Blackbody Radiation Research Articles

High temperature thermographic phosphors YAG:Tm;Li and YAG:Dy in reduced oxygen environments

Phosphor thermometry for surface temperature measurements has become an established remote thermometry technique. However, measuring at temperatures above 1700 K is still challenging because of the weak phosphorescence and intense background from black-body radiation, leading to low signal-to-noise ratios. Therefore, lifetime-based phosphor thermometry with YAG:Tm;Li and YAG:Dy for high-temperature applications were investigated in this study with the aim of improving the precision of high-temperature measurements. The phosphors were coated on an alumina-oxide disc, which was placed in a temperature-controlled oven that exposed the phosphors to temperatures of up to 1930 K. The emission spectra and temporal decay of the luminescence were recorded for the investigated phosphors including their sensitivity to oxygen concentration in the gas environment. Knowledge of oxygen environment sensitivities for measurements of reduced oxygen concentrations at high temperatures, such as in combustion, is of great importance to increase confidence in the measurement. The results suggest that performing a mono-exponential decay time fit in a region of the decay curve that is dominated by a single lifetime component reduces the sensitivity to changes in the gas oxygen concentration for YAG:Tm;Li. Moreover, YAG:Tm;Li performs better than YAG:Dy in terms of signal-to-noise ratio (SNR), with a peak signal value and SNR almost an order of magnitude higher. With an appropriate decay curve fitting procedure, the effects of oxygen quenching can be minimized, such that the measurement error due to oxygen quenching is within the measurement precision for both phosphors.

Recent Progress in Development of Carbon-Nanotube-Based Photo-Thermoelectric Sensors and Their Applications in Ubiquitous Non-Destructive Inspections.

The photo-thermoelectric (PTE) effect in electronic materials effectively combines photo-absorption-induced local heating and associated thermoelectric conversion for uncooled and broadband photo-detection. In particular, this work comprehensively summarizes the operating mechanism of carbon nanotube (CNT)-film-based PTE sensors and ubiquitous non-destructive inspections realized by exploiting the material properties of CNT films. Formation of heterogeneous material junctions across the CNT-film-based PTE sensors, namely photo-detection interfaces, triggers the Seebeck effect with photo-absorption-induced local heating. Typical photo-detection interfaces include a channel-electrode boundary and a junction between P-type CNTs and N-type CNTs (PN junctions). While the original CNT film channel exhibits positive Seebeck coefficient values, the material selections of the counterpart freely govern the intensity and polarity of the PTE response signals. Based on these operating mechanisms, CNT film PTE sensors demonstrate a variety of physical and chemical non-destructive inspections. The device aggregates broad multi-spectral optical information regarding the targets and reconstructs their inner composite or layered structures. Arbitrary deformations of the device are attributed to the macroscopic flexibility of the CNT films to further monitor targets from omni-directional viewing angles without blind spots. Detection of blackbody radiation from targets using the device also visualizes their behaviors and associated changes.

Ion-loss events in a hybrid trap of cold Rb-Ca+ : Photodissociation, blackbody radiation, and nonradiative charge exchange

We theoretically investigate the collisional dynamics of laser-cooled $^{87}$Rb ground-state atoms and $^{40}$Ca$^+$ ground-state ions in the context of the hybrid trap experiment of Ref. [Phys. Rev. Lett. 107, 243202 (2011)], leading to ion losses. Cold $^{87}$Rb$^{40}$Ca$^+$ ground-state molecular ions are created by radiative association, and we demonstrate that they are protected against photodissociation by black-body radiation and by the $^{40}$Ca$^+$ cooling laser at 397~nm. This study yields an interpretation of the direct observation of $^{87}$Rb$^{40}$Ca$^+$ ions in the experiment, in contrast to other hybrid trap experiments using other species. Based on novel molecular data for the spin-orbit interaction, we also confirm that the non-radiative charge-exchange is the dominant loss process for Ca$^+$ and obtain rates in agreement with experimental observations and a previous calculation.

Symmetry Breaking in Sticky Collisions between Ultracold Molecules.

Ultracold molecules undergo "sticky collisions" that result in loss even for chemically nonreactive molecules. Sticking times can be enhanced by orders of magnitude by interactions that lead to nonconservation of nuclear spin or total angular momentum. We present a quantitative theory of the required strength of such symmetry-breaking interactions based on classical simulation of collision complexes. We find static electric fields as small as 10 V/cm can lead to nonconservation of angular momentum, while we find nuclear spin is conserved during collisions. We also compute loss of collision complexes due to spontaneous emission and absorption of black-body radiation, which are found to be slow.

