

304

Visible Light Emission from Atomic Scale Patterns Fabricated by the Scanning Tunneling Microscope  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Scanning tunneling microscope (STM) induced light emission from artificial atomic scale structures comprising silicon dangling bonds on hydrogen-terminated Si(001) surfaces has been mapped spatially and analyzed spectroscopically in the visible spectral range. The light emission is based on a novel mechanism involving optical transitions between a tip state and localized states on the sample surface. The wavelength of the photons can be changed by the bias voltage of the STM. The spatial reso...

Thirstrup, C.; Sakurai, M.; Stokbro, Kurt; Aono, M.

1999-01-01

305

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...

T-c, Wu; Hung Chien-Fu; Chang Chih-Long; Tsen Shaw-Wei D; Kt, Tsen; Kiang Juliann G

2007-01-01

306

Modeling visibility for assessment.  

Energy Technology Data Exchange (ETDEWEB)

The visibility assessment scoping model (VASM), a Monte Carlo technique for simulating and assessing regional-scale impairment of visibility, is described. The input requirements of the method for each receptor are modest: geometric means and standard deviations describing the within-season distributions of daily concentration of each of the six principal particle species; matrices of interspecies partial correlations of daily concentrations; relative humidity (RH) climatology; and seasonal mean concentrations for each particle species. The lognormal distribution parameters and the correlation matrices are abstracted from past observations. For those particle species with emission precursors that are varied in the policy scenarios, the concentration means are obtained from a regional atmospheric transport model; the means of the other particle species are assumed to be statistically similar to previous observations. Seasonal distributions of haze intensity are produced from sets of short-term Monte Carlo realizations of concentrations and RH and appropriate formulae for light extinction. VASM simulations for rural sites in both the relatively hazy eastern United States and the more pristine western United States compare favorably with transmissometer observations. Application of VASM, in concert with utility SO2 emission projections and atmospheric transport modeling, indicates that the median seasonal reduction of haziness expected at Shenandoah by the year 2010, relative to 1990 conditions, will range from 1.3 deciviews in winter to 2.2 deciviews (dv) in summer. If calculated as visual range, the corresponding improvements are 14 and 24%, respectively.

Shannon, J. D.; Trexler, E. C., Jr.; Sonnenblick, R.; Environmental Research; DOE; Lumina Decision Systems, Inc.

1997-01-01

307

Developments in THz range ellipsometry  

CERN Document Server

Ellipsometry is a technique whereby the measurement of the two orthogonal polarization components of light reflected at glancing incidence allows a characterization of the optical properties of a material at a particular frequency. Importantly, it obviates the need for measurement against a standard reference sample, and so can provide reliable spectroscopic information even when surface morphology is unknown, of marginal quality and/or a reference is unavailable. Although a standard technique in the visible range, it has not been widely applied in the Terahertz (THz) spectral range despite its potential utility. This is largely because of the technical difficulties that these frequencies present. This review details recent progress in the implementation of THz range ellipsometry. We discuss a variety of configurations including various kinds of laboratory and facility based sources using both continuous wave and pulsed spectroscopic methods. We discuss the general problems encountered when trying to import t...

Neshat, M

2013-01-01

308

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) OMI operational retrieval algorithm to derive the slant column density (SCD) of water vapor using the 430-480 nm spectral region after extensive optimization. We convert from SCD to vertical column density (VCD) using the air mass factor (AMF), which is calculated using look-up tables of scattering weights and assimilated water vapor profiles. Our Level 2 product includes not only water vapor VCD but also the associated scattering weights and AMF. In the tropics, our standard water vapor product has a median SCD of 1.3 × 1023 molecules cm-2 and a median relative uncertainty of about 11%, about a factor of 2 better than that from a similar OMI algorithm that uses a narrower retrieval window. The corresponding median VCD is about 1.2 × 1023 molecules cm-2. We have examined the sensitivities of SCD and AMF to various parameters and compared our results with those from the GlobVapour product, the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Aerosol Robotic NETwork (AERONET).

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

2014-06-01

309

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

310

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

311

Differential responses to different light spectral ranges of violaxanthin de-epoxidation and accumulation of Cbr, an algal homologue of plant early light inducible proteins, in two strains of Dunaliella.  

Science.gov (United States)

Unicellular green algae of the genus Dunaliella, similar to higher plants, respond to light stress by enhanced de-epoxidation of violaxanthin and accumulation of Cbr, a protein homologous to early light inducible proteins (Elips) in plants. These proteins belong to the superfamily of chlorophyll a/b binding proteins. Two Dunaliella strains, D. bardawil and D. salina, were compared for these two responses under light in the UVA, blue, green and red spectral ranges. In D. bardawil, the two stress responses were similarly induced under UVA, blue or red light and to a lesser extent under green light. In D. salina, a similar spectral range dependence was exhibited for violaxanthin de-epoxidation. However, Cbr accumulated only under UVA or blue light but not under green or red light. A strong synergistic effect of a low dose of blue light superimposed on red light resulted in Cbr accumulation. These results reveal strain-specific differences in spectral range requirements of the two light-stress responses. In the two strains, violaxanthin de-epoxidation is triggered under photosynthetically-active spectral ranges but at least in D. salina, Cbr accumulation appears to require a specific light signal additionally to a signal(s) generated by light stress. PMID:10580288

Banet; Pick; Malkin; Zamir

1999-11-01

312

Visibility of pulsar emission: motion of the visible point  

CERN Document Server

A standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, $\\psi$, defining a trajectory on a sphere of radius $r$. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al. 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of $\\psi$. The RVM tends to underestimate the range of $\\psi$ over which emission is visible. We suggest that the geometry alone stro...

Yuen, R

2014-01-01

313

Caracterización espectral y mineralógica de los suelos del valle del río Cauca por espectroscopía visible e infrarroja (400 - 2.500 nm) / Soil spectral characterization and mineralogy of the Cauca River Valley by visible and infrared (400 - 2,500 nm) spectroscopy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish Las librerías espectrales se utilizan para identificar diferentes tipos de suelo a partir de análisis espectrales que caracterizan su composición mineralógica y química. Los objetivos del presente trabajo consistieron en determinar si existen diferencias en el perfil espectral de los suelos del vall [...] e geográfico del río Cauca a nivel de subgrupo taxonómico; y cuantificar en sus perfiles espectrales la abundancia de minerales arcillosos. Por medio de un análisis de conglomerados se seleccionaron las muestras más homogéneas de cada subgrupo taxonómico para construir el perfil espectral de cada uno de ellos. El modelo linear spectral unmixing se utilizó para determinar las concentraciones de minerales arcillosos. A nivel de subgrupo taxonómico se observaron diferencias en la magnitud de los perfiles espectrales, así como en sus longitudes de onda a los 1.400, 1.900 y 2.200 nm. El modelo utilizado permite caracterizar de manera objetiva las concentraciones de minerales arcillosos de cada suelo a partir de su perfil espectral. Abstract in english Spectral libraries are used to identify different soil types based on spectral analyses which feature their mineralogical and chemical composition. On these grounds, the objective of the present work consisted in determining whether there are any differences in the spectral profile of the soils of t [...] he geographical Cauca Valley at the taxonomic subgroup level; and to assess their spectral profiles in terms of the abundance of clay minerals. By means of cluster analysis we selected the most homogeneous samples of each taxonomic sub group to elaborate its spectral profile. Clay mineral concentrations were determined by means of a linear spectral unmixing model. Differences among taxonomic subgroups were found in both the magnitude of the spectral profiles and their wavelengths (1.400, 1.900 and 2.200 nm). Based on soil spectral profiles, the applied model can be used to objectively characterize clay mineral concentrations.

Ernesto, Bastidas-Obando; Javier A., Carbonell.

2010-08-01

314

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

315

The Shining Future of UV Spectral Synthesis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

With the coming generation of instruments and telescopes capable of spectroscopy of high redshift galaxies, the spectral synthesis technique in the rest-frame UV and Far-UV range will become one of a few number of tools remaining to study their young stellar populations in detail. The rest-frame UV lines and continuum of high redshift galaxies, observed with visible and infrared telescopes on Earth, can be used for accurate line profile fitting such as PV@1118,1128A, CIII@11...

Pellerin, Anne; Finkelstein, Steven L.

2009-01-01

316

Visible-infrared properties of controlled laboratory soils  

Science.gov (United States)

Almost all surfaces available for remote observation consist of particulate materials or soils. The distribution of mean particle sizes depend on the original material and physical and chemical processes that have acted on the surface over time. It is well known that the optical and infrared spectral properties of materials depends on the particle size. There has been little detailed study, however, of natural soils, namely particulate materials with a range of particle sizes. Current models for intimate mixing typically use an average particle size in calculations and are most successful when the particle size is constrained by known sieve fractions. Preliminary results of a study in which soils were prepared with a known composition and range of particle sizes are reported. This discussion presents the overall visible to infrared properties of these synthetic soils and evaluates the mid-infrared properties.

Pieters, C. M.; Mustard, J. F.; Pratt, S. F.; Sunshine, J. M.; Hoppin, Andrew

1993-01-01

317

Modeling visibility for assessment  

Science.gov (United States)

Thevisibility assessment scoping model (VASM), a Monte Carlo technique for simulatinga and assessing regional-scale impairment of visibility, is described. The input requirements of the method for each receptor are modest: geometric means and standard deviations describing the within-season distributions of daily concentration of each of the six principal particle species; matrices of interspecies partial correlations of daily concentrations; relative humidity (RH) climatology; and seasonal mean concentrations for each particle species. The lognormal distribution parameters and the correlation matrices are abstracted from past observations. For those particle species with emission precursors that are varied in the policy scenarios, the concentration means are obtained from a regional atmospheric transport model; the means of the other particle species are assumed to be statistically similar to previous observations. Seasonal distributions of haze intensity are produced from sets of short-term Monte Carlo realizations of concentrations and RH and appropriate formulae for light extinction. VASM simulations for rural sites in both the relatively hazy eastern United States and the more pristine western United States compare favorably with transmissometer observations. Application of VASM, in concert with utility SO 2 emission projections and atmospheric transport modeling, indicates that the median seasonal reduction of haziness expected at Shenandoah by the year 2010, relative to 1990 conditions, will range from 1.3 deciviews in winter to 2.2 deciviews (dv) in summer. If calculated as visual range, the corresponding improvements are 14 and 24%, respectively.

