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• 1. [Article] Temperature dependence of dark current in a CCD

  We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor ...

  Citation × Citation Citation Abstract Copy Title: Temperature dependence of dark current in a CCD Author: Widenhorn, Ralf, Blouke, Morley M., Weber, Alexander, Rest, Armin, Bodegom, Erik Year: 2002 We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, characterized by the band gap of silicon, is uniform for all pixels. At low temperatures, the depletion dark current, characterized by half the band gap, prevails, but it varies for different pixels. Dark current spikes are pronounced at low temperatures and can be explained by large concentrations of deep level impurities in those particular pixels. We show that fitting the data with the impurity concentration as the only variable can explain the dark current characteristics of all the pixels on the chip. Title: Temperature dependence of dark current in a CCD Author: Widenhorn, Ralf, Blouke, Morley M., Weber, Alexander, Rest, Armin, Bodegom, Erik Year: 2002 We present data for dark current of a back-illuminated CCD over the temperature range of 222 to 291 K. Using an Arrhenius law, we found that the analysis of the data leads to the relation between the prefactor and the apparent activation energy as described by the Meyer-Neldel rule. However, a more detailed analysis shows that the activation energy for the dark current changes in the temperature range investigated. This transition can be explained by the larger relative importance at high temperatures of the diffusion dark current and at low temperatures by the depletion dark current. The diffusion dark current, characterized by the band gap of silicon, is uniform for all pixels. At low temperatures, the depletion dark current, characterized by half the band gap, prevails, but it varies for different pixels. Dark current spikes are pronounced at low temperatures and can be explained by large concentrations of deep level impurities in those particular pixels. We show that fitting the data with the impurity concentration as the only variable can explain the dark current characteristics of all the pixels on the chip. Close

• 2. [Article] The Relationship Between Precipitation and Temperature Over the Contiguous United States

  The correlation between monthly total precipitation and monthly mean temperature over the 80-year period from 1905 to 1984 at nearly 1000 stations in the contiguous United States was calculated and analyzed. ...

  Citation × Citation Citation Abstract Copy Title: The Relationship Between Precipitation and Temperature Over the Contiguous United States Author: Zhao, Weining, Khalil, M. A. K. Year: 1993 The correlation between monthly total precipitation and monthly mean temperature over the 80-year period from 1905 to 1984 at nearly 1000 stations in the contiguous United States was calculated and analyzed. Both local and field significances were tested by using statistical methods. Areas of both negative and positive precipitation-temperature correlations were found. Over most of the United States, summer precipitation and temperature were negatively correlated, which indicates that warm summers tended to be dryer. This is particularly true in the central and southern Great Plains. The area south of the Great Lakes covering the eastern portion of the Corn Belt was the only major area where a significant positive correlation was found in winter. Title: The Relationship Between Precipitation and Temperature Over the Contiguous United States Author: Zhao, Weining, Khalil, M. A. K. Year: 1993 The correlation between monthly total precipitation and monthly mean temperature over the 80-year period from 1905 to 1984 at nearly 1000 stations in the contiguous United States was calculated and analyzed. Both local and field significances were tested by using statistical methods. Areas of both negative and positive precipitation-temperature correlations were found. Over most of the United States, summer precipitation and temperature were negatively correlated, which indicates that warm summers tended to be dryer. This is particularly true in the central and southern Great Plains. The area south of the Great Lakes covering the eastern portion of the Corn Belt was the only major area where a significant positive correlation was found in winter. Close

• 3. [Article] Optical properties of β″-(ET)2SF5CH2CF2SO3: A layered molecular superconductor with large discrete counterions

  We report the polarized infrared and optical reflectance of β″-(ET)₂SF₅CH₂CF₂SO₃ as a function of temperature. This fully organic superconductor displays weakly metallic behavior over the entire temperature ...

