scholarly journals A spectro-photometric comparison of the emissivity of solid and liquid gold at high temperatures with that of a full radiator

1912 ◽  
Vol 87 (597) ◽  
pp. 451-465 ◽  
Keyword(s):  
High Temperatures ◽  
Wave Length ◽  
Emission Spectra ◽  
Black Body ◽  
Metallic Surface ◽  
Liquid Gold ◽  
Relative Emissivity

It is well known that copper and gold emit greenish or bluish light at high temperatures. Kirchhoff's radiation law obviously suggests a connection between this selective emissivity and the selective reflectivity of these metals at ordinary temperatures, which gives rise to their colour. According to that law the emissivity E' of a surface at a temperature T is connected with its absorptivity A, by the relation E'/E = A, where E is the emissivity of a full radiator or “black body” at the same temperature T. This relation holds for each particular wave-length. The ratio E'/E may be conveniently called, and will be referred to hereafter in this paper as, the “relative emissivity” of the surface. The above law then states that the relative emissivity of a body is equal to its absorptivity for the same wave-length and temperature. For opaque bodies, such as metals, the reflectivity R is equal to 1 — A: and hence the relative emissivity E'/E = A = 1 — R. This relation holds strictly only if emission and reflection take place at the same temperature; but if, as stated by several investigators, the reflectivity of metals for visible rays does not vary with the temperature, a heated metallic surface should emit well those rays for which it is when cold a poor reflector, and vice versâ . This has actually been observed qualitatively for gold and copper by Schaum and Wüstenfeld in a recent photographic comparison of the emission spectra of these metals with that of an approximate “black body.” They also draw attention to the “green-glow” which first makes its appearance when these metals are heated, instead of the usual "red-glow."

The Use of Ratio-Recording Interferometry for the Measurement of Infrared Emission Spectra: Applications to Oxide Films on Copper Surfaces

1975 ◽  
Vol 29 (6) ◽  
pp. 496-500 ◽  
Author(s):  
D. Kember ◽  
N. Sheppard
Keyword(s):  
Emission Spectra ◽  
Black Body ◽  
Infrared Emission ◽  
Thin Layers ◽  
Oxide Surface ◽  
Surface Layers ◽  
Selective Reflection ◽  
Copper Surfaces ◽  
Emission And Absorption Spectra ◽  
Direct Correspondence

Infrared emission spectra from metal samples with oxide surface layers are shown to be very advantageously studied using the spectrum-ratioing facility of a recording infrared interferometer. The emission from a given sample is ratioed against that from a black-body emitter at the same temperature so as to give emittance as a function of wavenumber directly. This method has very useful application to irregularly shaped metal emitters. In the absence of selective reflection there is a direct correspondence between emission and absorption spectra for thin layers of an emitting substance. However, the presence of selective reflection leads to reduced emission and to considerable differences in the appearance of “absorption” and emission spectra in regions of strong absorption. Emission spectra obtained from copper plates heated, above 150°C, for different periods in air are shown clearly to indicate the presence of cuprous, Cu(I), and cupric, Cu(II), oxides in the surface layer.

scholarly journals Galactic and extra-galactic radio frequency radiation due to sources other than the thermal and 21-cm emission of the interstellar gas

1958 ◽  
Vol 5 ◽  
pp. 37-43
Author(s):  
R. Hanbury Brown
Keyword(s):  
Thermal Emission ◽  
Wave Length ◽  
Black Body ◽  
Interstellar Gas ◽  
Ionized Gas ◽  
Radio Frequency Radiation ◽  
The Galaxy ◽  
Image Position ◽  
Galactic Radio ◽  
Frequency Radiation

At wave-lengths greater than about one metre the majority of the radio emission which is observed from the Galaxy cannot be explained in terms of thermal emission from ionized interstellar gas. This conclusion is widely accepted and is based on observations of the equivalent temperature of the sky and the spectrum of the radiation. The spectrum at metre wave-lengths is of the general form: where TA is the equivalent black-body temperature of a region of sky and A is the wave-length. The exponent n varies with direction but lies between about 2·5 and 2·8, and is thus significantly greater than the value of 2·0 which is the maximum to be expected for thermal emission from an ionized gas. Furthermore the value of TA is about 1050 K at 15 m and thus greatly exceeds the electron temperature expected in H 11 regions.At centimetre wave-lengths it is likely that the majority of the radiation observed originates in thermal emission from ionized gas; however, the present discussion is limited to a range of wave-lengths from about 1 m to 10 m where the ionized gas in the Galaxy is believed to be substantially transparent and where the origin of most of the radiation is believed to be non-thermal.