Multi-primary human-centric lighting based on the optical power ratio and the CCT super-smooth switching algorithms

The discovery of intrinsically photosensitive retinal ganglion cells related to circadian rhythms has led to an increased research focus on the physiological and psychological effects of artificial lighting sources, with the emerging concept of human-centric lighting. This study tuned the spectra of a six-primary lighting source based on pulse width modulation to obtain the best visual and non-visual performances in work, leisure, and daytime indoor applications. The adopted method uses indicators, including the circadian action factor, goodness-of-fit coefficient, color rendering index, and correlated color temperature (CCT). Among these, a CCT super-smooth switching algorithm has been proposed to achieve the change trajectory of the chromaticity coordinates in the Commission Internationale de L'Eclairage color diagram close to the blackbody radiation curve during the CCT switching process in different cases. Finally, this study can provide useful guidance for improving light qualities and achieving human-centric lighting based on a six-primary lighting source with light-emitting diodes.

Experimental Determination of Absolute Spectral Radiance and Emissivity of a Photonic Crystal Filament

A recent discovery of super-Planckian radiation in the far-field has attracted a great deal of interest in thermal radiation control using photonic crystals (PC) architecture. The finding is based on a careful comparison of radiation intensity emitted from a PC nano-filament and a blackbody at the same temperature and same wavelength at λ∼1.7 μm. Extending that finding, we determined the absolute spectral radiance of such a PC filament at λ∼1.7 μm at elevated temperature, T = 445–723 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> °</sup> K, and compared its value to that predicted by Planck's blackbody radiation law. Our data confirmed that the PC spectral radiance surpassed that of a blackbody by an order-of-magnitude. We also determined the spectral emissivity of our PC filament and showed that its value far exceeded unity at resonance and fell below unity away from resonance. The observation of non-equality between absorptivity and emissivity suggests that a strong optical non-reciprocity takes place in our PC nano-filament.

Simplified Multiple-Well Approach for the Master Equation Modeling of Blackbody Infrared Radiative Dissociation of Hydrated Carbonate Radical Anions.

Blackbody infrared radiative dissociation (BIRD) in a collision-free environment is a powerful method for the experimental determination of bond dissociation energies. In this work, we investigate temperature-dependent BIRD of CO3·-(H2O)1,2 at 250-330 K to determine water binding energies and assess the influence of multiple isomers on the dissociation kinetics. The ions are trapped in a Fourier-transform ion cyclotron resonance mass spectrometer, mass selected, and their BIRD kinetics are recorded at varying temperatures. Experimental BIRD rates as a function of temperature are fitted with rates obtained from master equation modeling (MEM), using the water binding energy as a fit parameter. MEM accounts for the absorption and emission of photons from black-body radiation, described with harmonic frequencies and infrared intensities from quantum chemical calculations. The dissociation rates as a function of internal energy are calculated by Rice-Ramsperger-Kassel-Marcus theory. Both single-well and multiple-well MEM approaches are used. Dissociation energies derived in this way from the experimental data are 56 ± 6 and 45 ± 3 kJ/mol for the first and second water molecules, respectively. They agree within error limits with the ones predicted by ab initio calculations done at the CCSD(T)/aug-cc-pVQZ//CCSD/aug-cc-pVDZ level of theory. We show that the multiple-well MEM approach described here yields superior results in systems with several low-lying minima, which is the typical situation for hydrated ions.

A terahertz detector based on superconductor-graphene-superconductor Josephson junction

Graphene is an attractive material for terahertz (THz) detectors due to its unique properties of extremely weak electron-phonon interaction and small electronic heat capacity. In this paper, we demonstrate a lens-antenna-coupled THz detector based on a diffusive superconductor-graphene-superconductor (SGS) junction, which has a sharp resistive transition at 1.4 K due to the proximity Josephson coupling. The SGS Josephson detector, measured with a dc superconducting quantum interference device (SQUID) readout, exhibits an electrical noise equivalent power (NEP) as low as 5 × 10−17 W/Hz0.5 at 0.1 K, which is still limited by the readout noise. Furthermore, the optical performance of the SGS Josephson detector is measured with a cryogenic blackbody radiation source, giving an optical NEP of 2.5–5 × 10−16 W/Hz0.5 at 1.4 THz in the temperature range from 0.1 K to 0.6 K.

Detection band expansion by independently tunable double resonances in a long-wavelength dual-color QWIP.

Multi-resonance light coupling management is a promising way to expand the operating spectral ranges of optoelectronic devices. The classical strategies are either lack of independent tunability for each resonance or involved with complex fabrication. Here, we propose a new scheme for expanding the operating spectral range of an optoelectronic device through a dual-color active material integrated with a simple resonant waveguide structure. The TM waveguide mode and the SPP mode of the resonant waveguide structure are regulated to match the two active regions of the dual-color material both spectrally and spatially. Applying this scheme to a long-wavelength infrared quantum well photodetector, the absorption efficiencies at the two peak detection wavelengths of the dual-color quantum wells are both enhanced by more than 10 times compared with the case of a standard 45° edge facet coupled device with the same detection material. The simple light coupling structure is easy to accomplish and compatible with focal plane arrays. For thermal radiation detection, the absorption efficiency of the 300 K blackbody radiation by our dual-color detector is 83.8% higher than that by a single-color detector with the optimized structural parameters. Moreover, either polarization sensitive or polarization insensitive detection could be achieved in this dual-color infrared quantum well photodetector by using anisotropic or isotropic gratings.