  Citation × Citation Citation Abstract Copy Title: Optical properties of β″-(ET)2SF5CH2CF2SO3: A layered molecular superconductor with large discrete counterions Author: Dong, J., Musfeldt, J. L., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 We report the polarized infrared and optical reflectance of β″-(ET)₂SF₅CH₂CF₂SO₃ as a function of temperature. This fully organic superconductor displays weakly metallic behavior over the entire temperature range of our investigation. The electronic properties present several unusual features including the lack of a conventional free carrier (Drude) response at low temperature, infrared localization phenomena, and an unexpected temperature dependence of the oscillator strength. Similar behavior is observed in other β and β″ superconductors above Tc, suggesting that this class of compounds is very close to a metal→insulator transition where electronic correlations are important and the Drude response carries very little spectral weight. Vibronic features increase in intensity with decreasing temperature in the infrared, as expected. The temperature dependence of key anion vibrational modes are discussed in terms of intermolecular hydrogen bonding within the anion pocket. [S0163-1829(99)04330-1] Title: Optical properties of β″-(ET)2SF5CH2CF2SO3: A layered molecular superconductor with large discrete counterions Author: Dong, J., Musfeldt, J. L., Schlueter, J. A., Williams, Jack M., Nixon, P. G., Winter, Rolf Walter, Gard, Gary L. Year: 1999 We report the polarized infrared and optical reflectance of β″-(ET)₂SF₅CH₂CF₂SO₃ as a function of temperature. This fully organic superconductor displays weakly metallic behavior over the entire temperature range of our investigation. The electronic properties present several unusual features including the lack of a conventional free carrier (Drude) response at low temperature, infrared localization phenomena, and an unexpected temperature dependence of the oscillator strength. Similar behavior is observed in other β and β″ superconductors above Tc, suggesting that this class of compounds is very close to a metal→insulator transition where electronic correlations are important and the Drude response carries very little spectral weight. Vibronic features increase in intensity with decreasing temperature in the infrared, as expected. The temperature dependence of key anion vibrational modes are discussed in terms of intermolecular hydrogen bonding within the anion pocket. [S0163-1829(99)04330-1] Close

• 4. [Article] Surface-enhanced Raman scattering at elevated temperatures

  The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by ...

  Citation × Citation Citation Abstract Copy Title: Surface-enhanced Raman scattering at elevated temperatures Author: Leung, P.T., Hider, M. H., Sánchez, Erik J. Year: 1996 The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is relatively insensitive to the change of substrate temperature. A tentative explanation is provided for our modeling results, and the implications from these results are discussed. Title: Surface-enhanced Raman scattering at elevated temperatures Author: Leung, P.T., Hider, M. H., Sánchez, Erik J. Year: 1996 The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is relatively insensitive to the change of substrate temperature. A tentative explanation is provided for our modeling results, and the implications from these results are discussed. Close

• 5. [Article] Computation of dark frames in digital imagers

  Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm ...

  Citation × Citation Citation Abstract Copy Title: Computation of dark frames in digital imagers Author: Widenhorn, Ralf, Rest, Armin, Blouke, Morley M., Berry, Richard L., Bodegom, Erik Year: 2007 Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best temperature sensors. We use the dark current of a several hundred hot pixels to sense the chip temperature and predict the dark current of all pixels on the chip. Dark current computation is not a new concept, but our approach is unique. Some advantages of our method include applicability for poorly temperature-controlled camera systems and the possibility of ex post facto dark current correction. Title: Computation of dark frames in digital imagers Author: Widenhorn, Ralf, Rest, Armin, Blouke, Morley M., Berry, Richard L., Bodegom, Erik Year: 2007 Dark current is caused by electrons that are thermally exited into the conduction band. These electrons are collected by the well of the CCD and add a false signal to the chip. We will present an algorithm that automatically corrects for dark current. It uses a calibration protocol to characterize the image sensor for different temperatures. For a given exposure time, the dark current of every pixel is characteristic of a specific temperature. The dark current of every pixel can therefore be used as an indicator of the temperature. Hot pixels have the highest signal-to-noise ratio and are the best temperature sensors. We use the dark current of a several hundred hot pixels to sense the chip temperature and predict the dark current of all pixels on the chip. Dark current computation is not a new concept, but our approach is unique. Some advantages of our method include applicability for poorly temperature-controlled camera systems and the possibility of ex post facto dark current correction. Close

• 6. [Article] The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures

  The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure ...

  Citation × Citation Citation Abstract Copy Title: The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures Author: Leung, P.T., Chiang, Hai-Pang, Tse, W. S. Year: 1998 The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more realistic modeling as well as systematic experimental studies. The implication of this result to other surface photochemical processes is discussed. Title: The surface plasmon enhancement effect on adsorbed molecules at elevated temperatures Author: Leung, P.T., Chiang, Hai-Pang, Tse, W. S. Year: 1998 The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more realistic modeling as well as systematic experimental studies. The implication of this result to other surface photochemical processes is discussed. Close

• 7. [Article] Meyer-Neldel rule for dark current in charge-coupled devices

  We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from ...