Spectroscopic Observation of Chemical Species From High-Temperature Air Pulverized Coal Combustion

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Nelfa Desmira ◽  
Takuya Nagasaka ◽  
Kimihito Narukawa ◽  
Akira Ishikawa ◽  
Kuniyuki Kitagawa ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Flame Temperature ◽  
Chemical Species ◽  
Emission Spectra ◽  
Video Camera ◽  
Spectroscopic Observation ◽  
Pulverized Coal ◽  
In Situ Monitoring ◽  
Lean Combustion

In situ monitoring of chemical species from the combustion pulverized coal in high-temperature air is examined using several different spectroscopic diagnostic at different equivalence ratios. Two-dimensional (2D) distributions of flame temperature were obtained using a thermal video camera. The experimental results showed the temperatures to range from low to 1400 °C under various conditions of fuel-lean, stoichiometric, and fuel-rich. The highest temperature and flame stability were obtained under fuel-lean combustion condition. The chemical species generated from within the combustion zone were analyzed from the spontaneous emission spectra of the flame in the Ultraviolet–visible (UV-Vis) range. The spatial distribution of NO, OH, and CN were identified from the spectra. The 2D distribution of emission intensity visualized and recorded for NO, OH, and CN revealed high-temperatures close to the root of the flame that rapidly dispersed radially outward to provide very high temperatures over a much larger volume at further downstream locations of the flame.

scholarly journals Effect of Diamond Polishing and Thermal Treatment on Carbon Paramagnetic Centers’ Nature and Structure

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7719
Author(s):  
Ira Litvak ◽  
Avner Cahana ◽  
Yaakov Anker ◽  
Sharon Ruthstein ◽  
Haim Cohen
Keyword(s):  
Thermal Treatment ◽  
High Temperatures ◽  
Black Body ◽  
Black Body Radiation ◽  
Visible Range ◽  
Paramagnetic Centers ◽  
Polishing Process ◽  
Paramagnetic Resonance ◽  
Visual Appearance ◽  
Carbon Radicals

Diamonds contain carbon paramagnetic centers (stable carbon radicals) in small concentrations (at the level of ~1 × 1012 spins/mg) that can help in elucidating the structure of the nitrogen atoms’ contaminants in the diamond crystal. All diamonds that undergo polishing are exposed to high temperatures, owing to the friction force during the polishing process, which may affect the carbon-centered radicals’ concentration and structure. The temperature is increased appreciably; consequently, the black body radiation in the visible range turns orange. During polishing, diamonds emit an orange light (at a wavelength of about 600 nm) that is typical of a black body temperature of 900 °C or higher. Other processes in which color-enhanced diamonds are exposed to high temperatures are thermal treatments or the high-pressure, high-temperature (HPHT) process in which the brown color (resulting from plastic deformation) is bleached. The aim of the study was to examine how thermal treatment and polishing influence the paramagnetic centers in the diamond. For this purpose, four rough diamonds were studied: two underwent a polishing process, and the other two were thermally treated at 650 °C and 1000 °C. The diamonds were analyzed pre- and post-treatment by EPR (Electron Paramagnetic resonance), FTIR (Fourier transform infrared, fluorescence, and their visual appearance. The results indicate that the polishing process results in much more than just thermal heating the paramagnetic centers.

scholarly journals 37. Galactic radio emission and the distribution of discrete sources: Introductory Lecture

