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All-Sky Observational Evidence for An Inverse Correlation Between Dust Temperature and Emissivity Spectral Index
We show that a one-component variable-emissivity-spectral-index model (the free- model) provides more physically motivated estimates of dust temperature at the Galactic polar caps than one- or two-component fixed-emissivity-spectral-index models (fixed- models) for interstellar dust thermal emission at far-infrared and millimeter wavelengths. For the comparison we have fit all-sky one-component dust models with fixed or variable emissivity spectral index to a new and improved version of the 210-channel dust spectra from the COBE-FIRAS, the 100-240 micrometer maps from the COBE-DIRBE and the 94 GHz dust map from the WMAP. The best model, the free-alpha model, is well constrained by data at 60-3000 GHz over 86 per cent of the total sky area. It predicts dust temperature (T(sub dust)) to be 13.7-22.7 (plus or minus 1.3) K, the emissivity spectral index (alpha) to be 1.2-3.1 (plus or minus 0.3) and the optical depth (tau) to range 0.6-46 x 10(exp -5) with a 23 per cent uncertainty. Using these estimates, we present all-sky evidence for an inverse correlation between the emissivity spectral index and dust temperature, which fits the relation alpha = 1/(delta + omega (raised dot) T(sub dust) with delta = -.0.510 plus or minus 0.011 and omega = 0.059 plus or minus 0.001. This best model will be useful to cosmic microwave background experiments for removing foreground dust contamination and it can serve as an all-sky extended-frequency reference for future higher resolution dust models.
Compact far ultraviolet emission source with rich spectral emission 1150-3100 A
The article describes a compact hollow Pt cathode emission source for the far UV, developed for use as a high-resolution wavelength standard in laboratory work or on spacecraft (specifically, the NASA International UV Explorer - IUE). The source is small, rugged, lightweight, spectrally rich, bright in the 1150-3200 A region, features long service life, low operating voltage, and lower power drain, and stably emits a large number of very sharp lines with a spectrum lending itself to projection onto the focal plane of a spectrograph. The source has successfully passed exacting environmental tests, and serves as a transfer standard for absolute sensitivity calibration of spectrometric instruments.
Reflectance determination of optical spectral emissivity of metal surfaces at ambient conditions
Optical pyrometry requires knowledge of both spectral radiance and spectral emissivity to accurately measure temperature. No reliable compendium of spectral emissivity data currently exists for common metals in the optical and near-infrared spectral regions where pyrometry is typically performed. In this paper, we measure the spectral reflectivity of numerous common metals, with known surface finishes, between 400 and 1100 nm. The measurements are carried out under ambient conditions, near 300 K at an atmospheric pressure of ~0.78 bar. We then calculate the emissivity as a function of the wavelength for each sample. We define and use the illumination and collection geometries most practical for applying these measurements to radiometric thermometry. We also examine the effect of surface finish upon the relative spectral emissivity of a given material and find qualitative guidelines for predicting the increase in emissivity with increasing surface roughness. Finally, these measurements can both improve the accuracy and precision of optical pyrometry and provide the necessary reference value for converting emerging diagnostic measurements of relative spectral emissivity under extreme dynamic conditions into absolute dynamic spectral emissivity.
Compositional Dependence of Normal Spectral Emissivity of Molten Cu-Fe Alloy
Normal spectral emissivity of molten Cu-Fe alloy with different compositions was measured at the wavelength of 807 nm using an electromagnetic levitator superimposed with a static magnetic field, which is capable of producing accurate normal spectral emissivity data because the applied static magnetic field suppresses translational and surface oscillations of a levitated sample to consequently reduce measurement uncertainties. Cu-Fe alloy samples used in this study were Cu{sub 97}Fe{sub 3}, Cu{sub 93}Fe{sub 7}, Cu{sub 92}Fe{sub 8}, Cu{sub 90}Fe{sub 10}, Cu{sub 80}Fe{sub 20}, and Cu{sub 70}Fe{sub 30}. The strength of the static magnetic field and temperature ranged from 3.0 to 3.5 T and 1350 to 1750 K, respectively. The measured normal spectral emissivity indicated negligible temperature dependence in a wide temperature range. In contrast, the compositional dependence indicated a distinct tendency in which the emissivity increased markedly with the composition of Fe up to 10 at pct.