Shannon, Jack D.; Trexler, Edward C.; Sonnenblick, Richard

318

Integration of the Ultraviolet-Visible Spectral Clementine Data and the Gamma-Ray Lunar Prospector Data: Preliminary Results Concerning FeO, TiO2, and Th Abundances of the Lunar Surface at Global Scale  

Science.gov (United States)

The Clementine mission (CLM) produced global multispectral data that resulted in a map of FeO and Ti02 concentrations of the lunar surface. The recent Lunar Prospector (LP) mission returned the first global data for the distribution of surface abundances of key elements in lunar rocks, using a gamma-ray spectrometer (GRS) and neutron spectrometer(NS). Integrating CLM mineralogical spectral reflectance and LP chemical data is important to enhance our view of lunar crust origin and evolution, lunar volcanism, and surface processes. Iron, Ti, and Th having relatively large compositional variation over the lunar surface, as well as strong isolated peaks in the GRS spectra, information concerning the distribution and concentration of these elements has been derived from maps of corrected (cosmic ray, nonsymmetric response of the instrument) counting rates only, without converting them into absolute abundances. Maps produced contain count rates in equal-area projection averaged into 5 x 5 degrees latitude/longitude bins, from -90 to +90 degrees latitude and -180 to +180 degrees longitude. In this work, we have used the CLM global FeO and Ti02 abundances (wt%) maps converted at the LP spatial resolution (about 150 km/pixel) to produce FeO and TiO2 GRS abundance maps, through a linear regression based on the analysis of the scatter distribution of both datasets. The regression coefficients have been determined from the data taken between -60 and +60 degrees latitude to avoid uncertainties in the CLM spectral data due to nonnominal conditions of observation at high latitudes. After a critical assessment of the validity of these coefficients for every class of absolute abundance, the LP data have been transformed into absolute abundances for the whole Moon. The Th LP data have been converted into abundances (ppm) using Th concentrations in average soils from the Apollo and Luna sites given. Values of Th abundances for these samples range between 0.5 and 13 ppm. A nonlinear regression has been applied to the LP data, except for low count rate values (corresponding to Th abundances below 1.27 ppm) for which a first-order linear regression has been applied. Statistical tests demonstrate that the Lunar Prospector FeO, TiO2, and Th abundances estimates we have produced through the regressions are reliable. For the LP maps, the uncertainty of absolute FeO and Ti02 estimates is on the same order as that for CLM, i.e., 2 and 1.5 wt% respectively. For the Th, abundance estimates, the uncertainty is about 1-2 ppm. At first order, our global FeO and Ti02 abundances maps from LP are in very good agreement with those obtained from CLM. The Th abundance map is also in good agreement with a recent global Th abundance map, although concentrations have a higher range (0-20 ppm) in our case, and may be slightly overestimated. However, a more detailed comparison between CLM and LP abundance maps of FeO and Ti02 reveals regional differences. Differences between the two datasets are expected because of instrumental and observational causes (spatial resolution, depth of observation), but also because they are sensitive to different types of information (mineralogy vs. chemistry). Maps of differences in abundances between LP and CLM data have been produced for both FeO and Ti02. In relation to the precision of the LP and CLM data, we consider that differences between the two datasets exceeding 2 wt% are significant. Concerning FeO contents, differences up to 4-5 wt% are observed in the South Pole Aitken Basin, and generally at high latitude (up to 70 degrees) in the southern hemisphere, as well as in the northern border (Iridum-Gruithuisen domes region) and the southern border (Sinus Aestum) of the Imbrium Basin. Most important differences, up to 6-7 wt%, are found in Mare Serenitatis, Crisium, and Fecunditatis. Concerning Ti02, most important differences (4-5 wt%) between LP and CLM abundances are located within Mare Tranquillitatis. Differences (about 2-3 wt%) also occur in the northern border of the Imbrium Basin (Ir-Gruithuisen domes region) and in

Chevrel, S. D.; Pinet, P. C.; Barreau, G.; Daydou, Y.; Richard, G.; Maurice, S.; Feldman, W. C.

1999-01-01

319

Estimation of visibility using a visual image.  

Science.gov (United States)

Optical-based visibility measurement instruments have been widely used to quantify atmospheric light extinction for decades. The light extinction coefficient is converted to visual range using a well-known formula since visibility is defined as the longest distance at which a black object can be observed against the horizon. In this study, a camera-based visibility monitoring technique was introduced to directly estimate visual range using a visual image obtained from a camera system. It was denoted as image visual range. The visual, optical, and geographical visibility monitoring were conducted to investigate the relationship between image visual range and distance from camera installed at the monitoring site. The visibility estimation formula, which is the function of the y position of the coordinates in the visual image, was introduced. And image visual range was estimated from the visual image using the chromatic analysis. It was found that the relationship between the image visual range and the y position of the visual image was a nonlinear function. The average relative error of image visual range less than 50 km was acceptable from the results of the relationship between optical-based visual range and image visual range. It was estimated that the relative error between two variables was not only attributed to the perspective and the faint outline of the visual image in the chromatic analysis but also associated with the assumption of the uniform distribution of the light extinction by aerosol within the field of view in the optical monitoring. PMID:25647796

Kim, Kyung Won

2015-03-01

320

Normal spectral emissivity changes of tungsten at 633 nm in the range from room temperature to melting point under pulse-heating conditions  

Science.gov (United States)

The classical steady-state technique for the measurement of thermophysical properties at high temperatures suffer from many limitations (for example, chemical reaction, evaporation, loss of mechanical strength, etc. may exist). These problems may be overcome by transient techniques of sub-second durations. Pulse-heating experiments were performed on tungsten strip specimen, taking the specimen from room temperature to the melting point based on rapid resistive self-heating of the specimen. The normal spectral emissivity of the specimen was measured by integrating sphere reflectometry developed at HIT. At the same time, the radiance temperature is measured by high-speed pyrometer from 1200K to the melting point. Details of the measurement technique, measurement apparatus and of the calibration technique are described. Results of the normal spectral emissivity of tungsten at 633nm from room temperature to melting point are presented and discussed.

Li, Chengwei; Yi, Fan; Dai, Jingmin

2002-09-01

 
 
 
 
321

Scanning picosecond optical parametric source using potassium dihydrogen phosphate in the visible and near infrared  

International Nuclear Information System (INIS)

An optical parametric source using angle-tuned type II potassium dihydrogen phosphate (KDP) as the nonlinear medium and pumped with 35-ps, 355-nm pulses from an active--passive mode-locked Nd:YAG laser, is described. With a 1.35-mJ pump pulse, conversion efficiencies ranging from 1%--40% in the spectral range 450--650 and 800--1600 nm have been achieved. The ???t products can approach the transform limit, although 15--30 times transform limited is more typical. The merits of the combination of pump wavelength and phase match used here are discussed with respect to the tuning range, spectral width, and ease of operation. Automated scanning was achieved by placing the crystals on stepper-motor controlled rotation stages. A convenient, easily reproducible high peak power source rapidly tunable over much of the visible and near infrared is obtained

322

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.

323

Triggered single-photon emission in the red spectral range from optically excited InP/(Al,Ga)InP quantum dots embedded in micropillars up to 100 K  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Systematic excitation power and temperature-dependent measurements on the emission lines of single self-assembled InP/(Al0.20Ga0.80)0.51In0.49P quantum dots embedded in micropillars have been performed. The quantum dots were excited optically via a pulsed laser and their luminescence was collected using a micro-photoluminescence setup. The exciton and biexciton intensity, linewidth, and spectral position was investigated in a temperature range from ...

Bommer, Moritz; Schulz, Wolfgang-michael; Roßbach, Robert; Jetter, Michael; Michler, Peter; Thomay, Tim; Leitenstorfer, Alfred; Bratschitsch, Rudolf

2011-01-01

324

Temperature dependence of the dielectric function in the spectral range (0.5–8.5) eV of an In{sub 2}O{sub 3} thin film  

Energy Technology Data Exchange (ETDEWEB)

We present the dielectric function of a bcc-In{sub 2}O{sub 3} thin film in the wide spectral range from near-infrared to vacuum-ultraviolet and for temperatures 10?K–300?K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.

Schmidt-Grund, R., E-mail: Schmidt-Grund@physik.uni-leipzig.de; Krauß, H.; Kranert, C.; Bonholzer, M.; Grundmann, M. [Institut für Experimentelle Physik II, Universität Leipzig, Linnéstr. 5, 04103 Leipzig (Germany)

2014-09-15

325

[Research on spectral reflectance characteristics for Glycyrrhizae Radix].  

Science.gov (United States)

In order to study the spectral reflectance differences of Glycyrrhizae Radix under different growth conditions and lay the foundation for quantitative monitoring of Glycyrrhizae Radix remote sensing images, spectra of Glycyrrhiza species under different growth period and different varieties and different regions were measured by a portable spectrometer. The results showed that the reflectivity of annual G. uralensis was obviously higher than that of the two years plant in the visible light band own to the contents of crown layer chlorophyll. The reflectivity of two years G. pallidiflora was higher than that of G. uralensis in the near infrared band own to the leaf area index and the content of leaf water. The red edge spectrum of annual plant fluctuated largely than that of two years plant due to vegetation coverage and leaf area index. G. pallidiflora grew well than G. uralensis. Under different regions of the Glycyrrhiza species, spectral data analysis showed that within a certain range, the average annual precipitation and average annual evaporation were the major factors to affect the differences of Glycyrrhiza species spectral data under different regions owe to the leaf water content, the higher leaf water content, the lower spectral reflectance. The principal component analysis and continuum-removed method of the spectral data under different regions found that, within a certain range, the average annual precipitation and average annual evaporation were the major factors caused by the differences of Glycyrrhiza species spectral data under the different regions, Glycyrrhiza species spectral similarity related to the spatial distance. PMID:24946542

Li, Hui; Xie, Cai-Xiang; Li, Xiao-Jin; Wen, Mei-Jia; Jia, Guang-Lin; Shi, Ming-Hui; Guo, Bao-Lin; Jia, Xiao-Guang

2014-02-01

326

Spectral ellipsometry study in the range of electronic excitations and band structure of [(CH{sub 3}){sub 2}CHNH{sub 3}]{sub 4}Cd{sub 3}Cl{sub 10} crystals  

Energy Technology Data Exchange (ETDEWEB)

Optical dielectric functions ?(E) of the (IPA){sub 4}Cd{sub 3}Cl{sub 10} crystal were measured in the spectral range of fundamental electronic excitations 3.5–10 eV and in the temperature range of 310–400 K containing the phase transition point between the orthorhombic phases Cmce and Pbca. Measurements were performed by spectroscopic ellipsometry with using of synchrotron radiation. Electronic band structure, density of states and dielectric functions ?(E) of (IPA){sub 4}Cd{sub 3}Cl{sub 10} were calculated and analyzed on the basis of the density functional theory. Top valence and bottom conduction bands were found to be formed mainly by the cadmium–chlorine complexes of the crystals. - Highlights: ? Spectral ellipsometry in the VUV range is used for study of (IPA){sub 4}Cd{sub 3}Cl{sub 10} crystals. ? Band structure of (IPA){sub 4}Cd{sub 3}Cl{sub 10} crystal has been calculated for the first time. ? Origin of the lowest energy spectral band of dielectric function is determined. ? Width of temperature dependency of dielectric permittivity is large (near 50 K). ? Maximum of temperature dependency of dielectric permittivity is small (near 2%)