1957 ◽  
Vol 4 ◽  
pp. 211-217
Author(s):  
R. Hanbury Brown
Keyword(s):  
Radio Emission ◽  
Thermal Emission ◽  
Wave Length ◽  
Black Body ◽  
Interstellar Gas ◽  
Ionized Gas ◽  
Introductory Lecture ◽  
The Galaxy ◽  
Image Position ◽  
Galactic Radio

At wave-lengths greater than about 1 metre the majority of the radio emission which is observed from the Galaxy cannot be explained in terms of thermal emission from ionized interstellar gas. This conclusion is widely accepted and is based on observations of the equivalent temperature of the sky and the spectrum of the radiation. The spectrum at metre wave-lengths is of the general form: where TA is the equivalent black-body temperature of a region of sky and λ is the wave-length. The exponent n varies with direction but lies between about 2·5 and 2·8, and is thus significantly greater than the value of 2·0 which is the maximum to be expected for thermal emission from an ionized gas. Furthermore, the value of TA is about 1050K. at 15 metres and thus greatly exceeds the electron temperature expected in H 11 regions.At centimetre wave-lengths it is likely that the majority of the radiation observed originates in thermal emission from ionized gas; however, the present discussion is limited to a range of wave-lengths from about 1 to 10 metres where the ionized gas in the Galaxy is believed to be substantially transparent and where the origin of most of the radiation is believed to be non-thermal.

scholarly journals The melting point of palladium

1929 ◽  
Vol 125 (798) ◽  
pp. 517-531 ◽  
Keyword(s):  
Melting Point ◽  
High Temperatures ◽  
Scale Up ◽  
Planck Equation ◽  
Black Body ◽  
The United States ◽  
Measuring Instruments ◽  
Independent Basis ◽  
Thermodynamic Scale ◽  
Melting Point Of Palladium

The melting point of palladium is a convenient reference point for the measurement of high temperatures. In fixing a scale of temperature the aim is, of course, to approximate as closely as possible to the thermodynamic scale. From the absolute zero up to moderately high temperatures this ideal scale is realised most directly and accurately through the medium of the gas thermometer. However, with increase of temperature beyond a certain limit, the experimental difficulties of gas thermometry multiply rapidly, so that ultimately it becomes necessary to adopt another basis for obtaining the scale. This is conveniently found in the laws governing the radiation from a black body, which have a sound theoretical foundation and permit the use of measuring instruments of precision. The establishment of a practical scale of temperature on the lines above indicated has been the subject of considerable discussion between the national standardising laboratories of Germany, Great Britain and the United States of America. As a result, proposals for the definition of an "International Temperature Scale" were submitted to the 7th General Conference of Weights and Measures, and approved by them. In effect, the basis of the scale up to the melting point of gold is the gas thermometer, and beyond this temperature the Wien or Planck law of radiation with an agreed value for the constant c 2 . Owing to the difficulty of absolute measurements of radiation, no attempt has so far been made to place the radiation scale on an independent basis by fixing the other constant in the Wien or Planck equation. Consequently the scale is defined, for the present, relatively to a fixed point on the thermodynamic scale, as given by the gas thermometer, namely the melting point of gold (1063°C.).

Luminescence from Photosystem I at High Temperatures

1980 ◽  
Vol 35 (3-4) ◽  
pp. 289-292 ◽  
Author(s):  
P. V. Sane ◽  
T. S. Desai ◽  
V. G. Tatake
Keyword(s):  
High Temperatures ◽  
Photosystem I ◽  
Fluorescence Intensity ◽  
Emission Spectra ◽  
Delayed Fluorescence ◽  
Fluorescence Maximum ◽  
Different Temperatures ◽  
Spinach Leaf

Abstract The changes in the fluorescence and delayed fluorescence intensity of spinach leaf as affected by temperature were studied. It was observed that the delayed fluorescence showed a maximum at about 45 °C whereas the fluorescence maximum was at about 55 °C. An examination of the emission spectra of delayed fluorescence at different temperatures showed that at higher temperatures the relative emission at 735 nm was increased. It is argued that at higher temperatures the luminescence from photosystem I contributes to delayed fluorescence.

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