Thermal radiation

About: Thermal radiation is a research topic. Over the lifetime, 12290 publications have been published within this topic receiving 197186 citations. The topic is also known as: heat radiation.

Infrared Radiative Energy Transfer in Gases

Abstract: Publisher Summary This chapter illustrates the incorporation of spectroscopic information into the radiative transfer equations and presents a reasonable means of treating radiative energy transfer within gases. Specific restriction is made to infrared gaseous radiation that results from molecular transitions involving both vibrational and rotational energies, and emphasis is placed upon the application of the molecular band models to radiative transfer analyses. The chapter also reviews the infrared band spectra, introduces simple band models, and discusses the formulation of total band absorptance information with the aid of these models. The basic equations describing the radiative transfer within an infrared absorbing–emitting gas are formulated and these allow for the radiatively induced departures from local thermodynamic equilibrium. The chapter also presents some illustrative radiative transfer analyses, with emphasis upon physical interpretations and the relative importance of thermal radiation versus molecular conduction as energy transport mechanisms.

Thermal radiation and near-field energy density of thin metallic films

Abstract: We study the properties of thermal radiation emitted by a thin dielectric slab, employing the framework of macroscopic fluctuational electrodynamics. Particular emphasis is given to the analytical construction of the required dyadic Green's functions. Based on these, general expressions are derived for both the system's Poynting vector, describing the intensity of propagating radiation, and its energy density, containing contributions from non-propagating modes which dominate the near-field regime. An extensive discussion is then given for thin metal films. It is shown that the radiative intensity is maximized for a certain film thickness, due to Fabry-Perot-like multiple reflections inside the film. The dependence of the near-field energy density on the distance from the film's surface is governed by an interplay of several length scales, and characterized by different exponents in different regimes. In particular, this energy density remains finite even for arbitrarily thin films. This unexpected feature is associated with the film's low-frequency surface plasmon polariton. Our results also serve as reference for current near-field experiments which search for deviations from the macroscopic approach.

Experimental observation of laser-induced radiation heat waves.

Abstract: The propagation of a radiation heat wave through a thin foil of solid gold was investigated experimentally. The wave is driven by the intense thermal radiation in 1--3-mm-diam gold cavities heated by an intense laser pulse (duration 0.8--0.9 ns, wavelength 0.35 \ensuremath{\mu}m) to temperatures of more than 200 eV. Evidence of the propagating wave was obtained from the delayed onset of intense thermal emission from the outer side of the foil. The results agree with theoretical predictions for a self-similar ablative heat wave and with numerical simulations.