Andriyevsky, B., E-mail: bohdan.andriyevskyy@tu.koszalin.pl [Faculty of Electronics and Computer Sciences, Koszalin University of Technology, ?niadeckich Str. 2, PL-75-453 Koszalin (Poland); Dorywalski, K.; Jaskólski, M. [Faculty of Electronics and Computer Sciences, Koszalin University of Technology, ?niadeckich Str. 2, PL-75-453 Koszalin (Poland); Czapla, Z. [Department of Physics, Opole University of Technology, Ozimska Str. 75, PL-45-271 Opole (Poland); Institute of Experimental Physics, Wroclaw University, M. Born Sq. 9, PL-50-204 Wroclaw (Poland); Patryn, A. [Faculty of Electronics and Computer Sciences, Koszalin University of Technology, ?niadeckich Str. 2, PL-75-453 Koszalin (Poland); Esser, N. [Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., Department Berlin, Albert-Einstein-Str.9, 12489 Berlin (Germany)

2013-05-15

327

The ultraviolet spectral albedo of planet earth  

Science.gov (United States)

The solar backscattered ultraviolet spectral radiometer on the Nimbus 7 satellite provides a unique set of radiation measurements which allows an evaluation of the spectral albedo of the earth and its atmosphere in the wavelength range 300 to 340 nm. Near 340 nm, the derived spectral albedo expressed as a function of latitude and month exceeds that in the visible part of the spectrum, with values near 45 percent existing equatorward of 30 deg and an increase to 60-80 percent toward the poles. At middle to high latitudes, the monthly mean spectral albedo exceeds the contribution from Rayleigh scattering alone by factors of 1.4 to 2.2. At wavelengths from 300 to 310 nm, where absorption by stratospheric ozone is significant, the daylight averaged spectral albedos receive negligible contribution from scattering by tropospheric clouds, yet the derived values exceed those predicted for Rayleigh scattering from a clean stratosphere. These observations are consistent with the presence of an atmospheric scattering layer, distinct from cloudiness, located at an altitude above the tropopause.

Frederick, John E.; Serafino, George N.

1987-01-01

328

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

329

COLLI - a Monte Carlo program for calculating neutron spectral fluences in the energy range 10 keV to 20 MeV - description and application  

International Nuclear Information System (INIS)

The program described can be applied to calculating the transport of neutrons through an arrangement of bodies that can be extensively varied in geometry and materials. The information obtainable by this program includes data on the spectral fluence of scattered neutrons for a set of up to 10 random measuring points. Fortran IV is the programming language. For the calculation of neutron interactions, point cross sections of the ENDF data library are used, either in the original version or in a condensed form. The data are processed for the following elements: Hydrogen, carbon, nitrogen, oxygen, aluminum, silicon, calcium, iron, copper, tungsten, and lead. (orig./HP)

330

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

331

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

332

Chinese visible human project.  

Science.gov (United States)

Research on the digital visible human is of great significance and has considerable application value. The US visible human project created the first digital image dataset of a complete human (one male and one female) in 1995. To promote worldwide application-oriented visible human research, additional visible human datasets, representative of different populations of the world, are needed. The Chinese visible human (CVH) male (created in October 2002) and female (created in February 2003) Project achieved greater integrity of images, better blood vessel identification, and were free of organic disease. The most noteworthy technical advance of the Chinese visible human project (CVHP) was the construction of a low temperature laboratory, which prevented loss of small structures (including teeth, nasal conchae, and articular cartilage) from the milling surface. Thus, better integrity of images was achieved. To date, we have acquired five CVH datasets and volume rendered them for visualization on a PC. 3D reconstruction of some organs and structures has been completed and work to segment a complete dataset is under way. Although there is still a long way to go to make the visible human meet the application-oriented needs in various fields, progress is being made toward acquiring new datasets, performing segmentation, and setting up a platform of computer-assisted medicine. Here, we review the history and highlights of the CVHP and foresee its future development as well. PMID:16506203

Zhang, Shao-Xiang; Heng, Pheng-Ann; Liu, Zheng-Jin

2006-04-01

333

Analysis of the influence of the plasma thermodynamic regime in the spectrally resolved and mean radiative opacity calculations of carbon plasmas in a wide range of density and temperature  

International Nuclear Information System (INIS)

In this work the spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated for a wide range of plasma conditions which cover situations where corona, local thermodynamic and non-local thermodynamic equilibrium regimes are found. An analysis of the influence of the thermodynamic regime on these magnitudes is also carried out by means of comparisons of the results obtained from collisional-radiative, corona or Saha–Boltzmann equations. All the calculations presented in this work were performed using ABAKO/RAPCAL code. -- Highlights: ? Spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated. ? Corona, local thermodynamic and non-local thermodynamic equilibrium regimes are analyzed. ? Simulations performed using the computational package ABAKO/RAPCAL. ? A criterion for the establishment of the thermodynamic regime is proposed.

334

Spectral filtering for plant production  

Science.gov (United States)

Both plants and animals have one general commonality in their perception of light. They both are sensitive primarily to the 400 to 700 nm wavelength portion of the electromagnetic spectrum. This is referred to as the visible spectrum for animals and as the photosynthetically active radiation (PAR) spectrum for plants. Within this portion of the spectrum, animals perceive colors. Relatively recently it has been learned that within this same spectral range plants also demonstrate varying responses at different wavelengths, somewhat analogous to the definition of various colors at specific wavelengths. Although invisible to the human eye, portions of the electromagnetic spectrum on either side of the visible range are relatively inactive photosynthetically but have been found to influence important biological functions. These portions include the ultraviolet (UV approximately equal to 280-400 nm) and the far-red (FR approximately equal to 700-800 nm). The basic photoreceptor of plants for photosynthesis is chlorophyll. It serves to capture radiant energy which combined with carbon dioxide and water produces oxygen and assimulated carbon, used for the synthesis of cell wall polysaccarides, proteins, membrane lipids and other cellular constituents. The energy and carbon building blocks of photosynthesis sustain growth of plants. On the other hand, however, there are other photoreceptors, or pigments, that function as signal transducers to provide information that controls many physiological and morphological responses of how a plant grows. Known photomorphogenic receptors include phytochrome (the red/far-red sensor in the narrow bands of 655-665 nm and 725-735 nm ranges, respectively) and 'cryptochrome' (the hypothetical UV-B sensor in the 280-320 nm range). Since the USDA team of W. L. Butler, S. B. Hendricks, H. A. Borthwick, H. A. Siegleman and K. Norris in Beltsville, MD detected by spectroscopy, extracted and identified phytochrome as a protein in the 1950's, many other investigators have found evidence of its control functions in plants. Considerably less, however, is known about the yet non-isolated cryptochrome. The information-transferring roles of photoreceptors in plants at specific spectral ranges quite naturally stimulated plant scientists and engineers to consider physically manipulating light to achieve desired physiological and morphological characteristics. One way to manipulate light is to filter it through materials that selectively transmit portions of the sun's spectrum in and near the PAR range.

Young, Roy E.; Mcmahon, Margaret J.; Rajapakse, Nihal C.; Decoteau, Dennis R.

1994-01-01

335

Disk-resolved spectral reflectance properties of Phobos from 0.3-3.2 micron: Preliminary integrated results from Phobos 2  

Science.gov (United States)

The Phobos 2 mission provided multispectral observations of Phobos over a large wavelength range and with relatively high spectral resolution. Here, researchers integrate results from three multispectral detectors by determining the ultraviolet-visible near infrared spectral properties of color and brightness features recognized in VSK TV images. Researchers present evidence that there are two fundamental spectral units within the region of overlapping coverage by the detectors. They describe the units' spectral and reflectance properties and discuss the implications of these results for the composition of Phobos.

Murchie, Scott L.; Erard, Stephane; Langevin, Yves; Britt, Daniel T.; Bibring, Jean-Pierre; Mustard, John F.; Head, James W.; Pieters, Carle M.

1991-01-01

336

Human Contrast Threshold and Astronomical Visibility  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 p...

Crumey, Andrew

2014-01-01

337

AEROSOL CHARACTERISTICS AND VISIBILITY  

Science.gov (United States)

This report summarizes progress in measuring the optical properties of aerosols and in relating aerosol characteristics to visibility reduction made in the author's laboratory during the period 1965-1971. An instrument, the integrating nephelometer, which measures the scattering ...

338

Visible Embryo: 16 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Dr. R B Armstrong (Washington State University)

2006-10-31

339

Visible Embryo: 36 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

340

Visible Embryo: 18 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

 
 
 
 
341

Visible Embryo: birth  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

342

Visible Embryo: 24 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

343

Visible Embryo: 22 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

344

Visible Embryo: 34 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

345

Tree-Visibility Orders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we introduce a new class of partially ordered sets, called tree-visibility orders, extending the class of interval orders in a fashion similar to the extension of interval graphs to chordal graphs. This class contains interval orders, duals of generalized interval orders and height one orders. We give a characterization of tree-visibility orders by an infinite family of minimal forbidden suborders and present an efficient recognition algorithm.

Kratsch, Dieter; Rampon, Jean-xavier

1995-01-01

346

Strain-induced tuning of the emission wavelength of high quality GaAs/AlGaAs quantum dots in the spectral range of the 87Rb D2 lines  

Science.gov (United States)

Reversible biaxial strains are used for tuning the emission wavelengths of high quality GaAs/AlGaAs quantum dots (QDs) in the spectral range of the 87Rb D2 lines. The strain is transferred by integrating free standing (Al)GaAs nanomembranes, containing QDs, onto piezoelectric actuators. Narrow excitonic emission lines as sharp as 25 ?eV are shown, and a tuning range larger than 5 nm is demonstrated. This range corresponds to an induced anisotropic biaxial strain of the order of 0.15%, as evaluated from the shift in the emission of the GaAs from the nanomembranes. The presented on-chip technology is potentially interesting for future quantum memories based on hybrid semiconductor-atomic interfaces.

Kumar, S.; Trotta, R.; Zallo, E.; Plumhof, J. D.; Atkinson, P.; Rastelli, A.; Schmidt, O. G.

2011-10-01

347

Microfluidics integration of aperiodic plasmonic arrays for spatial-spectral optical detection.  

Science.gov (United States)

We demonstrate successful integration of aperiodic arrays of metal nanoparticles with microfluidics technology for optical sensing using the spectral-colorimetric responses of nanostructured arrays to refractive index variations. Different aperiodic arrays of gold (Au) nanoparticles with varying interparticle separations and Fourier spectral properties are fabricated using Electron Beam Lithography (EBL) and integrated with polydimethylsiloxane (PDMS) microfluidics structures by soft-lithographic micro-imprint techniques. The spectral shifts of scattering spectra and the distinctive modifications of structural color patterns induced by refractive index variations were simultaneously measured inside microfluidic flow cells by dark-field spectroscopy and image correlation analysis in the visible spectral range. The integration of engineered aperiodic arrays of Au nanoparticles with microfluidics devices provides a novel sensing platform with multiplexed spatial-spectral responses for opto-fluidics applications and lab-on-a-chip optical biosensing. PMID:23482027

Lee, Sylvanus Y; Walsh, Gary F; Dal Negro, Luca

2013-02-25

348

The Estimation of Snowfall Rate Using Visibility.  