  Citation × Citation Citation Abstract Copy Title: Meyer-Neldel rule for dark current in charge-coupled devices Author: Widenhorn, Ralf, Mündermann, Lars, Rest, Armin, Bodegom, Erik Year: 2001 We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from a linear behavior in the form of continuous bending. However, as a first approximation, the dark current, D, can be expressed as: D=Dₒ exp(−ΔE/kT),where ΔE is the activation energy, k is Boltzmann’s constant, and T the absolute temperature. It was found that ΔE and the exponential prefactor Dₒ follow the Meyer–Neldel rule (MNR) for all of the more than 222,000 investigated pixels. The isokinetic temperature, Tₒ, for the process was found as 294 K. However, measurements at 313 K did not show the predicted inversion in the dark current. It was found that the dark current for different pixels merged at temperatures higher than Tₒ. A model is presented which explains the nonlinearity and the merging of the dark current for different pixels with increasing temperature. Possible implications of this finding regarding the MNR are discussed. Title: Meyer-Neldel rule for dark current in charge-coupled devices Author: Widenhorn, Ralf, Mündermann, Lars, Rest, Armin, Bodegom, Erik Year: 2001 We present the results of a systematic study of the dark current in each pixel of a charged-coupled device chip. It was found that the Arrhenius plot, at temperatures between 222 and 291 K, deviated from a linear behavior in the form of continuous bending. However, as a first approximation, the dark current, D, can be expressed as: D=Dₒ exp(−ΔE/kT),where ΔE is the activation energy, k is Boltzmann’s constant, and T the absolute temperature. It was found that ΔE and the exponential prefactor Dₒ follow the Meyer–Neldel rule (MNR) for all of the more than 222,000 investigated pixels. The isokinetic temperature, Tₒ, for the process was found as 294 K. However, measurements at 313 K did not show the predicted inversion in the dark current. It was found that the dark current for different pixels merged at temperatures higher than Tₒ. A model is presented which explains the nonlinearity and the merging of the dark current for different pixels with increasing temperature. Possible implications of this finding regarding the MNR are discussed. Close

• 8. [Article] Approximate Equations of State in Two-Temperature Plasma Mixtures

  Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring ...

  Citation × Citation Citation Abstract Copy Title: Approximate Equations of State in Two-Temperature Plasma Mixtures Author: Ramshaw, John D., Cook, Andrew W. Year: 2014 Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring the separated materials to be in temperature and pressure equilibrium. Iterative numerical algorithms have been employed to enforce this equilibration and compute the resulting approximate state relations in single-temperature mixtures. In partially ionized gas mixtures, there is both theoretical and empirical evidence that equilibrating the chemical potentials, number densities, or partial pressures of the free electrons is likely to produce more accurate results than equilibrating the total pressures. Moreover, in many situations of practical interest the free electrons and heavy particles have different temperatures. In this paper, we present a generalized algorithm for equilibrating the heavy-particle and electron temperaturesand a third user-specified independent thermodynamic variable in a two-temperature plasmamixture. Test calculations based on the equilibration of total pressure vs. electron pressure are presented for three different mixtures. Title: Approximate Equations of State in Two-Temperature Plasma Mixtures Author: Ramshaw, John D., Cook, Andrew W. Year: 2014 Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring the separated materials to be in temperature and pressure equilibrium. Iterative numerical algorithms have been employed to enforce this equilibration and compute the resulting approximate state relations in single-temperature mixtures. In partially ionized gas mixtures, there is both theoretical and empirical evidence that equilibrating the chemical potentials, number densities, or partial pressures of the free electrons is likely to produce more accurate results than equilibrating the total pressures. Moreover, in many situations of practical interest the free electrons and heavy particles have different temperatures. In this paper, we present a generalized algorithm for equilibrating the heavy-particle and electron temperaturesand a third user-specified independent thermodynamic variable in a two-temperature plasmamixture. Test calculations based on the equilibration of total pressure vs. electron pressure are presented for three different mixtures. Close

• 9. [Article] Mechanisms of Methane Transport Through Trees

  Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport ...