The Effects of Surface Longwave Spectral Emissivity on Atmospheric Circulation and Convection over the Sahara and Sahel
This study quantifies the impact of the inclusion of realistic surface spectral emissivity in the Sahara and Sahel on the simulated local climate and beyond. The surface emissivity in these regions can be as low as 0.6–0.7 over the infrared window band while close to unity in other spectral bands, but such spectral dependence has been ignored in current climate models. Realistic surface spectral emissivities over the Sahara and Sahel are incorporated into the Community Earth System Model (CESM) version 1.1.1, while treatments of surface emissivity for the rest of the globe remain unchanged. Both the modified and standard CESM are then forced with prescribed climatological SSTs and fixed present-day forcings for 35-yr simulations. The outputs from the last 30 years are analyzed. Compared to the standard CESM, the modified CESM has warmer surface air temperature, as well as a warmer and wetter planetary boundary layer over the Sahara and Sahel. The modified CESM thus favors more convection in these regions and has more convective rainfall, especially in the Sahara. The moisture convergence induced by such inclusion of surface spectral emissivity also contributes to the differences in simulated precipitation in the Sahel and the region south to it. Compared to observations, inclusion of surface spectral emissivity reduces surface temperature biases in the Sahara and precipitation biases in the Gulf of Guinea but exacerbates the wet biases in the Sahara. Such realistic representation of surface spectral emissivity can help unmask other factors contributing to regional biases in the original CESM.
Spectral emissivity of highly doped silicon
Spectral emissivity of highly doped silicon
Infrared emissivities of silicates - Experimental results and a cloudy atmosphere model of spectral emission from condensed particulate mediums.
IR emissivities of powdered silicates and cloudy atmosphere model of spectral emission for radiative transfer in condensed powder
Spectral emissivity of metals after damage by particle impact
Spectral emissivity of polished metals after microparticle impact damage
Spectral emissivity measurements of land-surface materials and related radiative transfer simulations
Spectral radiance measurements have been made in the laboratory and in the field for deriving spectral emissivities of some land cover samples with a spectroradiometer and an auxiliary radiation source in the wavelength range 2.5-14.5 micrometers. A easy and quick four-step method (four steps to measure the sample and a diffuse reflecting plate surface under sunshine and shadowing conditions, respectively) has been used for simultaneous determination of surface temperature and emissivity. We emphasized in-situ measurements in combination with radiative transfer simulations, and an error analysis for basic assumptions in deriving spectral emissivity of land-surface samples from thermal infrared measurements.
SPECTRAL EMISSIVITIES OF ELECTRODE MATERIALS
Spectral emittance of electrode material for thermionic converter
Spectral emissivities and optical constants of electromagnetically levitated liquid metals as functions of temperature and wavelength
The development of a noncontact temperature measurement device utilizing rotating analyzer ellipsometry is described. The technique circumvents the necessity of spectral emissivity estimation by direct measurement concomittant with radiance brightness. Using this approach, the optical properties of electromagnetically levitated liquid metals Cu, Ag, Au, Ni, Pd, Pt, and Zr were measured in situ at four wavelengths and up to 600 K superheat in the liquid. The data suggest an increase in the emissivity of the liquid compared with the incandescent solid. The data also show moderate temperature dependence of the spectral emissivity. A few measurements of the optical properties of undercooled liquid metals were also conducted. The data for both solids and liquids show excellent agreement with available values in the literature for the spectral emissivities as well as the optical constants.
Spectral Emissivity of Highly Doped Silicon
Spectral normal emissivity of highly doped opaque silicon determined by free carrier absorption theory
TECHNIQUES OF MEASURING NORMAL SPECTRAL EMISSIVITY OF CONDUCTIVE REFRACTORY COMPOUNDS AT HIGH TEMPERATURE
High temperature spectral emission of refractory compounds
Spectral emissivity calculations for the parallel bands of carbon dioxide at 4.3 microns.
Spectral emissivity calculations for parallel bands of carbon dioxide at 4.3 microns between 150-600 degrees K, comparing experimental measurements with theoretical calculations
Study on the spectral emissivity of carbon particles produced by a rocket motor Final report
Spectral emissivity of carbon particles in exhaust gases of rocket engines using oxygen and RP-1 PROPELLANTS
Spectral Emissivity of Highly Doped Silicon
P- and n-type silicon spectral emissivity measured at several temperatures and wavelengths for carrier concentrations and direct current resistivities
The Investigations of the Temperature and Spectral Emissivity Characteristics of Cloud Tops and of the Earth's Surface Second Semiannual Progress Report
Temperature and spectral emissivity characteristics of cloud tops and surface of earth