Science.gov (United States)

The relationship between liquid equivalent snowfall rate and visibility is investigated using data collected at the National Center for Atmospheric Research Marshall Snowfall Test Site during two winter field seasons and using theoretical relationships. The observational data include simultaneous liquid equivalent snowfall rate, crystal types, and both automated and manual visibility measurements. Theoretical relationships between liquid equivalent snowfall rate and visibility are derived for 27 crystal types, and for `dry' and `wet' aggregated snowflakes. Both the observations and theory show that the relationship between liquid equivalent snowfall rate and visibility depends on the crystal type, the degree of riming, the degree of aggregation, and the degree of wetness of the crystals, leading to a large variation in the relationship between visibility and snowfall rate. Typical variations in visibility for a given liquid equivalent snowfall rate ranged from a factor of 3 to a factor of 10, depending on the storm. This relationship is shown to have a wide degree of scatter from storm to storm and also during a given storm. The main cause for this scatter is the large variation in cross-sectional area to mass ratio and terminal velocity for natural snow particles.It also is shown that the visibility at night can be over a factor of 2 greater than the visibility during the day for the same atmospheric extinction coefficient. Since snowfall intensity is defined by the U.S. National Weather Service using visibility, this day/night difference in visibility results in a change in snowfall intensity category caused by only whether it is day or night. For instance, a moderate snowfall intensity during the day will change to a light snowfall intensity at night, and a heavy snowfall intensity during the day will change to a moderate snowfall intensity at night, for the same atmospheric extinction coefficient.Thus, the standard relationship between snowfall intensity and visibility used by many national weather services (1/4 mile or less visibility corresponds to heavy snowfall intensity, between 5/16 and 5/8 mile corresponds to moderate intensity, and greater than 5/8 mile corresponds to light intensity) does not always provide the correct indication of actual liquid equivalent snowfall rate because of the variations in snow type and the differences in the nature of visibility targets during day and night. This false indication may have been a factor in previous ground-deicing accidents in which light snow intensity was reported based on visibility, when in fact the actual measured liquid equivalent snowfall rate was moderate to heavy.

Rasmussen, Roy M.; Vivekanandan, Jothiram; Cole, Jeffrey; Myers, Barry; Masters, Charles

1999-10-01

349

Generation of high-power femtosecond supercontinua in the near-IR spectral range using broadband parametric frequency conversion in LBO and DCDA crystals pumped at ? = 620 nm  

Science.gov (United States)

The pump wavelength of parametric amplifiers based on CLBO, DCDA and LBO crystals and pumped by the second harmonic of a femtosecond Cr : forsterite laser (620 nm) is close to optimal for broadband amplification because of the proximity of group velocities of interacting pulses. Injection of a broadband continuum into the range of the signal-wave gain in LBO and DCDA parametric amplifiers, pumped at ? = 620 nm, leads to generation of broadband femtosecond pulses with a spectrum ranging from 1050 to 1600 nm and peak powers up to 20 MW.

Podshivalov, A. A.; Potemkin, F. V.; Sidorov-Biryukov, D. A.

2014-09-01

350

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 resultsprocessor 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

351

BESSY SX/700: A monochromator system covering the spectral range 3 eV < approx. h/2?? < 700 eV  

International Nuclear Information System (INIS)

A concept of a highly flexible synchrotron-radiation monochromator-system combining plane grating and Wadsworth optics is described. It is designed to cover the energy range 3 eV < approx. h/2?? < 700 eV with fixed exit beam and excellent suppression of higher orders. (orig.)

352

Multilayer structure for a spectral imaging sensor.  

Science.gov (United States)

We investigate the possibility of recovering spectral information using a multilayer structure realized through microelectronics technologies and compatible with a matrix arrangement. The structure is made of photoabsorbing layers, acting as local photodetectors, alternating with transparent layers. The whole structure lies on a reflective surface. A stationary wave containing the spectral information of the source is generated within the structure. We determine the intensity of the stationary wave at any position, taking into account absorption and multireflections at each transition as well as the signal detected by the photoabsorbing layers. The model forecasting the detected signal is then validated using p-i-n diodes of different thicknesses made of hydrogenated amorphous silicon (a-Si:H) encompassed between indium tin oxide (ITO) electrodes. The detected signal depends on the wavelength of the incident light, the thickness of the detecting layer, and the latter's position within the structure. A specific spectral response can then be associated to each photoabsorbing layer. We show how spectral information can be retrieved from this kind of structure in the visible spectrum range. PMID:19151837

Parrein, Pascale; Moussy, Norbert; Poupinet, Ludovic; Gidon, Pierre

2009-01-20

353

Graphite oxide–TiO2 nanocomposite and its efficient visible-light-driven photocatalytic hydrogen production  

International Nuclear Information System (INIS)

Highlights: ? GO–TiO2 nanocomposites were fabricated by a facile hydrothermal process. ? The implanted GO expand the spectral responsive range of TiO2 to visible light for H2 production. ? As a result, stable photocatalytic H2 production efficiency were obtained over GO–TiO2. - Abstract: Graphite oxide (GO)–TiO2 nanocomposite was prepared by a facile hydrothermal process and was characterized by X-ray powder diffraction, Transmission electron microscopy, UV–vis diffusion reflectance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. TiO2 particles with average particle size of ?20 nm in the nanocomposites are attached to the surface of GO and/or intercalated into the interlayer of GO. The obtained GO–TiO2 was used as photocatalyst for H2 production under visible light (? ? 420 nm) irradiation, and an optimal photocatalytic H2 production rate of 380 ?mol h?1 can be obtained over 2 wt% GO–TiO2. The encouraging results presented here demonstrate that GO can serve as visible-light-driven photocatalyst and photosensitizer to expand the photoresponsive range of TiO2 to visible light for H2 production. The possible mechanism for H2 production was proposed for better understanding the visible-light-driven photocatalytic behaviour of the GO–TiO2 nanocomposub> nanocomposite.

354

USGS Digital Spectral Library splib06a  

Science.gov (United States)

Introduction We have assembled a digital reflectance spectral library that covers the wavelength range from the ultraviolet to far infrared along with sample documentation. The library includes samples of minerals, rocks, soils, physically constructed as well as mathematically computed mixtures, plants, vegetation communities, microorganisms, and man-made materials. The samples and spectra collected were assembled for the purpose of using spectral features for the remote detection of these and similar materials. Analysis of spectroscopic data from laboratory, aircraft, and spacecraft instrumentation requires a knowledge base. The spectral library discussed here forms a knowledge base for the spectroscopy of minerals and related materials of importance to a variety of research programs being conducted at the U.S. Geological Survey. Much of this library grew out of the need for spectra to support imaging spectroscopy studies of the Earth and planets. Imaging spectrometers, such as the National Aeronautics and Space Administration (NASA) Airborne Visible/Infra Red Imaging Spectrometer (AVIRIS) or the NASA Cassini Visual and Infrared Mapping Spectrometer (VIMS) which is currently orbiting Saturn, have narrow bandwidths in many contiguous spectral channels that permit accurate definition of absorption features in spectra from a variety of materials. Identification of materials from such data requires a comprehensive spectral library of minerals, vegetation, man-made materials, and other subjects in the scene. Our research involves the use of the spectral library to identify the components in a spectrum of an unknown. Therefore, the quality of the library must be very good. However, the quality required in a spectral library to successfully perform an investigation depends on the scientific questions to be answered and the type of algorithms to be used. For example, to map a mineral using imaging spectroscopy and the mapping algorithm of Clark and others (1990a, 2003b), one simply needs a diagnostic absorption band. The mapping system uses continuum-removed reference spectral features fitted to features in observed spectra. Spectral features for such algorithms can be obtained from a spectrum of a sample containing large amounts of contaminants, including those that add other spectral features, as long as the shape of the diagnostic feature of interest is not modified. If, however, the data are needed for radiative transfer models to derive mineral abundances from reflectance spectra, then completely uncontaminated spectra are required. This library contains spectra that span a range of quality, with purity indicators to flag spectra for (or against) particular uses. Acquiring spectral measurements and performing sample characterizations for this library has taken about 15 person-years of effort. Software to manage the library and provide scientific analysis capability is provided (Clark, 1980, 1993). A personal computer (PC) reader for the library is also available (Livo and others, 1993). The program reads specpr binary files (Clark, 1980, 1993) and plots spectra. Another program that reads the specpr format is written in IDL (Kokaly, 2005). In our view, an ideal spectral library consists of samples covering a very wide range of materials, has large wavelength range with very high precision, and has enough sample analyses and documentation to establish the quality of the spectra. Time and available resources limit what can be achieved. Ideally, for each mineral, the sample analysis would include X-ray diffraction (XRD), electron microprobe (EM) or X-ray fluorescence (XRF), and petrographic microscopic analyses. For some minerals, such as iron oxides, additional analyses such as Mossbauer would be helpful. We have found that to make the basic spectral measurements, provide XRD, EM or XRF analyses, and microscopic analyses, document the results, and complete an entry of one spectral library sample, all takes about

Clark, Roger N.; Swayze, Gregg A.; Wise, Richard A.; Livo, K. Eric; Hoefen, Todd M.; Kokaly, Raymond F.; Sutley, Stephen J.

2007-01-01

355

[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

356

Laboratory investigation of visible shuttle glow mechanisms  

Science.gov (United States)

Laboratory experiments designed to uncover mechanistic information about the spectral and spatial characteristics of shuttle glow were conducted. The luminescence was created when a pulse of O atoms traveling at orbital velocities was directed toward NO molecules previously adsorbed to aluminum, nickel, and Z306 Chemglaz (a common baffle black) coated surfaces held at various temperatures. Spectral and spatial measurements were made using a CCD imaging spectrometer. Corroborative spectral information was recorded in separate measurements using a scanning monochromator and gated photomultiplier arrangement. The e-folding distance at several temperatures was calculated from images of the surface glow using the photometrics image processing capability of the imaging spectrometer. The e-folding distance was not altered as a function of incoming O beam velocity. The results are presented and the observations provide direct evidence that the visible shuttle glow results from recombination of oxygen atoms and surface bound NO.

Leone, A.; Swenson, G. R.; Caledonia, G. E.; Holtzclaw, K. W.