Thermostatistical properties of the blackbody radiation and Debye crystal model through Fibonacci oscillators

Thermostatistical properties of the blackbody radiation and Debye crystal model through Fibonacci oscillators

First-Principle Derivation of Single-Photon Entropy and Maxwell-Jüttner Velocity Distribution.

This work is devoted to deriving the entropy of a single photon in a beam of light from first principles. Based on the quantum processes of light-matter interaction, we find that, if the light is not in equilibrium, there are two different ways, depending on whether the photon is being added or being removed from the light, of defining the single-photon entropy of this light. However, when the light is in equilibrium at temperature T, the two definitions are equivalent and the photon entropy of this light is hν/T. From first principles, we also re-derive the Jüttner velocity distribution showing that, even without interatomic collisions, two-level atoms will relax to the state satisfying the Maxwell-Jüttner velocity distribution when they are moving in blackbody radiation fields.

Ytterbium optical lattice clock with instability of order 10−18

We have built an ytterbium optical lattice clock with improvements over our previous version. An in-vacuum blackbody radiation (BBR) shield is employed to provide a well characterized BBR environment. The effective temperature felt by the atoms can be determined at an accuracy level of 13 mK, leading to a total BBR frequency shift uncertainty of 9.5 × 10−19. We have also built an ultra-stable optical cavity system to pre-stabilize the clock laser, achieving a flicker frequency instability of ∼3 × 10−16. Rabi spectroscopy of the lattice-trapped atoms can achieve sub-Hertz linewidth spectra. Two ytterbium clocks have been operated in an antisynchronized configuration, with real-time BBR-Stark-shift corrections applied to both of them. By comparing the two clocks, we demonstrate a single-clock instability of 5.4 × 10−18 in 4500 s. This clock will be applied for frequency comparisons to other optical clocks of different atomic species in the future.

The Principle and State-of-Art Approach for Black Hole Detection

Black hole is a kind of special celestial subject whose density is so great that even the light cannot escape, which has always been a popular topic. This study will present the recent progress of observation related to three quantities of black holes. As a leading-in, we first introduced some of the most commonly discussed black holes by demonstrating their field equations, metric, and some other representative quantities. On this basis, the formation process of a black hole will be described. In addition, a picture of the detectors used in cosmology observation is discussed before getting any further into the methods applied in observation. Subsequently, we summarized observations regarding the three elements of a black hole (mass, charge and spin). For these three different characters of black hole, different methods and theories were put into use, including gravitational retro-lensing, twin-peak QPOs, accretion disks, continuum fitting method, and black body radiation. Eventually, possible limitations are evaluated and possible improving approaches on current observations are proposed. Overall, these results shed light on guiding further researches focusing on exploring the black holes.

Einstein on measurement theory: A heuristic point of view

Einstein did not contribute significantly to the quantum mechanics we are familiar with, but he did contribute to its theoretical foundations. In a seminal theory on black body radiation, he used two physically distinct sets of coordinates, a classical set to describe the continuity of heat energy with Maxwell Boltzmann statistics and an atomic set to describe discrete energy states required by the Planck radiation law. His methods are extended here to reveal that matrix mechanics is an incomplete description of atomic structure. In addition to the discrete energy states of the diagonal matrix elements, classically derived components of kinetic energy are necessary. We conclude that the diagonalized matrix elements and eigenvalues of the Schrödinger equation both describe characteristics of the steady states, but the physical variables they describe are different, because they are measured with respect to different coordinate systems. Einstein’s assumptions lead to a resolution of the measurement problem by introducing statistical laws at the microscopic level.

Compensation for Vanadium Oxide Temperature with Stereo Vision on Long-Wave Infrared Light Measurement.

In this paper, using automated optical inspection equipment and a thermal imager, the position and the temperature of the heat source or measured object can effectively be grasped. The high-resolution depth camera is with the stereo vision distance measurement and the low-resolution thermal imager is with the long-wave infrared measurement. Based on Planck's black body radiation law and Stefan-Boltzmann law, the binocular stereo calibration of the two cameras was calculated. In order to improve the measured temperature error at different distances, equipped with Intel Real Sense Depth Camera D435, a compensator is proposed to ensure that the measured temperature of the heat source is correct and accurate. From the results, it can be clearly seen that the actual measured temperature at each distance is proportional to the temperature of the thermal image vanadium oxide, while the actual measured temperature is inversely proportional to the distance of the test object. By the proposed compensation function, the compensation temperature at varying vanadium oxide temperatures can be obtained. The errors between the average temperature at each distance and the constant temperature of the test object at 39 °C are all less than 0.1%.