  Citation × Citation Citation Abstract Copy Title: Mechanisms of Methane Transport Through Trees Author: Kutschera, Ellynne Marie Year: 2013 Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport are relatively unknown. Methane emissions from the common wetland tree species Populus trichocarpa (black cottonwood) native to the Pacific Northwest were measured under hydroponic conditions in order to separate plant transport mechanisms from the influence of soil processes. Roots were exposed to methane enriched water and canopy emissions of methane were measured using a canopy enclosure. Methane accumulation in the canopy was generally linear and the average canopy methane flux was 3.0 ± 2.6 μg CH4 min-1. Flux magnitudes from stem experiments scaled to the area of the main tree stem are comparable to whole-canopy flux values, indicating that the majority of methane emitted from the tree leaves through the stem. Samples for stable carbon isotope composition were taken during the canopy experiments. Compared to the isotopic composition of root water methane, canopy methane was depleted in 13C on average by 8.6 ± 3.3 permil; this indicates that methane moving through the tree is not following a purely bulk flow pathway (where no depletion would occur), but is instead subject to at least one fractionating mechanism. When temperature was varied, the flux at the coolest temperature was significantly different from the higher flux at the warmest temperature (p-value less than 0.02). The calculated Q10 for methane flux was 2.4, which indicates a positive feedback with temperature increase. Analysis of δ13C values of emitted CH4 in the temperature experiments shows increasing depletion with cooler temperatures and lower flux. This indicates that not only does the magnitude of flux vary with temperature, but the actual dominant transport mechanism changes as well. Title: Mechanisms of Methane Transport Through Trees Author: Kutschera, Ellynne Marie Year: 2013 Although the dynamics of methane (CH4) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport are relatively unknown. Methane emissions from the common wetland tree species Populus trichocarpa (black cottonwood) native to the Pacific Northwest were measured under hydroponic conditions in order to separate plant transport mechanisms from the influence of soil processes. Roots were exposed to methane enriched water and canopy emissions of methane were measured using a canopy enclosure. Methane accumulation in the canopy was generally linear and the average canopy methane flux was 3.0 ± 2.6 μg CH4 min-1. Flux magnitudes from stem experiments scaled to the area of the main tree stem are comparable to whole-canopy flux values, indicating that the majority of methane emitted from the tree leaves through the stem. Samples for stable carbon isotope composition were taken during the canopy experiments. Compared to the isotopic composition of root water methane, canopy methane was depleted in 13C on average by 8.6 ± 3.3 permil; this indicates that methane moving through the tree is not following a purely bulk flow pathway (where no depletion would occur), but is instead subject to at least one fractionating mechanism. When temperature was varied, the flux at the coolest temperature was significantly different from the higher flux at the warmest temperature (p-value less than 0.02). The calculated Q10 for methane flux was 2.4, which indicates a positive feedback with temperature increase. Analysis of δ13C values of emitted CH4 in the temperature experiments shows increasing depletion with cooler temperatures and lower flux. This indicates that not only does the magnitude of flux vary with temperature, but the actual dominant transport mechanism changes as well. Close

• 10. [Article] Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm

  The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature ...

  Citation × Citation Citation Abstract Copy Title: Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm Author: Leung, P.T., Do, Nhan, Yavas, Oguz, Tam, Andrew C., Leung, Wing P., Park, Hee K., Grigoropoulos, Costas P., Boneberg, Johannes, Leiderer, Paul Year: 1993 The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature for 752 nm, while the refractive index decreases and the extinction coefficient increases for 632.8 nm. The rate of increase of the extinction coefficient at 632.8 nm is twice as much as that for 752 nm. Title: Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm Author: Leung, P.T., Do, Nhan, Yavas, Oguz, Tam, Andrew C., Leung, Wing P., Park, Hee K., Grigoropoulos, Costas P., Boneberg, Johannes, Leiderer, Paul Year: 1993 The temperature dependence of the optical properties for amorphous silicon is studied at wavelengths of 632.8 and 752 nm. Both the refractive index and extinction coefficient increase linearly with temperature for 752 nm, while the refractive index decreases and the extinction coefficient increases for 632.8 nm. The rate of increase of the extinction coefficient at 632.8 nm is twice as much as that for 752 nm. Close