1991-01-01

357

Development of hybrid CMOS visible focal plane arrays at Rockwell  

Science.gov (United States)

Silicon-based hybrid CMOS visible focal plane array (FPA) technology is emerging as a strong contender for scientific applications that require broad spectral response with low noise, highly integrated functionality and radiation hardness. CMOS-based FPAs offer many advantages in high speed, low-noise detection and signal processing. As a high performance alternative to advanced CCD imaging arrays, the hybrid design enables independent optimization of the silicon detector array and silicon readout electronics. Multiplexer commonality with the instrument's IR channels is another attractive feature for integrators of sensor sites such as for hyperspectral spectrometers. In this paper, the technical merits of Rockwell's CMOS-based hybrid visible FPAs are described including key detector performance aspects, interface electronics requirements, radiation hardness and concomitant implications for diverse imaging applications. At this time we have developed 640 X 480 and 1024 X 1024 hybrid imagers with approximately equals 100% optical fill factor, high broadband QE spanning ultraviolet (UV) through near infrared (NIR), wide dynamic range, and high pixel operability. Dark current of approximately equals 0.01e-/sec and read noise approximately equals 6e- have been measured on one prototype 1024 X 1024 FPA that uses Hawaii readout integrated circuit (ROIC). Initial radiation data indicate a total ionization dose (TID) tolerance greater than 35 Krad for our standard CMOS process.

Bai, Yibin; Montroy, John T.; Blackwell, John D.; Farris, Mark C.; Kozlowski, Lester J.; Vural, Kadri

2000-07-01

358

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

359

Lanthanide tri-fluorides: a survey of the optical, mechanical and structural properties of thin films with emphasis of their use in the DUV-VUV-spectral range  

Science.gov (United States)

The present candidates for low loss dielectric optical coatings at VUV excimer laser wavelengths are fluorides. Within this group, only one material - namely lanthanum fluoride - is used almost exclusively as high index film material. In search of additional high index film materials for use in VUV we investigated a broader spectrum of lanthanide tri-fluorides since little is known about their properties and the advantages or disadvantages with regards of their use in DUV- and VUV - optical stacks. Fluorides of lanthanum, neodymium, samarium, gadolinium, ytterbium and also yttrium were evaporated thermally. Precision VUV-measurement were initiated to give an overview of the ranges of UV-transparency up to the absorption edges and to determine the optical indices of these coating materials. Supplementary, also stress measurements, atomic force microscopy and XRD measurements were performed to scrutinize the properties of the films.

Uhlig, H.; Thielsch, R.; Heber, J.; Kaiser, N.

2005-09-01

360

Visible Embryo: 14 weeks  

Science.gov (United States)

a comprehensive resource of information on human development at 14 weeks of gestation (80-90mm, 25g), designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-10-31

 
 
 
 
361

Visible Embryo: 28 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-11-01

362

Visible Embryo: 30 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-11-01

363

Multimodal visible embolisation particles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Embolisation - the blocking of vessels - is a key procedure in Interventional Radiology. It plays a steadily growing role in the treatment of various tumour lesions, with hepatic cellular carcinoma and uterine fibroids the main focus. We produced multimodal visible embolization particles, which can be visualized in X-ray based fluoroscopy and computer tomography (CT) as well as radiation free magnetic resonance imaging (MRI).

Bartling, So?nke H.; Budjan, Johannes; Sadick, Maliha; Aviv, Hagit; Margel, Shlomo; Reis, Christian; Diehl, Steffen

2011-01-01

364

SI-Traceable Solar Spectral Irradiance Measurements: The NPOESS TSIS Spectral Irradiance Monitor  

Science.gov (United States)

One of the highest priority recommended missions in the NRC Earth Science Decadal Survey is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission that has separate agency components for implementation by NASA and NOAA. The NOAA portion of CLARREO includes the continuation of solar irradiance measurements (both total and spectral) by the Total Solar Irradiance Sensor (TSIS) as part of NPOESS. This addresses the need for the long-term, high accuracy time series of incident solar irradiance. The Spectral Irradiance Monitor (SIM) is included as part of TSIS to continue the measurement of solar spectral irradiance (SSI) in the ultraviolet, visible and near infrared, which began as part of the SOlar Radiation and Climate Experiment (SORCE), operational since 2003. The TSIS SIM builds upon the experiences gained from the SORCE SIM with significant improvements in the SI-traceable absolute accuracy (pre-launch and on-orbit), the radiometric precision, and the on-board, long-term degradation tracking to maintain the full calibration over the operational lifetime. The measurement requirements for SIM are derived from an analysis of the solar variability over a solar cycle in the visible and infrared spectral regions, namely 0.05-0.1%. The requirement to measure solar variability appropriate for climate studies is that SIM must have a relative uncertainty of 0.01% and a combined absolute uncertainty of TSIS SIM. These include refractive dispersion (via single optical element), variable spectral resolution, extremely precise wavelength control, accurate radiometric detectors, and robust long-term degradation knowledge at all wavelengths. To address the absolute accuracy, we have invested in a comprehensive characterization and end-to-end calibration program for the SIM calibration utilizing the NIST Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS). SIRCUS is a reference calibration facility to calibrate detectors and radiometers for spectral irradiance and radiance responsivity from the UV to the IR. SIRCUS relies on laser based integrating sphere sources with superior intensity and wavelength stability tied to transfer standard detectors calibrated against the NIST Primary Optical Watt Radiometer (POWR), the primary US standard for radiant power measurements. For the 200-2400 nm spectral range the relative combined standard uncertainty in irradiance responsivity for the calibration is <2×10-3.

Richard, E. C.; Harder, J. W.; Lawrence, G. M.; Pilewskie, P.; Kopp, G.; Sparn, T.; Woods, T.; Brown, S.; Lykke, K.; Smith, A.

2008-12-01

365

A wide dynamic range CMOS image sensor with 200-1100 nm spectral sensitivity and high robustness to UV right exposure  

Science.gov (United States)

A highly UV-light sensitive and sensitivity robust CMOS image sensor with a wide dynamic range (DR) was developed and evaluated. The developed CMOS image sensor includes a lateral overflow integration capacitor in each pixel in order to achieve a high sensitivity and a wide DR simultaneously. As in-pixel photodiodes (PDs), buried pinned PDs were formed on flattened Si surface. The PD has a thin surface p+ layer with a steep dopant concentration profile to form an electric field that drifts photoelectrons to the pinned n layer. This structure improves UV-light sensitivity and its stability. In addition, a buried channel source follower driver was introduced to achieve a low pixel noise. This CMOS image sensor was fabricated by a 0.18-µm 1-polycrystalline silicon 3-metal CMOS process technology with buried pinned PD. The fabricated image sensor has a high sensitivity for 200-1100 nm light wave band, high robustness of sensitivity and dark current toward UV-light exposure and a wide DR of 97 dB. In this paper, the PD structures, the circuit, the operation sequence and the measurement results of this CMOS image sensor are discussed.

Nasuno, Satoshi; Kawada, Shun; Koda, Yasumasa; Nakazawa, Taiki; Hanzawa, Katsuhiko; Kuroda, Rihito; Sugawa, Shigetoshi

2014-01-01

366

Polarization gratings for visible and near-infrared astronomy  

Science.gov (United States)

We report on the development of polarization gratings that can be used for polarimetry and/or high throughput broadband spectroscopy in astronomy. Polarization gratings are able to overcome fundamental limitations on the diffraction efficiency of conventional gratings to provide near 100% diffraction efficiency over a broad bandwidth. The broad spectral coverage of these devices will be useful for observations of gamma-ray bursts and supernovae of unknown the redshift, where spectral features may fall over a range of wavelengths. As a spectropolarimeter a polarization grating would be ideal, for example, for the study of dusts and hazes, whose polarimetric properties vary with wavelength. We present the results of a series of laboratory measurements of the diffraction efficiency and modulation efficiency of a prototype grating designed for operation from 500 to 900 nm. We find that the grating is able to achieve greater than 90% diffraction efficiency from 500 to 850 nm and modulate incident circular polarized light with an efficiency of ~ 99%. Our future plans include on-sky testing at a small local telescope, with an eventual goal of incorporating a polarization grating into the design of a microshutter array- based multi-object visible/NIR spectrograph for a 10m class facility.

Millar-Blanchaer, Max; Moon, Dae-Sik; Graham, James R.; Escuti, Michael

2014-07-01

367

Spectral imager based on Fabry-Perot interferometer for Aalto-1 nanosatellite  

Science.gov (United States)

The Aalto-1 is a 3U-cubesat project coordinated by Aalto University. The satellite, Aalto-1, will be mainly built by students as project assignments and thesis works. The Aalto-1 is planned to launch on 2014. VTT Technical Research Centre of Finland is developing the main Earth observation payload, a miniaturized spectral imager unit, for the satellite. The spectral imager unit contains a spectral imager, a visible RGB-camera and control electronics of the cameras. Detailed design of the spectral imager unit has been completed and assembly of the spectral imager unit will be done in the autumn 2013. The spectral imager is based on a tunable Fabry-Perot interferometer (FPI) accompanied by an RGB CMOS image sensor. The FPI consists of two highly reflective surfaces separated by a tunable air gap and it is based on a piezo-actuated structure. The piezo-actuated FPI uses three piezo-actuators and is controlled in a closed capacitive feedback loop. The spectral resolution of the imager will be 8-15 nm at full width at half maximum and it will operate in the wavelength range 500-900 nm. Imaging resolution of the spectral imager is 1024x1024 pixels and the focal length of the optics is 32 mm and F-number is 3.4. Mass of the spectral imager unit is approximately 600 grams, and dimensions are 97 mm x 97 mm x 48 mm.

Mannila, Rami; Näsilä, Antti; Viherkanto, Kai; Holmlund, Christer; Näkki, Ismo; Saari, Heikki

2013-09-01

368

Validation of short-pulse-laser-based measurement setup for absolute spectral irradiance responsivity calibration.  

Science.gov (United States)

This paper describes the validation process of mode-locked lasers in the "tunable lasers in photometry" (TULIP) setup at Physikalisch-Technische Bundesanstalt (PTB) regarding spectral irradiance responsivity calibrations. Validation has been carried out in the visible spectral range, 400-700 nm, with two different photometer heads and in the long wavelength range, 690-780 nm, with a filtered radiometer. A comparison of the results against those from two different validated measurement setups has been carried out for validation. For the visible spectral range, the comparison is conducted against the data obtained from a lamp-based monochromator setup for spectral irradiance responsivity calibrations and against the photometric values (integral quantity) measured at the photometric bench setup of PTB. For the long wavelength range, comparisons against results from two different lamp-based monochromator measurement setups were made. Additionally, the effect of different radiation bandwidths on interference oscillations has been determined for a filter radiometer without a diffuser. A procedure for the determination of the optimum bandwidth of the setup for the respective measurement device is presented. PMID:24921865

Schuster, Michaela; Nevas, Saulius; Sperling, Armin

2014-05-01

369

High-speed multispectral videography with a periscope array in a spectral shaper.  