Black-body radiation-induced photodissociation and population redistribution of weakly bound states in H2 +

Molecular hydrogen ions in weakly bound states close to the first dissociation threshold are attractive quantum sensors for measuring the proton-to-electron mass ratio and hyperfine-induced ortho-para mixing. The experimental accuracy of previous spectroscopic studies relying on fast ion beams could be improved by using state-of-the-art ion trap setups. With the electric-dipole moment vanishing in H and preventing fast spontaneous emission, radiative lifetimes of the order of weeks are found. We include the effect of black-body radiation that can lead to photodissociation and rovibronic state redistribution to obtain effective lifetimes for trapped ion experiments. Rate coefficients for bound-bound and bound-continuum processes were calculated using adiabatic nuclear wave functions and nonadiabatic energies, including relativistic and radiative corrections. Effective lifetimes for the weakly bound states were obtained by solving a rate equation model and lifetimes in the range of 4–523 and >215 ms were found at room temperature and liquid nitrogen temperature, respectively. Black-body induced photodissociation was identified as the lifetime-limiting effect, which guarantees the purity of state-selectively generated molecular ion ensembles. The role of hyperfine-induced g/u-mixing, which allows pure rovibrational transitions, was found to be negligible.

Sustainable Energy and the Second Law of Thermodynamics: An Introduction to the Special Issue

At the end of the 19th century, the field of physics was considered nearly complete, encouraging triumphal statements by some of the most eminent physicists of the day, for instance, "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement (William Thompson, Baron Kelvin of Largs). Only a few random clouds troubled this bright horizon, for instance, the vexing negative result of the Michelson-Morley experiment, some puzzling aspects to the photoelectric effect, and a the lack of a coherent explanation for the blackbody radiation spectrum. Nothing terribly serious, nothing that wouldn’t be mopped up eventually. In fact, the first would soon be key to Einstein’s revolutionary special theory of relativity, the second would win him the Nobel prize in physics, and the third, in the able hands of Max Planck, would crack open the door to the paradigm-shattering quantum world. Indeed, every moment is the end of physics or its beginning-–depending on one’s curiosity. Viewed through the lens of Thomas Kuhn’s The Structure of Scientific Revolutions, physics’ sudden turnabout was to be expected. Whenever experts consider a field complete, beware and be amused, for it will likely erupt in revolution. This is because the nature of knowledge itself guarantees scientific paradigms will invariably germinate the seeds of their own destructions. They must. When a paradigm is established, it is encumbent upon scientists to explore it as fully as possible, to extend its domain to the fullest possible extent.

Superposition of forward and backward motion

Abstract I consider black body radiation. The wall of the black body exchanges photons with the radiation field in equilibrium, therefore with a common temperature in Planck’s radiation law. The underlying process of radiation consists of creation and annihilation of photons. I want to present an alternate model of motions, where the process of radiation consists of small steps in positive and negative direction, not zero in mean. The detection of radiation consists of storing and restoring of packages of energy. I get an analogue of Planck’s radiation law, where the common temperature emerges from the underlying common model of small steps. The object of the law is not the radiation, but a storage of packages of energy, which belongs to the wall of the black body.

Dipoles in blackbody radiation: momentum fluctuations, decoherence, and drag force

An expression is derived for the momentum diffusion constant due to photon scattering of a small polarizable particle in blackbody radiation, and is shown to be related to the long-wavelength collisional decoherence rate for such a particle in a thermal environment. We show how this diffusion constant appears in the steady-state photon emission rate of two dipoles induced by blackbody radiation. We consider in addition the Einstein–Hopf drag force on a small polarizable particle moving in a blackbody field, and derive its relativistic form from the Lorentz transformation of forces. We obtain an expression for the rate of change of the field energy density associated with changes in the particles’ kinetic energies and relate it to the Kompaneets equation for the case of Compton scattering by thermalized electrons.

Effect of shock strength on the radiation of focusing shock wave

High temperature radiating Air is produced experimentally by focusing a shock wave with the help of a spherically converging test section attached to a shock tube. The converging section concentrates the shock to a point with minimum diffusion losses. A shift in radiation towards the UV region was observed with an increase in the strength of the focusing shock wave. The atomic and molecular emission was observed from the radiation spectrum. Along with the emission from molecules of Air, emissions from contaminations were also observed. The temperature of the radiating gas was estimated using the blackbody radiation curve and was observed to be 13000 K.