Science.gov (United States)

We present a simple method for continuous snapshot multispectral imaging or multispectral videography that achieves high-speed spectral video recording without the need for mechanical scanning and much computation for datacube construction. The enabling component of this method is an array of periscopes placed in a prism-based spectral shaper that spectrally separates the image without image deformation. As a proof-of-principle demonstration, we show five-color multispectral video recording in the visible range (200×200 pixels per spectral image frame) at a record high frame rate of at least 2800 frames per second. Our experimental results indicate that this method holds promise for various industrial and biomedical applications such as remote sensing, food inspection, and endoscopy. PMID:25503036

Hashimoto, Kazuki; Mizuno, Hikaru; Nakagawa, Keiichi; Horisaki, Ryoichi; Iwasaki, Atsushi; Kannari, Fumihiko; Sakuma, Ichiro; Goda, Keisuke

2014-12-15

370

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

371

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

372

Spectral characterisation and discrimination of burnt areas  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spectral properties of recent burns charaterised, in the visible, near infrared, mid-infrared, thermal infrared, and microwave spectral domains. Fire-induced reflectance changes are also compared for varios ecosystems and biomes, and discussed in terms of the cological effects of phytomass combustion. The spectral signaturess of combustion products and of burnt areas are compared with those of various plant material and land cover types, in order to graphically represent relevant aspects of b...

Pereira, Jose?; Sa?, Ana; Sousa, Ade?lia; Santos, Teresa; Carreiras, Joa?o

1999-01-01

373

Miniaturized spectral imager for Aalto-1 nanosatellite  

Science.gov (United States)

The Aalto-1 is a 3U-cubesat project coordinated by Aalto University. The satellite, Aalto-1, will be mainly built by students as project assignments and thesis works. VTT Technical Research Centre of Finland will develop the main Earth observation payload, a miniaturized spectral imager, for the satellite. It is a novel highly miniaturized tunable filter type spectral imager. Mass of the spectral imager will be less than 400 grams, and dimensions will be approximately 80 mm x 80 mm x 45 mm. The spectral imager is based on a tunable Fabry-Pérot interferometer (FPI) accompanied by an RGB CMOS image sensor. The FPI consists of two highly reflective surfaces separated by a tunable air gap and it is based either on a microelectromechanical (MEMS) or piezo-actuated structure. The MEMS FPI is a monolithic device, i.e. it is made entirely on one substrate in a batch process, without assembling separate pieces together. The gap is adjusted by moving the upper mirror with electrostatic force. Benefits of the MEMS FPI are low mass and small size. However, large aperture (2-10 mm) MEMS FPIs are currently under development, thus it is not yet known if their performance is adequate. The piezo-actuated FPI uses three piezo-actuators and is controlled in a closed capacitive feedback loop. The drawback of the piezo-actuated FPI is its higher mass. However, it has a large aperture which enables a shorter exposure times. Selection of the FPI type will be done after thorough evaluation. Depending on the selected FPI type, the spectral resolution of the imager will be 5 - 10 nm at full width at half maximum and it will operate in the visible and/or near infrared range.

Mannila, Rami; Näsilä, Antti; Praks, Jaan; Saari, Heikki; Antila, Jarkko

2011-11-01

374

Visible Spectrum Incandescent Selective Emitter  

Energy Technology Data Exchange (ETDEWEB)

The purpose of the work performed was to demonstrate the feasibility of a novel bi-layer selective emitter. Selective emitters are incandescent radiant bodies with emissivities that are substantially larger in a selected part of the radiation spectrum, thereby significantly shifting their radiated spectral distribution from that of a blackbody radiating at the same temperature. The major research objectives involved answering the following questions: (1) What maximum VIS/NIR radiant power and emissivity ratios can be attained at 2650 K? (2) What is the observed emitter body life and how does its performance vary with time? (3) What are the design tradeoffs for a dual heating approach in which both an internally mounted heating coil and electrical resistance self-heating are used? (4) What are the quantitative improvements to be had from utilizing a bi-layer emitter body with a low emissivity inner layer and a partially transmissive outer layer? Two approaches to obtaining selective emissivity were investigated. The first was to utilize large optical scattering within an emitter material with a spectral optical absorption that is much greater within the visible spectrum than that within the NIR. With this approach, an optically thick emitter can radiate almost as if optically thin because essentially, scattering limits the distance below the surface from which significant amounts of internally generated radiation can emerge. The performance of thin emitters was also investigated (for optically thin emitters, spectral emissivity is proportional to spectral absorptivity). These emitters were fabricated from thin mono-layer emitter rods as well as from bi-layer rods with a thin emitter layer mounted on a substrate core. With an initially estimated energy efficiency of almost three times that of standard incandescent bulbs, a number of energy, economic and environmental benefits such as less energy use and cost, reduced CO{sub 2} emissions, and no mercury contamination was initially projected. The work performed provided answers to a number of important questions. The first is that, with the investigated approaches, the maximum sustained emitter efficiencies are about 1.5 times that of a standard incandescent bulb. This was seen to be the case for both thick and thin emitters, and for both mono-layer and bi-layer designs. While observed VIS/NIR ratios represent improvements over standard incandescent bulbs, it does not appear sufficient to overcome higher cost (i.e. up to five times that of the standard bulb) and ensure commercial success. Another result is that high temperatures (i.e. 2650 K) are routinely attainable without platinum electrodes. This is significant for reducing material costs. A novel dual heating arrangement and insulated electrodes were used to attain these temperatures. Another observed characteristic of the emitter was significant grain growth soon after attaining operating temperatures. This is an undesirable characteristic that results in substantially less optical scattering and spectral selectivity, and which significantly limits emitter efficiencies to the values reported. Further work is required to address this problem.

Sonsight Inc.

2004-04-30

375

Low-loss multilayered metamaterial exhibiting a negative index of refraction at visible wavelengths  

Science.gov (United States)

Over the last decade, metamaterials have attracted a great interest thanks to their potential to expand the range of electromagnetic properties found in natural materials. In particular, the possibility of achieving negative refractive index media (NIM) enables us to implement superlenses and optical storing devices. Since the first experimental demonstration at microwave frequencies, much effort has been put in extending negative refraction to the visible spectrum, where we can take full advantage of NIM properties. For instance, the superior imaging ability of NIM would be essential for visible microscopy. The desired features for NIM are low loss and isotropy. This last property includes polarization independence and negative-index behavior in all spatial directions. None of these features have been attained in previous experiments. Thus, the current challenge is to improve such aspects in order to make NIM suitable for practical applications. In this work, we experimentally demonstrate a low-loss multilayer metamaterial exhibiting a double-negative index in the visible spectrum, while presenting polarization independence at normal incidence. This has been achieved by exploiting the properties of a second-order magnetic resonance of the so-called fishnet structure, in contrast to previous works that used first-order magnetic resonances, both related to gap surface plasmon polariton (SPP) modes. The low-loss nature of the employed magnetic resonance, together with the effect of the interacting adjacent layers, results in a figure of merit as high as 3.34. A wide spectral range of negative index is achieved, covering the wavelength region between 620 and 806 nm with only two different designs. The fabricated metamaterials are the first experimental multilayer NIM in the visible spectrum, which entails an important step towards homogeneous NIM in this range. Finally, we found that the SPP modes determining the permeability resonance display weak angular dispersion.

Garcia-Meca, Carlos

2012-02-01

376

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

377

Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one as a visible photoinitiator  

International Nuclear Information System (INIS)

Photoinitiators that operate in the visible range of the electromagnetic spectrum have widespread applications. Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one (TX-MPA) was synthesized and the characterization of this initiator was confirmed by spectral analysis methods. TX-MPA has excellent absorption properties in the visible range (?480nm=3576 L/mol.cm). Photophysical studies; fluorescence quantum yield (?f=0.22, DPA), phosphorescence lifetime (?p=115 ms) and triplet lifetime (?=190 ns) were explored. To explore the initiation mechanism of TX-MPA, besides the photophysical and photochemical studies, the polymer (PMMA) obtained from the photopolymerization studies was subjected to a phosphorescence study and ?p was found to be 105 ms compared to 115 ms for the initiator TX-MPA which proved attachment of the initiator to the polymer. Possibly both intermolecular and intramolecular hydrogen abstraction, occur during the initiation stage depending on the concentration of the initiator. Highlights: ? Synthesis and photophysical properties of a visible photoinitiator (TX-MPA) are proposed. ? TX-MPA has high molar absorption values in the visible region. ? TX-MPA can initiate photopolymerization of methylmethacrylate monomer under UV and sunlight. ? Inter or intramolecular hydrogen abstraction mechanisms occur depending on initiator concentration

378

Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one as a visible photoinitiator  

Energy Technology Data Exchange (ETDEWEB)

Photoinitiators that operate in the visible range of the electromagnetic spectrum have widespread applications. Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one (TX-MPA) was synthesized and the characterization of this initiator was confirmed by spectral analysis methods. TX-MPA has excellent absorption properties in the visible range (?{sub 480} {sub nm}=3576 L/mol.cm). Photophysical studies; fluorescence quantum yield (?{sub f}=0.22, DPA), phosphorescence lifetime (?{sub p}=115 ms) and triplet lifetime (?=190 ns) were explored. To explore the initiation mechanism of TX-MPA, besides the photophysical and photochemical studies, the polymer (PMMA) obtained from the photopolymerization studies was subjected to a phosphorescence study and ?{sub p} was found to be 105 ms compared to 115 ms for the initiator TX-MPA which proved attachment of the initiator to the polymer. Possibly both intermolecular and intramolecular hydrogen abstraction, occur during the initiation stage depending on the concentration of the initiator. Highlights: ? Synthesis and photophysical properties of a visible photoinitiator (TX-MPA) are proposed. ? TX-MPA has high molar absorption values in the visible region. ? TX-MPA can initiate photopolymerization of methylmethacrylate monomer under UV and sunlight. ? Inter or intramolecular hydrogen abstraction mechanisms occur depending on initiator concentration.

Do?ruyol, Sevnur Keskin [Department of Chemistry, Y?ld?z Technical University, Davutpasa Campus, Esenler, 34220 Istanbul (Turkey); Do?ruyol, Zekeriya [Department of Engineering Science, Istanbul University, 34850, Avc?lar, Istanbul (Turkey); Arsu, Nergis, E-mail: narsu@yildiz.edu.tr [Department of Chemistry, Y?ld?z Technical University, Davutpasa Campus, Esenler, 34220 Istanbul (Turkey)

2013-06-15

379

Visibility of comet nuclei  

International Nuclear Information System (INIS)

Photography of the nucleus of comet Halley is the goal of several planned space missions. The nucleus of a comet is surrounded by a cloud of dust particles. If this cloud is optically thick, it will prevent observation of the nuclear surface. Broadband photometry of nine comets has been analyzed to determine the visibility of their nuclei. Only in the case of comet West near perihelion was the dust dense enough to interfere with imaging. Comparison of the visual brightness of the well-observed comets with that of Halley in 1910 leads to the conclusion that the nucleus of Halley can be imaged without significant obscuration by the dust

380

Spectral and Spread Spectral Teleportation  

Energy Technology Data Exchange (ETDEWEB)

We report how quantum information encoded into the spectral degree of freedom of a single-photon state is teleported using a finite spectrally entangled biphoton state. We further demonstrate how the bandwidth of a teleported waveform can be controllably and coherently dilated using a spread spectral variant of teleportation. We present analytical fidelities for spectral and spread spectral teleportation when complex-valued Gaussian states are prepared using a proposed experimental approach, and we discuss the utility of these techniques for integrating broad-bandwidth photonic qubits with narrow-bandwidth receivers in quantum communication systems.

Humble, Travis S [ORNL

2010-01-01

 
 
 
 
381

Spectral plasma diagnostics in welding with CO2 lasers  

International Nuclear Information System (INIS)

The spectral emission of the laser induced plasma is investigated during the welding process of steel. In this study, emission spectroscopy in the visible spectral range is used. A method is presented for determining the electron temperature, the electron density as well as the density of the neutral atoms in the welding plasma. In these metallic studies the relative line intensity technique was used, in which the radiation from a pair of spectral lines is compared as a function of electron temperature. The technique eliminates the need for a calibration source and can be used easily in the plasma monitoring applications. Some examples of the estimations of the plasma temperature, the electron and the neutral atom density are demonstrated. Time and space resolved measurements of the keyhole emission are presented. The application of the spectral diagnostic during the keyhole formation at the beginning of the metal sheet as well as at the end of the welding process at the end of the sheet is shown. The results help to explain the plasma absorption inside the keyhole. Some aspects of the spectral diagnostic as a basic method for a welding control are discussed

382

Comparison of visible and near-infrared Raman cross-sections of explosives in solution and in the solid state.  

Science.gov (United States)

Raman cross-sections of explosives in solution and in the solid state have been measured using visible and near-infrared excitation via secondary calibration. These measurements are valuable for both fundamental scientific purposes and applications in the standoff detection of explosives. The explosive compounds RDX, HMX, TNT, 2,4-DNT, 2,6-DNT, and ammonium nitrate were measured using discrete excitation wavelengths ranging from 532 nm to 785 nm. A comparison of the spectral features and cross-sections between the solid state and solution was performed. Comparison is also made to cross-sections measured with deep ultraviolet excitation. PMID:22732533

Emmons, Erik D; Guicheteau, Jason A; Fountain, Augustus W; Christesen, Steven D

2012-06-01

383

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

384

The spectral shift function and spectral flow  

CERN Document Server

This paper extends Krein's spectral shift function theory to the setting of semifinite spectral triples. We define the spectral shift function under these hypotheses via Birman-Solomyak spectral averaging formula and show that it computes spectral flow.

Azamov, N A; Sukochev, F A

2007-01-01

385

Understanding Visible Perception  

Science.gov (United States)

One concern about human adaptation to space is how returning from the microgravity of orbit to Earth can affect an astronaut's ability to fly safely. There are monitors and infrared video cameras to measure eye movements without having to affect the crew member. A computer screen provides moving images which the eye tracks while the brain determines what it is seeing. A video camera records movement of the subject's eyes. Researchers can then correlate perception and response. Test subjects perceive different images when a moving object is covered by a mask that is visible or invisible (above). Early results challenge the accepted theory that smooth pursuit -- the fluid eye movement that humans and primates have -- does not involve the higher brain. NASA results show that: Eye movement can predict human perceptual performance, smooth pursuit and saccadic (quick or ballistic) movement share some signal pathways, and common factors can make both smooth pursuit and visual perception produce errors in motor responses.

2003-01-01

386

The visible and total emission of flares deduced from Sun-as-a-star observations.  

Science.gov (United States)

During solar flares, the impact of the accelerated particles on the chromosphere results in heating of the surrounding materials that then dissipate the received energy though electromagnetic emission at all wavelengths. The most dramatic increase occurs in the extreme ultraviolet and soft X-rays emission coming from the hot coronal plasma. However, small increases of the visible emission that are less easily detectable can contain a significant part of the total radiated energy. The statistical analysis of solar irradiance observations allows to quantify the energy radiated by the flare at all wavelengths and reveals that the visible component constitutes the core of the total emission for most of the flares. We discuss the origin of this white light emission and how its energy compares with the energy released in the soft X-ray and extreme ultraviolet spectral ranges. We next investigate how the spectral distribution of the flare energy evolves with the flare X-ray class and we estimate the power law exponent for the frequency distribution of the total flare emission.

Kretzschmar, Matthieu

2012-07-01

387

HARD X-RAY IMAGING OF SOLAR FLARES USING INTERPOLATED VISIBILITIES  

International Nuclear Information System (INIS)

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 uvsmooth, is compared with other RHESSI image reconstruction algorithms currently in use and its advantageithms currently in use and its advantages summarized. We also illustrate the application of the method using RHESSI observations of four solar flares.

388

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

Wu T-C

2007-06-01

389

Effects of Dopant Concentrations on Thin Films with Coherent Formulation at Visible Wavelengths  

Directory of Open Access Journals (Sweden)

Full Text Available Semiconductor materials with coatings have a wide range of applications in MEMS and NEMS. This work uses transfer-matrix method for calculating the radiative properties. Dopped silicon is used and the coherent formulation is applied. The Drude model for the optical constants of doped silicon is employed. Results showed that for the visible wavelengths, more emittance occurs in high concentrations and the reflectance decreases as the concentration increases. In these wavelengths, transmittance is negligible. Donars and acceptors act similar in visible wavelengths. The effect of wave interference can be understood by plotting the spectral properties such as reflectance or transmittance of a thin dielectric film versus the film thickness and analyzing the oscillations of properties due to constructive and destructive interferences. But this effect has not been shown at visible wavelengths. At room temperature, the scattering process is dominated by lattice scattering for lightly doped silicon, and the impurity scattering becomes important for heavily doped silicon when the dopant concentration exceeds 1018cm-3.

M. Omidpanah

2012-01-01

390

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.  

Science.gov (United States)

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. PMID:21639488

Carlie, N; Anheier, N C; Qiao, H A; Bernacki, B; Phillips, M C; Petit, L; Musgraves, J D; Richardson, K

2011-05-01

391

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  

Energy Technology Data Exchange (ETDEWEB)

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.

Carlie, Nathan; Anheier, Norman C.; Qiao, Hong (Amy); Bernacki, Bruce E.; Phillips, Mark C.; Petit, Laticia; Musgraves, Jonathan D.; Richardson, Kathleen

2011-05-01

392

Measurement of the refractive index dispersion of As{sub 2}Se{sub 3} bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range  

Energy Technology Data Exchange (ETDEWEB)

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 {mu}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.

Carlie, N.; Petit, L.; Musgraves, J. D.; Richardson, K. [School of Materials Science and Engineering/COMSET, Clemson, South Carolina 29640 (United States); Anheier, N. C. Jr.; Qiao, H. A.; Bernacki, B.; Phillips, M. C. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99352 (United States)

2011-05-15

393

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

394

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.

395

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

396

Sensitivity of a receiver using GaInAsSb/AlGaAsSb SAM avalanche photodiode for long-wavelength optical communication systems in the mid-infrared spectral range  

Science.gov (United States)

Low- noise avalanche photodiodes for the spectral range of 1.6-2.4 ?m were created using the GaInAsSb solid solution in the absorption region and the wide-gap GaAlX(As)Sb alloy of resonant composition (x=0.04) in the multiplication region. This APD has a very high ratio of ionization coefficients, ?/?>30 and low excess noise factor, F~1.6 (M=10). The sensitivity of a receiver for longwavelength communication (?=1.6-2.5 ?m) based on GaInAsSb/AlGa(As)Sb SAM APD is reported. The sensitivity for a direct detection receiver using the SAM APD was calculated according to the treatment of Personick at bit rate B=500 Mbit/s. The dependence of minimum detectable power ? on multiplication M for the SAM APD for the wavelength ?=2.1 ?m was calculated and compared with one for a standard Ge APD operating at ?=1.55 ?m. A minimum detectable power level ? = -42.3 dBm at Mopt=34-39 and ?=-41.8 dBm at Mopt=10 of the receivers with the GaInAsSb/GaAl(As)Sb SAM APD and the Ge APD, respectively were obtained. These results demonstrate the potential of an optical receiver with the GaInAsSb/GaAl(As)Sb SAM APD for use in mid-IR wavelength optical communication system as well as of great interest for their potential applications in laser range-finding system.

Mikhailova, M. P.; Andreev, I. A.; Kunitsyna, E. V.; Yakovlev, Yu. P.

2009-05-01

397

Sensitivity of a receiver using GaInAsSb/AlGaAsSb SAM avalanche photodiode for longwavelength optical communication systems in the mid-infrared spectral range  

Science.gov (United States)

Low- noise avalanche photodiodes for the spectral range of 1.6-2.4 ?m were created using the GaInAsSb solid solution in the absorption region and the wide-gap GaAlX(As)Sb alloy of resonant composition (x=0.04) in the multiplication region. This APD has a very high ratio of ionization coefficients, ?/?>30 and low excess noise factor, F~1.6 (M=10). The sensitivity of a receiver for longwavelength communication (?=1.6-2.5 ?m) based on GaInAsSb/AlGa(As)Sb SAM APD is reported. The sensitivity for a direct detection receiver using the SAM APD was calculated according to the treatment of Personick at bit rate B=500 Mbit/s. The dependence of minimum detectable power ? on multiplication M for the SAM APD for the wavelength ?=2.1 ?m was calculated and compared with one for a standard Ge APD operating at ?=1.55 ?m. A minimum detectable power level ? = -42.3 dBm at Mopt=34-39 and ?=-41.8 dBm at Mopt=10 of the receivers with the GaInAsSb/GaAl(As)Sb SAM APD and the Ge APD, respectively were obtained. These results demonstrate the potential of an optical receiver with the GaInAsSb/GaAl(As)Sb SAM APD for use in mid-IR wavelength optical communication system as well as of great interest for their potential applications in laser range-finding system.

Mikhailova, M. P.; Andreev, I. A.; Kunitsyna, E. V.; Yakovlev, Yu. P.

2009-05-01

398

Efficient generation of 3.9 W of diffraction-limited green light with spectrally combined tapered diode lasers  

DEFF Research Database (Denmark)

We propose an efficient concept increasing the power of diode laser systems in the visible spectral range. In comparison with second harmonic generation of single emitters, spectral beam combining with subsequent sum-frequency generation enhances the available power significantly. Combining two 1060 nm tapered diode lasers, we achieve a 2.5-3.2 fold increase of green light with a maximum power of 3.9 Watts in a diffraction-limited beam. At this level, diode lasers have a high application potential, for example, within the biomedical field. In order to enhance the power even further, our concept can be expanded combining multiple diode lasers.

Müller, André; Jensen, Ole Bjarlin

399

Results and lessons from a decade of Terra MODIS on-orbit spectral characterization  

Science.gov (United States)

Since launch in 1999, the NASA EOS Terra MODIS has successfully operated for more than a decade. MODIS acquires data in 36 spectral bands with wavelengths ranging from visible (VIS) to long-wave infrared (LWIR) and at three nadir spatial resolutions: 250m for 2 bands, 500m for 5 bands, and 1km for 29 bands. In addition to its on-board calibrators (OBC), designed for sensor radiometric calibration and characterization, MODIS was built with a unique device called the spectro-radiometric calibration assembly (SRCA), which can be configured into three different modes: radiometric, spatial, and spectral. When it is operated in the spectral mode, the SRCA can monitor changes in sensor spectral performance for the VIS and near-infrared (NIR) spectral bands. For more than 10 years, the SRCA operations have continued to provide valuable information for Terra MODIS on-orbit spectral performance. This paper briefly describes Terra MODIS SRCA on-orbit operations and calibration activities and presents results derived from its decade-long spectral characterization, including changes in the VIS and NIR spectral bands center wavelengths (CW) and bandwidths (BW). It demonstrates that the SRCA on-orbit wavelength calibration capability remains satisfactory. For most spectral bands, the changes in CW and BW are less than 0.5 nm and 1.0 nm, respectively. As expected, results and lessons from Terra MODIS on-orbit spectral characterization have and will continue to benefit the operation and calibration of its successor, Aqua MODIS, and the development of future missions and sensors, which have stringent requirements on sensor spectral performance.

Xiong, Xiaoxiong; Choi, Taeyoung; Che, Nianzeng; Wang, Zhipeng; Dodd, Jennifer; Xie, Yong; Barnes, William

2010-10-01

400

ATST visible broadband imager  

Science.gov (United States)

The Advanced Technology Solar Telescope (ATST) is a 4 meter class telescope for observation of the solar atmosphere currently in the construction phase. The Visible Broadband Imager (VBI) is a diffraction limited imaging instrument planned to be the first-light instrument in the ATST instrumentation suite. The VBI is composed of two branches, the "VBI blue" and the "VBI red", and uses state-of-the-art narrow bandwidth interference filters and two custom designed high speed filter wheels to take bursts of images that will be re-constructed using a Graphics Processing Unit (GPU) optimized near-real-time speckle image reconstruction engine. At first light, the VBI instrument will produce diffraction-limited movies of solar activity at eight discrete wavelengths with a field of view of 2 arc minutes square. In this contribution, the VBI design team will discuss the capabilities of the VBI and describe the design of the instrument, highlighting the unique challenges faced in the development of this unique instrument.

McBride, William R.; Wöger, Friedrich; Hegwer, Steve L.; Ferayorni, Andrew; Gregory, B. Scott

2012-09-01

 
 
 
 
401

Spectral Reflectance Response of Three Turfgrasses to Leaf Dehydration  

Directory of Open Access Journals (Sweden)

Full Text Available Spectral reflectance assessment of turfgrass canopies is likely to enhance our ability to refine irrigation management technology. Reliable spectral detection of water stress is dependent upon knowledge of wavelengths most sensitive to leaf water content. The purposes of this study were (1 to determine wavelengths at which turfgrass canopy reflectance is most sensitive to progressive dehydration in the visible and near infrared portions of the spectrum and (2 to investigate whether different turfgrasses exhibit spectrally unique canopy reflectance responses to progressive dehydration. Two consecutive studies were conducted using established field plots of hybrid bluegrass (Poa pratensis L. x Poa arachnifera Torr. (HBG, Kentucky bluegrass (Poa pratensis L. (KBG and perennial ryegrass (Lolium perenne L. (PRG. Field plots were brought to field capacity, irrigation was then withheld and spectral reflectance and Leaf Water Content (LWC measured as dehydration progressed. In study I, turfgrass canopy spectral reflectance within 616-696 nm in HBG, 658-688 nm in KBG and 630-688 in PRG were well correlated to LWC with maximum coefficients of determination (R2 occurring at 664, 672 and 664 nm for HBG, KBG and PRG, respectively. In study II significant coefficients of determination ranged from 642-694, 594-698 and 638-678 nm with maximum r2 occurring at 668, 672 and 660 nm for HBG, KBG and PRG, respectively. Within the near infrared range only KBG exhibited correlation between canopy reflectance and decreasing leaf water content. Within 734-878 nm range, three species exhibited different degree of reflectance change between fully turgid and wilted turf; indicating the rank of canopy reflectance sensitivity to dehydration was KBG>PRG>HBG, the reverse order of their drought resistance ranking.

Y.L. Qian

2011-01-01

402

Two fast methods for high-quality line visibility.  

Science.gov (United States)

Lines drawn over or in place of shaded 3D models can often provide greater comprehensibility and stylistic freedom than shading alone. A substantial challenge for making stylized line drawings from 3D models is the visibility computation. Current algorithms for computing line visibility in models of moderate complexity are either too slow for interactive rendering, or too brittle for coherent animation. We introduce two methods that exploit graphics hardware to provide fast and robust line visibility. First, we present a simple shader that performs a visibility test for high-quality, simple lines drawn with the conventional implementation. Next, we offer a full optimized pipeline that supports line visibility and a broad range of stylization options. PMID:20616387

Cole, Forrester; Finkelstein, Adam

2010-01-01

403

Visible wavelength free electron oscillator  

International Nuclear Information System (INIS)

The overall goal of the visible oscillator program is to demonstrate that a large FEL interaction strength can be obtained at approximately 600-nm wavelength. The gain extraction product increases with increasing wiggler length, and a 5-m length with hybrid SmCo5 technology was identified at the program start as providing satisfactory interaction strength, reasonable cost, and an acceptable extrapolation from previous wigglers. The 120-MeV LINAC comprises five accelerator sections, each powered by a 12-MW peak output RF klystron power station. The operating frequency is 1.3 GHz. The structure is a constant gradient traveling wave (TW), operating in the 3?/4 mode. A TW design was chosen to accommodate the wide range of beam loading conditions required in the FEL experimental series. The radio frequency (RF) LINAC current format is a series of high-current micropulses spaced at the two way oscillator cavity transit time. The envelope of these pulses, the macropulse, is selected to be long enough to examine the laser startup and beam quality physics, nominally 100-200?s. 9 refs., 5 figs

404

Spectral imaging for contamination detection in food  

DEFF Research Database (Denmark)

Spectral imaging is a technique with a big potential for surface chemistry mapping of heterogeneous samples. It works by making a spectrum in every pixel of an image, and this spectrum may under the right circumstances be transformed into abundance maps for chemical components. One important application of the technique is finding anomalies I supposedly homogeneous matter or homogeneous mixtures. This application occurs frequently in the food industry when different types of contamination are to be detected. Contaminants could be e.g. foreign matter, process-induced toxins, and microbiological spoilage. Many of these contaminants may be detected in the wavelength range visible to normal silicium-based camera sensors i.e. 350-1050 nm with proper care during sample preparation, sample presentation, image acquisition and analysis. This presentation will give an introduction to the techniques behind the VideometerLab instrument, that implements the thoughts above, and show examples including fusarium detection inbarley, measuring microbial meat spoilage, and making humidity maps. It will also illustrate methodology for spectral image analysis.

Carstensen, Jens Michael Technical University of Denmark,

405

Validation of UV-visible aerosol optical thickness retrieved from spectroradiometer measurements  

Directory of Open Access Journals (Sweden)

Full Text Available Global and diffuse UV-visible solar irradiances are routinely measured since 2003 with a spectroradiometer operated by the Laboratoire d'Optique Atmosphérique (LOA located in Villeneuve d'Ascq, France. The analysis of the direct irradiance derived by cloudless conditions enables retrieving the aerosol optical thickness (AOT spectrum in the 330–450 nm range. The site hosts also sunphotometers from the AERONET/PHOTONS network performing routinely measurements of the AOT at several wavelengths. On one hand, comparisons between the spectroradiometer and the sunphotometer AOT at 440 nm as well as, when available, at 340 and 380 nm, show good agreement. On the other hand, the AOT's spectral variations have been compared using the Angström exponents derived from AOT data at 340 and 440 nm for both instruments. The comparisons show that this parameter is difficult to retrieve accurately due to the small wavelength range and due to the weak AOT values. Thus, AOT derived at wavelengths outside the spectroradiometer range by means of an extrapolation using the Angström parameter would be of poor value, whereas, spectroradiometer's spectral AOT could be used for direct validation of other AOT, such as those provided by satellite instruments.

C. Brogniez

2008-02-01

406

Deriving atmospheric visibility from satellite retrieved aerosol optical depth  

Science.gov (United States)

Atmospheric visibility is a measure that reflects different physical and chemical properties of the atmosphere. In general, poor visibility conditions come along with risks for transportation (e.g. road traffic, aviation) and can negatively impact human health since visibility impairment often implies the presence of atmospheric pollution. Ambient pollutants, particulate matter, and few gaseous species decrease the perceptibility of distant objects. Common estimations of this parameter are usually based on human observations or devices that measure the transmittance of light from an artificial light source over a short distance. Such measurements are mainly performed at airports and some meteorological stations. A major disadvantage of these observations is the gap between the measurements, leaving large areas without any information. As aerosols are one of the most important factors influencing atmospheric visibility in the visible range, the knowledge of their spatial distribution can be used to infer visibility with the so called Koschmieder equation, which relates visibility and atmospheric extinction. In this study, we evaluate the applicability of satellite aerosol optical depth (AOD) products from the Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) to infer atmospheric visibility on large spatial scale. First results applying AOD values scaled with the planetary boundary layer height are promising. For the comparison we use a full automated and objective procedure for the estimation of atmospheric visibility with the help of a digital panorama camera serving as ground truth. To further investigate the relation between the vertical measure of AOD and the horizontal visibility data from the Aerosol Robotic Network (AERONET) site Laegeren (Switzerland), where the digital camera is mounted, are included as well. Finally, the derived visibility maps are compared with synoptical observations in central Europe.

Riffler, M.; Schneider, Ch.; Popp, Ch.; Wunderle, S.

2009-04-01

407

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

408

Spectral weight in holographic scaling geometries  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We compute the low energy spectral density of transverse currents in theories with holographic duals that exhibit an emergent scaling symmetry characterized by dynamical critical exponent $z$ and hyperscaling violation exponent $\\theta$. For any finite $z$ and $\\theta$, the low energy spectral density is exponentially small at nonzero momentum. This indicates that any nonzero momentum low energy excitations of putative hidden Fermi surfaces are not visible in the classical b...

Hartnoll, Sean A.; Shaghoulian, Edgar

2012-01-01